CS^/3/2 'O/HPA-3 NOAA Technical Memorandum OMPA-3 J* °' c °+. A GEOCHEMICAL AND SEDIMENTOLOGICAL STUDY OF THE DREDGED MATERIAL DEPOSIT IN THE NEW YORK BIGHT R. Dayal M.G. Heaton M . Fuhrmann I. W. Duedall Boulder, Colorado February 1981 noaa NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Office of Marine Pollution Assessment NOAA Technical Memorandum OMPA-3 A GEOCHEMICAL AND SEDIMENTOLOGICAL STUDY OF THE DREDGED MATERIAL DEPOSIT IN THE NEW YORK BIGHT R. Dayal 2 M. G. Heaton M. Fuhrmann I. W. Duedall Marine Sciences Research Center State University of New York Stony Brook, New York 11794 Boulder, Colorado February 1981 'Present Address: Department of Nuclear Energy Brookhaven National Laboratory, Upton, New York 11973 "Interstate Electronics Corporation, P. Anaheim, California 92803 Box 3117, /'CtttW' UNITED STATES NATIONAL OCEANIC AND Office of Marine ° ^UHi 'UW a t DEPARTMENT OF COMMERCE ATMOSPHERIC ADMINISTRATION Pollution Assessment CL Q Malcolm Baldrige, James P. Walsh, R.L. Swanson, o o (7i O G. Secretary Acting Administrator Director Final Report Submitted to Marine Ecosystems Analysis (MESA) National Oceanic and Atmospheric Administration Stony Brook, New York 11794 DISCLAIMER The National Oceanic and Atmospheric Administration (NOAA) does not approve, recommend, or endorse any proprietary product or proprietary material mentioned in this publication. No reference shall be made to NOAA or to this publication furnished by NOAA in any advertising or sales promotion which would indicate or imply that NOAA approves, recommends, or endorses any proprietary product or proprietary material mentioned herein, or which has as its purpose an intent to cause directly or indirectly the advertised product to be used or purchased because of this publication. 11 CONTENTS Page Abstract xi 1. INTRODUCTION 1 2. SAMPLING AND METHODOLOGY 4 2.1 Field Sampling 4 2.1.1 Vibracoring Cruise 4 2.1.2 Interstitial Water Chemistry Cruise 7 2.2 Methodology 9 2.2.1 Core Processing 9 2.2.2 Water Content and Bulk Density 11 2.2.3 Combustible Organic Matter 12 2.2.4 Total Metal Analysis 12 2.2.5 Interstitial Metal Analysis 16 2.2.6 Sedimentological Analyses 18 3. DREDGED MATERIAL INPUTS TO THE BIGHT 22 3.1 Source Areas 22 3.2 Volume and Mass Estimates 22 3.3 Dredged Material Characteristics 27 3.4 Metal Inputs 28 4. DEPOSITIONAL RECORD 28 4.1 Bathymetry 31 4.1.1 1936 Survey . , . . . 31 4.1.2 1973 Survey 33 4.1.3 1978 Survey 33 4.1.4 Cross-sectional Profiles , . , . . 34 4.1.5 Net Bathymetric Changes 34 4.1.6 Sedimentation Rates 36 4.1.7 Volume and Mass Estimates 38 n i Page 4.2 Description of Sediment Types 39 4.2.1 Black Mud 42 4.2.2 Clay Types 47 4.2.3 Greensand 50 4.2.4 Coarse Sands 54 4.2.5 Artifact Material 60 4.3 Gravel/Sand/Mud Depth Profiles 61 4.4 Overall Stratigraphy 70 4.5 Sedimentary Processes 72 4.5.1 Large-Scale Sediment Differentiation 73 4.5.2 Sand Incursion 90 4.6 Geochemical Depositional Record 94 4.6.1 Depth Distributions of Metals and Organic Matter 94 4.6.2 Intracore Variability in Metal Concentrations . 1 1 1 4.6.3 Metal Enrichments in Coastal Deposits 114 4.6.4 Geochemical Correlations 116 4.6.5 Depositional Record of Metal Inputs 1 28 4.6.6 Interstitial Water Chemistry 1 33 4.6.7 Stratigraphy , 146 5. MASS BALANCE OF DREDGED MATERIAL AMD ASSOCIATED METALS. .. .155 5.1 Dredged Material... 155 5.2 Trace Metals........ 157 6. GEOCHEMICAL CONSEQUENCES OF DREDGED MATERIAL DUMPING 161 7 . CONCLUSIONS 162 8 . ACKNOWLEDGEMENTS 165 9 . REFERENCES 1 66 Appendix A. WATER CONTENT, BULK DENSITY, AND BULK POROSITY PROFILES 172 IV LIST OF TABLES Table No. Page 1 Schedule and location of vibracores collected at the Dredged Material Dumpsite, New York Bight 6 2 Schedule and location of gravity cores for use in the sampling of interstitial water 10 3 Summary of atomic absorption methods for bulk and interstitial metal analyses 15 4 Precision of bulk metal analyses using atomic absorption 17 5 Precision of interstitial water analyses using atomic absorption 19 6 Estimates of amounts of material dredged and dumped at the mud dumpsite during the period 1936-78 26 7 Average metal concentrations in dredged material sediments based on published data 2 - 8 Estimates of metal inputs from sources areas, via dredged material dumping, to the mud dumpsite 30 9 Rates of dredged material accumulation at the dumpsite 37 10 Estimates of amounts of accumulated material in the deposit during the period 1936-78 40 11 An overview of the major sediment types observed in the dredged material deposit 41 12 Mean composition, standard deviation, coefficient of variation, and the compositional range for the sediment cores collected in the New York Bight 74 13 Range of metal concentrations and organic matter in sediment cores from the dredged material deposi t 100 14 Average concentrations of metals and organic matter and their enrichments in dredged material deposit.. 103 Table No. Page 15 Mean, standard deviation and range of concentra- tions (calculated on a gravel free basis) for dredged material and natural sediment in the cores collected at the dumpsite, New York Bight 112 16 Metal enrichments in coastal sediment deposits 115 17 Interelement correlation coefficients in dredged material deposit sediments 117 18 Correlation coefficients between metals and organic matter and mud content in dredged material deposit sediments 118 19 Anthropogenic inputs of metals and organic matter associated with dredged materials dumped in New York Bight during the periods 1936-73 and 1973-78.. 129 20 Interstitial concentrations of iron, manganese, and zinc in cores 41, 61, 81, and 91 132 21 Estimates of the diagenetic flux of dissolved Fe, Mn, and Zn in dredged material sediments, New York Bight 143 22 Estimates of dredged material dumped during the period 1936-78 and material present in the deposit. 156 23 Average metal concentrations of dredged material derived from the source areas and from the deposit. 158 24 Comparison of mass and rates of metal inputs associated with dredged material dumping during 1973-78 with the metal inputs based on the depo- sitional record 159 VI LIST OF FIGURES Figure No. Page 1 Map of the New York Bight showing the various dumpsites 3 2 The general study area of the dumpsite, showing the two sampling transects I and II and the vibracoring stations 5 3 The photographs show the vibracorer being deployed: (a) vibratory head attached to the core barrel; and (b) a core being brought on board vessel 8 4 Dredging areas and dredged material dumpsite 23 5 The annual volumes of material dumped at the mud dumpsite for the period 1930-1978 based on reported federal dredging projects. Private dredging estimates are not involved 24 6 Bathymetric surveys of the study area: (a) 1936 survey; (b) 1973 survey; and (c) 1978 survey 32 7 Cross-sectional profiles of the deposit, based on the 1936, 1973, and 1978 surveys, along the tran- sects A, B, and C as shown in Figure 2 35 8 Ternary plot showing the relative percentages of gravel, sand, and mud contents of all core samples analyzed 43 9 Color photograph showing sections of core 3 44 10 Gravel fraction of black mud in dredged material sediments: (a) shell fragments in core 6 at 650 cm depth; (b) coal in core 7 at 10 cm depth; and (c) iron flakes in core 9 at 15 cm depth 46 11 Color photograph showing a massive bed of gray clay in sections 0A, AB, and BC of core 1 49 12 A section of the gray clay bed in core 1, con- taining a sand ball 51 13 A peel section of core 10 showing the burrowed texture observed in the greensand bed 52 VI 1 Figure No. Page 14 Color photograph showing a greensand bed in section FG of core 4 53 15 Color photograph showing black mud at the surface overlying white, gravelly sand in core 7 56 16 Gravel fraction of four sandy sediment types from cores 4, 7, and 10: (a) core 7 at 70 cm depth; (b) core 4 at 510 cm depth; (c) core 10 at 240 cm depth; and (d) echinoderm assemblage observed in the white sand present in core 4 at 330 cm depth... 57 17 Color photograph showing dredged material at top of section 0A of core 10 underlain by fine grained white sand 58 18 Color photograph showing sections CD, DE, and EF represent 3 meters of natural sandy sediment observed below the dredged material /natural sediment boundary in core 4 59 19 Artifact material observed in core 9 62 20 Artifact material found in the dredged spoils at the dumpsite: (a) in core 9 at 5 cm depth; (b) in core 3 at 620 cm depth; (c) in core 9 at 460 cm depth; and (d) in core 2 at 270 cm depth 20 21 Artifact material observed in the dredged spoil sediment: (a) the fragmented, fossilized remains of a crab; (b) industrially shaped mica flakes 64 22 Depth distribution profiles of gravel, sand, and mud in cores 1, 2, 3, 4, 5 65 23 Depth distribution profiles of gravel, sand, and mud in cores 6, 7, 8, 9, and 10 66 24 Cross-sectional profile of the study area along the two transects I and II, illustrating the lithology of the deposit 71 25 Statistical variations about the mean value of gravel and mud fractions in each core, based on 95% confidence interval s 76 vm Figure No. Page 26 Color photograph showing distinct textural fea- tures in sections OA, AB, and BC of core 6: (A) varved red clay; (B) clay galls; (C) massive bedding; (D) graded bedding; and (E) laminated bedding 78 27 Contact prints of x-radiographs of the top six meters of core 6 79 28 Histograms showing the frequency of occurrence of beds of various thicknesses in cores 2, 3, and 6 within the dredged material deposit: (a) frequency of occurrence of beds varying in thickness from 0-5 to 25-30 cm; and (b) a breakdown of the first three intervals given in (a) into bed thicknesses varying from 0-1 to 14-15 cm 82 29 Plots of mean grain size versus standard deviation for dredged material deposit sediments: (a) for all samples analyzed; (b) for samples from core 10; (c) for samples from core 4; and (d) for samples from core 6 84 30 Two sections of core 6, showing the laminated sediment structure 86 31 Prints of x-radiographs of the lower sections of core 6 87 32 Prints of x-radiographs of the upper sections of core 4 88 33 Prints of x-radiographs of the lower sections of core 4 89 34 Typical interlayered sand and mud texture observed in dredged material in core 9 91 35 Sections EF and FG of core 6 92 36 Depth distribution profiles of metals and organic matter: (a) core 1; (b) core 2 95 37 Depth distribution profiles of metals and organic matter: (a) core 3; (b) core 4 96 38 Depth distribution profiles of metals and organic matter: (a) core 5; (b) core 6 97 IX Figure No. Page 39 Depth distribution profiles of metals and organic matter: (a) core 7; (b) core 8 98 40 Depth distribution profiles of metals and organic matter: (a) core 9; (b) core 10 99 41 Total iron- trace metals correlation plots 120 42 Total manganese-trace metals correlation plots...,. 121 43 Interelement correlation plots 122 44 Interelement correlation plots 123 45 Organic matter (LOI) metals correlation plots 124 46 Mud-metals correlation plots 125 47 Depth distributions of interstitial iron, manga- nese, and zinc in dredged material deposit cores: (a) core 41 (b) core 61; (c) core 81; and core 91 1 34 48 Cross-sectional profile of the deposit along the northwest-southeast transects showing the textural stratigraphy 147 49 Cross-sectional profile of the deposit along the northwest-southeast transects showing the metal stratigraphy 148 ABSTRACT Geochemical and sedimen to logical investigations of the dredged material deposit reveal that the sediments are composed of a wide variety of sediment types which can be classified as quartz and glauconitic sands, muds, sandy muds, gravel intermixed with muds, and artifact material such as coal and fly ash, wood, slag, metal flakes, glass, etc. Fine grained, black sandy mud is characteristic of dredged material. Glauconitic sand and gravelly quartzose sand are typical of the natural sediment underlying the deposit and in surrounding areas. The spatial distributions of heavv metals such as Pb, Cu, Ag, Hg, Cd, Fe, and Mn in the dredged material deposit exhibit highly variable and considerably elevated concentrations over those observed in sediment outside the deposit and in underlying natural sediment. Compared to metal enrichments reported for other coastal deposits, the enrich- ments observed in dredged material sediments are orders of magnitude greater. The calculated rates and magnitudes of sediment and metal inputs to the New York Bight, via dredged material dumping, are found to be orders of magnitude higher than those reported for other naturally deposited coastal sediments. A mass balance of total inputs to the dumpsite via dredged material dumping with inputs estimated from the depositional record for the period 1973-78 indicates that, although most of the dumped material is present in the deposit, most metals are lost from the system in varying degrees either during the dumping process or following deposition of the dumped material. Pore water data indicate a sediment derived flux of dissolved Fe, Mn, and Zn to the overlying water column. Other metals, such as Cd and Hg, were present at undetectably low concentrations in pore waters, indicating that their benthic flux is very small or practically negligible. Sedimentological data indicate that large scale differentiation of sediment takes place at the dumpsite. Laminated sediments and discrete beds of variable thickness are typical of the central part of the deposit which receives the bulk of direct dumping. In contrast, fine grained sediments, presumably derived from the center of dumping activity, are characteristic of the fringes of the deposit. In addition, sand, derived from surrounding areas, has been brought to the fringes of the deposit as storm entrained sediment and represents as much as 8% of the entire volume of the deposit. An overall stratigraphy of the deposit, defining the natural sediment basement and the various horizons of anthropogenic materials, has been developed. xi 1 . INTRODUCTION The most prominent sedimentological feature of the New York Bight is the dredged material deposit, centered in the Bight apex approxi- mately 8 km east of the New Jersey coast. The deposit has a peak ele- vation of 14 meters and covers an area of 36 km 2 (Freeland and Merrill, 1977). The cumulative effect of the continual disposal of dredged material since at least 1900 is this unique topographic feature in the Bight apex. On an annual basis, the dumpsite receives approximately 4.5 x 10 6 m 3 of material dredged principally from the New York Harbor. This amount is three times greater than the annual sediment load car- ried by the Hudson River to the harbor area (Meade, 1972; Panuzio, 1965) The total mass of material contained in the deposit corresponds to approximately 250 times the annual sediment discharge of the Hudson River (Panuzio, 1965). When compared to the total annual load of sus- pended sediment delivered by rivers to the entire east coast of the United States (Meade, 1972), the dredged material deposit has a mass that is ten times greater. To further evaluate the magnitude of dredged material dumping, in terms of sediment and metal inputs, it is essential to compare the dredged material input with natural sediment accumulation in a coastal area. The deposition of dredged material essentially represents an accelerated sedimentation process, in terms of mass and time, similar to episodic sedimentation periodically interrupted by some accumulation of natural sediment. The difference, however, lies in the fact that deposition of dredged material is highly localized in time and space whereas episodic deposition, such that occurs under flood conditions, involves accumulation of homogeneously dispersed material over a large area in a relatively longer period of time. The sediments discharged at the mud dumpsite have been primarily dredged from the Hudson River, particularly from around the dockage areas and from the channels of the inner Harbor, with smaller volumes taken from the Newark Bay and Raritan River areas (Conner et at., 1979), In addition, other types of material have been dumped in the Bight apex and their dumpsites are shown in Figure 1. Much of the sediment in the harbor areas has been contaminated with toxic metals and hydrocarbons, frequently as a result of raw sewage disposal and wastewater discharges into these waters (Gross, 1970; Mueller et at. , 1976; Conner et at. , 1979). Therefore, associated with dredged material dumping is the in- jection of toxic metals into the New York Bight at rates proportional to the frequency of the dump events and the mass and metal loading of the disposed material. In terms of time and space, the disposal of dredged material in the New York Bight represents perhaps the largest and most concentrated anthropogenic inputs of toxic metals to a coastal environment. The resultant dredged material deposit represents a sedimentary record of the dumping activities for the last 100 years or so with respect to rates and magnitudes of dumped material and the associated toxic metals. The primary objectives of our investigation were: (1) to identify the metal contaminants and their spatial distributions in the dredged 73 30 40 15 Tranfvart* Mwator Projection Figure 1. Map of the New York Bight showing the various dumpsites (after Gross, 1976). material deposit; (2) to determine the volume and mass of material deposited in the pile; (3) to develop a stratigraphic record of the deposit, defining the natural sediment basement; (4) to estimate the sediment and metal inputs to the Bight based on bathymetric changes and metal profiles observed in the deposit; (5) to define the lithology of the cores, describing the sediment types and the sedimentary structures observed in the deposit; (6) to determine the sedimentary processes that account for the observed distribution of the sediment types in the deposit; and (7) to evaluate the diagenetic remobilization of toxic metals in the deposit and their subsequent release to the overlying water column. 2. SAMPLING AND METHODOLOGY 2.1 Field Sampling 2.1.1 Vibracoring Cruise Ten vibracores, varying in length from 3.0 to 8.4 m were collected at the study site at stations located on two transects intersecting at the apex of the dredged material dumpsite (Figure 2). Information on the vibracores collected in the study area is summarized in Table 1. The coring was contracted to Ocean Seismic Survey, Inc. of Norwood, New Jersey. Coring was performed during three days, May 30 to June 1, 1978, aboard the R/V ATLANTIC TWIN. Each station was fixed by navi- gation with a Motorola Mini-ranger unit. The vibracorer consists of a steel pipe with plastic liner (9 cm i.d.) which is essentially hammered into the sediment by a pile driver 40° 30' 40° 20 74° 00' 73°50' Figure 2. The general study area of the dump site 3 showing the two sampling transects I and II and the vibracoring stations as indicated by black circles. Cross -sectional profiles of the deposit along the transects A, B and C are given in Figure 7 . CM ^ CD -a o lo O LO CO LO O r~- o~> CO ZJ CO i — r-* o cd. CO CO -i-> •r- o ■ — 1 — O i— i— <=d- cvj C\J <=r C7> LO LO LO ID LO LO LO LO LO LO C o o CO _l r~- CM CD o 00 LO 00 00 LO r^~ r^ o CO -a LO LO CVJ LO Ol cr> o^ ^d- "Sfr 1 — Z5 4-> i— CO >=fr CNJ CVJ CO *3- CD CD S- CD +-> sz (T3 +-> 3 Q. CD Q CO LO LO LO en r-- LO LO 00 o CO LO «3- LO CVJ CO 00 CNJ CO LO CO LO CVJ CVJ CVJ en LO oo i— o CO CVJ CVI o CVJ -o CD CO oo CO 00 CO CO CO CO 00 CO CD ■*-> r-~ r^ r^ r~- r^ l>. r-^ r^ r-^ r-~. ■M U 1 — „ *»«^ •» — , s,, "•v. ~^ ~-^ ~~^ ~«^ > CD (/) s- CD ■"3 CD CD > O0 E to CD O0 E fO CD O o -O. ■o CD +-> fO S- CD Q. O O fO c (0 o CD on ^Z $- +-> CD CD F E o to S- Cd 4- 1 •!■■ -o C CD ■i — +J Si u CD 1 jQ CO CD -D S- CD o -o o •r~ > CD o -C s- 1— D_ —4 CM located on top of the core assembly. The corer is supported on the sediment surface by a pyramid-shaped metal framework through the center of which was mounted an I-beam along which slid the core barrel (Figure 3). Affixed to the top of the barrel was the pneumatically powered vibratory head. The cored material was retained in a four inch plastic core liner. During the coring operation penetrometer records were ob- tained. This mechanism consisted of a chain driven potentiometer which read out on a recorder on deck. Each foot of penetration was displayed as a single line crossing the tape. Penetration was read off in feet per second. On occasion short cores were recovered on the first attempt. In these cases a new core liner was fitted to the barrel. But instead of repeating the entire length of the corer, water was pumped down the barrel "jetting" through the sediment to the level where previous re- covery had stopped. The water jet was then stopped and pneumatic coring resumed. After the corer was brought on board and the liner was withdrawn from the barrel the two ends were immediately capped. The liner and cored material were cut into one meter sections, capped, labeled, and stored in a vertical position. After this cruise the meter lengths were returned to MSRC and refrigerated prior to further subsectioning. 2.1.2 Interstitial Water Chemistry Cruise Gravity cores for sampling of interstitial waters were taken as close as possible to the original vibracoring stations. Four gravity o rQ 03 ^ 05 • . o 05 o o 05 rS o o 0) -N O g 03 03 V^s g Sh O o .8 0) 05 0) ft, cores were collected during a four day cruise, 26-29 March 1979, aboard the NOAA R/V KELEZ. Navigation was provided by Raydist while Loran C was used to locate the original stations. Station locations, water depths, and core lengths are listed in Table 2. Interstitial water was extracted from the sediment samples on board the research vessel. Immediately following retrieval, the core in its plastic liner (6.7 cm i.d.) was placed in a nitrogen-filled glove bag in a controlled temperature room. Sediment sections were extruded and loaded into Reeburgh-type sediment squeezers (Reeburgh, 1967). Nitrogen gas, gradually elevated to 120 psi, was used to pressurize the squeezers and force the interstitial water through a 0.45 ym Nucleopore membrane filter. All samples and apparatus remained in the glove bag under nitrogen until most of the interstitial water was removed (Troup &t at., 1974; Bray et at. , 1973), Squeezing temperatures were maintained within ± 3.5°C of in situ bottom temperatures which ranged between 4.5° and 6.0°C. Seven to ten interstitial water samples were collected from each of four cores retrieved at stations 4, 6, 8, and 9 (Table 2). p Samples were preserved by acidification with high purity Ultrex nitric acid and refrigerated until analyzed. 