The Sources and Sinks of Nuclides in Long Island Sound

THE SOURCES AND SINKS OF NUCLIDES IN LONG ISLAND SOUND K. K. TUREKIAN, J. K. COCHRAN,L. K. BENNINGER,* AND ROBERT.c. ALLERt Depurtment of Geology and Geophysics Yule University New Haven, Connecricirt

1. 2.

3. 4.

5.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sources of Trace Metals Delivered to Long Island Sound . . . . . . . . . 2.1. Stream Supply . . . . . . . . . . . . . . . . . . . . . . . . . 2.2. Sewer Outfalls: New Haven Harbor . . . . . . . . . . . . . . . . 2.3. Atmospheric Supply: The Record in a Salt Marsh . . . . . . . . . . . The Distribution of Trace Metals in Long Island Sound Sediments . . . . . . Trace-Metal Distributions in Mussels and Oysters: An Index of the Composition of Suspended Particles . . . . . . . . . . . . . . . . . . . . . . . . 4.1. Oysters . . . . . . . . . . . . . . . . , . . . . . . . . . . . 4.2. Mussels . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3. The Cause of the Observed Trace-Metal Distributions . . . . . . . . . Processes Affecting the Deposition and Accumulation of Trace Metals in Long Island Sound Sediments . . . . . . . . . . . . . . . . . . . . . 5.1. Water Column Scavenging . . . . . . . . . . . . . . . . . . . 5.2. Horizontal Distribution . . . . . . . . . . , . . . . . . . . . . . Processes Affecting the Vertical Distribution of Nuclides in the Sediment Pile . 6.1. Establishing Chronologies: Time Scales of Accumulation and Bioturbation 6.2. Determination the Final Repository of Metals Introduced into Long Island 6.3. Major Sources of Metals Delivered to Long Island Sound . . . . . . . Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I

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I. INTRODUCTION There is little doubt that the sedimentary record in most, if not all, estuaries is now indelibly marked by the products of human activity. Indeed, even deep-sea deposits have begun to respond to this influence. The concerns about possibly deleterious effects of this impingement of man on his oceanic environment have brought renewed interest to the problem of the fate of chemical species in the estuarine environment, * Present address: Department of Geology, University of North Carolina, Chapel Hill, North Carolina 275 14. t Present address: Department of Geophysical Sciences, The University of Chicago, Chicago, Illinois 60637. I29 ADVANCES IN GEOPHYSICS, VOLUME

22

Copyright 0 1980 by Academic Press. Inc. All rights of reproduction in any form reserved. ISBN 0-12-018822-8

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K. K.TUREKIAN et al.

The estuarine regions of the world are the sites of encounter of riverborne materials from the continents with the ocean. The estuary, however, is not a passive way station, but a combination tollgate and indoctrination center that extracts its fees from the transients and imposes a new way of life on the survivors of the passage. Long Island Sound is an estuary that also has the properties of a large protected settling basin. In such a system many of the processes affecting the behavior of material injected into the coastal zone can be followed more directly than in some other systems more responsive to large-scale and seasonal variables. Smaller systems such as “simple” river estuaries can typically accommodate very limited sediment accumulation and the meager record is highly susceptible to loss during floods or coastal storms; highly exposed coastal regions like the New York Bight do not confine inputs in a predictable way. In this article we summarize what we have learned about the behavior of metals in the Long Island Sound. Many of the insights can be transferred to other estuaries and should be useful in understanding the effects of human activities impinging on such systems. As reviewed in the first article in this volume, by Gordon, Long Island Sound came into existence as sea level rose after the end of the Wisconsin glacial age. The initially fresh-water reservoir was transformed by the rising sea into the present estuarine Long Island Sound about 8000 years ago. At that time a change in sediment properties is inferred to have resulted and this is now seen by sonic profiling as a strong reflector. Using the depth to this reflector (dated at 8000 yr BP by the sea level curve as discussed earlier), Bokuniewicz et al. (1976) calculated an average sediment accumulation rate in the mud and silt area covering 64% of the present Sound of 0.33 mm yr-’. Benninger (1976) showed that this could all be the result of mud and silt supply by the Connecticut River if the present-day sediment flux existed throughout the history of the Connecticut River and the Sound. Imprinted on this naturally accumulating sediment are the additions of materials resulting from human activity. These include dredge spoils, which are of local importance, and metals, organic matter, and other substances introduced from a number of sources including the atmosphere, industrially polluted rivers, and sewage outfalls. The subsequent behavior of metals transported to the coastal zone is determined by several factors of which the efficiency of scavenging from the water column, horizontal redistribution during deposition, and vertical redistribution after deposition are perhaps the most important. The first of these depends on the concentration and reactivity of the suspended particles in the water column. The last two result from tidal action, storms,

NUCLIDES IN LONG ISLAND SOUND

131

and estuarine circulation all affecting particles suspended in the water column, on the one hand, and physical and biological mixing of particles in the sediment column on the other. Using diagnostic natural radionuclides it is possible to identify the mechanisms and time scales of the processes. Members of the uranium decay series, particularly 234Th(halflife, 24 days) and 210Pb(half-life, 22 years), have proven useful in this pursuit. In addition, man-made radionuclides such as the plutonium isotopes and I3'Cs also have proven valuable tracers because of their sharply defined dates of introduction into the environment. Carbon-14 occupies a unique position in this constellation of useful radionuclides since its origins are both natural (cosmogenic) and man-made. The ''C/'2C ratio can be used not only as a time indicator, but as a tracer of the sources and fates of organic carbon as well. 2. SOURCES OF TRACEMETALS DELIVERED TO LONGISLAND SOUND The silt and clay composing the sediments of the central basin of Long Island Sound are derived ultimately from the weathering and erosion of the rocks of New England. As solid phases transported by streams they bear a burden of trace elements characteristic of their mineralogy and weathering history. This process has been going on since the Sound was formed about 8000 years ago and provides the background material on which is imposed the recent increase in trace-metal supply due to human activity. The primary methods of supply are by streams, sewer outfalls, and atmospheric transport. Maintenance or construction-related dredging of metal-contaminated sediments results in the transport of the material to other locations in the Sound where the dredge spoil is dumped. The identification of such dumping has been made in the New York Bight using trace metals and organic content as well as other indicators (Gross, 1976; Carmody et al., 1973), but as we shall see, other factors operate in Long Island Sound to compromise preservation of a local identity. 2.1. Stream Supply The trace-metal concentrations in streams are controlled not only by input from the weathering of rocks and from aerosols, but also by the chemical reactions occurring within the streams. The evidence from studies utilizing "OPb as a tracer for heavy-metal behavior in streams indicates rapid scavenging by particles associated with the flowing water (Bennin-

