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CONTAMINATION OF THE HUDSON RIVER The Sediment Record Richard F. Bopp and H. James Simpson Lamont-Doherty Geological Obervatory of Columbia University e ABSTRACT Measurements of natural and man-made radionuclides have been used to trace fine-grained sediment accumulation throughout the Hudson River system. The results, when com- bined with measurements of particle-associated pollutants, such as PCBs, chlorinated hydrocarbon pesticides, and trace metals, provide information on the sources, transport, dis- tribution, history, and fate of these contaminants. This technique has proven quite useful for monitoring contaminant levels in natural water systems and assessing the effect of various remedial actions, particularly the "no-action" alter- native. INTRODUCTION For over a decade, geochemists have studied the history of contami- nation of natural water systems with particle-reactive pollutants by using radioactive tracers to establish a time scale of sediment accu- mulation. Early practitioners of this technique have investigated poly- chlorinated biphenyl (PCB) and DDE accumulation in the Santa Barbara Basin (Hoary et al., 1974~; the accumulation of fallout radionuclides in Lake Michigan sediments (Robbing and Edgington, 1975~; trace metal pol- lution in Narragansett Bay, Chesapeake Bay, and the Savannah River Estuary (Goldberg et al., 1977, 1978, 1979), and kep one contamination of the James River (Cutshall et al., 1981~. Our work on contaminated Hudson River sediments has relied primar- ily on measurements of a few naturally occurring and man-made radio- nuclides that have a high affinity for fine-grained particles and thus serve as tracers for both recent sediment and sediment-associated pol- lutant accumulation. Cesium-137 (Cs-137) and Plutonium-239,240 (Pu- 239,240) are both derived from global fallout resulting from atmos- c, _~ rid Measurable fallout began in about 1954 and peaked in 1963 (Hardy et al., 1973~. An additional source of Cs - 137 to the lower 60 mi of the Hudson system is effluent from the Indian Point nuclear reactors (Figure 1), which began operation in the mid 1960s and had a maximum release in 1971 (Booth, 1975~. This source also contributes measurable amounts of Cobalt-60 (Co-60) to the sys- tem. A particularly useful natural radionuclide is Beryllium-7 (Be-7), ~ pheric testing of nuclear weapons. 401

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402 FIGURE 1 A map of the Hudson River with sediment core locations designated by mile point (mp). PC B INPUT _ ~ ~ ( DAM REMOVED ) mp 188.5 UPPER HUDSON Go R IVER FEDERAL ~ DAM mp 143.4 mp 91.8 m p 88.6 1( mp 53.8 ;' INDIAN POI NT REACTOR SITE . 11 /: ~ NEW YORK CITY ~ 1~ mp-~ 65;~: 0 20 I_. I I Miles which is produced in the atmosphere via cosmic ray-induced spallation of oxygen and nitrogen. It reaches the surface of the earth primarily via precipitation and has a half-life of about 53 days. Because of this relatively short half-life, measurable Be-7 is generally confined to near-surface sediments deposited within about a year prior to analysis. The particle-associated pollutants we have analyzed in Hudson sedi- ment samples include PCBs, chlorinated hydrocarbon pesticides, and trace metals. A major source of PCBs to the system was discharges from two General Electric (G.E.) company capacitor manufacturing facilities in the upper part of the drainage basin (Figure 1) over the period between about 1950 and 1976. Another significant source of PCBs to the system is wastewater discharges, which are dominated by inputs from the New York metropolitan area (Mueller et al., 1982; Figure 1~. Chlori- nated hydrocarbons analyzed include DDT-derived compounds and chlor- dane, while trace metal analyses focused on copper (Cu), lead (Pb), and zinc (Zn). For both classes of compounds, a strong New York metropoli- tan area source is indicated by the sediment data. Detailed descriptions of the sampling and analytical procedures used in the work described below can be found in Bopp (1979), Olsen (1979), and Williams et al. (1978~. Sediment cores were sectioned at 2- to 4-cm intervals with 0 cm defined at the sediment-water interface. Control Number (CN) designations unambiguously identify a particular core and are reported in all publications from this laboratory. Loca- tions on the Hudson River are given in mile points that correspond to