2.2 Methodology 2.2.1 Core Processing In the laboratory, the vibracores were bisected longitudinally with a circular saw which had been adjusted to allow the tungsten car- bide blade to cut only the plastic core liner. The sediment itself Qi r£ -P K V ca CO 3 fc 1 — 1 O • ^ * HJ> *fc» s o V s r*. cr» CO +-> • • • • • c— o i — CNJ C\J CO lo LO LO lo E o o CO _J r^ CD ZS s- o o +-> en CJJ 5- +J Q. QJ Q Ol CD +-> 03 Q O C_) CM O fO co LO LO C\J C\J o O oo CO C\J LO lo CM o <3- «3- C\J o <3- LO CO LO CO LO C\J LO LO CVJ C\J CnJ C\J co CNJ CO CsJ co en CT> CM CO LO CO en o CO QJ s- CJJ CO a> s- o o 03 s- -Q +-> A3 +-> co CJJ co • CD r— ■*-> a; +-> S «=£ ca a~> •>- • *-o r-j oo cjj LU -Q _1 r •f— LxJ LO S- i^ O x CO • -3" CD CO -o • co CJ3 c co O fD > *r— *v^ 4-> -2L a: 03 i — i -M 3 CD co h- JZ +J +-> O 03 i — i E I— o C -ZT. s- CJJ «sc 4- ^ _1 03 h- T3 +j «=c O S- "N*. CJJ CJJ Cd i — s i — CJJ O CO XI o CJJ -M S- CJJ o E S- o o CJJ s- 2 >> CJJ s_ 03 4-> o s- a u en cjj ^— CJJ CJJ i— -C -c o \— l— o 10 was separated into the two longitudinal sections with a plastic spatula. The two halves provided identical samples for detailed geochemical and sedimentological analyses. The cores were immediately photographed and color-coded and general sediment types were described. 2.2.2 Water Content and Bulk Density For determination of bulk density and percent water the wet sedi- ment section was placed in a pre-weighed, acid washed beaker and com- pressed so that air pockets were removed. A 30 nu syringe (with the tip removed, forming a cylinder) was presssed into the sediment until full to the 30 m£ mark. After checking to see that no voids were present, the sample was extruded into another pre-weighed beaker and the mass of wet sediment immediately determined. Bulk density was then calculated by dividing the mass of wet sediment by its bulk volume. The entire sample was then weighed and heated at 85°C to constant mass. The water content was calculated from the dry and wet masses of the sample as percent water. Porosity, the fraction of the sediment volume occupied by water, was calculated from the relation (Berner, 1971) Wd $ $ = uh — I TTJJXa (1) where Wd o + (l-W)d s w W = weight percent water (net weight/100) d = average density of sediment particles (2.7 g/cm 3 ) d = density of interstitial water (1.03 g/cm 3 ) . 11 Bulk density precision analysis was performed in replicate on four samples of different sediment types. Coefficients of variation ranged from 0.3 to 1.7% with no apparent relationship to grain size. 2.2.3 Combustible Organic Matter Subsamples of the dried and finely ground sediments used for total metal analyses were weighed and combusted at 550°C for five hours, allowed to cool in a dessicator to room temperature and reweighed. Percent weight loss on ignition (LOI) was calculated and is reported as percent combustible organic matter. This analysis is easily per- formed and has been found to correlate well with total carbon by dry combustion in C0 2 - free oxygen at 1500°C followed by gasometric analy- sis of the evolved C0 2 (Gross, 1970). To obtain an estimate of total carbon, the LOI value is divided by a factor of 1.8 to 1.9 (Jackson, 1958). High clay content in sediment may cause a positive error in the analysis due to water trapped in the clay lattice during drying and released during combustion (Gross, 1971). Determination of precision for this measurement was performed on replicate subsamples used for total metal precision determinations described later. Each subsample was combusted and the results com- pared. Coefficients of variation were found to be in the range of 0.3 to 5%. 2.2.4 Total Metal Analysis Sample Preparation . Sediment samples for geochemical analyses were carefully removed with a plastic spatula from the center of the 12 core to avoid potentially contaminated material which may have come in contact with the saw blade. These samples, generally taken at 10 cm intervals, were double sealed in plastic bags and refrigerated prior to analysis. Actual geochemical analysis was performed at 30 cm in- tervals with greater detail in many instances. Dried sediment samples were sieved through 2 mm nitex screen to remove the > 2 mm gravel fraction. The gravel -free fraction was ground to an approximately uniform grain size in an alumina-ceramic container. The ground sample was carefully homogenized and subsampled for analysis. Sediment Digestion . Ten mJl each of concentrated reagent grade HC1 and HN0 3 were slowly added to a 3 to 10 g sediment sample contained in D a Bel-Art polyethylene bottle. The loosely capped bottle was placed on an 85°C (± 3°C) sand bath in a fume hood for about four hours. The digest was then vacuum filtered, while still hot through an acid-washed Gelman Type A glass fiber filter into a 50 nu volumetric flask. The bottle and filter were rinsed with small quantities of HC1 and deionized distilled water which, after passing through the filter, were added to the volumetric flask. The digest solution and rinses were then brought to volume with deionized distilled water. The solutions were trans- ferred to polyethylene bottles and placed in a refrigerator for storage prior to analysis. This method has been found to be superior to the h^SO^ - HC1 method, specifically for Pb, where precipitation of PbSO^ causes loss of Pb during filtration (Anderson, 1974). The HN0 3 - HC1 and HN0 3 methods have been questioned for determination of Hg in soils (Ure and Shand, 1974) and 13 other materials (Reimers &t al., 1973) due to the volatility of Hg. However, Hoover et al. (1971) found recoveries using a similar method to be 95 to 102% in Hg spiked samples. It was determined that the HN0 3 - HC1 method was preferred and that the number of samples precluded using a separate digestion for Hg alone. Leachate Metal Analysis . The acid digests were analyzed for Fe, Mn, Pb, Cu, Cd, and Ag by direct aspiration of the sample into the air/acetylene flame of a Perkin-Elmer Model 403 atomic absorption spectrophotometer (AAS). Samples found to be outside the linear range were diluted. Standards were serial dilutions of Fisher Scientific atomic absorption standards. Hg determinations were performed by the cold vapor technique using the Perkin-Elmer MHS-10 Mercury/Hydride System attached to the Perkin- Elmer Model 403 AAS. In this procedure (Perkin-Elmer Corp., 1978) Hg 2 present in the acid sample solution is reduced to atomic Hg° by a 1% Na0H/3% NaBHi+ reductant solution and flushed out of the reaction vessel with nitrogen gas. The vapor passes through a quartz tube through which the spectrophotometer beam is focused. Absorption recorded is propor- tional to the quantity of total Hg in the sample. Standards were serial dilutions of Fisher Scientific atomic absorption standards preserved with 1.5% Ultrex R HN0 3 and a few drops of 5% KMn0 4 , Standards and reductant solution were prepared daily. The reader is referred to Table 3 for a summary of transition metal analyses. Precision of the total metal analysis was determined by homogenizing the dried < 2 mm sediment fraction and analyzing four subsamples of 14 "XI K a r^ T-^ ^ is O • « V -P o CO •^> £s gr 05 Q -P -K> S? « •^ CD C > 03 to 4-> CD oo oo < oo < cC < >=c I-H S- s- CO oo m v~> OO OO o oo 00 (/I o «=E «=c ex. «=c < cC Q. =£ et CD ai CD a> CD CD o_ zc +-> oo i- CO +-> to S- oo 03 03 03 03 03 03 03 +-> 4-> 4-> 4-> +-> -l-> -l-> +-> ■*-> +J O O O O O O O C c c c a. o o CO o s- ■»-> o CD a. CO c o Q. S- o oo _Q 03 U •r™ E O 4-> < 15 the same core section. This was repeated for four separate core sec- tions with differing grain size characteristics. The subsamples were ground, digested and analyzed and the resulting concentrations compared statistically. Precision of this analysis was generally better than 4% (Table 4). Greater error was observed for Cu and Pb in one sample (core 3, 620-630 cm) which contained what appeared to be flakes of oxidized metal . 2.2.5 Interstitial Metal Analysis Analysis of interstitial waters for Fe and Mn was accomplished by direct aspiration of the sample into the air/acetylene flame of a Perkin-Elmer Model 403 atomic absorption spectrophotometer with a background corrector. Some samples required dilution. Since Zn concentrations varied over a wide range, the samples were analyzed by both flame and flame! ess techniques on the Perkin-Elmer Model 5000 spectrophotometer. Samples containing Zn concentrations greater than about 12 ppb were analyzed using the air/acetylene flame with scale expansion and background correction. Samples contaning less than about 12 ppb Zn were analyzed by the method of additions using the HGA 500 attached to the Model 5000 spectrophotometer with background correction. Analysis for Cd and Cu were performed by flameless techniques with the HGA 500 attached to the model 5000 spectrophotometer with background correction. Since concentrations of both these metals were in the low ppb range, interferences were strong in the seawater matrix and error in the analyses were large despite the use of the method of additions. 16 Table 4. Precision of bulk metal analyses using atomic absorption. Coefficient Metal Sample No. 1 Mean Concentration of Variation (%) 2 Fe 3-620 4.1% 0.7 3.9 2.5 0.5 381 ppm 1.9 0.5 0.4 0.7 Pb 3-620 570 ppm 6.9 0.3 0.1 1.7 Cu 3-620 745 ppm 1.7 1.2 3.6 0.8 1 .6 0.3 4.3 Ag 3-620 4.9 ppm 2.0 0.3 3.3 Hg 3-620 3.2 ppm 3.1 0.3 3.1 ^our different sediment types were considered for precision deter- minations. 2 The precision values are based on four determinations of each sam- ple. 3-620 4.1% 4-230 2.2 9-520 3.2 9-450 3.7 3-620 381 ppm 4-230 135 9-520 545 9-450 393 3-620 570 ppm 4-230 55 9-520 9 9-450 229 3-620 745 ppm 4-230 63 9-520 17 9-450 150 3-620 3.8 ppm 4-230 1.0 9-520 <0.2 9-450 1.2 3-620 4.9 ppm 4-230 1.2 9-520 <0.2 9-450 2.4 3-620 3.2 ppm 4-230 1.0 9-520 <0.2 9-450 4.4 17 For Hg, the cold vapor method was employed using the MHS-10 unit attached to the Model 403 spectrophotometer with background correction. Potassium permanganate was added to the samples to promote oxidation of dissolved organics. All standard were dilutions of Fisher Scientific Atomic Absorption Standards. Precision of the analyses is given in Table 5. 2.2.6 Sedimentological Analyses Core Logging . The cut surfaces of the core sections were scraped clean, examined and logged for sediment texture and color. The Munsell Soil Color chart was used as a color reference. Immediately after logging, the cores were color photographed with Kodak Ektachrome II film under sunlight. Kodak Color Control Patches (Kodak Publication 9-13) were included in each photograph to show the veracity of color reproduction in each photograph. Before any sampling was done the cut surfaces of the cored material were again carefully scraped, fre- quently revealing fine layering and laminations which were obscured in the wet cores. Sections of particular interest were again photo- graphed, in close up, with Kodak Plus-X black and white film. X-radiography . Two cores, from stations 4 and 6, were x-radiographed at Brookhaven National Laboratory using a Fedrex 300 x-ray unit. The film used was Dupont Cronex NDT 55 with two minute exposure times (150 KVP, 4 amperes). The x-radiographs were photographically reduced to a smaller size and contact printed. Peel Sections . Peels of certain sections of the cores were made in order to both preserve the form of the material and to develop a 18 o to o +-> +-> c CD *? i— O CO r^ r-» o r-. c\j O O o s- +-> c a; o o o c n3 a; Q. a. i— OsJ O CO i— CM CL O- ■— O CO co <\j <3- a. c\j r-«- -a o a» ro c CD CD -a CD > o CD CO 3 OJ s- ro co a> 13 ro > o ro CD M u cu s- 19 three dimensional view of the overall texture within the core sections. The method used was a modification of that outlined by Hezeen and Johnson {in Bouma, 1969). Elmer's Glue-all was spread over the section to be preserved to a thickness of about one-eighth of an inch. This was allowed to soak in for two to five minutes. When necessary another lighter coating was applied followed by a coarsely woven stiff fabric which was pressed into the glue. A third coating was spread onto the top of the fabric. After drying for at least 48 hours the edges of the cloth were separated from the liner with a razor blade and the peel gently lifted from the core. The peel was then mounted on a strip of plywood, labeled and sprayed four times with laquer in order to adhere loose grains. Black and white photographs were made of the peel sections, Grain Size Analysis . Samples were taken at each distinct layer of sediment within the cores, as well as at certain small lenses of interest, Each sample was a two centimeter wide section removed from the core. These were labeled, logged, dried and then split with a Soil Test D Microsplitter into two samples. One split of each sample weighing 10 to 20 g was used for grain size analysis. All samples were dried, weighed, and soaked overnight in 50 m£ of 2% Calgon solution and then sonified for 10 seconds. Immediately after sonif ication, the samples were separated into gravel, sand, and mud fractions by wet sieving. The gravel and sand fractions were dried and weighed. The mud fraction was retained for further size analysis. The gravel was further differentiated by sieving through -20 (4 mm) and -1.50 (3 mm) screens. 20 The sand fraction was subsequently split and analyzed with a Rapid Sediment Analyzer. This device consists of a large settling tube which has two outlets spaced one meter apart. These are connected by tubing to a pressure transducer, which in turn, is coupled to an amplifier/recorder. By measuring the changes of hydrostatic pressure at the sensor outlet as sediment falls through the column and comparing these changes to fall time it is possible to rapidly determine the frequency percent/size distribution for the sand fraction. The mud fraction was analyzed by the hydrometer method (modified after Royse, 1970) using the Nomographic Chart for the Solution of Stokes Law by Soil Test Inc. A computer program was used to plot a cumulative frequency vs. grain size curve on a probability plot, si- multaneously calculating Folk's (1974) statistics of mean, skewness, kurtosis, and standard deviation. Oxidizable Carbon . One split of each sample was used for the determination of oxidizable organic content (Royse, 1970). Samples weighing approximately two grams were placed in weighed flasks. This sediment was digested at room temperature with an excess of 30% hydrogen peroxide. After the initial reaction had diminished the volume was brought to 50 mi. The reaction was allowed to continue for at least 24 hours. The samples were then rinsed with distilled water and set aside to settle. After decanting and oven drying for 24 hours at 85°C, the samples were reweighed. In some cases where the reaction was in- complete H 2 2 was again added after the sample had been dried. This particular method was chosen because there is a large body of data for the New York Bight which were obtained by this method (A. Cook, personal communication) . 21 3. DREDGED MATERIAL INPUTS TO THE BIGHT For a quantitative evaluation of the impact of dredged material dumping in the New York Bight, it is essential to have a knowledge of the input parameters. For this purpose, available records of the Corps of Engineers dredged material dumping projects in the New York Bight were examined. Data were compiled on the bulk volume and mass esti- mates of material dredged from the principal dredging sites, the bulk volume and mass of dredged material dumped annually at the mud dump- site, and the trace metal composition of the dredged material. These data were used to calculate estimates of inputs by volume and mass of material and the associated metals dumped. 3.1 Source Areas The sediments discharged at the mud dumpsite have been primarily dredged from the Hudson River Estuary, particularly from around the dockage areas and from the channels of the inner Harbor, with smaller volumes taken from the Newark Bay and Raritan River areas (Conner et at. , 1979). The general area contributing dredged material to the mud dumpsite is shown in Figure 4. 3.2 Volume and Mass Estimates The quantity of dredged material disposed at the mud dumpsite has fluctuated widely in the past. This is shown in Figure 5 which depicts the total volume of dredged material (federal projects) dumped annually at the site. During the period 1941 to 1946 (World War II), the dredged material was dumped in the harbor or in landfills-, no dumping took place at the dumpsite. However, just prior to that period and again after it, the volume of disposed material peaked at more than 6 x 10 6 m 3 /yr, 22 41' 40° 30 40* NAUTICAL MILES DREDGING SITES 73°30 Figure 4. Dredging areas and dredged material dumpsite, 23 00 o 00 0^ o o IN. Oi +i T~H O I g to TO *t3 to fc « TO £ ft'§ 0) to * ^ to ft, TO O) 3 0-4 a £ UJ TO Q_ t-s: to 5 TO 3 -P TO Q *\1 Sn (Z TO ft o < UJ ft lO >- "XI V G) ^ « TO ■^ Jn Sh ^ TO TO O TO CO^ TO "XS £ TO 3 +s o o ^ ft g g g "XI O TO <3 'XS ^ TO O TO to £ tg « g LO ( £ uu 9 oi^)Q3dwna iviubivi/v jo 3^nnoA TO &4 24 The year of the greatest annual discharge was 1973 when over 9 * 10 6 m 3 were disposed of at the mud dumpsite. A total volume of 203 x 10 6 m 3 of dredged material was dumped at the site during the period 1936- 1978. Approximately 156 x 10 6 m 3 were dumped between 1936 and 1973 and 52 x 10 6 m 3 between 1973 and 1978. These figures correspond to an average annual rate of dumping of 4.9 x 1C 6 m 3 /yr. The figures given above represent the COE estimates based on: (1) estimates of individual barge and hopper loads; and (2) estimates of the volume of sediment removed from specific sites through pre- and post-dredging bathymetric surveys. The data provided by the COE represent only federal dredging projects. Conner et at. (1979) pro- vide data for 1970 through 1976 which differentiates between federal and private dredging projects, showing that private projects contribute 24% of the volume dredged. We, therefore, have used the ratio of the volume of federal to private dredging to estimate the total volume of material dumped. Estimates of total bulk volume of dredged material deposited at the dumpsite during the period 1936-78 are given in Table 6. Also included in Table 6 are the average annual rates of dumping during this period. To obtain estimates of the mass of material dumped, we used an average bulk density value of 1.2 g/cm 3 based on the range of 1.1 to 1.3 g/cm 3 reported for New York Harbor sediments and dredged material in the hoppers (Gross, 1970; Mueller et al., 1976). A value of 270 x 10 12 g was obtained for the total wet mass of material dumped at the site during 1936-78. To calculate the total dry mass of ma- terial deposited, the average water content was taken as 50* of the 25 s « 3 co "tj C S- CO >> CO "*^ (0 o~> 5EI C\] 1— 1 >.c S- r— Q ^_-- to i~ on >> ro **"«s^ ^7. CD CM .^ ■ — i i — o 13 i — CO CD E s- =3 >> O ro <— O Z3 i— CQ — ^ T3 ID Q. Q +-> O E ro +-> O 00 . „ 00 CD ro CM S i-H o >> 1 — s- •» ' Q CM to * — * oo CD ro CM 3 CO o> , CD O 3 CQ -a o ■r— s- CD Q_ CD 13 Q CNJ CO LO CNJ O0 LO CNJ LO CD IT) ■3" O CNJ •3" C3i C\J OO co oo CTi CO CNJ CNJ CO CNJ CO CO CNJ CNJ LO co LO co o CNJ co oo r->- S- i ro oo CD r^ >l cr> i — LO 00 ro S- r*^ ro I cd UD >> oo CD r-~- i — oo 00 CO S- r~- ro I a> CO >> OO en cnj i — <3- CD CT) +-> C CD +■> o u s- CD ro CD t~-i CD « . ro S- -Li CO ai <» E > O ro s- — ^ a> E CD E CD jr C +-> O CNJ o • s- ^— o >> M- -Q 4- O +-> ■o JC CD CD CD i — Z5 •i — •i — i — CD Q. ro % E > o >) (J JD 00 •1 — &« T3 00 O S_ £Z LO o CD u "O <+- CD O S- -^ r— CD CD ZS 13 E JD i — •i— ro Q. ro > E 3 CD ro "O c= •1 — CD r— oo c ro zs •i — *i — 00 s- roi 3 CD +-> +-> ro ro ra -o +-> E ro CD -o ■o E CD 3 oo CD r— 00 "O o ra CD > E s- -a jx: j^ i — r^ c 13 Z2 o X* jQ • -a E E 'fD CD o O -r- 00 S- s- s- ro <+- 4_ CD X3 +-> T3 T3 ro 00 CD CD E CD +-> +-> +-> ro ro T3 ro ^~- i— CD E Z3 =3 CD *i — u O T3 +-> r^ .— CD 00 ro ro S- LU o o -a .— 1 CM en 26 total bulk weight of the harbor or dredged material sediments. This gave a value of 135 x 10 12 g for the total dry mass deposited during the same period. These estimates, along with the annual rates of dumping of the mass of dredged material during the period 1936-78, are compiled in Table 6. 