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K. K.TUREKIAN et a / .

ger et al., 1975; Lewis, 1977). Surfaces of organic debris and manganese and iron-oxide coatings appear to be the primary agents (Gibbs, 1967). Competing with this process is the formation of dissolved organic-chelated compounds. Much of the dissolved iron found in streams, for instance, is in this form (Sholkovitz, 1976). A study of Connecticut streams (Turekian, 1971) indicated that the trace metals, cobalt and silver, are maintained at low concentrations in solution as the result of the scavenging action of suspended particles. Even where acid industrial wastes are dumped into the stream, as in the Naugatuck River, which joins the Housatonic River, suspended particles act to lower the dissolved concentrations. We infer from studies involving the behavior of ‘“Pb in the Susquehanna River and of Co and Ag in the major Connecticut rivers that the dissolved trace-metal concentration is maintained at low levels in stream water and thus the primary mode of transportation to the estuarine zone is via particles. The work at Yale University on the Quinnipiac River, a river carrying effluents from the major metal industries of Meriden and Wallingford and entering into New Haven Harbor, supports this inference. Figure 1 shows the distribution of total silver in Quinnipiac River waters in 1965 and demonstrates an increase in concentration through Wallingford. In Wallingford, the >0.45-pm fraction (associated with particles) adds to the 3 pg/l delivered from the “uncontaminated” reservoirs. (Because of the possibility of atmospheric transport of metal contaminants, it is not likely that any nearby reservoir is truly uncontaminated.) Figure 2 shows that the bottom sediments of the system, sampled in 1973, are strongly impacted by the trace-metal injections from industry. Although the silver concentration is very high in the sediments close to the source of industrial contamination, this effect is strongly attenuated downstream. Indeed, as we shall see, the effect is not discernible in New Haven Harbor where other sources predominate. This implies that most of the metals are retained behind the dams and a relatively small fraction escapes to impact the estuary. About 15 km to the west of New Haven Harbor the Housatonic River with its heavily polluted tributary, the Naugatuck River, empties into the Sound. (The confluence occurs below the last dam on the Housatonic.) This river supplies a significant amount of trace metals to the adjacent part of Long Island Sound, mainly in particulate form (Turekian, 1971). This contrasts sharply with the Quinniapiac River and demonstrates that the construction of dams is certainly one important factor in inhibiting transfer of metal-polluted sediments to the estuarine zone. The Connecticut River, although the most important river draining into Long Island Sound, seems to be least important in the transport of metals

133

FIG.1. Silver in the Quinnipiac River (Connecticut) system in 1965 (previously unpublished Yale University data). All concentrations determined on unfiltered samples except where indicated. The measurements were made by emission spectrography after silver-free sodium chloride was added and the solution freeze-dried.

from human activities to the Sound. This is no doubt due in part to the extensive damming along the course of the river and in part to the minimal amount of metal fabrication along its length.

2.2. Sewer Outfalls: New Haven Harbor Applequist et al. (1972) showed that the mercury concentration in the sediments of New Haven Harbor varied in relation to distance from the several sewage-treatment plants discharging into the harbor (Fig. 3). As is the case with most of the older New England cities, storm sewers are combined with sanitary sewers and the effluent is processed through the sewage-treatment plants. During periods of high discharge associated with large storms, the treatment plant is bypassed and the unprocessed effluent

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K. K. TUREKIAN et a / .

d BROAD BROOK RES.

FIG.2. The concentrations of silver, lead, and copper in sediments of the Quinnipiac River (Connecticut) system (previously unpublished Yale University data). Analyses made by emission spectrography. Concentrations in parts per million.

is debouched directly into the harbor, resulting in organic carbon and metal enrichment of the sediment around the outfalls. In an unpublished report from Yale (Turekian et al., 1972), it is shown that a relation exists between high concentrations of Pb, Zn, Cu, and organic matter in sediments and proximity to a sewer outfall on the eastern shore of New Haven Harbor. A more cursory survey of the sediments on the west side of the harbor showed the same thing (unpublished results). Thus the pattern established by our mercury study, we believe, can be extended to the other elements associated with sewage sludge. Figure 4 is the representation of the relationship between Zn concentration and the weight lost on ignition (a rough expression of the combination of water loss from clay minerals and the degradation of organic matter) for a traverse up the New Haven Harbor shipping channel. This cuts across the two sewer outfall regions discussed earlier (see Fig. 3), and the strong correlation of Zn and the volatile solids concentration reflects their influence.

NUCLIDES IN LONG ISLAND SOUND

135

FIG.3. The distribution of mercury (in ppm) in the tops of sediment cores raised from New Haven harbor. The dominant control on mercury concentration is proximity to sewagetreatment plant outfalls, marked by arrows. (After Applequist el a/., 1972.)

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% VOLATLE SOLIDS FIG.4. The relation of zinc concentration to volatile solids (mainly organic matter with some adsorbed water in clays) in sediments from the New Haven harbor channel. Data from the U.S. Corps of Engineers files (New Haven Harbor Project: Report on Environmental Sampling and Testing, 1972).

136

K. K. TUREKIAN et a/.

2.3. Atmospheric Supply: The Record in a Salt Marsh

Salt marshes are a common feature of the Long Island Sound coast. Where they remain protected from wave erosion their surface is an index of high tide. If coastal submergence occurs over time, as has been the case in New England for at least the last 100 years, the protected marsh grows upward to maintain its surface at high tide and provides a record of previous environmental conditions. The surface of a marsh is exposed to the atmosphere most of the time. The highest point of the tidal cycle immerses the surface only about 5% of the time. Unlike marshes in other parts of the east coast, Long Island Sound marshes are not dominated by detrital sediment, but are constructed of the fibrous framework of the marsh vegetation. Because of this, burrowing by organisms does not appear to perturb the sedimentary record as occurs in the muddy sediments at the bottom of Long Island Sound (see later). As the marsh grows upward in response to the rising sea level, each layer should preserve a record reflecting the depositional environment of the time. Changes in detritus supply from streams, for example, should be recorded by sediment trapped in the fibrous framework. Similarly, the atmospheric flux records of metals delivered to the marsh surface should be maintained in the layers. McCaffrey (1977) and McCaffrey and Thomson (this volume) have shown that the 210Pbchronology from a vertical 'IoPb profile in a Connecticut salt marsh agrees with tide-gauge data (Fig. 5). This shows that during the past 100 years the sea level has been rising relative to the Connecticut coast. The agreement between the '"Pb and tide-gauge data is especially striking because the rate of coastal submergence has not been constant over the past 100 years. In addition, these researchers showed that the calculated Z'oPbflux, as determined by the standing crop of unsupported "OPb in the salt marsh, equaled the atmospheric flux as determined for New Haven by Benninger (1978). This implies that: (1) the trace-metal distribution vertically in the salt marsh reflects the changing flux over time and that no vertical migration of the trace metals is expected by diffusion or biological activity; and (2) that there should be an atmospheric flux of trace metals recorded in the growing salt marsh. Indeed, the calculated fluxes of Cu, Pb, and Zn (Fig. 6) appear to be almost solely atmospheric as the predicted fluxes of these metals are in agreement with the estimated atmospheric fluxes (Table I). The implication from both *IOPband trace-metal data is that the marsh surface, exposed above the sea surface most of the time, behaves like an atmospheric collector and can be used to monitor the changing atmospheric flux of trace metals over time.