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403 the number of statute miles upstream of the southern tip of Manhattan measured along the axis of the channel (Figure 1~. All contaminant concentrations and radionuclide activities in sediment samples are re- ported on a dry weight basis. RADIONUCLIDES IN HUDSON RIVER SEDIMENTS The advantage of combining sediment contaminant analyses with meas- urements of independent indicators of the time of deposition results from the heterogeneity of net sediment accumulation rates observed over short distances in natural water systems. Net sedimentation rates in the Hudson River range from less than 1 mm per year in much of the natu- ral channel to more than 10 cm per year in some dredged areas of New York Harbor (Olsen, 1979; Bopp, 1979~. Coarse resolution "dating," where the presence of Cs-137 in a sediment sample indicates a signifi- cant component of post-1954 deposition, has proven quite useful for establishing first order budgets for sediments and associated contami- nants in the Hudson. It has been applied to fine particles (Olsen et al., 1984-85), trace metals (Williams et al., 1978; Bower et al., 1978), and PCBs (Bopp et al., 1981~. Occasionally, cores were collected that could be dated in more detail. Most often, such cores exhibited interpretable Cs-137 profiles, penetrating to the first appearance of that radionuclide (1954) and reaching a midcore maximum Cs-137 level (1963) which then decreases toward the sediment-water interface (the date of coring). The interpretation of such sediment profiles can often be supported by data on other radionuclides, such as measurements of fallout Pu- 239,240 that yield a similar distribution with depth in the core, Be-7 determinations to provide a constraint on very recent rates of sediment accumulation, and, when downstream of mp 60, detection of a second Cs- 137 maximize that can be associated with the 1971 release from the In- dian Point nuclear reactors (Figure 1, Table 1~. This second maximum can be unambiguously identified by the presence of reactor-derived Co-60, an excellent marker for post-1971 sediment deposition in the lower Hudson (Simpson et al., 1976; Olsen et al., 1978; Bopp et al., 1982~. Ideal cores with continuous records of sediment deposition over the past few decades are relatively rare as a result of both natural disturbances, including large storms and other resuspension events, and human intervention, particularly dredging. Fortunately, when such cores are collected they have large enough net sediment accumulation rates (on the order of 1 cm per year or more) to prevent biological or tidal current mixing in the Hudson from significantly altering the sediment-associated radionuclide and contaminant profiles (Olsen et al., 1981~. From our collection of over 200 Hudson River sediment cores, we have found about 20, spanning the system, with radionuclide profiles that indicate a continuous record of sediment accumulation. Several examples are given in Table 1, and a few others were discussed by Bopp et al. (1982~. More recent sediment core data is shown in Figure 2. The core at mp 188.5 (ON 1852) was taken about 10 mi downstream of the

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404 TABLE 1 The Bases for Establishing the Timescale of Sediment Accumulation in Selected Hudson River Cores Location Date of (mp) collection Principal time indicators Reference - 188.5 July 1983 Fallout Cs-137 Figure 2 CN 1852 (1954, 1963) 143.4 July 1977 dredge boundary Bopp et al., 1982 CN 1298 (1972) 91.8 July 1977 Fallout Cs-137 and Bopp et al., 1982 CN 1329 Pu-239,240 (1954, 1963) 88.6 July 1986 Fallout Cs-137 (1954, Figure 2 CN 1984 1963); Be-7 53.8 January 1977 Fallout Cs-137 and Pu- Bopp et al., 1982 CN 1240 239,240 (1954-1963) and reactor Cs-137 and Co-60 (post-1971) 3.0 September Fallout Cs-137 and Bopp et al., 1982 CN 1380 1975 Pu-239,240 (1954, 1963); reactor Cs- 137 and Co-60 (post-1971) -1.7 September Fallout Cs-137 and Figure 2 CN 1472 1979 Pu-239,240 (1954, 1963); reactor Cs-137 and Co-60 (post-1971) -1.65 July 1984 CN 1923 Be-7; reactor Co-60 Figure 2 (post-1971) PCB inputs from the G.E. capacitor plants. This