3.3 Dredged Material Characteristics Mud is by far the most common material dumped, appropriately, on the mud dumpsite. Actually, much of this material would not strictly be described as mud according to the grain size classifications but is an "eyeball" classification made at the time of dredging. Another is "coarse-grained" material. According to COE dumping records (Conner et at. , 1979) for the period of 1970-74, this category consisted of sand, gravel, granular material and blasted rock. During these five years -0.52 x 10 6 m 3 of coarse grained material were discharged at the site. Artifact material incorporates the COE classifications of sludge, spent caustic soda, steam ash, concrete, chemical wastes, effluent wastes and iron oxide (Conner et at, , 1979). Significant amounts of coal ash were dumped in the New York Bight for many years. According to Gross (1972), an average amount of 0.1 x 10 6 tons were dumped annually during the period 1960-68. In the 1970's, however, the amount dumped was not significant. It should be noted that many of these materials are present in the sediments of the harbor area (Panuzio, 1965; 01 sen et at., 1978) and are therefore also present within the category of mud. 27 3.4 Metal Inputs To estimate the inputs of certain metals associated with the dredged material dumped at the site, average metal concentrations reported for the source area sediments were used. Conner et al. (1979) have reported the average concentrations of Cu, Cr, Pb, Ni, Hg, and Cd in dredged material sampled from the dredge hoppers (Table 7). Also in- cluded in Table 7 are averaged concentrations of Fe, Mn, and Zn in New York Harbor and Hudson River sediments reported by Williams et at. (1978). Estimates of total metal inputs, through dredged material disposal, to the New York Bight derived from the dredging sites are given in Table 8. The annual rate of metal inputs for the period 1936-78 are also included in Table 8. 4. DEPOSITIONAL RECORD The geochemical and sedimentological characteristics of the dredged material deposit are presented in this section. Estimates of bulk vol- ume and mass of material present in the deposit and rates of material accumulation for the period 1936-78 have been calculated using the 1936, 1973, and 1978 bathymetric surveys. These surveys also provide an insight into the evolution of the deposit over a period of time. Other sections include the spatial distributions of metals and organic matter in the deposit and the enrichments of metals in dredged material relative to the underlying natural sediment. Discussion of the sediment 28 to CD CO 0) CO CO i-Q ft, « o s o) 0) CO 5 S CU O c aj s- a» oo a -p 0) oo E rC CM CT> CD. TO « "P S- a> C O o Q- c o +-> ro S- +J c CD (J O a> CD ro s- cu > o o o o o <3- CO o CNJ ir> 00 -=d- co r- o ^t IT) i — r— r— LO CO LO CO CO rO +-> CD CU rvi ZS C_3 <_3 Ql •i- CD o CO -a re s- o -O s- ro in .^ S- o >- .»■ cu •ZL CO CO ro S- cu .E a. 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O o o o O o o -a 1 i— 1 — 1 — I— r— r— cu CO X X X X X X CO +-> CO CsJ CO «tf- o CO I-- -M S- CD r^ CD ^J- t— o 00 13 O i — • • • • • • D_ Q. ^ LO CM CO CO •vt- d on in ions re i — cu +-> ro co ro 4-> cu E Z3 JD CD -o ro S- CD Ll_ s: O Q- uz o CQ +-> 30 properties of the deposit includes the spatial distributions of dif- ferent sediment types present in the deposit, emphasizing the sedi- mentary structures and processes associated with dredged material dumping. Statistical grain size parameters were evaluated to distin- guish between natural sediment and dumped material in the deposit and to further clarify the sedimentary processes occurring at the dumpsite. Based on the sedimentary record, inputs of sediment and metals to the dumpsite have been estimated for the period 1936-78. Pore water chem- istry results are presented, with a discussion of the benthic processes that control the transfer of dissolved metals across the sediment/water interface. Fluxes of dissolved Fe, Mn and Zn have been estimated to evalu- ate the magnitude of the benthic fluxes of these metals. Finally, a stratigraphy of the deposit has been established based on characteristic sedimentological and geochemical features observed in the cores. 4.1 Bathymetry The most dynamic aspects of the New York Bight dredged material dumpsite are its size and shape. The evolution of the deposit is re- corded in the bathymetric charts of the area based on surveys made in 1936, 1973 and 1978 (Figure 6). The 1936 and 1973 charts are after Freeland and Merrill (1977) and the June 1978 survey (Figure 6c) was supplied by Dennis Suszkowski of the Corps of Engineers (COE) New York District Office. All soundings are corrected to mean low water. 4.1.1 1936 Survey The 1936 survey (Figure 6a) shows an area of the New York Bight that was modified by dumping only since 1845 on the northern 31 .•Q to &4 32 periphery of the study area (Freeland and Merrill, 1977). The continual disposal of material here since 1845 has formed a distinct submarine mound (Williams and Duane, 1974; Freeland and Swift, 1978). It was roughly circular in form with a diameter of about 2 km and a maximum elevation of 8 m. The remainder of the area was dominated by a gently sloping tongue-like trough delineated by the 28 m isobath. This trough projects to the northwest from the relatively straight 30 m contour that lies to the east of the site. It appears that dumping may have begun to fill in the trough resulting in the southerly extending lobe of the 26 m isobath found in the center of the area. In the south- eastern corner of the study area the observed shoaling is related to the Shrewsbury Rocks found to the south of the site. 4.1.2 1973 Survey Figure 6b is the bathymetric chart for the 1973 COE Survey (Freeland and Merrill, 1977). It shows a broad, elongated hill which has risen to a minimum depth of 16 m. It was approximately 3.5 km long and 3 km wide, within the study area. The steepest slope on the flank of the pile was found on the northeastern side of the site where a 10 m change in depth occurred over a distance of 1 km. A small trough was found south of the deposit at the 26 m isobath. The 38 m isobath was located just at the eastern edge of the study site. Slight shoaling was pre- sent in the southwest corner. 4.1.3 1978 Survey Figure 6c depicts the bathymetry of the 1978 COE survey (D. Suszkowski, personal communication). This is a more detailed survey than those of 33 earlier years. There are two peaks of the deposit that are 16 m in depth and one point which is only 14 m. The deposit has prograded to the south and has filled in much of the trough at the 26 m isobath. The most steeply sloped section of the site is on the eastern side of the deposit at transect A with a gradient of 8 m per km. There is shoaling in the southwest corner. 4.1.4 Cross-sectional Profiles Figure 7 shows cross-sections of the pile along the transects A, B, and C shown in Figure 2. The cross-sectional profiles of the dredged material deposit along the three transects are shown for the three survey years. Transect A runs from west to east at 40°24'N. Transect B also traverses the deposit from west to east but at 40°24.5'W Transect C presents a longitudinal cross-section of the pile running at 73°51.5'W. The cross-hatched regions of Figure 7 indicate erosion. 4.1.5 Net Bathymetric Changes 1973-1978 Period . Between 1973 and 1978 little change occurred in the overall shape of the dredged material deposit. There was, however, an accumulation of as much as 4 m of material on the southern and western slopes of the pile. The maximum sedimentation rate was, therefore, approximately 0.8 m per year. As a result of this accumu- lation, the minimum depth reached 14 m at two points. On the eastern side of the pile, it appears that some erosion took place at a rate of approximately 0.2 m per year. In Figure 7a, 2 m of material were added to the top of the deposit which had become more rounded in form. Near the top on the western 34 BATHYMETRIC PROFILES 1 km 40 24- 40 24.5 73 51.5 Figure 7. Cross-sectional profiles of the deposit, based on the 1926, 1972 and 1978 surveys, along the transects A, B and C as shown in Figure 2. Shaded areas indicate erosion. The vertical scale corresponds to the depth below sealevel (MLW) in meters. 35 slope there was a small amount of erosion with some deposition of material just below it. It is not known whether the bathymetry for the two survey years are accurate enough to detect such subtle changes, but it appears that a slump event occurred at this point. Figure 7b shows accumulation of a maximum of 4 m of material on the western slope of the mud dump. There were also approximately 2 m added to the top of the pile. To the east as much as 1 m was eroded from the deposit. Figure 7c shows that most of the accumulation took place along the southern slope of the deposit, with little addition of material in the north. This is to be expected since the dumpsite has recently been moved slightly to the south. A net change chart of the site, prepared by the COE for the period between 1973 and 1978 (Freeland and Merrill, 1977), shows that significant amounts of dredged material have been dumped to the west of the site. It also revealed that there were areas of erosion on the north and east slopes of the deposit. A trough appeared at 40°24.4'N, between the areas of little change and the area slightly farther to the south, where there was intense deposition. On the southern slope an elongated deposit of as much as 4 m thickness formed where the 1973 profile dropped off. There was 2 to 3 m infilling of the trough along the southern perimeter. 4.1.6 Sedimentation Rates Sedimentation rates, as calculated for the coring stations, based on 1936, 1973 and 1978 surveys are listed in Table 9. Comparison of 36 CU CD OO C-J co p— 5- to >s CO ****^. CT> E r— O CD +-> (C cu CO r- c: i o tO • 1 — oo -t-> CX> rO i — oo oo CTl o o o +-> CD S- o O oo tO tO tO UO tO tO O (XI tO tO oo o o CXI X ai Q. a* x a> Ql cu CU Q. O +-> t/1 ai +-> s- o c O Q. o cu Q. o to cu +-> S- o C o cu V) ro cu o -l-> to cu o to 4- o Ql O CU Q. o +-> to CU O to 4- O cu -a cu o +-> to cu o to 4- o cu I/) fO CO to oo en co -a cu to ra .a ■o cu to o D. cu ■a o cu 4-J 1/1 cu cu S- cr> ro to cu S- o • (J to +J to 01 S- 4-> J= ro S- 4-> _C fO U ^z c u •r- O •i — u -a 5- • r- CU +-> S- > CU +-> S_ E cu CU >, §= to -C JD 4-> sz o ro -l-> .a ro i — _Q ro co •i- r^ CO S- CT> r^ CU i— CT> 4-> i — ro -o E c ■a ro c •o ro CU UD cnoo #\ TT CTi oo CU r— r>. s_ en -o cu i — -C 4- 4J •N o UD E OO +J o CTl c s_ i — Z5 4- O CU E 1/1 .c ro cu 4-> +J i— ro c ro E o +J -r- O 4-> TD +-> to CU cu to cu ro -c c CO h- o PH CM 37 the sedimentation rates at different stations on the pile for the period 1936-78 show that the deposit apex has been the site of heaviest dumping during the period 1936-78. Lowest sedimentation rates were observed for station 8, located at the base of the northwest slope. Downslope stations, cores 2, 4, and 5, located on the southeast slope also exhibited low sedimentation rates for the period 1936-73. For the recent 1973-78 dumping period, however, the sedimentation rates at these stations are higher than those for the 1936-73 period by a factor of 3, 5, and 7, respectively, indicating that in recent times the dumping took place on the southeast slope of the deposit. This is also evident from higher sedimentation rates for the 1973-78 period at stations 2 and 6, located on the southeast slope, as compared with the pre-1973 rates. Stations 3, 8, and 9, located on the northwest slope, however, do not reveal significant differences in sedimentation rates for the two time periods. As expected, the sedimentation rates for the period 1936-78 are comparable to those estimated for 1936-73, the period during which most of the dumping took place. 4.1.7 Volume and Mass Estimates Estimates of bulk volume of dredged material accumulated at the mud dumpsite during the period 1936-78 were obtained from the net changes observed in the bathymetric charts based on surveys conducted in 1936, 1973, and 1978. The bulk density for accumulated material in the deposit was determined for over 500 samples of the cores taken 38 in this study. The average bulk density of these samples, excluding the natural basement sediment, was found to be 1.7 g/cm 3 . It is un- known how much compaction was caused by the vibracoring. This bulk density figure was applied to the bulk volumes to obtain bulk mass estimates. Dry mass estimates were obtained from bulk mass values using an average water content of 31% by weight for dredged material determined in this study for the same samples. Estimates of bulk volume, bulk mass, and dry mass of material deposited at the site since 1936 are given in Table 10. Table 10 shows that the annual accumulation rates of dredged material vary from 1.8 x 10 12 g/yr for the period 1973-78 to 2.9 x 10 12 g/yr for 1936-73; the overall rate for the period 1936-78 being 2.4 x 10 12 g/yr. 4.2 Description of Sediment Types Four major sediment types were found in the cores taken at the dredged material dumpsite. These were: (1) black mud and black sandy mud; (2) yellow and white coarse grained sands; (3) red and gray plastic clays; and (4) glauconitic sand (greensand). These sediment types were classified according to their color, grain size, and mineralogy. Sig- nificant quantities of artifact material such as coal and cinders were associated with the black mud. All of the aforementioned sediments are briefly described and discussed below. An overview of the major diagnostic parameters that define the observed sediment classes is given in Table 11. It includes information 39 rC 3 <_> U 00 >> 00 ^■^ fD CD 2: ,c s- i — Q ' ' 00 "iT 00 >> ro *^» 21 D> CM ^: i — i i — O 3 i — CO CD 13 5- r- =o O \ JXL to i— O T3 no O u CQ ' 00 ^-x oo cj> 03 cm O CM oo cn fO CM o -^ I — CQ CD 3m i— E o o -^ . — CQ CO CM "3" oo CM CTl CO *3- LO cm CD CM CO cd o oo o CD ■3- oo o CM CM oo o CM -o o •1 — S- , — . c r-. >> •1— CD Q. i— lo oo CO s~ r-> 03 i CD UD >> ro CTi r> i — CO oo 00 S- r*«. ro i CD > CO CD CM i — <3" -a CD CD T3 CD s- -a -o CD •I— 00 o CD- CD "D S- o ro E o E cn 4-> C CD O O i~ CD +-> f0 S CD CD fO S- CD > 03 CD .c: -M s- o CD CO CD r^ 4- s CD O i — >> >5 -Q -a +-> c •1— S3 CO 00 1 — c CO r~ CD CO -a 4- 1-^ O CTl _*: i — ■ — CD 3 3 ^ -O i — 03 CO fD > CD •~ CD 03 c # i — CD •I— oo C 3 •r— T3 OO CD 00 3 +-> CD U +-> oo 13 03 CD "D E +-> C •r- 03 o +-> E u OO •r— CD 4-> O0 oo >> CD CD CD E > 3 oo S- i — oo 3 o ro oo > E u -i*: j*: •r" i^ i — i — S-. 3 3 03 +■> -Q _a -r- CD S- f^ E o E CD .c s- S- 03 +-> 4- 4- E 03 .a -a -a -o CD • CD CD c: +-> n— +-> CD O 03 03 03 "O r— ■r™ i— CD "O 3 S- 3 S_ CD u CD O "O oo t— +-> i — to 03 03 03 4- CO O E C_) O I J CM m 40 c en S- o -o ai i- t> CD M- C ai •— -a ■— o cd o t/i c J- 3 O s: i— o o +1 •J CO r. CT> a t. +> O a E 13 c» l/l ■& l/l CO o t. ■»-> ts S- 3 <» S4 r£^ +s £ l/l •^ (/l 01 13 c CO to 00 » <♦- o O s 01 ,— ^t CT1 01 c > CD CO ee L. t-t U3 r-t to r-s .0 « E-t c o +■> D. S- o w 0) Q CD a. >> I— +J e 01 E "S O0 M T3 -* S- CO .* c O -r- ■ (O CD 1- c at E c/i r— "O t--> +-> S-— ' Ol-t- ■»-> E 3 o O (U g to a» CD to CO O >1 O (j 3C CO Z a. t/i Ct r- S LL. CO -* +^ Q. 3 Q_ CO M -i— CO -=> o +-) "O C t/1 CD t— IO i— CO - CJ IO CO CD Ol+J t- 1/1 o S- O 4- i- Q. IO S- *J E X) •■- IO t/i c 3 O -r- 3 3 +-> 1^ 3 t/1 •!- OI S- 3 ■ s_ o +-> ai 3 ^ O 01 C-- + J CO "D i~ CO to O Z 1— ^— Z O C_l <— zuw CO > CD ■•- « . o >> C S_ C71 E CO u U -t- CD t/1 to -t-> IO i- S- CD E CO i O t/1 -t- t — t_) * C ^ s_ > -O E O •— • CX CHT3 ... C CD >-, >>■•-> O 3 CO to •— i- CD S_ .— -t- ■*-> Ji^ O y t/l t/i l/l -o S- I c ai ai >, to « > s- i — t/1 "D c#_ -i- a> « > -o >,-(-> -o O CO C -O S- CD *t- CD CO "O O 3 ■*-> -C 3 VI CD 3 T3 • E -* -^ >> ai xi >, ul i t— 3 CD C r— >,-»-> O i— li nine tv ai o c: to ai s- 4J I- O -r- i— 3 3 O tD O.H- Q. CTJ3 E I— T3 ai cd >i E o to C C t- CQ O t>n 4_ > CD r- 1- O i- O tfl i- t*_ u ai •»- s_ o > ■<-> to O >> >> S- O CLr— r— » 3 U Ol O1"0 -* .•cc IU >, >>T3 O O 3 * J i_ c i- i- ai co 41 on grain size, texture, color, oxidizable organic matter, and the inferred sediment source. Figure 8 is a ternary plot showing the relative amounts of gravel, sand and mud in all of the samples analyzed for sedimento- logical study. In addition, ternary plots, showing the percentages of gravel, sand, and mud for all of the samples in each core, are provided in Fuhrmann, 1980. In addition, a core log for each station is presented. These include a lithological schematic of each core. Also depicted are Munsell color codes, percentages of gravel, sand, mud, oxidizable carbon, and water content (Fuhrmann, 198C). 4.2.1 Black Mud The principal sediment type in the dredged material dumpsite is black mud which frequently ranges to sandy mud. It occurs in varying frequency within the cores, The ubiquitous nature of this sediment type in the dumped material is clearly illustrated in the core logs (Fuhrmann, 1980), Figure 9 is a color photograph of a portion of core 3 (section 0-300 cm) which was primarily composed of black mud. Table 11 summarizes the characteristics of this material . Olsen et at. (1978), Gross (1972), McCrone (1967) and Panuzio (1965) have described the sediments of the Hudson River and the New York Harbor as black, clayey silts with high water and organic contents with frequent contamination of surficial sediment by metal flakes, coal, cinders, glass, brick and concrete fragments. 42 CO 0) O CO co -p s o 1 S e G to G Sh <3i CO Ss w « I5> 5s « CO g Es Cj CO 5s 3 43 B-C CORE 3 A-B O-A TOP — * — I f Figure 9. Color photograph showing sections of core 3. Section 0A 3 representing the top 100 cm y is underlain by sections AB and BC. Black mud (top of BC) , red clay (middle of BC) t and white sand (top of OA) can be seen. 44 This sediment type is not as variable in its parameters as the other sediment types (Table 11). The distinctive features of this material are, of course, the fine grain size and the black color. Often a strong odor of oil was noted in the mud samples. On the ternary plot (Figure 8), showing the grain size distribution, the cluster of points close to the mud apex represent the black mud sediment type. The continuous range of points, along the length of the mud/sand axis of the plot, reflect sand incorporated within the mud. The oxidizable organic content of the black muds in the dumpsite is generally high, ranging between 9% and 34%; the mode occurs around 15%. This is much higher than the levels reported for samples of Hudson River muds, upstream of the harbor, where values range between 2% and 5% (McCrone, 1967). Gross (1972) reported that the Lower Hudson River, the East River and Newark Bay sediments contained high total carbon content, frequently due to the presence of sewage in sediment. Much of the organic detritus of the dumpsite muds was present in the form of short fibers of plant matter, the coarsest of which, when dried, resembled peat. In all samples any coarse fraction that was present in the muds consisted, with few exceptions, of small bivalve shells, shell fragments and artifact material . The sand fraction was found to be a \/ery fine grained micaceous sand which often contained fly ash spherules. Figure 10 shows the gravel composition of individual samples of black mud or muddy sand from cores 6, 7, and 9. The variety of materials is evident from the three photographs. Figure 10a from core 6 is 45 (b) i **i HH I B ' y 1 7-10 6-650 LjJ _ OQ_ LlJ > QC QQ UJ o — ■ Q_ O « S CO O 5 o 0) r« CO r-H 0) O o o o 0) CO CB . C*5 52 Figure 14. Color photograph showing a greensand bed in section FG of core 4. Section GE represents the basal unit of core 4 and is located at a depth of 600-66 S cm. 53 New Jersey and entering the ocean around Sandy Hook (Boyer et al, 3 1977) Freeland and Swift (1978) report a lobe of sediment containing elevated concentrations of glauconite (characteristic of greensand) extending offshore from Sandy Hook, New Jersey. Glauconitic sand, which is exposed at erosion surfaces in the vicin- ity of the dumpsite (Freeland and Swift, 1978) has been episodically transported onto the mud dumpsite. It occurred in the dredged material deposit as irregular, frequently laminated sand lenses which are common throughout the cores. The presence of this material in the deposit has important implications with respect to the sedimentary processes at the dumpsite. 4.2.4 Coarse Sands A fourth sediment type consists of three varieties of sand and gravelly sand: (1) white, gravelly sand found in core 7; (2) yellow, coarse grained sand observed in core 4; and (3) a medium grained white/ gray sand found in cores 4 and 10. These three varieties of a single sediment type are all naturally occurring sediments in the area of the dumpsite. They are also seen within the dredged material deposit, generally in beds showing no internal structure. Thus, while most of this material, in the cores, is naturally occurring, some similar sed- iment has probably been dredged and dumped at the site. Table 11 pro- vides the basic sediment characteristics of these sands. All of these materials are found between the sand and gravel apices of Figure 8. Core logs depicting these materials are presented in Fuhrmann, 1980. 54 White Sand . Gravelly white sand, seen in core 7 (Figure 15), was originally natural surficial sediment. It is presumably derived from the Holocene veneer of sediment that covers the inshore con- tinental shelf (Freeland and Swift, 1978). Similar material was reported, on sediment distribution maps of the area (Jones et al. } 1979), to cover an elongated area extending to within 1 km of the New Jersey coast, offshore from Sandy Hook. The ternary plot and the core log show the high gravel content of this material (Fuhrmann, 1980). Figure 16 shows the gravel fraction, primarily well rounded quartz, of a sample from core 7. The sand fraction showed little iron oxide staining but the gravel fraction showed that as many as 50% of the grains were stained. Iron oxide coating occurs frequently in pits and grooves on the grains. Similar material was found in sand lenses near the bottom of cores 2 and 3. Fine Grained White Sand . Finer grained, white sand was observed underlying the dredged material in cores 4 and 10. This material was surficial sand that had been buried by dumping. It is similar in composition to the gravelly white sand but contains relatively less gravel (Figure 17; Table 11). A major difference between the two sediment varieties was the extremely intense burrowing that was evident in the fine grained sand. Yellow-brown Coarse Sand . A yellow-brown gravelly sand (Figure 18) was found immediately above the greensand bed of core 4. Table 11 summarizes its characteristics. A ternary plot showing the relative gravel, sand, and mud contents of this material is given in Fuhrmann (1980) 55 t Figure IS. Color photograph showing black mud at the surface overlying white y gravelly sand in core 7. Section OA represents the core top. 56 MJ 1M- $^ « '~-i g 03 ■p • 1 fc *« ftu ■p •P 0) 05 ^ .