137

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3. THEDISTRIBUTION O F TRACEMETALS IN LONGISLAND S O U N D SEDIMENTS

Greig et af. (1977)have recently made a detailed study of the distribution of a number of trace metals (Sb, Cd, Co, Cr, Cu, Pb, Mn, Ni, Ag, Sc, Zn) in the top 4 cm of Long Island Sound sediments collected using a Smith-McIntyre grab sampler. The 4-cm sampling fortuitously represents, to within a centimeter, the rapidly reworked portion of the sediments as determined using 234Th(Aller and Cochran, 1976). Figures 7-9 show concentration maps for Cu, Zn, and Pb constructed from the data of Greig et al. (1977). The primary control on the trace-metal concentrations is the grain size of the sediment. This can be seen by comparing the trace-metal maps with a grain-size distribution map (Fig. 10) for the Sound. The sand-rich sediments have the lowest trace-metal content. There is, however, an im-

138

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portant second-order effect related to the coastal sources of trace metals. Sediments adjacent to Throgs Neck, the Housatonic River (to the west), and New Haven Harbor are higher in trace metals than other sediments of the same grain size. These three areas are heavily impacted either by sewer outfalls or direct injection of industrial sewage along a contiguous channel (as in the Naugatuck-Housatonic system). A number of cores collected from central Long Island Sound have been analyzed for trace metals as a function of sediment depth (Thomson et al., 1975; Turekian, 1979; Benninger et al., 1979). They show roughly the same patterns for Cu, Zn, and Pb (Fig. 11): a roughly exponential decrease in concentration with depth. At greater depths there are occasional peaks of high concentrations. TABLEI. CALCULATED EXCESS METALFLUXTO THE SURFACE OF THE FARMRIVERSALT MARSHCOMPARED TO MEASURED ATMOSPHERICDEPOSITION RATESAT SELECTED SITES Site and date of collection Branford, Connecticut, salt marsh (1972) New York City (1969-1970) Nantucket, Massachusetts (1966- 1967)

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7 +- 4 McCaffrey (1977); and McCaffrey and Thomson (this volume) 35 Volchok and Bogen (1971) 8.5 Lazrus et a/. (1970)

NUCLIDES IN LONG ISLAND SOUND

139

COPPER pglgrn DRY SEDlMM

FIG. 7. Map of copper concentrations in surface sediments of Long Island Sound. (Constructed from the data of Greig et al., 1977.)

ZINC pglgm DRY SEDIMENT

FIG.8. Map of zinc concentrations in surface sediments of Long Island Sound. (Constructed from the data of Greig et al., 1977.) 1

LEAD pg/gm DRY SEDIMENT

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141

NUCLIDES IN LONG ISLAND SOUND

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142

K. K. TUREKIAN et

d.

As Fig. 11 shows, there is some variability in the integrated trace-element contents of cores from central Long Island Sound. These sediments are not located near intense sources of trace metals nor are there major grain-size differences. As we will show later, the differences in both metal concentrations and inventories can be related primarily to the intensity and depth of biological mixing of the sediment column. 4. TRACE-METAL DISTRIBUTIONS IN MUSSELS AND OYSTERS: AN

INDEX OF THE COMPOSITION OF SUSPENDED PARTICLES

Mussels and oysters (epifauna) are filter feeders which attach to hard surfaces. Their isolation from the sediment means that their trace-metal compositions are likely to be reflective, primarily, of the suspended material in the water. In this section, therefore, the data available on tracemetal concentrations in mussels and oysters from the Connecticut shore are reviewed. 4.1. Oysters

Feng and Ruddy (1974) made a detailed study of the composition of the soft tissue of oysters (Crassostrea virginica) harvested along the Con-

FIG.12. Zinc concentrations in the soft tissues of oysters as a function of location, along the Connecticut coast, and time, starting in June 1972 and ending in March 1974. (Plotted from the data of Feng and Ruddy, 1974.)

143

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FIG. 13. Cadmium concentrations in the soft tissues of oysters as a function of location, along the Connecticut coast, and time, starting in June 1972 and ending in March 1974. (Plotted from the data of Feng and Ruddy, 1974.)

necticut coast. A single stock of oysters obtained as yearlings were distributed among six stations: (1) Norwalk Harbor at the Northeast Utilities Company pier, (2) Bridgeport at the Pleasure Beach Bridge, (3) the Housatonic River below Devon, (4) New Haven Harbor at the Coast Guard Station finger pier, ( 5 ) New London Harbor at the U.S. Navy Underwater Systems Center pier, and (6) Noank at the University of Connecticut Marine Sciences Institute pier. The stock was then sampled periodically between June 1972 and April 1974 and tissue analyzed for Cd, Cu, Hg, Mn, and Zn. The oyster tissue did not vary significantly in the concentration of these elements from the native oysters also analyzed. The highest values for all of the trace elements except mercury were found at the Bridgeport and Housatonic sites. Figures 12-14 show the changes in composition with time, at each of the six locations, for Zn, Cd, and Cu, respectively. There is clearly a marked increase from the summer of June 1972 to the winter of 1974 for the Housatonic-Bridgeport region for all metals and a marked increase for zinc for all other locations except Norwalk, which seems to have gone through a maximum in the winter or spring of 1973.

144

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FIG. 14. Copper concentrations in the soft tissues of oysters as a function of location, along the Connecticut coast, and time, starting in June 1972 and ending in March 1974.