reach of the Hudson is characterized by a series of dams, the southernmost being the Federal Dam at mp 154. Downstream of this dam, the Hudson is a tidal system. The core at mp 88.6 (CN 1984) was collected in 1986 and was used to complement contaminant chronologies developed from a mp 91.8 core (CN 1329) collected in 1977 (Bopp et al., 1982~. The core at mp -1.7 con- tained measurable Co-60 in the top five samples, confirming the assign- ment of the upper Cs-137 maximum to releases from the Indian Point nuclear reactors. The 8-cm penetration of Be-7 in the mp -1.65 core indicates very rapid sediment accumulation (several cm per year) con- firmed by the detection of reactor-derived Co-60 to a depth of at least 50 cm. These two cores were used to develop contaminant chronologies

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405 Cs- 137 (pCi/g) FIGURE 2 Profiles of radionuclide TO 20 activity versus depth in some ~ , Hudson River sediment cores. ~ls~NG~E 20 tar (?) _ ~e 1963 . ~^ Ml~tD 40; 5aNDY mp 188.5 ( JULY 1983) - E 2c I , 4 C , L mp-1.7 60 t SEPT 1979) Cs-137 (pCi/g) Cs - 1 37 ~ pCi/g ) 0.5 1.0 I ~ ~ ~5 197 1 ,~ - ~ BLACK MUD ., SANDY ~ RE D CLAY mp 88.6 (JU LY 1986) ~ 1963 Be-7 (pCi/g) 2 4 ~-~ ~ 1 1984 963 10 ~ 1 954 20 _ 3C _ mp - I 65 JULY 19~34) for New York Harbor sediments from the mid 1950s to 1984. The radionuclide tracers in such cores can be used to determine levels of sediment contamination as a function of time at various loca- tions on the river (Bopp et al., 1982~. We estimate the uncertainty on the time of deposition for any given sample at approximately +2 years to account for possible changes in sediment accumulation rates in short time scales and the possibility of gaps in the depositional record between the individual radionuclide-based stratigraphic markers. POLYCHLORINATED BIPHENYLS Commercially used PCBs are mixtures of up to several dozen distinct congeners that vary in degree of chlorination and the arrangement of chlorine atoms on the molecules. An individual PCB congener may con- tain between one and ten chlorine atoms per molecule, but the particu- lar mixtures most used at the G.E. capacitor plants on the upper Hudson River (NYSDEC, 1975), designated Aroclor 1242 and Aroclor 1016, are dominated by di, tri, and tetrachlorobiphenyls with Aroclor 1242 also containing about 10 percent penta and hexachlorobiphenyls (Webb and McCall, 1973~. Throughout the Hudson River system, dated sediment cores show a maximum in total PCB concentration in the early to mid 1970s. This feature, shown in Figure 3 and for some additional cores in Bopp et al. (1982) has been attributed to the removal of a dam in 1973 that had pro- vided the first impoundment of water downstream of the G.E. discharges (Figure 1~. The dam removal destabilized large amounts of highly con- taminated sediments that were transported downstream in the fall of 1973 and with the unusually high runoff the following spring (Helling,

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406 FIGURE 3 Total PCB concentrations in Hudson River sediment cores ver- sus time of deposition. For all cores except mp 188.5, PCB concen- trations were based on measurements of 22 components resolved by packed- column gas chromatography (Webb and McCall, 1973~. For samples from mp 188.5, quantification was based on three PCB congeners that were ob- served to be highly persistent (i.e., resistant to dechlorination) in another core from the same cove (core 18-6, Brown et al., 1984~. This second core had a similar pro- file of total PCB concentrations as determined by quantification of all major congeners present (Brown et al., 1984; Bopp et al., 1985~. ppm PC B s Inn Innn Leon '~ ~~ ~ 198C x 197C o a: Q 1960 l gboL `~ 1 980 a: x 1970 o cr ~ 1 960 x I 950L an X' ~x/ I I o 143.4 ( X5) [x 188.5 ox X _ / /x o 88.6 x 91.8 ppm PCBs 1 0 20 30 5 1 0 15 _\ O xO~ ~ ~x' (-x X=x ox _ x~ MA _~ XX 53.8 l - ,x,x fix et al., 1978~. The maximum observed PCB concentration in sediments decreases with distance downstream from the former dam, reaching over 1,000 ppm in the upper Hudson. In the tidal Hudson, maximum observed concentrations range from about 100 ppm a few miles downstream of the Federal Dam to about 8 ppm in New York Harbor sediments. PCB Composition 0 -~.65 x-l.7 1 With