§ •« CO T3 c 03 Q 03 to -P C3 •p Sj r-i *S *« LO 3 £ « •p 03 CO « ■P fc ^ 3 K o 03 "P ^ Ss O ^ «K CO 03 o „^ s rQ 03 o v^ CO V rCi ■p ■^ Q CO rC « +i 03 Jh a. <5> CO C5 Cx. « «o r-i 0) 5^ 3 4? &4 57 CORE 10 B-C A-B 0-A TOP — W~ Figure 17 . Color -photograph showing dredged material at top of section OA of core 10 underlain by fine grained, white sand. The bottom of section BC> representing the basal unit of core 10 y consists of black sand. 58 TOP — I - Figure 18. Color photograph showing sections CD y DE and EF represent 3 meters of natural sandy sediment observed below the dredged material /natural sediment boundary in core 4. Section EF represents the basal unit of the core. 59 Figure 16b shows a light photograph of the gravel fraction of a sample of the yellow sand. The sand grains were notably more angular than those in the white sand shown in Figure 16a. The yellow color was presumably the result of iron oxide which was present as coatings on the grains and in the mud fraction. It is believed that the white, gravelly sand represents a more mature, reworked sediment, derived from material similar to that comprising the yellow sand. 4.2.5 Artifact Material Associated predominantly with the black muds was another type of material which was characteristic of the dredged material at the study site. This has been termed "artifact material" . The artifact material consists of: sludge, broken concrete, spent caustic soda and ash (Conner et at. , 1979). In our study, we observed that large amounts of artifact material were intermixed with the black muds, implying that the material was derived from the New York Harbor. The material in- cluded coal fragments, wood cinders, metal/rust flakes, glass shards, concrete fragments, a nail and a swatch of cloth. Microscopic exami- nation of the sand fraction revealed the presence of both metallic and glass fly ash spherules in the dredged material. Based upon COE data, the major component of artifact material was sewage sludge. This material, however, is often virtually indiscernible from harbor sediment because of the large volume of untreated sewage that is dumped into the harbor area (Gross, 1970). 01 sen et al. (1978) reported that in many parts of the Hudson River Estuary metal slag, fly ash, and coal were found in the top 10 cm 60 of the sediment. In the harbor area itself this material was found to depths of 250 cm. Coal and the combustion products of coal (fly ash and cinders), as mentioned previously, are common in the dredged material and tend to be associated with the black muds and sandy muds. In some cases, small but distinct beds of pea-sized coal were observed such as in core 3 at 440 cm depth. Coal ash has been dumped at the site contin- uously. Gross (1976) reported that between 1960 and 1968 an average annual mass of 0.1 x 10 12 g coal ash was dumped at the mud dumpsite. In 1970 a similar amount was disposed of (Conner eb at. , 1979). By 1975, apparently due to reductions in the use of coal as a fuel by power plants, and the increased use of the ash elsewhere, there was no coal ash disposed of at the site. It is thought that the coal hori- zons shown later in the textural stratigraphy may correspond to the year of peak input of coal ash in 1963. No grain size or precise description is given for the artifact material as there is no classification scheme available. To best il- lustrate the variety of artifact material found, light photographs of this material are shown in Figures 19-21. Gravel, cinders, shells, wood fragments, coal, metal flakes and glass are all present. Figure 23a displays the fossilized remains of a crab observed in core 5. 4.3 Gravel/Sand/Mud Depth Profiles Figures 22 and 23 represent the depth distributions of the gravel, sand, and mud fractions in cores 1-10. Water content, bulk density, 61 Ld cr o o o LU CV3 CO § OS s £ 0) to o S o ft. •555 t»» OS 62 £ CO Q •^ K CO v_- « s •ri •*> c a, co g CO to Cuto g ?H « o CO CO o CO O CO c^ !n CO CO £ to ^ CO • v o a, fX, « m: "xj <^i to CM ca C35 63 (a) I I I I I I II I Figure 21. Artifact material observed in the dredged spoil sediment- (a) the fragmented, fossilized remains of a crab; (b) industrially shaped mica flakes. 64 CORE 1 CORE 2 GRAVEL SAND (%) MUD (%) GRAVEL (%) SAND (%) MUD (%) 25 50 75 I00 25 50 75 IO0 25 50 75 I00 o 25 50 75 I0O 25 50 75 I00 25 50 75 K» I — 3 J I « 0. UJ 5 O 6 7 S GRAVEL SAND MUD GRAVEL SAND MUD {%) (%) (%) (%) (%) (%) 25 50 75 I00 25 50 75 I00 25 50 75 I00 25 50 75 I00 25 50 75 I00 25 50 75 00 GRAVEL {%) CORE 5 SAND {%) MUD (%) ,0 25 50 75 100 25 50 75 I00 25 50 75 I00 F 2 I 4 I- Q. uj 5 o 6 7 8 Figure 22. Depth distribution profiles of gravel, sand, and mud in cores 1, 2, 3, 4, and 5. 65 CORE 6 CORE 7 GRAVEL (%) SAND (%) MUD (%) GRAVEL (%) SAND (%) MUD (%) 25 50 75 100 25 50 75 100 25 50 75 100 25 50 75 100 25 50 75 100 25 50 75 100 GRAVEL {%) CORE 8 SAND (%) MUD (%) 25 50 75 100 25 50 75 100 25 50 75 100 H 4 o. UJ ° 5 6 7 L GRAVEL (%) CORE 10 SAND <%) MUD (%) 25 50 75 I00 25 50 75 I00 25 50 75 I00 e — 3 I £ 4 UJ Q 5 6 7 r (e) Figure 23. Depth distribution profiles of gravel, sand, and mud in cores 6 3 7 , 8, 9 S and 10. 66 and porosity were also determined on the same samples and their depth distributions are presented in Appendix A. The data, presented in Figures 22 and 23, depict the textural changes observed in the cores. The dredged materials are generally very erratic in texture. The depth profiles are characterized by a sawtooth form of distribution. Natural sediment is typically less varied and often shows a relatively smooth profile. The sawtooth form of distribution observed in a number of cores reflects the varied textural character of dredged material derived from various sources. The top meter of core 1 is comprised of natural sand mixed with clay, with the sand content ranging from about 5% to 97%. Beneath this depth is a bed of gray clay which, except for a few sand balls, ostrea shells and wood fragments, is very homogeneous, containing as much as 97% mud. Below a narrow zone of mixing there is a bed of greensand containing -90% sand and small amounts of mud and gravel (Figure 22a). Core 2 contains dredged material in all but the bottom 4 cm of its length (Figure 22b). It is composed of black, soft mud intermixed with bands of clean sand and gravelly sand. This core, like most of those containing primarily dredged material, has relatively little gravel, and exhibits a typical sawtooth form of distribution. The sand content, however, is highly variable ranging from 2% to 98%; while the depth distribution of mud is a mirror image of the sand distribution. At 250 cm depth there is a 10 cm long fragment of concrete. The segment of the core between about 1.5 and 2.5 m depth contains a thick bed of greensand. 67 Core 3 is entirely composed of dredged material which was, char- acteristically, black mud and sand with much interlayering of the two (Figure 22c). The gravel content in this core approached a high of -50% at 5 m depth. The sand and mud profiles are typically highly erratic, exhibiting a sawtooth form of distribution. Core 4 is particularly interesting because it penetrated the natural sediment to the greatest depth beneath the dredged material deposit (Figure 22d). In doing so it cored three beds of underlying natural sediment. The top 2.6 meters are dredged material, with the sand and mud contents being highly variable with depth. Beneath the dredged material is a 1.2 m thick bed of gray-green, medium grained sand bearing sand dollar shells. This material contains only 5% mud and about the same percentage of gravel. An 11 cm thick bed of gravel follows and this, in turn, is followed by a 1.5 m thick bed of coarse grained, iron-stained gravelly sand typical of some coastal plain out- crops nearby. Underlying this is a bed of fine grained glauconite sand which contains approximately 60% sand and 40% mud. The top =5 m of core 5 are dredged material consisting of the characteristic alternating sand and mud interlayers (Figure 22e) . The bottommost sediment in the core, a natural bed of glauconite sand, con- tains between 79% and 91% sand. Core 6 consists of entirely dredged material but contains less mud than is observed in other cores. The mud and sand contents are highly variable as a function of depth (Figure 23a). Each profile exhibits the erratic sawtooth pattern. Gravel is present throughout the core ranging from to 26%. 68 Core 7 was taken outside of the perimeter of the dumpsite (Figure 23b). However, the top 0.8 m are composed of black muddy sand which is clearly dredged material. The mud content was 18-36%. Underlying the dredged material was clean, quartzose, gravelly sand. The topmost 3.7 m of core 8 are comprised of dredged material (Figure 23c). In this particular core the distributions do not show the typical sawtooth form, instead there is a grading from almost 100% mud at the top to 20% mud at 3.6 m depth. This core contains the highest average mud content (65%) of the ten cores. It is located at the base of the northwest slope of the deposit where we believe fine grained materials are preferentially deposited. From 3.7 m depth to the base of the core is a bed of glauconite sand. Core 9 is, with the exception of the lowermost 4 cm, comprised entirely of mud and muddy sand with lenses of gravelly mud (Figure 23d) The mud layers are frequently cut by sand lenses. The gravel content of the dredged material was highest in this core than in any of the others; ranging from to 58%. Sand and mud contents are highly var- iable with depth. Core 10 was intended as background core but contained dredged material at the top (Figure 25e) . There is little mud present at all, with a maximum content of 12%. The dredged material at the core top is identifiable by the presence of gravel size, anthropogenic material. Clean, quartzose heavily bioturbated sand is present below the dredged material. Much of the gravel at the top of the core is composed of cinders, rust flakes and coal; the fine grained material apparently removed by the stronger currents and wave action in this area. 69 The mean grain size, standard deviation, coefficient of variation and ranges for gravel, sand and mud for each core are discussed later in terms of sediment differentiation processes. 4.4 Overall Stratigraphy Based on the spatial distributions of sediment types observed, an overall stratigraphy of the deposit has been established, defining the boundary between the dredged materials and the underlying sediment basement. A schematic cross-section, along the northwest-southeast transect, showing the lithology of the deposit is given in Figure 24. Also shown in Figure 24 are the core station locations. The quartzose sand observed in cores 7 and 10 and, to the south- east in Core 1, are materials typical of the inner continental shelf. The gravelly sand, in these cores, is part of a lobe of sediment that extends outward from the Mew Jersey coast immediately south of Sandy Hook (Freeland and Swift, 1978). The greensand stratum has been characterized previously. The bed apparently underlies the entire dumpsite deposit. Shallow seismic reflection profiling has indicated that this bed may extend as far inshore as core 10. The dumpsite itself rests directly upon the once exposed greensand bed. The dashed lines at the base of the greensand shown in Figure 24 indicate uncertainty of the thickness of the bed. Core 4 penetrated through both the dredged material and the 70 CM CD o ^r — — C\J CM 00 CM CD cm ro ro (w) Hld3Q U31VM T3 01 CD rC -P tO +i O G CD is ^s-g •p o G -P Cj K G \ i^ CO to -P CD G CO ?H *P 3 O ?S to ti Q) to H0> •^> CD G ^ S ■>+* H *X$ H «*-, o) O G> ^ ts £ CQ CD ■p na H g>£ § O fX, tO CD CD a is t« +i G CO CD CD S is S *P G *p t-^ Sj 3i -P ■~G to K S BV +i O cj CO -o -P "P is CD Jh CD f!C CD O -P E^- s s <*-, O • Cfl -p t-is cd *^ -P to co V O «5 Cf~, CV CD O CjT-^ is '"G G • ftj o S; nal the indi ^ | o ^ *P O CD 0' •P S ^Q CD 35'^ CD GjtO •P CO O s 1 to £ a) CO O CD g tO^tV •£5 O -P O '"G is "P is CD Co tO pQ to • <* Cvd CD is § •s» 71 underlying natural sediment. This station provided the greatest pene- tration of the natural sediment of any of the 10 cores. Core 4 revealed the presence of a trough in the greensand that was later filled with two other sediment types. The lowermost stratum is a yellow, gravelly sand overlain by a bed of medium grained sand that contained significant amounts of echinoid (Sand Dollar) shells. This same material v/as also observed, overlying the greensand, in an adjacent core at station 5. A bed of gray clay, believed to be part of a back bay deposit, was observed in core 1, located downslope southeast of core 4. 4.5 Sedimentary Processes A factor of principal concern in this study is the movement of sediment at the dumpsite. Here, we have used the sediment distribution, on the deposit itself, to determine sediment movement and large scale sorting. Comparison of the mud fraction from the dredged material, in each of the cores, has yielded significant differences among cores. This differential movement of sediment from one portion of the deposit to another and the associated bed forms appear to be the direct result of movement of suspended and resuspended material away from the center of deposition. Other bed forms indicate that natural continental shelf sands, which are typical of the nearby sediment, are brought onto the deposit probably through storm events. 72 4.5.1 Large-Scale Sediment Differentiation Table 12 gives the mean, standard deviation, coefficient of var- iation and the range of the percentages of mud, sand and gravel for the samples taken from each of the cores. These were calculated separately for natural sediment and for dredged material . Cores 1 and 10 which were taken outside the perimeter of the deposit are also included in Table 12. The mud content (Table 12) is higher in three downslope cores (5, 8 and 9) than in the cores from the crest. Both cores 5 and 8 contain natural sediment at their bases which is clearly distinguishable from the dredged material. For instance, in core 8 the mean mud content of the dumped material is 65% while that of the natural sediment is 15%. The sand content of most of the cores is higher in the natural sediment than in the dredged material but we found that sand is a less sensitive indicator than mud and therefore sand content was not used in this analysis. Gravel content is, in most cases, rather low. Clearly there are differences in the char- acteristics of the dredged material from one core to another. The analysis of variance discussed below lends further statistical support to the above statement by providing the 95% confidence intervals for the means of these parameters. In order to determine if there is any movement of the discharged material during or after dumping, an analysis of variance was performed on data for percentages of mud and gravel derived from the cores taken at the dumpsite. Only the dredged material component of each core was statistically analyzed. The results of the analysis of variance 73 Table 12. Mean composition, standard deviation, coefficient of variation, and the compositional range for the sediment cores collected in the New York Bight. Sediment Type Parameter Sediment Texture Core No. Mud (%) Sand U) Gravel {%) 1 Natural Mean 1 48 51 1 Sediment SD 2 41 40 2 CV 3 85 78 200 Range 1 * 1-97 2-97 0-8 2 Dredged Mean 45 51 4 Material SD 31 29 5 CV 69 57 120 Range 0.5-98 2-98 0-15 3 Dredged Mean 37 54 9 Material SD 32 33 13 CV 86 61 144 Range 0.3-95 5-99 0.3-50 4 Dredged Mean 47 52 5 Material SD 27 26 9 CV 57 50 180 Range 1-89 11-88 0-7 Natural Mean 27 68 3 Sediment SD 24 21 2 CV 89 31 67 Range 1-67 33-97 0-28 5 Dredged Mean 60 38 2 Material SD 33 31 4 CV 55 82 50 Range 1-96 4-99 0-15 Natural Mean 11 86 3 Sediment SD 7 5 3 CV 64 6 100 Range 4-21 79-91 0-8 6 Dredged Mean 40 53 7 Material SD 23 22 8 CV 58 42 114 Range 1-82 15-92 0.2-26 7 Dredged Mean 24 64 11 Material SD 7 10 7 CV 29 16 64 Range 18-36 56-79 3-18 Natural Mean 3 51 46 Sediment SD 3 19 21 CV 100 37 46 Range 0-9 21-81 9-77 8 Dredged Mean 65 31 4 Material SD 26 23 8 CV 40 74 200 Range 20-97 3-81 0-29 Natural Mean 15 82 3 Sediment SD 4 4 6 CV 27 5 200 Range 9-20 75-86 0-16 9 Dredged Mean 61 28 11 Material SD 24 18 16 CV 39 64 145 Range 26-97 3-63 0-58 10 Dredged Mean 5 54 41 Material SD 5 19 19 CV 100 35 46 Range 2-12 33-78 19-64 Natural Mean 2 93 5 Sediment SD 2 7 8 CV 100 8 160 Range 1-7 70-99 0-29 'Mean Composition Standard Deviation 'Coefficient of variation "•Composi tional range 74 are shown in a graphic form in Figure 25. Core 1 was omitted because it contained no dredged material. The results indicated that some cores contained significantly different amounts of gravel and mud. Dredged material from core 10 clearly was not related to the other cores based on gravel content. The differences in other cores were generally minor to each other in this respect. The high gravel content, representative of dredged material, in core 10 is surprising in view of the distance (-3 km) of this station from the designated disposal site. It is extremely unlikely that material in this size class could be transported to such an extent by any natural process. The probable cause of this anomaly is so-called "short dumping" outside the legally designated site and then winnowing of the fine fraction by currents. The analysis of variance of the percentages of the mud fraction of these samples (Figure 25b) clearly shows differences among the cores and the grouping is different than that of gravel content. Cores 5, 8, and 9 contain significantly more mud than do cores 2, 3, 6, 7, and 10. Core 4 falls between the two groups. The analysis of variance demonstrates that there is significantly more mud in cores taken at the base of the deposit (5, 8, and 9) than in those from the crest. All of the stations containing higher mud content are below 22 meters depth. Stubblefield et at. (1977) have observed, through surface grabs and side-scan sonar, that a high per- centage of mud is present in surficial sediments around the perimeter of the site. They also observed that mud deposits elsewhere in the bight generally occurred at depths greater than 24 m. The evidence, 75 A. ANOVA TABLE DF SS Treatments 8 6494 Error 128 12980 TOTAL 136 19473 MS=SS/DF 812 101 F -Ratio 8.00 25 GRAVEL (% 55 ANOVA Table Treatments Error Total DF 112 120 SS 29370 86169 115539 ■1S=SS/DF 3671 769 F -Ratio 4.77 20 20 MUD (%) 40 60 80 Figure 25. Statistical variations about the mean value of gravel and mud fractioni in each core, based on 95% confidence intervals. The core numbers are given. Core 1 is not included because it apparently contained no dredged material. 76 therefore, indicates that fine grained sediments are effectively trans- ported to and deposited on the slopes of the deposit, particularly the northwest slope. Recent work by Proni et at. (1980) wherein accoustic profiling was employed to trace individual dump events has demonstrated that there is an outward pulse, along the bottom, away from the site of the dump event. This pulse has been observed to reach velocities of 50-60 cm/sec, sufficient to transport unconsolidated sediment and to erode fine grained sands. Thus the shock wave generated by the dumping event provides a mechanism to move finer grained sediment away from the center of dumping. Bed Thickness . In the cores of the dredged material dumpsite the form and thickness of individual beds of sediment are important indi- cators of the individual dumping events. Color and sediment type were the obvious characteristics by which various distinct dump events could be recognized. For example, a color photograph of core 6 shows these features distinctly (Figure 26). In this section, seven discrete beds of clearly differentiated sediment can be seen. This observation is also evident in the x-radiographs of the same core section shown in Figure 27. The radiographs also reveal the internal structure of the sediment that may otherwise not be seen. This is illustrated by the mud layer found in the basal unit of section 0A in core 6 (Figure 27). The top part of the mud unit exhibits laminar structure while the lower portion of the unit has a mottled internal structure and may therefore be a separate dumping event. 77 0-A CORE 6 A-B B-C TOP — i — \ / B f^"> \/ Figure 26. Color photograph showing distinct textural features in sections OA, AB, and BC of core 6: (A) varved red clay.; (B) clay galls; (C) massive bedding; (D) graded bedding; and (E) laminated bedding. 78 Figure 27 . Contact prints of x -radiographs of the top six meters of core 6, Sections OA and EF represent the core top and the basal unit, respectively . 79 Very thick massive bedding (-1 m thick) is illustrated in section AB of core 6 shown in Figure 26. The material is relatively homogeneous, in this case a sandy mud containing small shell fragments. The x- radiographs (Figure 27) show it to have an undifferentiated mottled texture. Massive bedding also occurs in thinner layers and, again, is characterized by a lack of differentiation within the bed. This form of bedding is also seen in the natural sediment at the bottom of core 4. Although one would expect to see frequent examples of graded bedding occurring in the cores, there were actually very few observed. In these cases, the grading involved large gravel sized clasts which had sufficient mass to sink through the cloud of dumped material rapidly enough to settle first. Figure 26 (section OA) shows a coarsely graded unit. In most cases, the settling time appears to be too short to allow noticeable differentiation of sizes. In order to better define the thicknesses of the beds resulting from the discharge of sediment at the site, three cores 2, 3, and 6 from the apex of the pile were examined for bedding thickness. Only clearly defined, discrete beds were counted. In many cases there were thick beds present which showed no clear boundaries. These were not counted as it appears that they are the product of a series of dump events which deposited similar sediment. The cores taken at the edge of the pile show relatively few instances of discrete, identifiable beds. This would be expected if most of the sediment on the periphery of the deposit were transported material. This is borne out by the 80 statistical evidence mentioned previously and by the stratigraphy discussed later. The stratigraphic correlations are much better for the cores taken at the apex of the deposit than for those at the downslope stations. Figure 28 is a histogram showing the thickness of the observed beds in the dredged material deposit. Figure 28a illustrates a broad range of bed thicknesses; the most frequently occurring beds being 0-5, 5-10, 10-15 cm in thickness. A further breakdown of these three bed thicknesses is presented in Figure 28b, showing the overall average thickness to be approximately 10 cm, with about 50% of the sampled layers being 7 cm or less in thickness. Beds greater than 10 cm in thickness are relatively less common. Sediment Sorting and Mixing . An analysis of the data collected on mean grain size and standard deviation provides further information on the sediment differentiation processes within the deposit. A plot of standard deviation versus mean grain size shows the relationship of these two parameters for all samples analyzed. Standard deviation is the measure of spread within a sample; in this context, it has been taken to denote the degree of sorting of a sample. A low value of standard deviation means that the sediment is well sorted. According to Folk (1974), a sample with a standard deviation greater than 2

