PCB Concentrations and Congener Composition in Macrophytes and Sediments in the St. Lawrence River near Cornwall,Ontario

PCB concentration and congener composition were examined in sediments and two species of macrophytes in the St. Lawrence River downstream of Cornwall, Ontario. Total PCBs in the macrophytes ranged from 37 to 585 ng/g dry weight, with biota to sediment accumulation factors ranging from 0.3 to 10. The floating-leaved species Nuphar variegatum had generally higher PCB concentrations than the submerged species Myriophyllum spicatum, but the latter had higher biota to sediment accumulation factors. N. variegatum also had a higher lipid content, but lipid levels were not a good predictor of plant PCB concentrations. Congener specific analysis showed congener patterns shifted between plants and sediments; macrophytes tended to have higher levels of tetrachlorobiphenyl congeners. Given that contaminant levels in plants reflect those found in the sediments, the high biomass of macrophytes within the river and particularly in Lake St. Francis represents an important reserve of PCBs which may be transferred to the herbivorous and detrital food webs.     

Organic Priority Pollutants in Nearshore Fish from 14 Lake Michigan Tributaries and Embayments, 1983

Composite, nearshore, whole fish samples of selected species, collected in fall 1983 from 13 Lake Michigan tributaries and Grand Traverse Bay, were analyzed for a wide range of pesticides and priority pollutants using gas chromatography-mass spectrometry. This study was carried out to identify existing source areas for known and previously unrecognized toxic substances. Our strategy was to analyze those resident fish with the highest likely levels of contaminants. All fish analyzed (eight species from southern Michigan to the upper peninsula) exceeded the 2 mg/kg FDA action levels for PCBs, while 50% of the samples exceeded the DDTr IJC objective of 1 mg/kg. St. Joseph River common carp (Cyprinus carpio) carried the heaviest contaminant burden of all fish examined for PCBs (27.6 mg/kg), DDTr (10.2 kg/mg), and toxaphene (3.3 mg/kg); chlordane levels (0.85 mg/kg) were second highest to those in Kalamazoo River common carp (0.87 mg/kg). Concentrations of PCBs, toxaphene, DDT, DDE, and other pesticides were higher in bottom-feeding fish, such as common carp, than in top predators, e.g., northern pike (Esox lucius). Bottom feeders are relatively fatty fish, and live and feed near contaminated sediments, which increases their potential to bioaccumulate fat-soluble contaminants. Pesticides were also present in elevated concentrations in fish from sites with higher industrial and agricultural development.     

Sedimentary records of non-Aroclor and Aroclor PCB mixtures in the Great Lakes

Three sediment cores from Lake Ontario, Lake Erie and Indiana Harbor Ship Canal were collected, segmented and analyzed for Aroclor and non-Aroclor polychlorinated biphenyl congeners (PCBs). PCBs associated with the commercially produced Aroclor mixtures 1248 and 1254 dominate the sediment signal and the sum of all congeners (∑ PCB) peaks in concentration and accumulation around 1970 in the Great Lakes. This trend is very similar to Aroclor production history. In the Indiana Harbor Ship Canal, PCBs appear around 1935 and remain at very high levels between 1940 and 1980, probably reflecting the history of use at the nearby steel mill. In contrast, the non-Aroclor PCBs in the Lake Ontario and IHSC sediment cores, including PCB11 and heavily chlorinated congeners PCB206, 207, 208 and 209 reach a peak in the 1950s, decline and peak again in the 1970s or in the early 1980s. All five congeners have been previously measured in commercial paint pigment. PCB11 was found to peak about 5 years later than ∑ PCBs, and is probably associated with the production or use history of diarylide yellow pigments. The temporal distribution profiles of these non-Aroclor PCBs are well correlated with the production history of paint pigments and dyes. Although it is well known that the production of Aroclor PCBs is preserved in Great Lakes sediments, this study is the first to show that production of non-Aroclors are also preserved in the sediments as a record of long term trends in environmental exposure.     