the exception of the core at mp 188.5, the composition of sedi- ment-associated PCBs observed near this maximum closely resembles that of Aroclors 1242 and 1016. The composition of PCBs in sediments at mp 188.5 is shifted dramatically toward lower chlorinated biphenyls. This has been attributed to bacterially mediated anaerobic dechlorination of PCBs (Brown et al., 1984) and has been observed in other highly contami- nated sediments upstream of the Federal Dam (Brown et al., 1984; Bopp et al., 1984~. While anaerobic dechlorination may occur in sediments of the tidal Hudson, it is certainly much less significant than in the more highly contaminated sediments of the upper Hudson. Based on PCB component analysis in dated sediment cores of the tidal Hudson, Bopp et al. (1984) found no evidence of significant compositional changes in PCBs during 20 years of anaerobic burial. Such observations could sig- nificantly influence management decisions related to systems with PCB contaminated sediments. Since dechlorination generally lowers the per- sistence of PCBs in organisms and thus decreases their chronic toxicity

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407 (Hansen, 1979), the occurrence of significant in situ dechlorination would be one factor supporting a no-action alternative, while a lack of significant dechlorination would argue in favor of dredging or other remedial action. Furthermore, bacterially mediated dechlorination shows considerable promise as a hazardous waste treatment technology (Roberts, 1987~. In the upper Hudson River, between the former dam site and the Federal Dam, several surface sediment samples and each of the 10 sus- pended matter samples collected in 1983 and 1984 had PCB compositions that closely resembled Aroclors 1242 and 1016 (Bopp et al., 1985~. This maintains the connection between G.E. discharges and PCB contamina- tion throughout the system, but implies significant isolation of the highly contaminated sediments of the upper Hudson that exhibit gross dechlorination of PCBs. In the tidal Hudson, the composition of PCBs observed in the sedi- ments is most affected by suspended matter-water partitioning, water to air transport, and inputs from the New York metropolitan area (Bopp, 1979, 1983; Bopp et al., 1981~. All of these factors tend to increase the average degree of chlorination of sediment-associated PCB compo- nents; however, even in New York Harbor sediments, the PCB composition closely resembles Aroclor 1242 (Bopp et al., 1981~. Sources of PCBs to New York Harbor Sediments Figure 4 shows the importance of New York metropolitan area inputs of the highly chlorinated PCB congeners. Since about 1970, levels of hepta, octa, and decachlorobiphenyls have been much higher in New York Harbor sediments (mp -1.65 and -1.7) than in upstream tidal Hudson sediments (mp 88.6 and 91.8), despite the fact that during the 1970s the upstream cores had total PCB levels about twice those of the harbor cores. Although these highly chlorinated congeners generally comprise less than 10 percent of the total PCBs in Hudson River sediment samples, their toxicological significance is magnified by the fact that they are most persistent in higher organisms and tend to increase in relative abundance along a food chain (Hansen, 1979~. The major problem in quantifying New York metropolitan area inputs of PCBs to the Hudson River lies in the limited number of analyses per- formed on sewage effluent and urban runoff. Simple mass balances and PCB component ratio analysis (Bopp et al., 1981) indicates that between 1971 and 1976 approximately 75 percent of the total PCBs deposited in New York Harbor sediments were derived from downstream transport and about 25 percent from local metropolitan area inputs. Detailed analy- sis of the cores at mp -1.65 and 88.6 indicates that by the mid 1980s, the relative importance of local sources had increased significantly. In 1984, both cores recorded total PCB levels of about 1.3 ppm and by 1986, the level in the mp 88.6 core had dropped to 0.8 ppm (Figure 5~. Since at peak levels the harbor core had about half the total PCB concentration of the upstream core, local New York metropolitan area inputs now appear to at least equal the downstream supply of total PCBs to New York Harbor sediments.