o 40 o o U. ° 30 - > o z 1 1 1 3 20 o UJ or u_ 10 n UJ o z UJ or or => o o o >- o z UJ o UJ or 16 12 h 8 4 [ 10 15 20 25 (b) 30 I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 BED THICKNESS (cm) Figure 28, Histograms showing the frequency of occurence of beds of various thicknesses in cores 2, Z s and 6 within the dredged material deposit: (a) frequency of occurrence of beds varying in thickness from 0-5 to 25 30 cm; and (b) a breakdown of the first three intervals given in (a) into bed thicknesses varying from 0-1 to 14-15 cm. 82 plot of mean grain size versus standard deviation can be used to identify major groups of sediment within a deposit. Figure 29a depicts the mixing and modality of the study area samples. showing the presence of three distinct clusters. One is located between 0 and 2.5 on the grain size axis (group A) which is relatively well sorted. A second minor cluster (group B), around 3.5 on the grain size axis, is more diffuse and represents poorly sorted material. The third cluster (group C) represents fine grained (5-8), very poorly sorted material. In general, the dredged material muds are represented by group C and the natural sediments of the area are found in group A. The less distinct cluster, group B, may illustrate the mixing that occurs between the two and, in some cases, sediment types such as the greensand facies. This division is more clearly illustrated in Figure 29b-d which show mean grain size plotted against standard deviation for individual cores. Figure 29b represents core 10 containing, pri- marily, natural shelf sediment. The observed distribution closely resembles that of natural sediments shown as group A in Figure 29a. Figure 29c shows core 6 that contains only dredged material. As ex- pected, this distribution exhibits a wide scatter in terms of sorting and mean grain size. Comparison of this plot with Figure 29a shov/s an overlap with clusters B and C, representing dredged material and mixed sediments. Figure 29d illustrates core 4 that consisted of both dredged material and natural sediment. This is reflected by two dis- tinct clusters, within the sampling, the relatively well sorted, coarse grained material representing natural sediment and the very poorly 83 4 i- 3 - i- < > UJ p Q c Q or § i z < I- (a) • • . • • • • . • • • •*! . * 1 2 4 6 MEAN GRAIN SIZE () 8 4 r I • < > O cr < < (b) 2 4 6 MEAN GRAIN SIZE () 4 i- i 3h § S 2h o Q (E Z < (c) .» • • • • •• J_ -20246 MEAN GRAIN SIZE () 8 T 4 • "S 1 (d) • • • z _ • O • • b 3 • ••• < • • • • • > Ul •• • ; ••••. • ^ _ • • • ... ••• cr < z , A • < 1 • H 1 l i i i -2 2 4 6 MEAN GRAIN SIZE () Figure 29. Plots of mean grain size versus standard deviation for dredged material deposit sediments: (a.) for all samples analyzed, Note the clustering into three groups - natural sediments (A) 3 dredged material (C) and a mixture of the two (B); (b) for samples from core 10. Most of this material is natural sediment; (c) for samples from core 4. Approximately one-half of the length of this core was composed of dredged material and one-half was natural sediment underlying the deposit; and (d) for samples from core 6. Most of this material falls into the dredged material and. mixed sediment groups shown in (a). 84 sorted, fine grained sediment of the dredged material. This grouping corresponds to clusters A and C in Figure 29a. Sediment Lamination . Certain sedimentary structures which are illustrative of the processes that are associated with dumping were observed in the dredged material cores. For example, both laminated and coarsely interlayed sediments were frequently observed. Only one set of ripples and relatively few instances of graded bedding were noticed. Neither load deformation structures nor water escape structures were found. A major feature of many of the sediments found at the site was the presence of laminated beds 2-15 cm in thickness. This bed form was, generally, found to be comprised of sand and sandy muds and was seen throughout the cores. Individual laminae were observed to be about 1 mm or less in thickness and often each was composed of sediment that was clearly of a different nature than that of the adjacent laminae. The sediment structure being discussed here is not the inter- layered, f laser-like bedding of clean sand in thick beds of mud, rather, the horizontal beds of laminations of different sediment types. Fre- quently some of this material was clearly artifact in nature. Figure 30 depicts two typical beds of laminated sediment observed in sections of core 6, X-radiographs of cores 4 and 6. showing similar sedimentary structure, are given in Figures 31, 32 and 33. It is es- timated from these two cores that laminated sediments comprise a significant proportion of the material in the deposit. For example, the x-radio- graphs of the two cores show that in core 6, taken at the pile apex, 85 CORE 6 — TOP E-F 41 ' Si ' ' '61 ' '7 • 8 '9! ' 6 , 18 , £ •^ 03 CO CO CO 3 CO 03 O G fc •« E a to CO 03 1*4 3 ^ fc] O -P S CO 03 O +i v ci o +» &4 fe: o 03 £ CO O • •^ G • co s to 03 CO CQ 3 03 fe: Ss O » 03 °^3 , <+-, G G p O co ^ &H •^ C5 '"G rQ s fc, 03 o H-i 03 •^ ^ « r£ £ £ -P -p CO G '^ , 03 g «K CO tii G O 6q ^ «K CO o CO <4-.-4J> SOS a. O 03 o "^ ^ g •p -P 03 (55 CO rC! Q ^ 0) ?s r£ tO « size class. This sediment appears to be greensand. Therefore, this material is not only brought to the deposit in discrete lenses but also mixed with the dumped mud. The estimate of 8% addition to the volume of the deposit must therefore be regarded as a conservative estimate. 4.6 Geochemical Depositional Record 4.6.1 Depth Distributions of Metals and Organic Matter The metal concentration versus depth profiles are displayed in Figures 36-40. Results show that the concentrations of metals present in the dredged material sediments are highly variable and considerably elevated, in some cases more than three orders of magnitude, over con- centrations observed in sediment outside the deposit and in natural sediment underlying the deposit. Table 13 shows the range of values observed for each metal and organic matter within individual cores and from one core to another. Depth distribution of metals varies widely for individual metals and from one station to another. In most cases, Pb and Cu profiles show close correspondence. Ag, Cd, and Hg and Fe and Mn also co-vary strongly with depth. 94 ro sr in (w)Hld3Q r^ oo en O rQ 0) CO « E to o •fi to Cu In 95 o (\l h- Z £2 CO T' O * (/I (w)H±d3Q to O rCl ? G to G +i Q> S CB a. K o to ^5 i« °0 97 ^ oo °* (/> to °, o ^^ .««!«■»« -I I I 1 l_ h -M> I 1 I I I I £ lo q: q. - o s >i. . «j 1 i_ i i i i — OO E Q. Q. < few O _ o - E <° C O - 3 _ iT c\j n « ■ « ^ O — CNro^-mco^cDot (W)Hld3Q J 1 1 — ■%« ! » . — I 1 1 i i _1 i i_ i 1 I I 1 . 1 1 I I i •* 'A m . J? iX ^\ a o : Mr- i i i i -• i i i i i O — CM tO ^j- m id S m Hld30 O TO rQ o TO s CO TO s CO TO "i £ o CO a. TO TO s 98 o „ o E • a. 2 ro ^- A. A r*^ *"A / K £ LA / YK -2 i2? pj > V^ y o _ — i — i — i — i i i > i ■ CO to q o o to O r E So _i i i i_ o ~ oo E o _ o E w Q. £ o Ll M ■ I llffgfr_ o . C\J o J O ft . £ £o - CC CL - . o s \ <-> ^o l J\ o n p 1..L,.,, . 1 1 1 1 1 1 1 I , (W) Hld3Q ("J) Hld3Q O o « E •P I 1 E ro ■D CD ro 1 CO "S 4-> ro ■o CD 4-> •CT CU CO "8 Su c/> z: 1/1 z: oo z: OO z: oo z: OO ■a S> CTl S- CTl 1- TO 3 ■o 3 "O 3 -7. 3 ■o 3 ■o 3 CNJ r— r o C£> O ■~o o CT> o o o Lf) O CM O ir> O O O CM CTl CM *J- CM ID CM •a- CM CO CM f CM ■— CSI CM r— J o 1 o o O ■"" o 1 O O O CM O CTl O O O — CM CO CTl CTl r^ .— in i— CM CM •~ "~ •~ CO CM CM ■"" J CO ") o CM 00 ** o CTl 00 o in ■— CTl in cm *? 00 o o r-» o CO r— in co 1 — CO CO CO CO o CTl CO in in •(— CU • r- cu •i— ai s- E s- E S- F a> ■a 4-1 ■a 4-> ■o CO cu <0 cu H> cu s: O0 z: C/) z: c/1 "S ,_ -o ,— ■CT ,— ro CU «J cu ■a CTl t- CTU s- CT) i. T) 3 T3 3 "S 3 CU 4-> CU +-> 4-1 s- ro S- «J s- ro s- cu ■CT £ re ai . •»-> CM ■o o c 4-> ro + J +-> c cu cu c c i— S- T- cu E cu -o + J m ^ ■4-1 CU o ro c s_ cu cu cu s- E S .a cu ■!-> TJ " cu ro cu cu s. F t/) 1 — cu 5 T3 i— Q- CU ro (/l CTl S- i— TJ 3 1- ro Cll ■!-> O •t-> s- ro cl cu ■o C >-o -C CTl i— cu •!-> o s- t. a. CU T3 H- o ■CT O s. c cu cu ro 2 s- s_ ro •>-> T3 CU CD >> C -t-i "O 91 U 3 a. cu *-> i— i i — c ro 11 •u X) » ■o c B en CD CU O ■u ■o "h CJ ro "8 in 1— cj CU -o cu ro ro ••- r^ ro cu C CJl ro in CD in CD ■r- ■«-> sz ^ 4-> O B CU 4-> ^3- ■»-i ro E CU in CD 3 I.) cu CJ CJ 4-' T3 c (. C 1— ro cu o •<- ro IX oo oo o oo u 103 Concentrations of Ag, Hg, and Cd were generally near or below the detection limit of less than 0.2 ppm at all depths (Figure 36a). Relative to the underlying sediment, the core top (0-20 cm) showed some enrichment in Cd, Hg , Ag, and Pb while Fe and Mn concentrations were depressed. The profiles show that Pb and Cu and Fe and Mn co- vary with depth. The organic matter in core 1 varies from 0.9 to 6.6% by weight, the mean value being 3.6%. The depth distribution profile closely resembles the Fe and Mn distributions. Core 2 . This core was collected on the southeast slope of the pile on transect AB, about 1 km downslope from the apex of the pile. As seen in the cross-sectional profile of the pile (Figure 24), the core did not penetrate the underlying natural sediment. This is also evident from the^ metal profiles (Figure 36b). Generally, the metal profiles exhibit erratic distributions, showing no systematic trends with depth. Highest concentrations of Ag (26.7 ppm) and Hg (7.4 ppm) were found in this core. The enrichment factors range from 2.1 for Fe to 33.9 for Cu. The depth distribution of organic matter in core 2 displays elevated concentrations throughout the core, varying by more than an order of magnitude. Two sharp maxima dominate the profile at the top and bottom of the core. Both maxima approach concentrations of 12-13% by weight. A close correspondence exists between the depth distribution of organic matter and that of metal concentrations. 104 Core 3 . This station is located at the apex of the pile where the two sampling transects intersect (Figure 24). All the sediment sampled in this core was comprised of dredged material. Figure 37a shows erratic distributions of metals with depth. Relative to the other cores analyzed, this core exhibited the greatest variations in the concentrations of Fe, Cu, and Pb. Within the core, the concen- trations of Cu and Pb varied by more than three orders of magnitude (Table 13). Highest concentrations of Fe (7.71%), Cu (2230 ppm) and Pb (1550 ppm) were observed within the same sub-section at a depth of 6.1-6.2 m. Two distinct minima are present: one in the upper meter of the core at 0.6-0.7 m depth and another at about 2.5 m. The lower subminimum is followed by a sharp maximum at 6.1-6.2 m. The metal enrichments at this station were Fe, 2.2; Mn, 5.6; Pb, 30.6; Cu, 57.0; Cd, 9.8; Ag, 14.4; and Hg, 9.7. The enrichment factors for Cu and Pb were significantly higher than those found in core 2, Core 3 exhibits the greatest range of organic matter measured in all cores, varying from 0.85% at the core top to 31.6% at 7 m depth. The distribution displays a general trend of increasing concentration with depth interrupted by several maxima and minima recorded at various depths. The organic matter profile is similar to those observed for the metals, except for the presence of a sharp organic matter maximum at 7 m which does not coincide with the maxima observed for metals at a depth of 6 m. Core 4 . This core was taken at the base of the southeast slope, -2 km downslope from station 2 and -3 km from the apex of the pile. 105 As seen in the cross-sectional view of the pile (Figure 24) this core consists partly of dredged material underlain by natural sediment. This is particularly evident from the metal profiles shown in Figure 37b where a distinct inflection occurred at 2 m. For most metals, the sharpest drop in concentration was observed between 2 and 3 m. This transition was assumed to be the boundary between the dredged material pile and the underlying natural sediment. Using the boundary, the enrichment factors were calculated to be 1.3 for Fe, 6.6 for Mn, 4.7 for Pb, 4.6 for Cu, 2.3 for Cd, 2.1 for Ag, and 2.3 for Hg . The organic matter profile of core 4 displays a distinct maximum at a depth of 2 m. Above and below this inflection, the concentrations remain constant with depth. The observed maximum coincides with those recorded in the metal profiles. Relative to the underlying natural sediment, the dredged material was found to be enriched in organic matter by a factor of 2.2. Core 5 . This core was taken k km upslope from station 4 (Figure 24). As a result, most of the sediment sampled at this station was dredged material underlain by some natural sediment. Based on the depth distributions of metals in this core (Figure 38a), the transition to natural sediment appears to occur at a depth of 4.4 m. Above this boundary, the distributions exhibit elevated and highly variable con- centrations. The concentrations for most metals co-vary with depth; the general trend being a decrease in concentration with depth. The distributions exhibit distinct minima for all metals at 0.3-0.7 m depth, This sharp inflection is followed by strong maxima for most metals 106 at 0.9-1.1 m depth. Downcore at depth of 3.3-3.7 m, a submaximum is observed for all metals. Using average metal concentrations of dredged material and the natural sediment underlying the transition (Table 14), the enrich- ments in this core were found to be Fe-1.9, Mn-4.5, Pb-9.9, Cu-17.3, Cu-8.5, Ag-14.8, and Hg-7.3. The depth distribution of organic matter shown in Figure 38a is very similar to those observed for the metals in this core. Like the metal profiles, the profile of organic matter exhibits a sharp maxima at -1 m depth and several submaxima at other depths. The concentra- tions of organic matter vary by more than an order of magnitude; the observed maximum approaches a value of 13% by weight. The sharp drop in concentration of organic matter at a depth of 4.4 m reflects the transition of organic-rich dredged material to natural sediment. Using average concentrations of organic matter above and below this boundary, a value of 4.2 was calculated for the enrichment factor of organic matter in this core. Core 6 . This core was taken at the apex of the dredged material pile, near station 3. As can be seen from the cross-sectional profile of the pile (Figure 24), the entire length of this core consisted of dredged material. Depth distributions of metals (Figure 38b) exhibit highly variable and elevated concentrations throughout the core. The erratic distribution of metals observed in this core is similar to that observed in core 3 taken nearby. At a depth of 0.7 m, the sedi- ments exhibit a sharp increase in concentrations of all metals. This 107 feature is followed by another maximum at a depth of 2.1-2.2 m in the Fe and Mn distributions. At greater depth, the distributions display highly variable but systematic trends in metal concentrations. Com- parison of profiles indicate that Ag, Cd and Hg, and Cu and Pb co-vary with depth, particularly between 5.0 and 6.5 m where an extensive stepwise decrease occurs. Relative to background values obtained from other stations (Table 14), the enrichment factors were found to be Fe, 1.9; Mn, 5.9; Pb, 13.7; Cu, 19.2; Cd, 7.0; Ag, 7.9; and Hg, 7.3. The organic matter profile, displayed in Figure 38b, resembles closely the metal profiles discussed above. An enrichment factor of 3.2 was calculated for organic matter in dredged material in this core. Core 7 . This core was collected at the base of the northwest slope, about 4 km downslope from the apex, (Figure 24) and well out- side the designated dredged material disposal area. Depth profiles of metals (Figure 39a), exhibit metal enrichment in the upper meter of the core. These elevated levels decrease systematically until the concentrations approach background levels at a depth of - 1 m. Down- core the metal concentrations remain constant with depth. Based on the depth profiles, it appears that the boundary between the anthro- pogenic dredged material and the natural sediment basement lies at a depth of =1 m. As in other cores, the Pb and Cu profiles exhibit close resemblance as do Fe and Mn, and Ag, Hg, and Cd. The enrichment factors are given in the order of enrichment of metals: Cu (63.9), Pb (24.1), Mn (23.6), Fe (13.7), Hg (4.8), Ag (3.0), and Cd (1.8). 108 The Cu and Mn values represent the highest enrichment factors found for all the cores studied reflecting the extremely low concentrations found in the underlying natural sediment at this station. The depth profile of organic matter shows that the top k m of sediment in this core is greatly enriched in organic matter as com- pared with the underlying sediment. The profile of organic matter is identical to those observed for metals. The dredged material in this core was found to be enriched in organic matter by a factor of 12.6 as compared with natural sediment. This was the highest value found for the enrichment factor of organic matter. Core 8 . This core was collected at a station -2 km from the apex of the pile on the northwest slope. The vertical cross-sectional view of the pile (Figure 24) shows that this core penetrated the natural sediment underlying the pile. This is also evident from the depth distributions of metals (Figure 39b). The sharp drop in all concen- trations at 3.3-3.5 m depth reflects the transition to natural sediment. Overlying the natural sediment, the concentrations are variable, but display a systematic increase with decreasing depth toward the core top. The metals Pb, Cu , Fe , and Mn exhibit identical distributions with depth. Ag, Cd, and Hg also co-vary with depth. The calculated enrichment factors given in the order in which the metals are enriched: Cu (29.5), Pb (22.5), Ag (17.3), Hg (13.4), Cd (12.2), Mn (3.8), and Fe (2.1). The concentrations of organic matter decrease systematically with increasing depth until -3 m where, as with the metals, a sharp drop in 109 concentration occurs. Beyond 3.5 m depth, the concentration remains constant. Using average concentrations of organic matter above and below this boundary, an enrichment factor of 3.9 was calculated for this core. Core 9 . This core was taken at a station about 1 km upslope from station 8 and a similar distance from the mound apex on the northwest slope (Figure 24). The depth distributions of metals in this core are highly variable, showing no trends with depth. The Pb and Cu distributions again exhibit close resemblance. Fe, Mn , Cd, and Ag concentrations exhibit similar behavior with depth. This core did not penetrate the natural sediment basement. Enrichment factors were calculated to be: Cd (45.8), Cu (38.1), Pb (25.9), Ag (12.2), Hg (11.6), Mn (6.9), and Fe (2.5). The depth profile of organic matter, displayed in Figure 40a, shows that the concentrations of organic matter in core 9 are highly elevated and variable. In the 1.5-4.0 m depth interval, however, the concentrations remain relatively constant. This part of the pro- file resembles closely the profiles of Pb and Cu. The bottom part of the core (4-6 m) displays a highly erratic distribution; the con- centrations ranging from 3.3 to 11.1%. The enrichment factor was calculated to be 5.1 . Core 10 . This core was collected at a station located far out- side the dredged material deposit approximately equidistant (-6 km) from the New Jersy coast and the pile apex (Figure 24). The depth distributions of metals (Figure 40b) reveal two minima in concentrations 110 at depths of =0.3-0.7 m and 3 m; the inflection near the core top being more pronounced, perhaps indicating the presence of anthropo- genic dredged materials. As observed in other cores, Pb and Cu co- vary with depth. It must be noted that the elevated metal concentra- tions observed in the upper part of the core are considerably lower than maxima reported for other cores. The enrichment factors, given in Table 14, are much lower than for metals in other cores except Pb and Cu having values of 26.7 and 19.6, respectively. The organic matter profile for core 10 exhibits a distinct maximum at 0,2-0.3 m depth. This sharp inflection is followed by a gradual decrease in concentration down to a depth of =0.5 m. Downcore the concentrations remain constant with depth. The profile closely re- sembles those for metals in this core. The enrichment factor was found to be 2.1 . 