Impacts of channel morphology on residues and ecological risks of polychlorinated biphenyls in water and sediment in Chahe River

The impacts of channel morphology on the residues and ecological risks of 14 polychlorinated biphenyl(PCB) congeners in water and sediment were investigated in summer(July) and autumn(September) in the Chahe River,in Nanjing,China.The residual concentrations of trichlorobiphenyls(tri-CBs,PCB 18) and tetra-CBs(PCB 52) in water were significantly higher than those of penta-CBs to deca-CBs,and the average residual concentration of ∑PCBs(sum of 14 PCB congeners) in summer was about six times higher than in autumn.However,the residues in sediment did not change significantly.Redundancy analysis(RDA) indicated that channel morphology and the corresponding environmental indices had significant impacts on PCB residues and their composition profiles in water and sediment.The overflow weir and lake-type watercourse may remarkably reduce the residual concentration and ecological risks of PCBs in water.The highest reduction percentages of the residual concentration and ecological risks of ∑PCBs induced by an overflow weir were 78%and 67%,respectively,and those induced by a lake-type watercourse were 36%and 70%,respectively.The watercourses with different channel morphologies were ranked by residual ∑PCBs concentrations in the following descending order:the natural ecological watercourse,vertical concrete watercourse,and vegetation-type riprap watercourse.However,they were ranked by residual ∑PCBs concentrations in sediment in the following descending order:the vertical concrete watercourse,vegetation-type riprap watercourse,and natural ecological watercourse.     

Dioxin-like and non-dioxin like effects of polychlorinated biphenyls: Implications for risk assessment

Polychlorinated biphenyls (PCBs) are persistent, bioaccumulative and toxic contaminants in the environment. Individual PCB congeners exhibit different physicochemical properties and biological activities that result in different environmental distributions and toxicity profiles. The variable composition of PCB residues in environmental matrices and their different mechanisms of toxicity complicate the development of scientifically based regulations for risk assessment. Various approaches for the assessment of risks of PCBs have been critically examined. Recent developments in the toxic equivalency factor (TEF) approach for the assessment of toxic effects due to dioxin‐like PCBs have been examined. The PCB exposure studies that describe non‐dioxin‐like toxic effects, particularly neurobehavioural effects and their effective doses in animals, were compiled. A comparative assessment of effective doses for dioxin‐like and non‐dioxin‐like effects by PCBs has been made to evaluate the relative significance of non‐ortho and ortho‐substituted PCBs in risk assessment. Using mink as an example, relative merits and implications of using TEF and total PCB approaches for assessing the potential for toxic effects in wildlife were examined. There are several advantages and limitations associated with each method used for PCB risk assessment. Toxic effects due to coplanar PCBs occur at relatively smaller concentrations than those due to non‐dioxin‐like PCBs and, therefore, the TEF approach derives the risk assessment of PCBs in the environment. The need for the refinement of the TEF approach for more accurate assessment of risks is discussed.     

Chlorinated Contaminants in Surficial Sediments of Lakes Huron,St. Clair,and Erie: Implications Regarding Sources Along the St. Clair and Detroit Rivers

Surficial sediments from southern Lake Huron, Lake St. Clair, and Lake Erie have been analyzed for a broad spectrum of chlorinated organics including PCBs, chlorobenzenes, and several pesticides. The differences between sediment contaminant concentrations in Lake Huron and Lake St. Clair indicated sources of hexachlorobenzene, hexachlorobutadiene, octachlorostyrene, and several other chlorinated benzenes along the St. Clair River. Similar differences between sediment PCB concentrations in Lakes Huron/St. Clair and Lake Erie indicated major PCB sources along the Detroit River. Specific PCB congener analysis revealed that PCBs discharged to the Detroit River contained especially high concentrations of highly chlorinated hexa-, hepta-, and octachloro-biphenyls which are major constituents of the industrial mixture Aroclor 1260. The analysis of individual PCB congeners made it possible to trace PCBs of Detroit River origin to the central and eastern basins of Lake Erie, and to estimate the contribution of the Detroit River to the PCB burden in sediments of these basins.     