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408 FIGURE 4 Hepta + octachlorbiphenyl and decachlorobiphenyl concentra- tions in upstream tidal Hudson (mp 88.6 and 91.8) and New York Harbor HO (mp -1.65 and -1.7) sediment cores versus time of deposition. Quanti- fication of hepta + octachlorobi- phenyls are based on seven PCB com- ponents resolved by packed-column gas chromatography and the composi- tion of Aroclor 1260 (Webb and McCall, 19731. Decachlorobiphenyl quantifications are based on stan- dards prepared from the pure com- pound. LLI ~ 1 970 x o ~ 1960 Or 1980 llJ , 1970 x o 1960 Or 195C ppb HEPTA + OCTACHLOROBIPHENYLS o x x 100 200 300 1 00 200 300 , , , , , 1 o o of o _ oO X o oxx o 1 o 88.6 1 x x IX 91.8 1 _ ppb DECACHLOROBIPHENYL 0 20 30 , , , ) ~ _ ~ OX XX _ Xx X X xx ~ - x xx x xx _ X x Response Time To Pollution Events x x x x x x We believe that this situation is due primarily to the recovery of the system from the major pulse of PCBs associated with the dam removal in 1973 discussed above. Figure 5 shows details of the decrease in total PCB levels. At mp 88.6 concentrations over the last decade can be modelled rather well by a simple exponential decrease toward zero with a half-time of 3.5 years (Figure 4~. At mp -1.65, applying a similar time constant produces a curve that decreases asymptotically toward a value of about 0.5 to 0.7 ppm total PCBs. We interpret this "residual level" as resulting from local New York metropolitan area PCB inputs. This type of analysis was first employed by Bopp et al. (1982), who described the response of the system to two distinct types of pollution events involving sediment- associated contaminants. For pollutant inputs to the drainage basin, such as with fallout radionuclides or local DDT applications, a half- response time for Hudson sediments of about six to eight years was found. As would be expected, for pollutant inputs directly to the river, such as the pulse of PCBs associated with the 1973 dam removal, a much shorter half-response time was determined. Analysis of five sediment cores throughout the system gave half-response times of 1.3 to 3.8 years for PCB concentrations. This is in good agreement with the data presented in Figure 5, which is much more detailed than the ear- lier analysis and tracks the recovery for several additional years. o - 1.65 1 Ix -1 7 1 10 - 1.65 Ix - 1.7

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409 FIGURE 5 Detailed recent chronologies of total PCB concen- ations in sediments from an upstream tid- al Hudson core (mp 88.6) and a New York Harbor core (mp -1.659. 5 t0 is I I ~ O cr ~ ~ O ~ O x 1980 _ ~ 0 \ cr CL 1 970 _ 88.6 ppm PCB s t ~ 3. 5 y r s so To a` t '/2 - 3.5 yrs :~ (ASYM. to 0.5 ppm) o o -1.65 The natural cleansing of the river as indicated by decreasing sediment contaminant levels results both from burial of the most contaminated sediments and the removal of pollutants from the system with river dis- charge and associated suspended particle transport. PCB Budgets The PCB burden in sediments upstream of the Federal Dam and pos- sible remedial action in this reach of the river has been discussed in detail elsewhere (Sanders, this volume; Carcich and Tofflemire, 1982~. Although no PCB-directed remedial action has been planned for sediments of the tidal Hudson, we have identified two extensive depositional areas where such action is feasible. The first is New York Harbor. Based on average PCB concentrations and Cs-137 penetration depths in 16 sediment cores, Bopp (1979) estimated that about 23,000 kg of PCBs were associated with in situ sediments of New York Harbor. It was also esti- mated that an additional 37,000 kg of PCBs had been removed from the harbor as part of normal maintenance dredging and deposited on the shelf at the dredge spoil dump site about 11 mi from the mouth of the Hudson River. These estimates were considered accurate to about a fac- tor of two. The only other reach of the river identified as having significant recent sediment accumulation in the channel was near mp 90, where the river both widens and turns. From the only six cores avail- able at the time, an estimate of 12,000 kg of sediment-associated PCBs was obtained for the area from mp 85 to 93. Additional core collection in 1986 produced the coverage shown in Figure 6. Significant spatial heterogeneity of net sediment accumulation rates is indicated by the Cs-137 penetration depths given in centimeters by the numbers in paren- theses. From these data and the average recent sediment PCB concentra- tion of about 7 ppm observed in this region, our best (factor of two) present estimate is that about 21,000 kg of PCBs are associated with sediments of this reach. CHLORINATED HYDROCARBON PESTICIDES Chlorinated hydrocarbons, including DOT and chlordane, formed the