4.2. Mussels

Trace metals in Long Island Sound mussels collected in 1975 and 1976 were determined by Curran et al. (1980). A map of the sampling locations is shown in Fig. 15. [Additional samples were collected at other sites and analyzed. These are in part reported in Turekian (1979) and are included in this study.] The geographic variations of trace metals in native mussels (Figs. 16-20) show the same patterns as the oysters, although the concentrations are considerably lower in the mussels. The pattern holds for all the trace metals analyzed including Pb and Ni as well as Zn, Cd, and Cu. In addition to the high values associated with the Housatonic-Bridgeport area, a region of high metal concentration in the mussels is found in the area around Throgs Neck (an area not included in the oyster study).

4.3. The Cause of the Observed Trace-Metal Distribution Obviously both oyster and mussel tissue compositions are influenced by the trace-metal content of the particles they ingest. There should then be a relationship between the chemical properties of the particles of the surrounding water and the sediments and the compositions of the tissues.

NUCLIDES IN LONG ISLAND SOUND

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FIG.15. Location map of mussel sampling sites: MC, Morris Cove; UI, United Illuminating Company, New Haven harbor generating plant site; OB, Oyster Bay; EN, Eaton’s Neck; PJ, Port Jefferson; WC, west side of Connecticut River mouth; EC, east side of Connecticut River mouth.

Consequently, the chemical composition of the ingestible particles could be inferred from two environmental indicators: the composition of the sediments at the sediment-water interface, and the composition of the bulk water (including the fine-grained particles) associated with the or-

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FIG.16. Copper concentrations of soft tissues of mussels at sites designated in Fig. 15. The bar labeled LI represents the range of values from the Long Island north shore sites

OB, EN, and PJ. The locations designated WB, H, NH, and C are the Whitestone Bridge, Housatonic River, New Haven Harbor, and Connecticut River as shown in Fig. 15. (Data from sources described in text.)

K. K. TUREKIAN et a / .

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FIG.19. Lead concentrations of soft tissues of mussels in Long Island Sound. (See legends of Figs. 15 and 16 for key.)

147

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FIG.20. Nickel concentrations of soft tissues of mussels in Long Island Sound. (See legends of Figs. 15 and 16 for key.) Considering the trace-metal maps for the top 4 cm of Long Island Sound sediment cores (Figs. 7-9), there is a marked similarity between the areas of high metal concentrations in the sediments and high concentrations in the mussels and oysters. Similarly, a comparison of the nickel concentration in mussels (Fig. 20) with the coastal distribution of Ni in Long Island Sound water (Fig. 21) also shows a marked correlation. [Nickel is the only element determined in the mussel study that has also been extensively determined in water samples from along the Connecticut coast (Turekian, 1971).] We conclude that the primary source of the metals found in elevated levels in the soft tissues of mussels and oysters is the suspended organic-rich debris in the Sound. This is accentuated where a significant source of metal-bearing organic-rich particles from human activities is introduced by direct supply or secondary resuspension. Therefore, a strong correlation exists between high metal concentrations in all components of the coastal system: water, sediment, and organisms, and the proximity of polluted fresh-water stream and sewer discharges. 5 . PROCESSES AFFECTING THE DEPOSITION AND ACCUMULATION OF

TRACEMETALSIN LONGISLAND SOUND SEDIMENTS

In the previous sections the case was made for two major classes of trace-metal impingement on Long Island Sound. One type is the supply by polluted streams and sewer outfalls, which, on the basis of the distributions of trace metals in the sediments and near-shore suspensionfeeding bivalves, was inferred to be predominantly in the form of particles. The other is atmospheric supply, some part of which presumably is in

NUCLIDES IN LONG ISLAND SOUND

149

dissolvable form. Whatever the source, two processes act in the estuary to determine the ultimate distributions of the metals. The association with suspended particles in the Sound will remove metals from the dissolved state and the movement and, ultimately, the accumulation of this suspended material will, to a large degree, determine their final repositories, although some diagenetic redistribution may also occur. In order to follow these processes the natural radionuclides, 234Th(24 days), "OPb (22 yr), and 'Be (54 days) provide the best prospects for tracing both the rate of removal of nuclides to the sediment surface and the processes governing their ultimate horizontal and vertical distributions. The properties of each of these nuclides are listed in Table 11. 5.1. Water Column Scavenging

Benninger et al. (1975) and Benninger (1978) showed that the 210Pb concentration of unfiltered Long Island Sound water was correlated with the amount of suspended matter in the water sample and that the intercept at zero concentration of particles yielded a zero value for "'Pb (Fig. 22). This indicated that virtually no "'Pb was dissolved in the water despite the continuous supply from the atmosphere. Clearly the residence time for "'Pb in Long Island Sound water must be short relative to final removal to the sediment pile, since high 210Pbvalues are found in the surface waters of the open ocean where the residence time has been determined to be about 1 yr (Nozaki et al., 1976). We depend on other tracers to determine more precisely the residence time of highly adsorbed chemical species in Long Island Sound relative TABLE11. THEPROPERTIES OF NATURALRADIONUCLIDES USEFULIN DETERMINING METALPATHWAYS IN LONG ISLAND SOUND Method of production

Nuclide

Half-life

234Th

Decay of dissolved 23RUwhose concentration is directly proportional to salinity 54 days Cosmic rays on atmospheric atoms; delivery by precipitation 22 yr Predominantly supplied from the atmosphere where it is produced by the decay of 222Rn;delivery by precipitation

'Be 2'0Pb

24 days

150

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0

4 8 12 16 Suspended sediment ( x

20

24

gm/kg) FIG.22. Total *"Pb concentration in surface water of Long Island Sound versus suspended matter concentration. (After Benninger et al., 1975, and Benninger, 1978.)

to removal to the sediments. The most useful nuclides are 234Thand 'Be since they have sufficiently short half-lives to be used for the assay of scavenging on a short time scale. Aaboe et al. (1980) have shown that the residence time of 'Be in Long Island Sound is less than 10 days. Aller and Cochran (1976) and Aller et al. (1980) using the 234Th/238U in Long Island Sound water and the standing crop of unsupported 234Thin Long Island Sound sediments indicate that thorium has a residence time of less than 10 days and probably as low as 1 day. This is compatible with the observations of Kaufman et a / . (1980) on New York Bight apex waters. We conclude that the residence times relative to permanent removal to sediments of all metals behaving like Pb, Th, or Be during adsorption are short in Long Island Sound, and thus the metals will be transported to the sediments virtually irreversibly, although there may be preferred repositories such as tidal mud flats for some of the metals. 5.2. Horizontal Distribution Aller et al. (1980) have used the distribution of 234Thin the sediments of Long Island Sound to show that there is rapid homogenization of the