4.6.2 Intracore Variability in Metal Concentrations In order to compare the observed metal concentrations of dredged material and the underlying sediment in each core, their mean and standard deviation values were calculated. These values, including the range of concentrations observed in each core, are given in Table 15. Cores 1 and 10, located outside the perimeter of the dredged material deposit, are not included in Table 15. Overall the mean dredged material metal concentrations are sig- nificantly higher than the corresponding concentrations in the under- lying sediment. Using standard deviation as a measure of the variability 111 Table 15. Mean, standard deviation and range of concentrations (calculated on a gravel free basis) for dredged material and natural sediment in the cores collected at the dumpsite, New York Bight. Sediment Type Parameter Metal Concentrations (mq/Kq) Core No. Fe 1 Mn Pb Cu Cd Ag Hg Organic Matter 1 1 Natural Sediment Mean 2 SD 3 Range'* 2.4 1.4 4.2-0.8 170 100 318-45 8.0 7.0 33-2 10 6.0 17-2 d.l. 5 d.l. d.l. 3.6 2.5 7-1 2 Dredged Material Mean SD Range 2.3 1.0 4.3-0.4 274 140 547-24 115 95 286-5 118 105 302-4 2.1 2.1 7-d.l. 3.7 5.6 27 -d.l. 2.1 1.9 7-d.l. 5.8 3.7 14-2 3 Dredged Material Mean SD Range 2.4 1.5 3.6-0.3 244 134 605-54 161 288 1527-2 197 419 2197-2 1.9 1.6 6-d.l. 2.9 2.7 10-d.l. 1.9 1.5 5-d.l. 6.0 4.3 22-0.5 4 Dredged Ma ter i a 1 Mean SD Range 2.1 0.6 3.3-1.4 216 60 305-119 17 17 5-48 19 16 51-7.3 0.5 0.5 1. 7-d.l. 0.4 0.3 0.8-d.l. 0.5 0.5 1. 7-d.l . 4.1 1.2 4.6-3.0 Natural Sediment Mean SD Range 1.6 0.6 3.0-0.8 29 13 47-8 3.4 2.8 13.1 2.5 1.7 6-1 d.l. d.l. d.l. 1.7 0.5 2.5-1.0 5 Dredged Material Mean SD Range 2.5 1.0 3.7-0.4 280 120 511-5 79 70 245-2 82 74 268-2 1.7 1.9 7-d.l. 2.9 2.4 18-d.l. 1 .5 1.2 4-d.l . 5.8 2.6 11-0.8 Natural Sediment Mean SD Range 1.3 0.5 1.8-1.2 63 24 96-30 8.0 10 25-2 4.7 2.4 8-2 d.l. d.l. d.l. 1.4 0.6 2.2-0.9 6 Dredged Material Mean SD Range 2.1 0.7 3.8-0.6 255 123 545-57 73 81 359-4 68 78 357-4 1.4 1.5 35-d.l. 1.6 1.8 6-d.l . 1.5 1 .6 4-d.l. 4.3 1.9 8-1.2 7 Dredged Material Mean SD Range 1.5 0.2 1.7-1.3 130 21 154-113 66 12 77-53 42 2.2 44-40 0.4 0.1 0.5-0.3 0.7 0.4 1.0-d.l. 0.9 0.0 1.0-0.9 3.6 0.3 3.8-3.3 Natural Sediment Mean SD Range 0.1 0.1 9-0.3 5.0 6.7 23-0.7 2.5 2.7 10-d.l 0.6 1.3 4-0.1 d.l. d.l. d.l. 0.3 0.2 0.7-0.1 8 Dredged Material Mean SD Range 2.8 0.9 4-1.3 276 121 554-100 153 59 240-96 130 74 283-23 2.4 2.1 7-d.l. 3.6 2.5 8-d.l. 2.8 1.5 5-0.6 7.9 3.7 13-2.4 Natural Sediment Mean SD Range 1.3 0.3 1.5-0.7 74 18 90-41 6.8 6.4 15-d.l 4.4 1.9 7.3 d.l. d.l. 0.21 0.1 0.2-d.l. 1.9 0.4 2.4-1.3 9 Dredged Material Mean SD Range 2.7 0.7 4-1.5 300 98 557-143 136 50 225-29 132 81 421-30 9.0 34 151 -d.l. 2.4 1.4 5-0.7 2.3 1.1 5-0.7 7.0 2.0 10-4 10 Dredged Material Mean SD Range 0.6 0.2 0.8-0.4 39 15 60-23 28 16 50-14 11 6.0 19-6 0.2 0.1 0. 4-d.l. 0.2 0.2 0.5-d.l. 0.2 0.1 0.3-d.l. 1.5 0.6 2.2-0.9 Natural Sediment Mean SD Range 0.5 0.1 0.9-0.3 13 5.0 31-8 1.1 0.7 4-d.l 0.6 0.4 2.4-0.3 d.l. d.l. d.l. 0.7 0.2 1.2-0.4 1 «10'* mg/Kg. 2 Mean metal concentration. Standard Deviation. "■Range of observed metal concentrations. s Belok" detection limit. 112 in concentration about the mean value, Table 15 shows that the stan- dard deviation values for all metal concentrations in dredged material are invariably greater than the corresponding standard deviation values for natural sediment. This can be attributed to the multipli- city of sources of dredged material as compared with the underlying naturally accumulated sediment. Also upslope cores 3 and 6 exhibit the maximum variability in metal concentrations. This indicates that the apex of the pile receives primary undifferentiated dredged material whereas the downslope areas of the deposit receive somewhat sorted secondary finer grained material. Comparison of the mean metal concentrations in dredged materials of cores 2, 3, 4, 5, 6, 7, 8, 9, and 10 reveals that the apex and up- slope cores 2 and 3 exhibit higher average concentrations of toxic metals than the downslope cores 4, 5, 7, 8, 9, and 10. Core 6, located upslope on southeast transect, however, has lower average metal con- centrations than cores 2 and 3 and some of the downslope cores. This can be attributed to a high sand content of sediment at this station, presumably resulting from either the removal of fine grained material in the water column during descent of the dredged material or to post- depositional erosional processes. Elevated mean metal concentrations in cores 8 and 9 can be explained on the basis of their high mud and organic matter contents (Table 15) as compared with other stations located on the slopes of the pile. Cores 4, 5, 7, 8, and 9 are enriched in Fe and Mn as compared with the underlying natural sediment. This indicates that dumping of 113 dredged material does contribute to anthropogenic input of Fe and Mn. Enrichment of both metals in the dredged material in the slope cores 8 and 9 can be attributed to the high organic matter concentrations and mud contents at these stations. 4.6.3 Metal Enrichments in Coastal Deposits Comparison of metal enrichments calculated for the dredged material deposit (Table 16) with other coastal deposits provides insight into the relative magnitude of metals deposited, via dredged material dumping, in the New York Bight. Table 16 gives enrichments of metals in nat- urally deposited sediments from several coastal areas. These areas are known to be heavily impacted by industrialization. Range of en- richment factors for the dredged material deposit are also included in Table 16. The enrichment factors at the lower end of the range of values for the dredged material deposit are comparable to those re- ported for other naturally sedimented coastal deposits. The low values correspond to the enrichments calculated for the downslope stations. The high values, representing enrichments in the apex or the upslope cores, are significantly greater than the enrichments reported for other areas. Even Fe and Mn, elements that normally show no significant enrichment in coastal deposits, are considerably enriched in the dredged material deposit. Table 16 shows that the metal inputs to the New York Bight, due to dredged material disposal, are significantly higher than the anthropogenic metal inputs resulting from natural sedimentary pro- cesses in coastal areas not impacted by dredged material dumping. 114 a> to vo m •— CT1 .— r— ai i— C\J i — r- Ol CO r— U3 .— i— ■— a* cti o o «3" lO .— |— ,— E 1 o .— r— -i- 0) 115 It must be pointed out, though, that the enrichment factors cal- culated for the dredged material deposit represent metal enrichments in dredged material relative to the underlying coarse grained sediment. Because of the difference in grain size of the two materials, the calculated enrichment factors could very well reflect liberal esti- mates. 4.6.4 Geochemical Correlations The three important factors that determine the distribution of trace metals in sediments are: (1) adsorption onto, or coprecipitation with, iron and manganese hydrous oxides; (2) formation of metal -organic complexes or adsorption on organic material; (3) association with clays by processes such as adsorption or ion exchange. In order to determine the relative importance of each of these processes, covariance cor- relations between metal concentrations and selected sediment parameters were used. A least squares linear correlation was performed for each pair of relevant geochemical parameters for all cores collected within the dredged material deposit. For this purpose cores 2, 3, 4, 5, 6, 8, and 9 were selected. Cores 1,7, and 10 were not included in the geochemical correlations because they were comprised predominantly of natural sediments. Table 17 gives interelement correlation coefficients between Fe, Mn, Cu, Pb, Cd, Hg, and Ag in the sediment core sections. The cor- relation coefficients between metals and organic matter and mud con- tent are listed in Table 18. All correlation plots are displayed in 116 CO £ CD CD < o o CD CO CO o CD cd CO CO +i S cu o CO s o « CD fc Jh o o +i s CD s CD CD Sh CD +i ■s en o o •a C_3 o o 00 o CX> 00 -Q o o CO oo 3 o o o o o oo o oo o oo o CO CO r-^ CO CO o LO ID CM CO CO CD o CO 00 O CO 00 CNJ o !*». CO r*. ID CO CO IX. CD CD .o. ■o c_> CD 117 -p s s o *■« s £ « Sh <» +i • ■+i CO a -p s K 0) o g: •^ ■c3 K ^j 8 <& fell CO fc O +i •^ *s CO o a a 0) CO T. V-J « t-~i +i « Qi •^ £ Sh Cfi S +i 0) a CS £ 3 +i ^ 0) 05 -Q ^ ^ to Sh s ^ 0) •«i S o M V JK «K 0) o s o V +i a to ca & fc O Co oo r-H so t--i rQ e &H -a C_5 QJ CM r--. C\J oo oo o t£> CO o 00 o oo en CNJ 1^. o 00 s- cd +-> fO o •I— e (0 CD s_ o CM e CD +J E O o "O r5 o -a e o CO s- a> +-> ro E • fO <_> CD S- o o LO lo ■o E 4-> ro (0 +-> e E o 0) ■i — +-> +J E •r— O E o CD ■r- -a CD E E ai ro cu to 2 +J E CD O J3 to E o CD -l-> -1- CJ) •1 — CD CD O 3 <_> i/) E ro O •^ ■Q +J CD ro s_ r— 3 CD to S- ro s- CD o Bf o i— i CM 118 Figures 41-46. The number of points on the correlation plots varied with the parameters plotted. Since concentration values below the detection limit for Hg, Cd, and Ag could not be included, correlation plots of these metals contain fewer points. In addition, a few ex- tremely high values were not considered since these concentrations lie out of the range of the selected scale on the axes. Concentrations of all geochemical parameters used in the correlation analysis are considered on a gravel -free basis. The number of points plotted ranged from 187 for mud-organic matter plots to 132 for Cd - Ag plots. Interelement Correlation . The Fe-metal plots (Figure 41) indicate that Fe concentrations are strongly related to Mn but only moderately to the other metals determined in this study (Table 17). Characteristic of the plots of Fe against the trace metals (Cu, Pb, Hg, Ag , and Cd) is scatter along the ordinate, i.e., a wide range of Fe concentrations at low metal levels. This scatter decreases in most of these plots at higher concentrations. Another interesting feature in these plots is a fairly large presence of Fe (1-2%) where other metals are nearly absent. This can be attributed to the presence of relatively uncon- taminated sediment such as the natural sediment underlying the deposit. Since a strong interrelationship is observed between Fe and Mn, the Mn versus trace metal correlation plots (Figure 42) are similar to those observed for Fe. Cu and Pb show a stronger relationship with Mn than Cd, Ag and Hg . Figures 43 and 44 present the trace metals plotted against each other. The correlations among these metals are strong, particularly 119 *b <*8 o0 o0 r> o °( o°*°o 00 o"~o °° o?» «o o. o°9d°o O^g 0(BP( E Ql ~ _ 00 - % * O - ; •.»: ** 8 o^° - CD e * CL Q. o o o o ( o o o 8 0(00 CO ftoo Q 10 °a E o a. o Q. OJ - — O O °0 d? o° ° ° ° °°°o O^o ° 0c $V§Soo B C°o 0n » e°° "^ *& ° °ce^cBo 00 , ,° °9° «>&.£%, o E Q. fO CNJ (%)3d „o° °o 00 * 8 a o 00 o ^0 ° °o°o °°„o° oo°<°c? °o° , ,0 s J* So 1 oqo of a, rO OJ (%)9J - CO - t E Q_ Q. < - O 0^ ° ■ °rf> 2 ° ° °° ° oo%S ° o„ o°%V*o Oj 0° - ° f£*o° °° 0°** \p ° 8 ^b J^co cfc - <£> .1 X CO o s o -p 6 o o to e -p I K o e •p o 120 oo" § 80&0 O^ p oo' oo o ° 8 3 0°, o o0 8 o 6*° o oo o o n o<*? o ° o j a_i *»° gflQcf <0 oo«« <£ «>0 o o^aPyoeToo o° E Cl O Q. o— - C\J _Q CL «b° o «r ° o oiJP a E Q. cvi rj O O O to o o o o (LUdd)U|/\| > 008 o o o o o o° & o O ^ o o* % $ °° $ o° o' o^PvP ° ^o °_ o o 10 Q. X o o o o o o - o o o ? oo o o o 6~> o _ fi° ° °o° % ° o o o o afi o ?, o° ° o o» °* o o o 1° 1 ° OoV^o °° ° °*^, op o o J 3 a o%o ^"6, . ,o , ° o O0D o o 3 ° o® ft o o o feo». 0^ # °§ »crf> °° o a o a o t> aap ° 1 1 1 IT) E ° o m o ^ o o o Oo°o°d8 O<0D CO o^or 00 6> ^° o o - 1 CD ° O O <°< o _ o o o O o o o o o o I 1 1 o m o o o o CVJ (uudd)qd - CO E CL Q. cn o o o _ o o o o o o o o - ° cP o o o °8? o oo °o o n o D o °tf° o o % oo o Q o o o o*§° oOOOOOq 8 o o <£» " o f*% 1 1 1 1 1 1 1 CO o 8 *° qO tfft> © 08 °W> <*? oo« o o o o o o ° o 00 200 Pb(ppm) 400 2 4 Cd(ppm) 400 E Q. 3200 O * o o o o"o 8 °c o o >o o 200 400 Mn(ppm) 600 12 o o ° - cP Oo° o ° o o o o o o o o a°o o e °0 o o° o °^ n o %°o' o° o of e - S 0O °^ O o° O °« ° eg o?A V> o fl^Po 1 1 1 1 200 Cu (ppm) o o ° " °8° E O O u J ** ° t O o « o dBo oo q^o.9 „ o °oy ? o 400 o 200 Pb(ppm) 400 12 o° o° o o o o o o o o ° °o 0° o o ft> 8 o O 8 4 ° °§ vf* o ° o °° °«>o * o <£o o 1 1 1 1 1 Ag(ppm) o o 2 o o o o o ao o ; ° o^c o o 8 o°° o o *°p° _o o o° o* O o o o 8 o^o^So O co^°° O o o o o o o 4 So 1 1 1 1 1 1 1 Hg(ppm) Figure 45. Organic matter (LOT) - metals correlation plots. 124 100 80 §5 60 Q Z) »40 20 100 80 Si 60 o o O q Jo °o o %aP<&r. o 8 1 o o 1 1 Q 40 20 100 80 0^60 r»o n o 0° ° ° ~ O oo © o o o <6 OjO o ° °o 40 20 100 80 o^60 o o o „ o o 50 „ o° ° CD* 8 ° O 0° - °o o8 ° °o e O 8 oo° 8 o° cP°o °° "°o°o ° °o e o°o - ° oo 0° Q 3 Sn 1 to 1 01 1 -L-O- 1 1 Cd(ppm) Q Z> 40 20 00 00 <*8 °° ° 0° % o 00 °°o °° oo ° o° - °o V oo _o%> o O°JoO 0% o8° B o S ° "0 8 8 ° e O <£ ft K? 1 1 1 1 OfT 8 * Oo - $ ft ° D « OO 3? 00 "• «° Oo % o°oo 00 to. ©^'" ° VA* eP* 1 1 °n 1 1 1 1 200 400 Mn (ppm) 600 P*o * 8 • * ° \$ • o° 3 o° • 8 % O £ oo °J ii-» ° 8 o °o o o , 00 o o o °(S° o o O % I Q L -Lo- Hg(ppm) 4 8 L.O.I. (%) 12 400 [0° °o °o° 0° ° "cf°° ° ° 00 ° O _ % o° OO J= 0* 6°o , °8<&Q % 0< o o T)^ O ° 0o ©V © / « 8)^ n O? 1 n 1 1 1 Figure 46. Mud-metals correlation plots. 125 for Cu versus Pb. Unlike the Fe and Mn versus trace metal plots, the scatter along the lower ends of axes is minimal but increases at higher concentrations. As expected from their similar chemistries and the predominantly natural sources of these metals, Fe and Mn are strongly correlated in the dredged material deposit. The wide spread in Fe and Mn concen- trations at low trace metal levels (Figures 41 and 42) indicates that the dredged materials originate in widely varied environments in terms of anthropogenic metal inputs and that the natural sediment underlying the deposit contains natural concentrations of Fe and Mn but is depleted in trace metals. Overall the metals exhibit strong correlation with Fe and Mn. It appears that iron hydrous oxides and to a lesser extent, manganese hydrous oxides play a significant role in the adsorption of Cu, Pb, Cd, Hg, and Ag. Correlations of Fe and Mn versus Cd and Hg have been observed at other dredged material disposal sites (MSRC, 1978; Heaton, 1978). The strong interrelationships among some of the metals indicate that they behave similarly geochemically and probably are associated with the same minerals in dredged material sediments. Metal -Organic Matter Correlation . Correlation between metals and organic matter (Table 18) indicate strong association of Cd, Hg, and Ag with organic matter in dredged material sediments. Correlation plots of Fe and Mn versus organic matter (Figure 45) exhibit a similar relationship but the Mn covariance is weaker. The organic matter versus toxic metal plots (Figure 45) are fairly similar, all showing 126 scatter at low metal concentrations, but the variation in the relation- ships differs. The Pb and Cu plots are strongly linear while those for Ag, Cd and Hg are slightly more scattered. The variation in organic matter content at low metal concentra- tions implies that plant debris from relatively pristine environments Is intermixed with other waste such as sewage derived organic matter. As previously mentioned, the dredged material is taken from areas which are exposed to widely varied degrees of pollutant loading. Mn and Cd appear to be less associated with the organic fraction than the other metals studied. On the basis of the correlation plots, the degree of covariance for the metals with organic matter in the dredged material sediments follows the sequence: Pb>Fe>Cu>Hg>Ag>Mn>Cd. The strong relationships of organic matter with the metals indicate that the organic matter may have a significant control over Fe, Mn, Pb, Cu, Hg, Ag, and Cd in dredged material sediments. This agrees with previous studies in other locations for both natural and polluted sediments (Rashid and Leonard, 1972; Nissenbaum and Swaine, 1976; Gross, 1976; MSRC , 1978). Metal -Mud Content Correlation . The degree of association of the metals with mud content of dredged material sediment follows the se- quence: Fe>Mn>Cu=Pb>Hg>Ag-Cd. Compared to metal -organic matter cor- relations, the metal versus mud content correlations (Figure 46) are significantly weaker for each pair indicating that the organic matter, rather than mud content has significant control over the distributions of Fe, Mn, Pb, Cu, Cd, Hg, and Ag in the dredged material sediments. 127 Because of the highly organic rich nature of much of the dredged sediment,, the mud fraction of the sediment does not appear to be the controlling factor with respect to the distribution of metals. Sewage- related materials may add large quantities of metals and organic matter without substantially altering the grain size of the samples. From the results obtained, it is only possible to make certain generalizations. It appears that organic matter plays the most sig- nificant role in the distribution of metals in the dredged material sediments. Iron and manganese hydrous oxide phases may also control the metal distributions especially of Cu and Pb. 4.6.5 Depositional Record of Metal Inputs We calculated the inputs of certain metals (Fe, Mn, Pb, Cu, Cd, Ag, Hg) and organic matter from estimated sedimentation rates at each station for the periods 1936-73 and 1973-78 and the observed depth distributions of metals in each core (Table 19). The arithmetical averages of metal concentrations in upper and lower units of each core, above the basement, corresponding to 1973-78 and 1936-73 accu- mulations, respectively, were used for the calculations of pre- and post-1973 metal inputs. A value of 2.6 gm/cm 3 was assumed for the density of the solid phases and 31% as the average water content of deposited dredged material. The wide distribution of coring stations in the study area pro- vides information about the inputs of metals deposited in different parts of the dumpsite over a period of time. For example, the highest metal input values are obtained for the apex stations (cores 3 and 6) 128 •§"5 "§•? +> IN. « I •<-> to CO r-H w 1— IT) O •— 1— o o •— "O 1— ID w- 129 for the period 1936-73. As expected, the lowest metal inputs are re- corded in cores taken at the downslope stations (cores 4 and 8). Other stations, located on the top and middle of the slopes (cores 2, 5, and 9), exhibit intermediate input rates; the upslope cores showing higher values than the downslope cores. For the period 1973-78, however, highest input values for some trace metals are obtained for the upslope cores 2 and 5, lying on the southeast slope of the pile. The pile apex cores (3 and 6) exhibit relatively low inputs. This can be explained by the recent dumping that took place at a site to the southeast of the designated dumpsite used before 1973. Overall the southeast slope stations exhibit higher metal inputs than those located on the northwest slope. For the period 1936-73, the inputs of Pb and Cu at the apex and downslope stations (cores 3 and 4, respectively) vary by more than two orders of magnitude; Cd, Ag, and Hg by one to two orders of mag- nitude. The Pb and Cu inputs in each core are very similar as well as the inputs of Cd, Ag, and Hg. The organic matter and Fe inputs are also comparable. Mn input is slightly higher than those for Pb and Cu. In a given core, input rates among the metals vary in proportion to their average concentrations in the deposit. For most cores, the order is organic matter >Fe>>Mn>Pb-Cu>>Ag>Cd-Hg. For the period 1973-78, the input values for the trace metals vary over a smaller range, the maxima being relatively lower and the minima higher than the corresponding values for the 1936-73 period. The general order of the magnitude of the metal inputs is the same as above. 130 To put the calculated input values in the right perspective, it is best to compare these values with the anthropogenic inputs of metals in naturally deposited coastal sediments of other areas such as the California Basin, the Baltic Sea, and the Naragansett Bay (Table 16). The compilation in Table 20 shows that Pb, Cu, Cd, and Ag inputs to the New York Bight, through dredged material dumping, are generally much larger; up to two to three orders of magnitude higher than those for the other sites. This is particularly true in the central areas of the dredged material deposit. Relative to the Pb and Cu inputs to the Naragansett Bay sediments, these metals are depositing on the apex of the pile, as a result of dumping, at rates higher by factors of 40-80 and 30-70, respectively. Inputs of Pb and Cu at the downslope stations on the deposit are comparable to those reported for the Naragansett Bay. As reported by Goldberg et al. (1977), the Cu and Pb inputs to the Naragansett Bay sediments are two orders of magnitude higher than those from the Baltic Sea and the California Basins. Anthropogenic inputs of Fe and Mn to the sediments of the California Basins, the Baltic Sea, and the Naragansett Bay are reported to be negligible (Bruland et al. , 1974; Erlenkeuser et al. t 1974; Goldberg et al. , 1977). However, Table 14 shows large anthropogenic enrichments of Fe and Mn in New York Bight dredged material as compared to the underlying natural sediment. This leads to a strong anthropogenic input of these metals, via dredged material dumping, to the New York Bight (Table 16). Bruland et al. (1974) reported average values of natural inputs of Fe and Mn for the California Basin deposits to be 131 K£> V£> OJ i— .