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410 FIGURE 6 A map of the Hudson River from mp 86 to 93. Sediment core loca- tions are marked with x's and labelled by mile point. Numbers in parentheses indicate the depth of penetration of Cs-137 in centimeters. it, /92.1 E {4 I 92.1M{/4) ~ if', ~X, ?~ x, 9 1.8 (36) ~1; /9 1 .7 {32} at' - ra 4(~ go,' X' , PORT E W E N l ' 90. 3 (32 J< \~89.5 it\ gs(/6J: X '\' V\ ~ ' \ ~88'6~ WAX 8 7, 9(>67J: ) \ ' i \ x\ X ~ X87.i(2~)S bloc ,*,Xf~ J {>64J ~ , A) J'x ` ,`86.s(8); lyre basis of our insect control strategy in the 1950s and 1960s. They are now well-known for their persistence and ubiquity in the environment. A DDT-derived compound found in recent sediments throughout the Hudson is pp'-DDD produced via anaerobic dechlorination of pp'-DDT carried out by bacteria. Pollution chronologies for this compound in Hudson sedi- ments (Bopp et al., 1982; Figure 7) are characterized by maximum values in the 1960s and early 1970s that decline significantly toward the present. This indicates the effectiveness of the ban on DDT use in the United States imposed by the U.S. Environmental Protection Agency (EPA) in 1972. Sediments from New York Harbor (mp -1.65 and -1.7) show much higher levels of pp'-DDD than sediments from mp 91.8 at comparable time horizons (Figure 7), however, other upstream cores (e.g., mp 53.8) have been found that reach peak levels of almost 100 ppb pp'-DDD (Bopp et al., 1982~. This suggests that both downstream transport, resulting from DOT applications in the drainage basin, and local New York metro- politan area inputs are significant contributors to the pp'-DDD contami- nation observed in New York Harbor sediments. Chlordane in New York Harbor sediments shows a similar profile. Peak levels of a major chlordane component, '-chlordane, were found in the 1960s and early 1970s. The mp -1.65 and -1.7 cores peak at about 48 ppb (Figure 7~. By the mid 1980s levels had decreased by more than 50 percent, to about 16 ppb in the above mentioned cores. This decrease is consistent with the banning of chlordane for most uses by the EPA in 1975. For chlordane, the dominance of New York metropolitan area inputs is most pronounced. Tidal Hudson sediments upstream of New York Harbor were always found to contain less than 5 ppb ,-chlordane with mid 1980s levels typically less than 2 ppb. Further discussion of chlori- nated hydrocarbon pesticide chronologies in the Hudson River can be found in Bopp et al. (1982~.

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411 FIGURE 7 Chronologies of pp'-DDD concentrations in sediments from an upstream tidal Hudson core (mp 91.8) and pp'-DDD and ,-chlordane concentration in sediments from New York Harbor cores (mp -1.65 and -1.7~. The most recent data point on the upstream (mp 91 . 8) pp'-DDD chronology is from the 0-2 cm sample of a core at mp 88.6 collected in 1986. This sample contained significant Be-7, indicating that it was deposited within about a year prior to coring. User Lo ~ 197C x o a: cat 196C TRACE METALS pp'- DDD (ppb ) 20 40 60 . , ~ I O`\ _ _ \ X- are OX X l X 1950 / mp 91.8 1980 In . 