NUCLIDES IN LONG ISLAND SOUND

151

incohesive fine-grained fraction deposited at the sediment-water interface. Figure 23 shows that in the top 0-1 cm of the sediment pile there is a close correlation between unsupported 234Th(produced in the water column by the decay of 238Uand adsorbed) and 232Th,which is an indicator of the fine-grained fraction. Moreovx, Aller et al. (1980) showed that there is no strong relationship between the 234Thinventory in the sediments and the 234Thproduction in the immediately overlying water. The latter should be directly related to the depth of water and salinity, which together determine the total production rate of 234Thfrom 238U. Instead, the 234Thinventory (limited mainly to the top 5 cm of the sediment pile) is largely determined by the amount of fine-grained component present at each location, and this fine-grained component is homogenized over the range of water depths on a time scale rapid compared with the halflife of 234Th(24 days). Because a trace-metal concentration distribution map shows a texture that is not related exclusively to grain-size, but also to point sources of pollution along the Connecticut coast (Figs. 7-9), this means that the net

FIG.23. Excess (unsupported)234Thconcentrationversus total 232Thconcentrationin the 0-1-cm depth layer of cores from Long Island Sound. (From Aller et al., 1980.)

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homogenization process cannot be instantaneous or Sound wide. It probably works most effectively perpendicular to the long axis of the Sound, since tidal mixing does not lead to efficient homogenization along the long axis. The maintenance of gradients across the Sound axis implies either that the rate of supply of the metal from the coastal source is sufficiently high to survive the homogenization process or that different depths of biological mixing alter the trace-metal concentration in the surface sediments. The results of Curran et al. (1980) on the Z'oPoP'oPbcomposition of the soft tissue of mussels collected west-east along the long axis of the Sound (Fig. 24) may speak to the efficiency of homogenization along the tidal axis. The mussels from the western part of the Sound have 2'0Po/210Pb activity ratios generally less than 10 (with one set of high values at Rye, New York). Starting at Milford Point, east of the Housatonic River mouth, the ratio increases eastward toward the open ocean from about 12 to 36. A similar increase in this ratio from shore to open ocean was observed for plankton by Turekian et a/. (1974) and the same effect may be the cause of this trend in the mussels. This effect in both cases could be due to the dilution of low 210Po1210Pb sediment detritus with high 210Po/2'0Pb biogenic debris. Whatever the reasons for this gradient, it does show that homogenization of the suspended particles sensed by the mussels is not complete along the axis of the Sound. In summary, we believe that "reactive" trace elements and other substances are adsorbed very rapidly in Long Island Sound, with the mean

1 1

i

FIG.24, The 2'0Pof"Pb activity ratio in soft tissue of mussels from the Connecticut coast (see Fig. 15 for locations). (After Curran et al., 1980.)

NUCLIDES IN LONG ISLAND SOUND

153

life relative to removal to the sediment pile of the order of 1-10 days. We also believe that homogenization of the fine-grained fraction need not be basin wide, but may depend on the strength of the sources of the trace metals as well as the nonisotropic effects of tidal mixing. 6. PROCESSES AFFECTING THE VERTICAL DISTRIBUTION OF NUCLIDESIN THE SEDIMENT PILE 6.1. Establishing Chronologies: Time Scales of Accumulation and Bioturbation

Figure 1 1 shows a number of trace-element profiles in sediment cores raised from Long Island Sound. The increase in concentrations of the trace metals as the sediment-water interface is approached from below is interpreted as primarily the result of human activity in mobilizing these elements in greater and greater amounts since the industrial revolution. Establishing a chronology for metal input to the Sound is not straightforward, however. In sediments deposited from anoxic or quasi-anoxic waters, such as some of the Gulf of California basins, certain fjords, and Santa Barbara basin, there is no macrofauna disturbing the sediment. In such environments the sedimentary pile is an uncomplicated record of the changing properties of the sequentially added materials, and *"Pb has proven to be an invaluable tool to confirm or establish a chronology. Once established, this chronology acts as a firm measure of the year by year changes in trace-metal supply to that basin. In coastal sedimentary basins (like Long Island Sound) that remain oxygenated at the sediment-water interface for most of the time, a lush macrofauna exists. The burrowing and related activities of these organisms strongly influence the vertical distribution of sediments and generally act to confound the simple chronology of accumulation. Although it is true that below the zone of biological mixing (or "bioturbation") time-averaged sedimentary properties are retained, the length of the intervals averaged may be longer than the resolution required for interpreting relatively recent events. The depths and rates of particle mixing in Long Island Sound sediments have been studied by Aller and Cochran (1976), Benninger et al. (1979), Aller et al. (1980), and Krishnaswami et al. (1980). Depth profiles of both 234Thand 'Be show that the top 4-5 cm of Long Island Sound sediments must be mixed rapidly in order to distribute these short-lived nuclides throughout this zone. The mixing process can be quantitatively described

154

K. K. TUREKIAN et a/.

by analogizing it to eddy diffusion. Then the steady-state distribution of a radioactive tracer in the sediments is given by the following equation: a2N dN Dg--S-AN = 0 az2 az where D Bis the particle-mixing coefficient, N is the number of atoms of nuclide of interest, S is the sediment accumulation rate, A is the decay constant, and z is the depth in the sediment column. [Porosity and the mixing coefficient are assumed to be constant in Eq. (6.1).] The effect of S on the solution to Eq. (6.1) depends upon its value relative to the rate of decay of the nuclide of interest. For short-lived nuclides like 234Th and 7Be, sediment accumulation is negligible over several half-lives and their distributions in the sediment column are governed by mixing and radioactive decay. For '"Pb (see later) this is not the case, and both mixing and sedimentation effects must be considered. Values of D, in surficial sediments of Long Island Sound have been determined from the distribution of 234Th(Aller et al., 1980); DB ranges (3-10) x cm2 sec-I. The fact that these values pertain to the upper few centimeters of sediment is shown from depth distributions of longer lived tracers. Such an example is shown in Fig. 25, which compares '"Pb profiles from two stations in the central Sound. In both cases, the "OPb activity is nearly constant in an upper zone of 4-10 cm and decreases quasi-exponentially below. One interpretation of the decrease in '"Pb activities is that it is due to sediment accumulation alone. Rates of 0.1-0.6 cm yr-' are calculated from the profiles. However, this explanation cannot be valid if the average rate of accumulation of 0.033 cm yr-' for the central Sound (Bokuniewicz et al., 1976; see Gordon, this volume) is taken as typical of present accumulation rates. Indeed, the presence of Pu in the zone of "OPb decrease in one of these cores (NWC-102975:Benninger et al., 1979) suggests that both sediment accumulation and mixing are important in producing the observed 'I0Pb distributions. Benninger et al. (1979) used the Pu profile in core NWC-102975 to calculate a DB of -2 x cm' sec-' below the surficial mixed zone (Fig. 26). This is at least an order of magnitude less than values obtained for the top few centimeters using 234Th. Using the calculated mixing coefficients for a rapidly mixed surficial layer and a more slowly mixed deep layer, Benninger et al., (1979) were able to reproduce the observed "OPb profile. On the basis of this analysis, the interpretation of exponential decrease in 'IOPb Long Island Sound sediments as reflecting a sediment accumulation rate (see e.g., Thomson et al., 1975) is not valid, and the effects of mixing may be dominant. Extending this concept of particle mixing by organisms further, it is