Horizontal and Vertical Distribution of PCBs in Southern Lake Michigan Sediments and the Effect of Waukegan Harbor as a Point Source

The spatial distribution of PCBs in southern Lake Michigan sediments was obtained from the analysis of 66 box cores and 8 grab samples. PCB concentrations in surficial sediments were closely related to sedimentation zone and to the oxidizable organic matter content of the sediments. Average surficial sediment concentrations ranged from 81 ng/g in depositional zones to 7.2 ng/g in non-depositional zones. The vertical distribution of PCBs was determined at several sites and was used to estimate the areal burden and flux of PCBs in each of the southern sedimentation zones. The total sediment PCB burden in the southern portion of the lake was estimated to be 5,900 kg. Southern Lake Michigan has received PCBs since approximately 1930 at an average flux of 7.1 μg/m² yr.The effect of Waukegan Harbor as a point source of PCBs to Lake Michigan was evaluated by comparing the PCB distribution and Aroclor composition of harbor sediments to those of sediments of decreasing distances from the harbor. Significant differences in total PCB concentration between non-depositional zones near the harbor and those in other areas of the basin indicate that Waukegan Harbor has influenced the PCB burden of Lake Michigan.     

Distribution and Bioaccumulation of Chlorinated Diphenyl Ethers in a Contaminated Embayment of Lake Ontario

Polychlorinated diphenyl ethers (PCDEs) are halogenated aromatic hydrocarbons that have structural similarities to polychlorinated biphenyls, dibenzo-p-dioxins, and dibenzofurans. PCDEs have been detected in piscivorus fish, fish eating birds and humans, but little is known about the transfer of these compounds through aquatic ecosystems. At sampling stations in the contaminated area of Whitby Harbour on the north shore of Lake Ontario, mean concentrations of total PCDE congeners in sediment were between 622 and 1,929 ng/g dry weight. Analysis of semipermeable membrane devices (SPMDs) deployed at several stations around the harbor indicated that PCDEs were distributed homogeneously in the water. Mean total PCDE concentrations in biota were as high as 672 ng/g wet weight (105 μg/g lipid) in white sucker (Catostomus commersoni) and 791 ng/g wet weight (55 μg/g lipid) in brown bullheads (Ameiurus nebulosus). The patterns of 45 PCDE congener analytes differed among the SPMDs, sediment, and biota, but between invertebrates and fish the congener patterns were relatively homogeneous. Bioamagnification factors (BMFs) calculated for total PCDEs in a simple benthic food chain (oligochaetes to white suckers) and a simple pelagic food chain (plankton to pumpkinseed) indicated that there was biomagnification, with BMFs < 50 on a lipid-normalized basis and BMFs < 5 on a wet weight basis. For individual PCDE congeners, there was a slight trend to increasing BMFs with increasing chlorine substitution.     

PCBs in Lake Superior, 1978–1980

Polychlorinated biphenyls (PCBs) were measured in the water column of Lake Superior during the summers of 1978 to 1980. The total PCB water concentrations were relatively uniform areally and vertically within any one year: 1978, 1.3 ± 1.3 ng/L; 1979, 3.8 ±1.9 ng/L; 1980, 0.9 ±0.4 ng/L. The volume-weighted abiotic PCB burden in the water column fluctuated with climatic conditions between ～10,000 and 40,000 kg, but would be in the range of 10,000 to 20,000 kg most of the time. Analysis of 24 large volume, filtered samples from 1980 showed that 27±12% of the PCBs were in the paniculate phase. The distribution coefficient for PCBs, defined by use of a glass-fiber filter, ranged from 10⁴ to 10⁷ L/kg, exhibiting a strong, inverse log relationship to the suspended solids concentration. This behavior is partially attributed to the differences in the organic carbon content of the sampled particles in different regions of the lake and to artifacts of the filtration process. The elevated total PCB concentrations in the summer of 1979 in conjunction with the previous winter's severe weather conditions are evidence of seasonal fluctuations of PCBs in the water column resulting mostly from sediment resuspension.     

Interaction between Macroinvertebrate Abundance and Habitat Use by Diving Ducks during Winter on Northeastern Lake Ontario

Although numbers of buffleheads (Bucephala albeola), common goldeneyes (Bucephala clangula) and long-tailed ducks (Clangula hyemalis) over-wintering on Lake Ontario have increased substantially over the past two decades, factors influencing habitat use and the potential for competition have not been investigated. The purpose of this study was to determine the relationship between prey availability and community structure of diving ducks during winter on northeastern Lake Ontario. Benthic and nektonic samples collected during fall, winter, and spring 2002–2004 indicated that macroinvertebrate numbers differed by location but generally did not decline throughout winter. Large accumulations of macroinvertebrates, apparently moved by wave action and currents, were documented in nearshore areas. Surveys showed that diving ducks congregated in mixed species flocks within areas of higher food abundance. Mixed species flocks were common in nearshore areas, likely because energydense foods (Amphipoda and Chironomidae) were abundant in the narrow zone of shallow water, close to shore. Although macroinvertebrate numbers likely affected habitat use by diving ducks, birds did not greatly reduce abundance of macroinvertebrates. It is unlikely that exploitative competition was occurring and interference competition appeared below threshold levels that would cause species to spatially segregate. Overall, our results suggest that food availability is not a limiting factor for buffleheads, common goldeneyes, or long-tailed ducks wintering on northeastern Lake Ontario.     