1970 x o Q 1 960 ISSO pp - DDD (ppb ) 50 1 00 1 50 8o 86`x x - x tax x x x~ ,x a - 1.65 x x -1.7 N.Y. HARBOR r- CH LO RDA N E (ppb) 40 80 120 O 00~ 0~` x x' _ ~ x ,x/ 10 I.6sl In 1 X -1.7 N. Y. HARBOR A characteristic of our industrial society is elevated levels of trace metals such as copper, lead, and zinc in sediments of natural water systems. Williams et al. (1978) described tidal Hudson sediment levels of these trace metals in teems of three end members: "old" (pre- industrial) sediment with average shale levels, recent (i.e., Cs-137 bearing) sediments upstream of New York Harbor, and recent New York Harbor sediments. Over the past two years, several of the cores in Table 1 have been analyzed to provide chronological data on the trace metal content of recent Hudson sediments. The results, shown for Cu and Pb in Figure 8, confirm the observations of Williams et al. (1978), that New York metropolitan area inputs dominate the sources of these metals to New York Harbor sediments. Average harbor sediment levels of Cu and Pb are more than twice as large as levels observed in upstream sediments of the tidal Hudson at comparable time horizons (Figure 8~. The other outstanding feature of this data is the recent decline in trace metal levels seen in sediments of the upstream tidal Hudson core (mp 88.6~. The drop of about 50 percent in Cu and Pb levels over the past decade could indicate recent decreases in the substantial indus- trial discharges of trace metals to the upper Hudson (Rohmann et al., 1985) or it could be related to the recent implementation of secondary treatment for sewage of the city of Albany, whose discharge is to the

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412 FIGURE 8 Chronologies of cop- per and lead concentrations in sediments from upstream tidal Hudson cores (mp 88.6 and 91.8) and New York Harbor cores (mp -~.65 and -1.7~. Results of replicate analyses of separate aliquots of sediment are shown for several sections of the mp -1.7 core. 1 98C car 1 97C x o or 1960 1950 1940 cr 1970 hJ x x x x x 1 960 o 195C 1 94C II-372 ppm COPPE R an an '~n 200 400 600 ~ '' 1 O8 ~ do o if,= O xx )o< x fo 88.61 Ix 91.8 1 ppm LEAD x ~ _ to -l 651 lx -1.7 1 200 400 600 x x x 0~; oo x )0< xx 34< xx INK xx x x x x -o 88.6 - 10 -1.65 x ~ x 91.8 lo -1.7 Hudson a few miles downstream of the Federal Dam. Similar trace metal results have been reported for a core at mp 46 (feller and Bopp, 1985~. This core also penetrated to pre-industrial sediment with Cu and Pb levels of about 25 ppm. Most curious is the lack of any substantial improvement in Cu and Pb levels in New York Harbor sediments over the past decade, as indi- cated by the data from cores at mp -1.65 and 1.7. This is particularly puzzling in the case of Pb. Mueller et al. (1982) report that waste- water, urban runoff, and downstream transport are the dominant sources of this metal to the lower Hudson. Improvements in sewage treatment between the early 1970s and 1982 (Mueller et al., 1982) should have decreased wastewater loading of Pb. The switch from leaded to unleaded gasoline, which produced a two-thirds decrease in atmospheric Pb deposi- tion in New York City between 1970 and 1980 (Freely et al., 1976; Toon- kel et al., 1980) should also have significantly decreased the urban runoff of Pb, and--as discussed above--our best estimate for the down-

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413 stream transport of Pb would be a decrease of 50 percent over the past decade. Despite these indications of decreases in loading, New York Harbor sediments show little or no recent improvement in Pb levels (Figure 8~. This apparent contradiction indicates the need for further research into the sources and behavior of trace metals in the lower Hudson and suggests that additional attention be paid to regulation of these important environmental contaminants. CONCLUSIONS AND RECOMMENDATIONS The case study of sediment contamination in the Hudson River demon- strates that the measurement of radionuclide time indicators is crucial to the interpretation of pollutant levels in sediments. We recommend that this technique be universally applied to particle-associated con- taminant monitoring and the assessment of related problems. We are con- tinuing this practice in detailed studies of adjacent systems, includ- ing Raritan Bay, Newark Bay, Jamaica Bay, and the nearshore coastal environment. Pollutant chronologies that can be developed from this technique are useful indicators of contaminant sources and can provide a detailed assessment of what is commonly called the "no-action" alternative. In the case of PCBs in the Hudson River, levels on particles transported downstream in the mid 1980s are several times lower than in the mid 1970s, despite continued postponement of the removal of the most highly contaminated sediments from the upper Hudson (i.e., no action). Assess- ment of