NUCLIDES IN LONG ISLAND SOUND

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FIG.25. The 2’0Pb“rates” of accumulation for cores at NWC-102975 and DEEP-102375 (see Fig. 1la for locations). The highest “rate” also has the highest standing crop of *“Pb. The 210Pbversus depth plot, which formally yields a “rate,” is inferred to be due primarily to biological mixing. (Data from Benninger ef al., 1979 and unpublished results obtained at Yale University.)

possible to imagine mixing rates continuing to decrease with depth in the sediment column. Figure 27 shows the effect such a pattern will have on depth profiles of nuclides with different half-lives where mixing rates are assumed constant over discrete sediment layers. In addition to eddy diffusion-like mixing of sediment, Fig. 27 also shows the existence of singlemixing events by deep burrowers that bypass concentration gradients and result in tracer input below a zone of continuous mixing. This is an explanation of the “spikes” of metal and ’‘OPb concentrations observed by Thomson et al. (1975) and Benninger et al. (1979) at depths well below the beginnings of the anthropogenic trace-metal imprint on Long Island Sound. After a long enough period of time, there will be a distribution of trace metals and long-lived man-made radionuclides like plutonium and the bomb-produced component of the ‘4C burden to yield a mixing coefficient for long-term, deep-particle mixing. The fact that this deep bioturbation rate constant is considerably smaller

156

K. K.TUREKIAN et a/.

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FIG. 26. Approximate best fits to normalized 239.240Pudata (filled circles) assuming Pu transport in layer 2 by particle "diffusion" only. Co, concentration (dpdcm') in depth interval 0-2 cm. Layer 2 begins at (a) x = LI = 2 cm and (b) x = LI = 3 cm; in (b) the Pu data are recalculated on the assumption that the Pu concentration is uniform over 0-3 cm. For both (a) and (b) particle diffusion is considered to stop at x = Lz = 10 cm. Solid and broken curves represent two different boundary conditions for the top of layer 2. Solid inventory in 0-10 curve: C, const. = Co,0 < x < LI for all t 2 0. Broken curves: 239.240Pu cm of core NWC-102975 contained in 0 < x < LI at t = 0, with no further addition of Pu. t = 0 is taken to be 1965, so that the time available for diffusive transport is 10 yr. (From Benninger et al., 1979.)

than the near-interface values can be seen by comparing the I4Clong-term rate of accumulation with the expected geophysically determined rate. Such a study was made by Benoit et al. (1979) on the same core analyzed by Benninger et al. (1979). Figure 28 shows the I4Cdistribution with depth in the organic fraction of the core, sampled with the aid of x-radiography to avoid obvious low density and recent burrows. The samples showed no *loPbor trace-metal spikes and therefore would not be expected to show any bomb I4C spikes. Another factor, however, rules out the possibility of observing too high a spike even if near-surface sediments were transported into the deep burrows; the I4C-rich planktonic material is metabolized rapidly in the strongly bioturbated zone of the upper 5 cm of the sediment pile. [Benoit et al. incorrectly estimated a residence time of this carbon source of about 24 days in their paper. The correct residence time is about two years (Turekian et al., 1980).] The carbon preserved in the sediment column is refractory organic matter probably mainly derived from land as evidenced by its 2300 yr BPage at the time of deposition. The I4C rate of accumulation determined for this core is about 0.07 cm yr-I, which is not very different from the geophysically estimated rate for this location of 0.06 cm yr-'. Nevertheless, the figure is higher than the rate of 50.05 cm yr-' calculated from "OPb and plutonium systematics (Benninger et al., 1979) and may indicate that the rate of accumulation

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is lower than that calculated by ignoring the effect of deep bioturbation on the l4C profile. 6.2. Determination of the Final Repository of Metals Introduced into Long Island Sound

An additional effect of the rate and depth of long-term mixing is seen in the 210Pbprofiles in Fig. 25: As the rate and depth of mixing increase so does the integrated amount of '"Pb in the core. This is also seen by plotting the integrated '"Pb activity as a function of the apparent sediment accumulation (largely dominated by mixing) in cores from a traverse from New Haven to Long Island (Fig. 29). The geophysically determined sediment accumulation rates do not vary by more than a factor of 2, but the '"Pb apparent rates vary by a factor of at least 6. Although it is possible that the 210Pbdata represent true differences in local sediment accumu-

158

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NUCLIDES IN LONG ISLAND SOUND