Dynamics of PCBs in the Food Web of Lake Winnipeg

The bioaccumulation of polychlorinated biphenyls (PCBs) is examined in the food web of Lake Winnipeg using measured contaminant concentrations, stable isotopes of nitrogen, and a food web model. Measured concentrations of the sum of 103 PCB congeners are higher in south basin water, sediment, and biota compared with the north. The trophic positions of the top predators as well as the extent of biomagnification of PCBs per unit trophic level do not differ significantly between the north and the south basins. We therefore conclude that the higher PCB concentrations in the south basin are due primarily to higher PCB loadings via riverine sources to the south rather than food web processes. In contrast, the data from the north basin suggest lower total loadings of which a higher fraction is from atmospheric deposition. We find that rainbow smelt (Osmerus mordax) are not associated with elevated exposure of contaminants to top predators of the north basin. This surprising result is attributed to their reduced fitness in this relatively shallow and warm system, which may prevent them from feeding at an elevated trophic level compared with other forage fish. Finally, we hypothesize that high nutrient associated DOC in water decreases PCB bioavailability to lower trophic level organisms and hence the entire food web.     

Spatial and temporal variations of persistent organic pollutants impacted by episodic sediment resuspension in southern Lake Michigan

The impacts of large-scale, episodic sediment resuspension on the cycling of polychlorinated biphenyl congeners (PCBs) were examined using a spatially coordinated air and water sampling strategy conducted in southern Lake Michigan in the late winters of 1998, 1999, and 2000. We found no significant temporal changes in gas phase, dissolved phase, or suspended sediment PCB concentrations despite large-scale seasonal storms occurring before and after sampling campaigns. Only gas phase and suspended sediment PCBs varied spatially. Higher total suspended material (TSM) concentrations and fraction organic carbon (f_oc) were measured at sampling stations located in the near-shore region of southern Lake Michigan than at open-water sampling stations. Gas phase concentrations (ΣPCB_g) were higher in the west (0.436 ± 0.200 ng/m³, n = 11) and south (0.408 ± 0.286 ng/m³, n = 5) than the east (0.214 ± 0.082 ng/m³, n = 10) and central (0.253 ± 0.145 ng/m³, n = 8) regions of southern Lake Michigan. Dissolved phase concentrations (ΣPCB_d) averaged 0.18 ± 0.024 ng/L (n = 52); suspended sediment concentrations (ΣPCB_s) accounted for between 4% and 72% (23 ± 4%, n = 52) of the total ΣPCB concentrations (ΣPCB_T = ΣPCB_d + ΣPCB_s). Despite no consistent temporal variations in both dissolved phase or suspended sediment ΣPCB concentrations, there were temporal and spatial variations in the distribution shift between phases that can be linked to sediment resuspension, not a state of equilibrium. Specifically, our analysis suggests sediment resuspension results in preferential sorption of heavier, more chlorinated PCB congeners.     

Historical Changes in PCB Patterns in Lake Ontario and Green Bay,Lake Michigan, 1971 to 1982, from Herring Gull Egg Monitoring Data