our general nationwide efforts to limit pollution is also pos- sible. There is evidence that New York Metropolitan area inputs of PCBs to the Hudson have decreased recently, probably in response to EPA restrictions on the manufacture and use of PCBs in the United States in the late 1970s. Hepta, octa, and decachlorobiphenyl levels in New York Harbor sediments have declined by about a factor of two over the past decade (Figure 4), while the New York metropolitan area contribution to total PCBs in New York Harbor sediments was estimated at 0.8 ppm in the mid 1970s (Bopp, 1979) and 0. S to 0.7 ppm in the mid 1980s (Figure 5) . Restrictions on chlorinated hydrocarbon pesticide use in the United States promulgated by the EPA in the 1970s are most likely responsible for the recent decline in levels of pp'-DDD and chlordane in Hudson sediments (Figure 7~. Finally, with respect to trace metals, New York Harbor sediment chronologies indicate little or no recent improvement (Figure 8) despite recent upgrading of sewage treatment and restric- tions on lead in gasoline. This is a most direct recommendation for further study of the sources and fate of these contaminants, not only in the Hudson River, but in other major natural water systems as well. ACKNOWLEDGMENTS We would first like to thank our scientific and technical collabor- ators, Bruce Deck, Curt Olsen, Nadia Kostyk, Dave Robinson, Kathleen Ledyard, Charles Lester, Ellen Kalb, Yu-Pin Chin, Robert Trier, Sue

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414 Williams, Peter Kay and Linda Hubbard. Financial support for our pre- sent work on the Hudson is provided by the Hudson River Foundation. Past research efforts have been funded by the New York State Department of Environmental Conservation, the National Science Foundation, the National Oceanic and Atmospheric Administration, and the U.S. Envi- ronmental Protection Agency. This is LDGO contribution number 4342. REFERENCES Booth, R. S. 1975. A compendium of radionuclides found in liquid eff- luents of nuclear power stations. ORNL-TM-3801. Oak Ridge National Laboratory, Oak Ridge, Tenn. Bopp, R. F. 1979. The Geochemistry of Polychlorinated Biphenyls in the Hudson River. Ph.D. Thesis, Columbia University, New York. Bopp, R. F., H. J. Simpson, C. R. Olsen, and N. Kostyk. 1981. Poly- chlorinated biphenyls in sediments of the tidal Hudson River, New York. Environ. Sci. Technol. 15:210-216. Bopp, R. F., H. J. Simpson, C. R. Olsen, R. M. Trier, and N. Kostyk. 1982. Chlorinated hydrocarbons and radionuclide chronologies in sediments of the Hudson River and estuary, New York. Environ. Sci. Technol. 16:666-676. Bopp, R. F. 1983. Revised parameters for modeling the transport of PCB components across an air water interface. J. Geophys. Res. 88:2521-2529. Bopp, R. F., H. J. Simpson, B. L. Deck, and N. Kostyk. 1984. The persis- tence of PCB components in sediments of the lower Hudson. Northeast- ern Env. Sci. 3:180-184. Bopp, R. F., H. J. Simpson, and B. L. Deck. 1985. Release of Polychlor- inated Biphenyls from Contaminated Hudson River Sediments, NYS C00708 Final Report. New York State Department of Environmental Conservation. Bower, P. M., H. J. Simpson, S. C. Williams, and Y.-H. Li. 1978. Heady metals in the sediments of Foundry Cove, Cold Springs, New York. Environ. Sci. Technol. 12:683-687. Brown, J. F., R. E. Wagner, D. L. Bedard, M. J. Brennan, J. C. Carna- han, R. J. May, and T. J. Tofflemire. 1984. PCB transformations in upper Hudson sediments. Northeastern Env. Sci. 3: 166-178. Carcich, I. G. and T. J. Tofflemire. 1982. Distribution and concentra- tion of PCB in the Hudson River and associated management problems. Environ. Internat. 7:73-85. Cutshall, N. H., I. L. Larsen, and M. M. Nichols. 1981. Man-made radio- nuclides confirm rapid burial of kepone in James River sediments. Science 213:440-442. Feely, H. W., H. L. Volchok, and T. N. Toonkel. 1976. Trace Metals in Atmospheric Deposition. EML-308. Washington, D.C: Department of Energy. Goldberg, E. D., E. Gamble, J. J. Griffin, and M. Kiode. 1977. Pollu- tion history of Narragansett Bay as recorded in its sediments. EstuarO Coast. Mar. Sci. 5:549-561. Goldberg, E. D., V. Hodge, M. Kiode, J. Griffin, E. Gamble, O. P.

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