159

lation rates obscured by the geophysical survey, the more likely reason for this disparity appears to lie in the spatial variability in rates of deep burrowing. Excavation of deep burrows and their subsequent infilling exchanges 210Pb-and metal-poor older particles for 'IoPb- and metal-rich surficial, younger particles. Rapid turnover of the upper 4-5 cm of the sediment column by resuspension and lateral mixing of fine-grained sediments provides a continuing source of "OPb- and metal-rich particles. Slower turnover of the deeper sediment horizons results in storage of these particles in the areas of the bottom where deep burrowing is intense. These variations in mixing depth and intensity are consistent with the kinds of macrofauna dominating along the transect (McCall, 1977; Aller, this volume). Another expression of this is found in the copper distribution in the upper parts of cores along the transect (Fig. 30). Sampling at 1-cm intervals shows that the copper distribution with depth differs across the Sound. FOAM-I, which shows little or no deep bioturbation, shows a sharp decrease in Cu and a small average concentration, whereas DEEP1, at the other extreme, is marked by a consistently high concentration of Cu at all depths sampled, indicating deeper bioturbation. The two NWC cores occupy intermediate positions. From these insights we conclude that the total burden in the sediment pile of a substance introduced at the sediment-water interface over a period of time will depend on the rate and depth of mixing. Rapid mixing to great depths will yield a higher total burden of the substance introduced isotropically into the Sound than mixing limited to very shallow depths in the sediment pile. Thus, the final repositories of metals in Long Island Sound depend not only on their association with the fine-grained fraction and the extent of its horizontal homogenization, but also on the spatial variability in depth and rate of vertical particle mixing that govern the total integrated metal content in the sediment column. 6.3. Major Sources of Metals Delivered to Long Island Sound From our knowledge of what controls the distribution of *'OPbin Long Island Sound sediments we can test the following question: How much of the trace-metal content of Long Island Sound sediments may be explained by an atmospheric source and how much by supply from injections along the coast by sewer outfalls and polluted streams? To answer the question, we integrate the total excess "OPb in a core and compare it with the integrated excess metal content. Benninger (1978) has shown that the 2roPbcontent in Long Island Sound sediment is due predominantly to atmospheric supply and that there is no loss from the Sound. We then

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TABLE111. TOTALEXCESSMETALTO EXCESS"'Pb STANDING-CROPRATIOSFOR SALTMARSHAND LONGISLAND SOUND DEPOSITS Total excess metal (pg cm-') to "'Pb standing crop (dpm cm-') Location Farm River salt marsh (Branford, Connecticut) Long Island Sound sediment cores Station NWC Station TTM-2

CuP'OPb

ZnI2"Pb

Pb?"Pb

13

19

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12 11

compare the ratio of integrated excess trace-metal content to integrated 210Pbcontent found in sediment cores to the same ratio found by McCaffrey (1977) and McCaffrey and Thomson (this volume) in the Farm River salt marsh. This normalization overcomes the problem of both horizontal and vertical mobility in the sediment so long as the excess metals are confined to the same depth horizons that contain excess 2'0Pb. (This is possible because the intense human mobilization of metals began about 100 years ago, which is also the range of '"Pb excess.) When such a calculation is made for two cores (Table HI),one analyzed by Thomson et al. (1975) and the other by Benninger et al. (1979), it shows that all the Pb could be explained as of atmospheric origin, and half the zinc and copper. Presumably the additional burden of zinc and copper comes from the coastal high metal-particle sources discussed earlier. 7. SUMMARY

Our observations about the distribution of trace metals in Long Island Sound, as elucidated by our studies of the behaviors of 234Thand "OPb, lead us to the following generalizations: (1) Comparison of trace-metal distribution maps for Cu, Zn, and Pb with a sediment grain-size map shows that the primary control is the association of Cu, Zn, and Pb with the fine-grained fraction. (2) Imprinted on this feature is the increase in concentration of these trace metals near metal-polluting sources such as the Housatonic River and the East River (in New York). Thus, although the association of trace metals with the fine-grained fraction is established, the complete homogenization of this fraction does not proceed fast enough to obliterate intensive local sources of metals. (3) 234Th,produced by the decay of 238Udissolved in seawater, is re-

162

K. K.TUREKIAN e l a/.

moved to the sediments on a very rapid time scale (with a mean residence time in the water column of less than 10 days). The distribution of 234Th in the upper few centimeters of sediments throughout Long Island Sound is controlled by the amount of fine-grained material (identified either by percent loss on ignition or 232Thconcentration), similar to the trace metals. The lack of a positive correlation between the integrated 234Thactivity in the sediments and water depth implies that the fine-grained component tends to be homogenized on a rapid time scale, at least over distances that include a range of depths of water. However, the preservation of trace-metal patterns that reflect local pollution sources suggests that homogenization, although rapid, is not basin wide. (4) In a north-south transect across the Sound, the long-term sediment accumulation rate (based on the sediment thickness to a reflecting horizon inferred to correspond to 8000 years ago) varies by no more than a factor of 2. The "sediment accumulation rates" formally calculated from the exponential decrease of excess '"Pb with depth in cores along this traverse are at least a factor of 2 greater than the long-term rates and vary by an order of magnitude, with the higher values toward the deeper parts of the Sound. We infer that these exponential curves are dominated by particle mixing by infauna which transport 'IOPb deep into the sediment pile. ( 5 ) There is a direct correlation between the formal 210Pb"sediment accumulation rate" and the total standing crop of excess '"Pb in the sediment column. This indicates that although the top centimeter of the sediment core is homogenized on a rapid time scale, the rate and depth of bioturbation determine the amount of storage of "OPb in the sediment column at different locations in the Sound. Examination of macrofauna in the cores studied supports the argument for the biological control on '"Pb inventories. Areas of high *IOPbinventory are characterized by deeper mixing by infauna than are sediments with low 210Pbinventory. (6) The general pattern is seen for copper and by inference for other metals and thus can be used to predict the long-term repositories of trace metals injected since the beginnings of marked human use of metals. (7) Scaling the measured "OPb atmospheric flux in the region to the total atmospheric flux of metals over the past 100 years as determined in a salt marsh, the relative contributions of atmospheric and stream and sewage supply of metals to the Sound sediment can be estimated. In two cores so analyzed, all of the lead is inferred to be of atmospheric origin and about half of the copper and zinc. These proportions can be expected to vary westward along the axis of the Sound as local source terms from municipal and industrial pollution become more important. Thus, in relatively sheltered Long Island Sound, the long-term storage

NUCLIDES IN LONG ISLAND SOUND

163

of anthropogenically mobilized trace metals that became associated with fine-grained material is most affected by the rate and depth of biological particle reworking. In less protected areas such as the New York Bight, the role of physical disruption and redistribution becomes more important. ACKNOWLEDGMENTS This research has been supported mainly by the Department of Energy through grant EY75-5-02-3573. The United Illuminating Company also provided some financial assistance. Acknowledgment is also made to the donors of the Petroleum Research Fund administered by the American Chemical Society.