— CO •— •— CSJ CSJ CSJ CSJ CSJ CSJ .— CSJ CSJ i— r OOOOr-p-WWNOJ r-^ oo cm in co no ^ooooroNt 0t v* ld o lo lo o *j-cocsju">ct>csjcxicq i— r- »— csj cnj m i i i i i i i i LT)Cr>*3-CT*«d-CTt^-0^ * — r- CSJ CJ ro ro ^- fl- «tr-coLO(\JCfnOfoorN I I I I I I O'd-aDOJLOcncNjcr* »— r— i— CSJ CSJ OLDOLnOLDOLO r- CSJ CSJ CO p-) ^j- ^j- Or-^*3-f— oolocsjcti<£>»— r— CSJ CSJ CO «3" «3" U") *JD QJ OJ ■5 $ c .— TIT) C T3 T3 C C 3 3 d «jm o E E V "1 t- E E >>>,>,>> >, >, "O "O T3 "O " T3 T3 (310333310(0 _*_«:_*: c _*: jl ^ _* u u u 3 u o o u IOIQiOOIOiOIDII] i— t— i— S-r— i— .— r— _Ci-OJD_O_a_O-0.Q T3T3TJT3-D 3 3 3 3 3 E E E E E •OTJT3-DTJTJ CCCCCC-OT3 (0(0(0(0(0(033 (/)(/)(/lcotrt(/)EE 3UUUUUUU OTDfT3(TD , — i— 0) F rn > > (O ,>>>,>,>,>, >> >, "O "O "O "O "O "O " "OT3 cccccc-o cc i/ivii/>(/)t/i(/)E(Oi/it/i _^_^_^_^_^_^_^ o -*: -*: ouuouuu uu m ii > s .- o O i- 1- 132 18 g/m 2 /yr and 0.15 g/m 2 /yr, respectively. The Mn and Fe inputs to the New York Bight through disposal of dredged material are more than two to three orders of magnitude higher than the natural weathering rates recorded in the California Basin sediments. 4.6.6 Interstitial Water Chemistry The dissolved Fe, Mn, and Zn concentration profiles for each core are displayed in Figure 47 and the results of the analysis are given in Table 20. The interstitial concentrations of Fe, Mn, and Zn in sediment cores at the study site exhibit highly variable concentration levels and distribution profiles. The minimum and maximum values ob- served for dissolved Fe, Mn, and Zn in the four cores were <0.2-90 ppm, 0.3-6.9 ppm, and 5-81 ppb, respectively. The interstitial waters were also analyzed for dissolved Cu, Cd, and Hg; their concentrations were below 6 ppb for Cu, 1 ppb for Hg, and 2 ppb for Cd for all samples. In core 41 shown in Figure 47a, Fe and Mn profiles display maxima just below the core top, the concentrations decreasing down the core until minimum values are observed at -33 cm near the core bottom. The Zn profile is similar to the Fe and Mn profiles except that the minimum is reached at -18 cm. Zn concentrations increase below this depth approaching those observed at the core top. Maxima and minimum con- centrations for Fe, Mn, and Zn observed in this core were 89.8 and 5.5 ppm, 6.9 and 1.0 ppm, and 81 and 31 ppb, respectively. The pore water presented in the 22.5 to 29.5 cm section of the core could not be extracted because of high sand content. 133 (a) (b) CORE 41 CORE 41 CORE 41 CORE 61 CORE 61 CORE 61 D 40 80 2 4 6 40 80 40 80 2 4 6 40 80 10 ■ III! i i i I i i i 111! 20 - 1 - 'l - ', 1 1 1 E Z 30 1 "1 1 1 1 I 1 . 1 X £ 40 a 1 1 i I ' 1 " 1 50 1 1 1 60 70 IRON (ppm) " MANGANESE (ppm) ZINC (ppb) IRON (ppm) ~ MANGANESE (ppm) ZINC (ppb) CORE 8 1 (c) CORE 81 40 80 2 4 6 "P 1 f~ 20 - 1 3 30 - x a. uj 40 h Q 50 h 60 70 L 1 — I — i — i — r -I IRON (ppm) - I - I CORE 81 40 80 MANGANESE (ppm) 1 ' 1 1 1 1 1 1 1 1 J 1 1 ZINC (ppb) (d) CORE 91 CORE 91 40 80 2 4 6 n — i — i — r IRON (ppm) i 1 r MANGANESE (ppm) CORE 9 I 40 80 -\ — i — i — r I ZINC (ppb) Figure 47. Depth distributions of interstitial iron, manganese, and zinc in dredged material deposit cores: (a) core 41; (b) core 61; (c) core 81; and (d) core 91. 134 The Fe, Mn, and Zn profiles for core 61 (Figure 47b) are mirror images of those observed in core 41, the minima being at 15-19 cm depth The pore water present in the top 0-15 cm of core 61, could not be extracted because the sediment was predominantly sand. The Fe profile exhibits a systematic increase with depth, approaching a maximum of 79.4 ppm in the bottom-most section of the core. This concentration is comparable to the maximum observed at the top of core 41. The Zn profile is similar to that for Fe, increasing down the core to a maximum of 59 ppb at -35 cm, but decreasing somewhat in the lower sec- tions. Mn concentrations show little variability in this core, re- maining relatively constant below 20 cm at about 2.5 ppm. Depth distributions of Fe, Mn, and Zn in core 81 (Figure 47c) are completely different from those observed in other cores taken in the study area. The profiles of all three metals are similar for this core, exhibiting two maxima at approximately 20 cm and 50 cm; however, the relative variability in concentrations differs among the metals. Minimum values for the three metals were found near the sediment-water interface. The interstitial Fe and Mn profiles in core 91 display minima at the core top (0-9 cm) where a strong H 2 S odor was present (Figure 47d) . The concentrations increase systematically with depth until maxima are reached for both metals at 24-30 cm. These profiles are similar to those observed in core 61 where the distributions are shifted down to a greater depth in the core as a result of the sandy horizon at 0-15 cm. The Zn profile in core 91 shown in Figure 48d is also similar to that 135 in core 61 but the range in concentrations is smaller. The maximum in the Zn profile again occurs higher in the core (-18 cm) than those for Fe and Mn. Like Fe and Mn, the Zn minimum occurs near the core top. The interpretation of the observed interstitial metal profiles is given below. Mn Profiles . As discussed, significant differences exist between the Mn profiles at different stations. The highest interstitial Mn concentration was observed in core 41 just below the sediment/water interface (4-8 cm). This indicates rapid removal of oxygen from the interstitial waters and transformation of solid oxide Mn phases into dissolved Mn 2+ . Below the maximum in core 41, manganese concentrations drop rapidly and this must reflect removal of Mn 2+ into a solid phase, probably rhodochrosite (MnC0 3 ). In contrast to core 41, the dissolved Mn maxima in cores 61, 81, and 91 are recorded at greater depths, indicating that the oxic/anoxic boundary may be located deeper in these cores. The interstitial Mn profiles described above can be represented qualitatively as a two-layer system where the boundary between the upper unit and lower unit corresponds to the observed maximum in the profile; a depth where maximal Mn remobilization occurs (Elderfield, 1979; Calvert and Price, 1972; Li et at. , 1969). This boundary prob- ably corresponds to the transition zone from oxic to anoxic sediment. The upward decrease in manganese concentration above the boundary is related to the vertical migration of Mn by diffusion and advection, resulting from a concentration gradient and burial compaction, respec- tively. The decreasing concentration of Mn with depth, below the boundary, probably results from a diffusion gradient caused by dissolution 136 and precipitation of solid Mn phases, such as oxides and carbonates, respectively (Calvert and Price, 1972; Elderfield, 1979). In areas of high sedimentation rate, such as those examined here, the surface sediment is oxidized while the sub-surface sediment is reduced. As sedimentation proceeds, the surface sediment, containing both Fe and Mn oxide phases, is buried and microbial oxidation of sedimentary organic matter results in the reduction and dissolution of the oxide phases at depth. With compaction, the dissolved Mn mi- grates toward the sediment-water interface. Using the average bottom water manganese levels reported by Segar and Cantillo (1976) as concentrations at the sediment/water interface, the concentration gradients, above the maxima, vary by an order of magnitude: 0.09 yg/cm 1 * in core 91 to 0.86 yg/cm 4 in core 41. Compared with cores 61 and 91, the rather steep concentration gradient in core 41 results mainly from the location of the concentration maximum close to the core top. Fe Profiles . The interstitial Fe profiles closely resemble the dissolved Mn profiles. However, the concentration gradients calculated for dissolved iron are greater than those observed for dissolved man- ganese. It has been reported that Fe concentrations in anoxic interstitial waters are controlled by the solubilities of various iron sulfide minerals such as greigite and mackinawite and amorphous sulfides (Berner, 1971), More recently, several workers have reported the precipitation of vivianite, Fe 3 (P0 [+ ) 2 • 8H 2 0, as the controlling factor 137 for dissolved Fe concentration in reducing sediments containing high concentrations of dissolved phosphate (Bray et al., 1973; Emerson, 1976; Martens et al. t 1978). Since the dissolved Fe profiles closely follow the dissolved Mn profiles, it seems likely that processes similar to those described above for Mn also control the dissolved Fe concentrations. That is, the observed maxima in the profiles correspond to the zones of maximal Fe remobilization. Decreasing concentrations towards the core top, above the maxima, indicate diffusive and/or advective transport of dissolved Fe to the oxic sediment and/or the overlying water column. Like the interstitial Mn profiles, the decline in Fe concentrations below the maxima with depth indicate a diffusion gradient resulting from the dissolution and precipitation of solid Fe mineral phases such as oxides, and sulfides and phosphates, respectively. The observed concentration gradients for Fe 2 display the same pattern as those observed for Mn 2 . The values range from 1.84 yg/cm 4 in core 91 to 11.23 yg/cm 14 in core 41. The concentration gradients for Fe 2+ are greater by more than an order of magnitude than those for Mn 2+ . This implies a greater rate for the remobilization of Fe 2+ than for Mn 2+ . However, since the iron concentrations of bulk sediment are two orders of magnitude greater than those for manganese, the sediments may serve as a relatively more efficient trap for remobilized Fe 2+ as compared with Mn 2+ . 138 Zn Profiles . Although some divergences were observed, particularly at the core bottoms, the interstitial In profiles follow similar trends to those for Fe and Mn. It is expected that similar sedimentary pro- cesses control the dissolution and precipitation of Fe, Mn, and Zn. Coprecipitation (and dissolution) of Zn with Mn and Fe oxyhydroxides may be partly responsible for the similarity in the distributions of these three metals. In reducing sediments, sulfide precipitation is generally thought to control interstitial Zn concentrations. However, dissolved silica and C0 3 ~ species have been postulated as possible controlling factors in natural systems (Hem, 1972; Willey, 1977). Chelation by dissolved organic matter in sediments may also reduce the activity of free Zn 2 ions in interstitial water solutions and thereby maintain higher total dissolved Zn levels than theoretically predicted based on saturation equilibrium calculations. Segar and Cantillo (1976) found a wide range of concentrations for dissolved Zn present in the bottom water of the New York Bight Apex with an average value determined to be 32 ppb. This is close to the average concentration of 30 ppb found in this study for inter- stitial waters in sediments from the dredged material deposit. These data indicate that the dredged material deposit may be a diffusional source of dissolved Zn to overlying waters in some areas (e.g., Core 41) and a sink in other areas (e.g., Cores 61, 81, and 91) of the deposit depending upon the concentrations ambient in the sediments and the overlying water at the time. However, since concentrations 139 in both water and sediments appear to be relatively similar, it is unlikely that diffusional transport of dissolved Zn is significant in any case. Cu, Cd and Hg Profiles . Dissolved Cu, Cd, and Hg in all inter- stitial water samples were found to be below 6 ppb, 2 ppb, and 1 ppb, respectively. It is generally believed that in reducing sediments the dissolved concentrations of these trace elements reach saturation with respect to their sulphide phases resulting in the precipitation of authigenic metal sulphides. However, higher than equilibrium saturation concentrations have been reported for interstitial trace elements for other areas (MSRC, 1978; Elderfield and Hepworth, 1975; Lindberg and Harris, 1974; Presley et at. , 1972; Brooks etal., 1968). In these cases, like interstitial Zn discussed above, processes other than metal sulphide precipitation are believed to control the dissolved Cd, Cu, and Hg concentrations. In contrast to the relatively high concentrations of interstitial Fe 2+ and Mn 2+ observed in the sediment cores, the dissolved Cu, Cd, and Hg concentrations are extremely low, indicating that these elements are practically immobile in the dissolved state and retained by the sediments most effectively. Benthic Fluxes of Dissolved Fe, Mn, and Zn . The net fluxes of dissolved Mn, Fe, and Zn from sediment to the overlying water column can be calculated from the observed concentration gradients recorded above the maxima in the profiles of Fe, Mn, and Zn. The profiles, below the maxima, reflect dissolution and precipitation reactions and 140 can be ignored in the flux calculations. The interstitial waters, however, are not significantly enriched in zinc relative to its con- centration in the overlying water. Therefore, the zinc diffusional flux is considered to be negligible and not calculated here. The upward flux can be calculated using the equation: J(Fe,Mn) = -D |j| - wc (3) where D is the apparent molecular diffusion coefficient of Fe 2+ or Mn 2+ , c is the concentration of Fe 2+ or Mn 2+ in the interstitial water, and dc/dz their concentration gradients, z is depth in the core (z = at the core top; z = I at the depth of maximum concentration), and w is the rate of sedimentation, used here as an advective velocity term. To obtain maximum flux values, we assume a linear concentration gradient. The concentrations of dissolved Fe and Mn at depth, z = are 12 and 8 ppb, respectively, as reported by Segar and Cantillo (1976) for bottom water sampled in the dredged material dumpsite area. For estimating advective fluxes of Fe, Mn and Zn average values of their concentrations above the observed maxima were used for c. Assuming negligible interaction between Fe 2+ and Mn 2+ ions and the sediment host particles, a value of 1.06 x 10" 6 cm 2 /sec is used for the apparent diffusion coefficient for both Fe 2+ and Mn 2+ at 4°C as reported by Manheim (1976). Sediment tortuousity and porosity corrections have been made in the D value given above. Rates of sedimentation, assumed to be constant over a period of time, are used to calculate the advective flux term. 141 Table 21 gives the observed concentration gradients for Fe 2+ and Mn 2+ , the concentration maxima depths, the sedimentation rates at each station, and the calculated diffusive, advective, and total fluxes of Fe 2+ and Mn 2+ at each station. Also included in Table 21 are the advective flux values for Zn. It is clear that the advective process dominates the net benthic flux of Fe 2+ , Mn 2+ , and Zn 2+ . This is to be expected considering the high sedimentation rates in the area. The effect is most pronounced at station 61, where the calculated sedi- mentation rate was found to be approximately 60 cm/year. The diffusive flux of Fe + or Fin + is a small fraction of their total benthic flux. Some precipitation of dissolved Fe and Mn will likely occur as these migrating ions encounter the oxidizing zone at the sediment/water interface. Therefore, the calculated flux values may reflect a liberal estimate. In order to evaluate the effect of hiqh sedimentation rate on the interstitial water profiles, it is important to determine the time scale of the diffusional process. The time required for an interstitial water profile to adjust to equilibrium conditions by diffusion is given by f£ < 4 > where t is the time scale of diffusion; x is the length of the diffusion path, and D is the diffusion coefficient for Fe 2+ or Mn 2+ . Using a value of 8 cm for x and %10" 6 cm 2 /sec for Dr » in equation (2), a value of ^2 years is obtained for t. This is approxi- mately the time required for the dissolved Fe 2+ or Mn 2+ to diffuse 142 £ 'a <*-, ro ^J- • — O CO O i— cn o 00 IT) i— O UD o o ■r- 0) -a 4-> ai ro CO oo CM CTt CTt CT> C d) C 0) ••- •— — • CM 143 through 8 cm of sediment in core 41. Assuming a constant sedimentation rate, the time scale of sedimentation at this station is comparable to that of diffusion, indicating that diffusion may be an important process at this station. In other cores, however, the characteristic time scale of dif- fusion (t) was found to range from 13 years for core 61 to 23 years for core 91. This implies that the time scale of sedimentation is too fast at these stations as compared with diffusion. In other words, diffusion is not a significant process at these stations. In our calculations of benthic fluxes, we have assumed that the sedimentation rate is constant over a period of time at the New York Bight dredged material disposal site. In reality, however, it is not constant but episodic; each episode corresponds to a dump event or a number of events having variable frequency and mass loads. During dump events, the impact of the load on the bottom may result in sediment compaction. Thus, in turn, will enhance the upward flow of interstitial water, resulting in a greater advective transfer of dissolved Fe, Zn, and Mn across sediment-water interface to the over- lying water. This episodic dumping may contribute more interstitial Fe, Zn, and Mn to the overlying water than that calculated above for the advective term. Sediment resuspension may also contribute to the benthic fluxes of metals. For example, the impact of individual dump events may result in resuspension of bottom sediments. This and other turbulent sediment resuspension processes, such as storm events, can result in 144 the release of dissolved Mn or Fe and other metals to the overlying water column. Lindberg and Harris (1974), Bricker and Troup (1975), and Sanders (1978) report that remobil ization of metals during sediment resuspension can be a significant process contributing metals to overlying waters. Additionally, a dump or a storm event may replace the metal-rich interstitial water with metal -depleted bottom water, resulting in a net flux via flushing. This process would operate at a faster rate than molecular diffusion. The importance of this process is a function of the depth to which flushing takes place, the frequency of individual events, and the extent of metal enrichment in the pore waters. The potential flux of interstitial metals due to a dump event can be estimated by taking cores before and after the event. The amount of metals transferred to overlying waters, as a result of a dump or storm, can be estimated from the difference in the interstitial metal profiles. Elderfield (1978) found lower zinc concentrations in pore waters of Conway estuary sediment, following a storm event. Using the difference in the concentration gradients of interstitial Zn, before and after the storm event, he was able to calculate a flux via flushing for the one-day storm. Similar observations were reported by Sanders (1978) for interstitial Mn in sediments of Calico Creek, North Carolina. Although bioturbation, as a benthic process, is known to enhance the flux of interstitial metals to overlying waters, it is unlikely that it is an important mechanism in the study area considering the high sedimentation rates. Pearce et al. (1976) have reported that 145 the dredged material dumpsite sediments are practically devoid of benthic organisms. The absence of benthic organisms is also indicated by our sampl ing. 4.6.7 Stratigraphy The stratigraphy of the dredged material deposit has been estab- lished using sediment texture and metal data from the cores collected in the study area. The stratigraphic sections of the deposit based on sediment texture and metal data are shown in Figures 48 and 49. The ten cores taken at the dumpsite are arranged in sequence. In Figures 48 and 49, cores 1 and 6 represent the end points of the northwest transect whereas the end points of the southeast transect are represented by cores 3 and 10. Cores 3 and 6 lie on the apex of the deposit where the two transects intersect. The vertical relationship of each of the cores is based on the tide corrected soundings taken at the time of the coring. The horizontal scale gives the relative distances between cores. Textural Stratigraphy . The sediment types chosen for stratigraphic correlation were distinctive in texture and generally were easily visually identifiable. Grain size and organic content were then used to ascertain the similarity of the sediment. The greensand layer provides the only natural sub-bottom horizon. In cores 5, 2, and 9 the greensand must have been exposed as an erosional surface because it comprises the top of the natural sediment, being directly overlain by dredged material. In other cores where the natural sediment was 146 X Q_ < < m <=> >- > _ KJIKO? ocnuocntnou. iOOEiBBHSDffl 4 Q. O _l CO CO UJ X h- tr o E x UJ Q_ < O or o < h- - CO Q LJ a. o _i CO CO < UJ X h- o CO 1 o (Sd313lAI)d31VM MO~l NV3W M0139 Hld3Q 0) CO CO -p 05 CO s 8 -p CO a •p 3 o CO I -p CO 05 ■p o K ■p o -P CO O SX, 05 05 rC ■P 05 ^ . o c^ ^ c CU is •$> ■P r-^ •P CO o •p -p O 05 5~^ co « I CO CO o 5h -P 05 3 1*4 147 z j 7 < < rr 2 hj < o < S s < _l o f < UJ tr 19 _i ~> n < Ill t- UJ 1- ir < rr LU o z o 2 4 LU Q- O _J co co UJ ce o E CL < LU _J CL O — o ce Ll. UJ o z. < I- co Q UJ CL CO CO < Ul X o CO - O *^ •^ -t-i CO ?H 0) -^ CO co CO ^ CO « o +S ■sti 148 sampled, the material underlying the dredged material was medium to coarse grained white or gray sand. The profile of the basement horizon conforms roughly to the 1936 bathymetry. The lithology is shown for the natural sediment in Figure 48 while the dredged material is simply shown by shading. The dark cross-hatched areas at the tops of cores 2, 3, 5, and 6 represent a thick bed of sand/mud/sand sequence. A similar sequence of sediment types was present in the basal units of dredged materials, overlying the natural sediment, in cores 4 and 5. The other horizons indicated on Figure 48 represent discrete beds of coal, gravel, mud, clay and fibrous organic material. The coal beds were present in two horizons. In cores 2, 4, and 5 coal was observed at depths of 3.4, 1.1, and 2.3 m, respectively. Coal was also found at 1 .6 m in core 9, and at 0.9 m depth in core 8 and throughout the 60 cm thick bed of dredged material at the top of core 7. The relative positions of occurrence of this material in the cores suggest that these beds may belong to the same horizon with gaps present in cores 3 and 6. The coal was generally angular anthracite of pebble size, associated with wood fragments. From the depth of the beds and the average sedimentation rates for each core it has been determined that the coal beds were deposited between 1962 and 1967. Gross (1976) reported that the annual dumping of coal ash peaked at 0.18 x 10 6 tons in 1963. The two coal beds may therefore have been associated with this dumping. 149 The red clay horizons were the most extensive. This material was found in a variety of forms, primarily in beds and in galls. The upper horizon was found in the top meter of cores 2, 3, 4, 5, and 6 occasionally mixed with the mud of the sediment sequence shown in Figure 48. A second horizon was found, just above the 1973 bathymetry horizon, in cores 2, 5, and 6. A third was observed just below the 1973 horizon in cores 3, 8, and 9. The fourth red clay horizon was found throughout the deposit in cores 2, 3, 5, 6, and 9. The lower- most clay horizon was found above the natural sediment basement in cores 8 and 9. It is believed that this clay type represents sediment derived from Newark Bay (D. Suskowski, personal communication). Thus, the red clay horizons observed in the deposit may reflect dumping of material dredged from that area. While muds are ubiquitous in the dumpsite there were certain distinct beds of organic rich mud which were recognizable by the par- ticularly high organic content and wery low gravel and sand percentages A horizon of this material was present in the top portions of cores 2, 3, 4, 5, and 6. The presence of this horizon may represent dumping of large amounts of sewage sludge at the site in late 1971 (Conner et at., 1979). This horizon has been correlated with horizon B of the metal stratigraphy discussed later. The 1973 horizon was established from the 1973 bathymetric sur- vey (Freeland and Merrill, 1977), based on interpolation between station locations. Note that the strike-lines for this horizon are generally parallel to those for the textural stratigraphy. This 150 indicates that there is good agreement between the two methods. Further, a sufficient number of horizons have been identified to demonstrate that individual dumping projects may be distinguished in the sedimentary record. In Figure 48, it may be seen that the stratigraphy of the north- west slope is less developed than for the central and southeastern sections of the deposit, particularly at the core tops. Above the 1973 horizon, there are no well defined strata in this part of the deposit. As expected, the dredged material deposit thins out towards the edges. Much of this spread is believed to be due to post-depositional dispersion of dumped material. Statistical tests applied to the per- centages of gravel and mud in samples from each core provide clear evidence that there is significantly more mud found in the peripheral cores that in those taken at the apex of the deposit. This indicates that fine grained sediment is winnowed from the crest of the site and re-deposited downslope. As a result of this sedimentary process, the stratigraphic record is rather tenuous along the fringes of the deposit. A similar observation has been made, in general, for bedding forms. Toward the fringes of the deposit the discrete beds of sediment that are seen in the central cores are less frequent, a result of the above mentioned processes. Metal Stratigraphy . A schematic representation of the strati- graphy of the dredged material deposit as deduced from the observed maxima in heavy metal concentration profiles of each core is displayed 151 in Figure 49. The metals used for this purpose were Ag, Pb, Cu, Cd, and Hg. The portion of each core that is composed of dredged material is shown by light shading. The sections of the cores that represent natural sediment are left unshaded. The surface of the dredged ma- terial deposit as it was indicated by the 1973 survey (Freeland and Merrill, 1977) is represented by the horizon marked with a triangle. The horizons indicated by black circles are maxima in the metal pro- files of the sample stations. The strike lines between the cores join segments of beds that apparently were synchronously deposited and reflect the same source material and dumping project. The maxima occur in two forms; (1) as thick beds of sediment having similar metal concentrations and depicted as darkly shaded sections of the cores marked with a dark circle; and (2) as discrete metal -rich layers represented by a single line also marked by a dark circle. To further differentiate these metal horizons, letters A, B, C, D, and E have been used in the stratigraphy (Figure 49). The basement of the deposit is represented by a horizon marked with open circles. It was defined as the depth where the metal pro- files exhibited a sharp drop in concentrations to lower and less variable values. Cores 2, 3, 6, and 9 did not penetrate to this depth. Cores 1, 7, and 10 are peripheral to the dredged material deposit. These stations show only background levels of metals with slight 152 elevation of metal content in the top half meter of the cores. They do not contribute to defining any stratigraphic metal horizons but do indicate the surficial spread of the dumped material. Of interest is the observation that these stations show little delineation of any strata within the dredged material. Rather, they are relatively homogeneous in their contaminated surficial material. This is in marked contrast to the cores taken from the center of the deposit which show frequent stratigraphic relationships. The correlation of horizons in Figure 49 is, in general, good for the five central cores. This correlation also agrees with the horizon based on the 1973 bathymetric survey. Cores 2 and 3 exhibit a spike of metal concentrations, just below the 1973 horizon. This is absent in station 6 presumably as a result of wide sampling intervals in the core. The bottom-most horizon of cores 3, 6, 8, and 9, does not appear in cores 2, 4, or 5 indicating that dumping started on the southeastern slope more recently than it did elsewhere on the deposit. This is also seen in the cross-sectional profile of the pile (Figure 24). All of the metal maxima comprising horizon B (Figure 49) lie above the 1973 horizon in the cores. Therefore, the material over- lying this horizon was dumped between 1973 and 1978. From the position of horizon B relative to the 1973 horizon, a reasonable estimate for the time of deposition of the metal rich sediment is 1975. Horizon B is also seen in the textural stratigraphy represented by a bed of highly organic mud. 153 Horizon C is seen throughout the dredged material pile. At station 3, 6, and 9 this horizon is found 1 meter below the 1973 stratum. Further to the south horizon C is found deeper in the cores, indicating that this area on the southern flank has only recently been subject to heavy dumping. This is also evident from the estimated sedimentation rates for the period 1973-78 and the net bathymetric change profile for this period. It is believed that horizon C represents the first massive input of sewage sludge to the dumpsite prior to 1973. According to Conner et at. (1979), approximately 4.4 x 10 6 m 3 of sewage sludge were dumped at the site during the period October-December, 1971. Textural stratigraphy exhibits the presence of an organic rich stratum at this depth in the deposit. Sewage sludge is known to be enriched in organic matter and certain heavy metals (Gross, 1970). The stratum, repre- sented by horizon C, does indeed exhibit these characteristics. The correlation between the textural stratigraphy and metal stratigraphy is generally very good. The location of the metal hori- zons agreed well with those based on sediment texture. In addition, the slopes of the strike-lines between adjacent cores are usually similar for the two stratigraphic profiles. Thus, the spatial dis- tribution of metals over a period of time in the dredged material deposit is basically controlled by the character and distribution of different sediment types in the deposit, This, in turn, is related to the nature and mass of the dredged material , the frequency of individual dump events, and the pre- and post-depositional sedimentary processes. 154 5. MASS BALANCE OF DREDGED MATERIAL AND ASSOCIATED METALS 5.1 Dredged Material Based on Tables 6 and 10, Table 22 has been compiled to provide a comparison of the amount of dredged material dumped with the amount of material actually found in the deposit for the period 1936-78. Estimates are also given for the periods 1936-73 and 1973-78. The total volume dumped during the period is estimated to be 208 x 10 6 m 3 . The estimated volume of material present in the deposit for the same time period is reported to be 120 * 10 6 m 3 . This figure corresponds to approximately 58% of the volume that was actually dumped, The bulk mass estimates, however, show that 82% of the mass of material dumped during the period 1936-78 is present in the deposit. This difference can be attributed to post-depositional compaction of dredged material in the deposit as indicated by the bulk density values of 1.2 g/cm 3 for harbor sediments and 1.7 g/cm 3 for dredged material in the deposit. Some of the compaction observed in our samples could have resulted during the vibracoring process. The dry mass of material was estimated from its water content. Table 22 shows that a total dry mass of 125 x 10 12 g of material was removed from the dredging sites during the period 1936-78. A value of 141 x 10 12 g was obtained for the total dry mass of material present in the deposit, indicating that approximately 10% more sediment is present in the deposit than the total mass dumped during the period 1936-78. This mass imbalance may be due to the deposition of sand 155 «fc. 3 — C i— CQ CO o o o CO «3- o 156 on the dumpsite from surrounding areas. As discussed earlier, we believe that as much as 8% of the total volume of material present in the deposit is sand, derived from surrounding areas, transported onto the dumpsite by natural processes such as storm events. However, considering the uncertainties in the data compiled in Table 22, it is quite conceivable that the discrepancy discussed above is not significant. It is interesting to note that for the short-time period 1973-78, the period for which the available data are most re- liable, the mass of material dumped approaches 98% of that present in the deposit. Therefore, in terms of mass balance, it appears that the mass of material dumped at the site over a period of time is conserved within the deposit. However, the differences in the volume estimates are significant and can be attributed to compaction of dredged material in the deposit. 5.2 Trace Metals The average metal concentrations of sediment sampled from the Mew York Harbor and from the dredge hoppers are given in Table 23. Also given in Table 23 are the average concentrations of metals ob- served in the dredged material deposit core sections corresponding to the dumping period 1973-78. Comparison of the mass of metals associated with dredged material dumping during the period 1973-78 with the mass of metals deposited at the dumpsite during the same dumping period is given in Table 24. 157 g o ft ^ CD £ "^ fc o , — VO CO o <£> r**» UD cr> CNJ CT> co CO -o CL CL o to -Q +-> fT3 a> ■^ -o S_ CD O O0 >- 2 cu a> q. o o o o LO CO o CNJ o co CO CO CO LO 0) CD Q. ■a c_> en CTi CD QJ O CJ) ■a c rO CO CT> <3 CD CO E ro >> -O T3 CD +J S- o a. a> s- rO >> -M -o ro 3 -O 4-> CO fO LO 4-> '1- d) si 158 "*a -tl s< It, 4) O -U 51 O «) E Si tt r-s tt> « * «> •^ ^ +i ti •^> *tt to w a- +> -M « •t-s X" !) o to tj to i» ft to to .H « +1 f^ t» E 5 w V, F «> CO i*" m •p +s <3 rC S-. +1 e I 159 The estimates given in Table 24 are compiled based on the information presented in Tables 6, 7, 8, 10, 22, and 23. Table 24 also includes estimates of annual metal inputs to the dumpsite based on the deposi- tional record and the available data on dredged material derived from source areas. The last column in Table 24 gives the percentages of metals retained in the deposit relative to the mass of metals dumped during the period 1973-78. The total inputs of metals to the dumpsite during the period 1973-78, via dumping, vary from 1.2 x 10 8 g for Cd to 11800 x 1 8 g for Fe. The Hg and Pb estimates are similar to those of Cd and Cu, respectively; the sequence of decreasing inputs of metals being: Fe > Mn > Cu > Pb > Hg > Cd. The total metal inputs for the same dumping period, based on the depositional record, are consistently lower for each metal, varying from 0.50 x 10 8 g for Cd to 6300 x 10 8 g for Fe. Approximately, 53 and 58% of the iron and manganese deposited at the dumpsite, via dredged material dumping during the period 1973- 78, are found in the deposit. Other metals exhibit much greater loss from the deposit than iron and manganese. We believe that the lower metal estimates for the deposit may be due to the following processes: 1. Transport of finer grained, metal rich material away from the center outside the perimeter of the deposit. As discussed earlier, preferential transport of fine grained material to the fringes of the pile can occur during descent of the material in the water column. Erosion of the fine grained component of deposited dredged material by storm events is known to occur in this area (Freeland and Merrill, 1977). This agrees with our observation that the apex and upslope 160 cores contain, on the average, more sand than the downslope cores. Stubblefield et aZ,(1977) also reported the presence of fine grained sediment in the outlying areas surrounding the deposit. 2. Possible desorption of certain metals during descent of dumped dredged material in the water column. Oxidation of metal sulphides present in reducing dredged material can also result in the loss of metals during descent in the water column. 3. Metal data for dredging source areas, compiled in Table 7, are based upon limited sampling and, therefore, may not be representative of all dredging sites. 4. As reported earlier, the transport of sand onto the dumpsite from surrounding areas may be a significant factor. The presence of this relatively uncontaminated sand can result in a dilution effect, giving rise to lower metal estimates. 6. GEOCHEMICAL CONSEQUENCES OF DREDGED MATERIAL DUMPING Considering the magnitude of the process of dredged material dumping in the New York Bight, it is important to evaluate its effect on the regional geochemical systems. Relative to other metal inputs to the New York Bight, dredged material dumping is the major contributor, accounting for 24 to 80% of the total input (Mueller et al. , 1976). Atmospheric metal inputs to the Bight, as reported by Duce et al. (1976) vary from 1.5% for Cd to 13% for Pb of the total metal inputs. Secondary inputs, related to wastewater discharges, land runoff, and sewage sludge dumping, are also significant. 161 Comparison of metal enrichments and inputs as recorded in the dredged material deposit with those reported for other coastal deposits shows clearly the impact of dredged material dumping in the New York Bight for the last 100 years or so. A mass balance of total inputs via dredged material dumping with the inputs estimated from the depositional record for the period 1973-78 indicates that, although most of the dredged material dumped is found in the deposit, all metals studied are lost from the system in varying degrees, either during the dumping process or following deposition. 7. CONCLUSIONS The sediments of the dredged material deposit are comprised of a wide variety of sediment types, which can be classified as quartz and glauconitic sands, muds, sandy muds, gravel intermixed with muds, and artifact material such as coal and fly ash, wood, slag, metal flakes, glass, etc. Fine grained, black sandy mud is characteristic of dumped dredged material. Glauconitic sand and gravelly quartzose sand are typical of the natural sediment underlying the deposit and in surrounding areas. The spatial distributions of heavy metals such as Pb, Cu, Ag, Hg, Cd, Fe, and Mn in the dredged material deposit exhibit highly variable and considerably elevated concentrations over those observed in sediment outside the deposit and in underlying natural sediment. Compared to metal enrichments reported for other coastal deposits, the degree of metal enrichment observed in dredged material sediments are orders of magnitude greater. 162 Organic matter appears to play a significant role in the distri- bution of metals in the dredged material sediments. Iron and manganese hydrous oxide phases also appear to control the trace metal distri- butions, especially for Cu and Pb. The estimated rates and magnitudes of metal inputs to the New York Bight, based on the depositional record, are found to be orders of magnitude higher than those reported for other naturally deposited coastal sediments. On a regional scale, it appears that dumping of dredged material affects the metal depositional record in the New York Bight. A mass balance of total inputs to the dumpsite via dredged material dumping with inputs estimated from the depositional record for the period 1973-78 indicates that, although most of the dumped material is present in the deposit, most metals are lost from the system in varying degrees either during the dumping process or following depo- sition of the dumped material. Pore water data indicate a sediment derived flux of dissolved Fe, Mn, and Zn to overlying water column due to diagenetic remobil ization of these metals in the dredged material . Because of the high sedimen- tation rates, the advective component dominates the benthic flux. Other metals like Cd, Cu, or Hg are present at extremely low concen- trations in the pore waters, indicating that their flux is yery small or practically negligible. Other processes, such as sediment resus- pension or flushing action of metal -rich pore water by metal -poor bottom water due to dump events, storms, and tidal action can enhance the flux of interstitial metals. Statistically significant differences in the mud content of pe- ripheral cores relative to centrally located cores have ascertained that large scale differentiation of sediment takes place at the dump- site. Laminated sediments and discrete beds of variable thickness are typical of the central part of the deposit which receives the bulk of direct dumping. Relatively undifferentiated, fine grained sediments are characteristic of the fringes of the deposit. We believe that most of the material deposited on the periphery of the deposit is the result of the movement of fine grained sediment after dumping. This material, settling slowly, is carried either by tidal currents or by the outward pulse generated by individual dumping events to be deposited away from the center of dumping activity. There is not only movement of fine grained material away from dumping centers, but there is movement of sand onto the edges of the dumpsite deposit. Flaser-like bed forms composed of greensand, typical of erosion windows of the shelf proximal to the deposit, represent as much as 8% of the entire deposit. This sand, derived from sur- rounding areas, has been brought to the site as storm entrained sed- iment. An overall stratigraphy of the deposit, defining the natural sediment basement and the various horizons of anthropogenic materials, has been developed. Sedimentation rates of various horizons have yielded ages that agree within a few percent of estimated times of deposition derived from dumping records. 164 8. ACKNOWLEDGEMENTS We gratefully acknowledge the assistance of the officers and crew of the R/V ATLANTIC TWIN and R/V KELEZ during the sediment sampling and pore water chemistry cruises. We also thank H. Bokuniewicz and A.E. Cok for participating in the seismic reflection profiling and sediment sampling cruises, respectively. We thank W. O'Brien, N. Moheban, B. Subramaniam, and R.J. Wilke for their help in the laboratory. We are particularly indebted to E. Quinn for typing this report and M.A. Lau for typing the first draft. At Brookhaven National Laboratory, A. Beckwith, J.J. Fuhrmann, T.C. Kycia, and R. Lorenz assisted in the x-radiographic analysis of the sediment cores. We thank them for their help. This work was supported by a research grant No. 0478B013 from the Marine Ecosystem Analysis Program of the National Oceanic and Atmospheric Administration and the New York District Office of the Army Corps of Engineers to R. Dayal and I.W. 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UJ Q 5 6 CORE 5 WATER CONTENT BULK DENSITY BULK (%) (g/cm 3 ) POROSITY 25 50 75 100 0.6 1.2 1.8 2.4 .25 .50 .75 1.0 I 2 i 3 E < a. LU Q 5 6 7 8 173 A-2. DEPTH PROFILES OF WATER CONTENT, BULK DENSITY, AND BULK POROSITY IN CORES 6, 7, 8, 9, AND 10. CORE 6 WATER CONTENT BULK DENSITY BULK (%) (g/cm 3 ) POROSITY CORE 7 WATER CONTENT BULK DENSITY BULK (%) (g/cm 3 ) POROSITY 25 50 75 100 0.6 1.2 1.8 2.4 .25 .50 .75 1.0 25 50 75 100 0.6 1.2 1.8 2.4 .25 .50 .75 1.0 0,-n 1 1 . I 1 1 1 1 I T ' 1 ' CORE 8 WATER CONTENT BULK DENSITY BULK (%) (g/cm 3 ) POROSITY CORE 9 WATER CONTENT BULK DENSITY BULK (%) (g/cm 3 ) POROSITY 25 50 75 100 OS 1.2 1.8 2.4 .25 .50 .75 1.0 25 50 75 100 0.6 1.2 1.8 2.4 .25 .50 .75 LO I 3 CORE 10 WATER CONTENT BULK DENSITY BULK (%) (g/cm 3 ) POROSITY 25 50 75 100 0.6 1.2 1.8 2.4 .25 .50 .75 1.0 _ 2 ■ E — 3 I t 4 5 h 6 7 it US GOVERNMENT PRINTING OFFICE 1981 779—043 174 ■_ 'iiBir A0000720m fl40