REFERENCES Aaboe, E., Dion, E. P., and Turekian, K. K. (1980). Be-7 in Sargasso Sea and Long Island Sound waters. J . Geophys. Res. (submitted). Aller, R. C., and Cochran, J. K. (1976). *'4Th?'"U disequilibrium in nearshore sediment: Particle reworking and diagenetic time scales. Earth Planet. Sci. Lett. 29, 37-50. Aller, R. C., Benninger, L. K., and Cochran, J. K. (1980). Tracking particle-associated processes in nearshore environments by use of 234Th?38Udisequilibrium. Earth Planet. Sci. Lett. 47, 161-175. Applequist, M. D., Katz, A., and Turekian, K. K. (1972). Distribution of mercury in the sediments of New Haven (CT) Harbor. Environ. Sci. Technol. 6 , 1123-1124. Benninger, L. K. (1976) The use of uranium-series radionuclides as tracers of geochemical processes in Long Island Sound. Ph.D. Thesis, Yale University, New Haven, Connecticut. Benninger, L. K. (1978) *"Pb balance in Long Island Sound. Geochim. Cosmochim. Acta 42, 1165-1174. Benninger, L. K., Lewis, D. M., and Turekian, K. K. (1975). The use of natural Pb-210 as a heavy metal tracer in the river-estuarine system. In "Marine Chemistry in the Coastal Environment" (T. M. Church, ed.), pp. 202-210. Am. Chem. SOC.Symp. Ser. 18. Benninger, L. K., Aller, R. C., Cochran, J. K., and Turekian, K. K. (1979). Effects of biological sediment mixing on the '"Pb chronology and trace metal distribution in a Long Island Sound sediment core. Earth Planet. Sci. Lett. 43, 241-259. Benoit, G. J., Turekian, K. K., and Benninger, L. K. (1979). Radiocarbon dating of a core from Long Island Sound. Estuar. Coastal Mar. Sci. Bokuniewicz, H. J., Gebert, J., and Gordon, R. B. (1976). Sediment mass balance in a large estuary (Long Island Sound). Estuar. coastal. Mar. Sci. 4, 523-536. Carmody, D. J., Pearce, J. B., and Yasso, W. E. (1973). Trace metals in sediments of the New York Bight. Mar. Pollut. Bull. 4, 132-135. Curran, D., Benninger, L. K., and Turekian, K. K. (1980). Metals, "'Pb and *"Pb in the soft tissue of the blue mussel (Mytilus edulis) as a function of location along the northern shore of Long Island Sound. In preparation. Feng, S.Y., and Ruddy, G. M. (1974). Zn, Cn, Cd, Mn, and Hg in oysters along the Connecticut coast. In "Final Report to office of Sea Grant Programs by the University of Connecticut Marine Sciences Institute," pp. 132-161. Gibbs, R. J. (1967). The geochemistry of the Amazon River System, Part I: The factors that control the salinity and the composition concentrations of suspended solids. Geol. SOC. Am. Bull. 78, 1203- 1232.

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Goldhaber, M. B., Aller, R. C., Cochran, J. K., Rosenfeld, J. K., Martens, C. S., and Berner, R. A. (1977). Sulfate reduction, diffusion and bioturbation in Long Island Sound sediments. Report of the FOAM group. Am. J. Sci. 277, 193-237. Greig, R. A., Reid, R. N., and Wenzloff, D. R. (1977). Trace metal concentrations in sediments from Long Island Sound. Mar. Pollut. Bull. 8, 183-188. Gross, M. G. (1976). Sources of urban waste. I n “Middle Atlantic Continental Shelf and the New York Bight” (M. G. Gross, ed.). Am. SOC.Limn. Oceanog. Spec. Symp. Ser. 2, pp. 150-161. Kaufman, A., Li, Y. H., and Turekian, K. K. (1980). The removal rates of Z34Thand 228Th from waters of the New York Bight. Earth Planet. Sci. Lett. (in press). Krishnaswami, S., Benninger, L. K., Aller, R. C., and Von Damm, K. L. (1980). Atmospherically-derived radionuclides as tracers of sediment mixing and accumulation in nearEarth Planet. shore marine and lake sediments: Evidence from ’Be, ”‘Pb, and 239.240Pu. Sci. Lett. 47, 307-318. Lazrus, A. L., Lorange, E., and Lodge, J. P., Jr. (1970). Lead and other metal ions in precipitation. Environ. Sci. Technol. 4, 55-58. Lewis, D. M. (1977). The use of ”‘Pb as a heavy metal tracer in the Susquehanna River system. Geochim. Cosmochim. Acta 41, 1557-1564. McCaffrey, R. J. (1977). A record of the accumulation of sediment and trace metals in a Connecticut, U.S.A., salt marsh. Ph.D. Thesis, Yale University. McCall, P. L. (1977). Community patterns and adaptive strategies of the infaunal benthos of Long Island Sound. J. Mar. Res. 35, 221-266. Nozaki, Y., Thomson, J., and Turekian, K. K. (1976). The distribution of ’“Pb and ”*Po in the surface waters of the Pacific Ocean. Earth Planer. Sci. Let?. 32, 304-312. Sholkovitz, E. R. (1976). Flocculation of dissolved organic and inorganic matter during the mixing of river water and sea water. Geochim. Cosmochim. Acta 40,831-845. Thomson, J., Turekian, K. K., and McCafTrey, R. J. (1975). The accumulation of metals in and release from sediments of Long Island Sound. I n “Estuarine Research” (L. E. Cronin, ed.), Vol. 1, pp. 28-44. Academic Press, New York. Turekian, K. K. (1971). Rivers, tributaries and estuaries. I n “Impingement of Man on the Ocear,” (D. W.Hood, ed.), pp. 9-73. Wiley, New York. Turekian, K. K. (1979). Trace metals. I n “New Haven Harbor Ecological Studies.” Summary Report-United Illuminating Report to Connecticut Dept. of Environmental Protection. Turekian, K. K., Berner, R. A,, and Gordon, R. B. (1972). Marine sediments, New Haven harbor, Connecticut: Results of analyses and proposals for dredge spoil disposal: Addendum 12 of Environmental Report, Coke Works Site, June 1971. (Conducted for the United Illuminating Co. and coordinated by Normandeau Associates, Inc.) Turekian, K. K., Kharkar, D. P., and Thomson, J. (1974). The fates of ”‘Pb and ’“Po in the ocean surface. J. Rech. Atmos. 8, 639-646. Turekian, K. K., Benoit, G. J., and Benninger, L. K. (1980). The mean residence time of plankton-derived carbon in a Long Island Sound sediment core: a correction. Estuar. Coastal Mar. Sci. 11 (in press). Volchok, H. L., and Bogen, D. (1971). Trace metals-fallout in New York City. I n “Health and Safety Laboratory Fallout Program Quarterly Summary Report.” U.S.A.C.E., April I , 1971, New York.