Patterns of PCB congener bioaccumulation were examined in archived herring gull (Larus argentatus) eggs collected from Big Sister Island in Green Bay, Lake Michigan, and Scotch Bonnet Island in Lake Ontario from 1971 to 1982 as part of the Canadian Wildlife Service's Great Lakes Herring Gull Monitoring Program. Concentrations of 97 PCB congeners were measured. From 1971 to 1982, ecological half-lives of most congeners, particularly the tri- through hexachlorobiphenyls, were greater in eggs from Green Bay than Lake Ontario. Comparing sum PCB levels in eggs collected in 1971 and 1982, concentrations declined 80% at Scotch Bonnet Island and 74% at Big Sister Island. PCB congener patterns were different in eggs from the two colonies. Principal components analysis showed that inter-site differences in congener patterns became more apparent after 1976. This indicated that regional PCB sources were the most influential in determining patterns of biologically-available PCBs during the 1971 to 1982 period in these two lakes, via recycling of historical PCBs from sediments or gradually decreasing loading. Trend analysis of selected congeners specific to Aroclors 1242, 1254, and 1260 revealed that the rapid decline of less chlorinated congeners, observed from 1971 to 1976 in Lake Ontario, was explained by a decrease in loading of Aroclor 1242 to the lake. At both colonies, ecological half life of the congeners was significantly (p < 0.001) correlated with log K_ow and with –log HLC. Changes in PCB composition, after 1976 in Lake Ontario and from 1971 to 1982 in Green Bay, could be explained by differences in the physical behavior of individual congeners affecting removal by volatilization and sedimentation.     

Temporal and Age-Related Trends in Levels of Polychlorinated Biphenyl Congeners and Organochlorine Contaminants in Lake Ontario Lake Trout (Salvelinus namaycush)

Concentrations of 21 organochlorine contaminants (OCs) and 61 polychlorinated biphenyl (PCB) congeners were determined in archived samples of whole lake trout (Salvelinus namaycush), age 4 years, collected yearly from eastern Lake Ontario between 1977 and 1993. Temporal trend data show decreases in all parameters analyzed in samples collected from 1977 to 1993. OC levels declined between 60 and 90% from 1977 to 1993. Trends of total PCB and PCB congeners concentrations were variable, but overall levels declined 80% between 1977 and 1993, from 9,060 ng/g in 1,977 to 1,720 ng/g in 1993. Reanalyzed total PCB levels vary randomly from the historical total PCB levels, but overall exhibit a much smoother trend. The means of the two sample sets were not significantly different at a probability of 0.05. Lake trout aged from 3 to 9 years old, collected in 1988, were analyzed to determine changes in contaminant concentrations with age. OC levels on average increased three-fold from 3-year-old lake trout up to 9-year-old lake trout. Total PCB levels increased from 2,760 ng/g in 3-year-old lake trout to 8,000 ng/g in 9-year-old lake trout, and PCB congener concentrations showed similar increases over the same age range. Lipid content declined 30% between 1977 and 1993, but lipid normalizing the data did not change the observed trends.     

PCB concentrations in walleyes and their prey from the Saginaw River,Lake Huron: A comparison between 1990 and 2007

Concentrations of polychlorinated biphenyls (PCBs) were measured in composited samples of walleyes Sander vitreus and their prey during 2005–2007 from Saginaw Bay, Lake Huron. There was a linear relationship between fish length and PCB concentrations in walleyes between 356 and 608 mm, but fish 680 mm had lesser concentrations than 608-mm fish. When fish 222–550 mm from 1990 were compared with those from 2007, there was a decrease of 1315 ng PCBs/g wet wt (ww). Concentrations of PCBs in gizzard shad Dorosoma cepedianum (190 ng PCBs/g ww) were three-fold less than fish collected in 1990 (516 ng PCBs/g ww). Round gobies Neogobius melanostomus collected from the Saginaw River had the greatest concentrations of PCBs (range: 200–350 ng PCBs/g ww) compared with other prey fishes (45–190 ng PCBs/g ww). Concentrations of PCBs in Saginaw River round gobies were three-fold greater than those from Saginaw Bay. Zooplankton from 1990 and 2008 contained 8.0 and 32 ng PCBs/g ww, respectively, while zebra mussels Dreissena polymorpha from 2008 contained 351 ng PCBs/g ww. Principal components analysis showed that PCB congeners differed between the largest walleyes and other fish. There are several possible explanations for lesser concentrations of PCBs observed in 2007. These include effects of dredging, changes in the food web related to round gobies, loss of alewife Alosa pseudoharengus, which was a major walleye prey item in 1990, and replacement by yellow perch Perca flavescens, or decreases in release of PCBs from sediments due to weathering, burial, or diffusion.     

Spatiotemporal trends of polychlorinated biphenyls (PCBs) in surface and suspended sediments from the Lake Ontario Canadian nearshore 1994–2018: A fish consumption advisory perspective

Spatiotemporal trends for polychlorinated biphenyls (PCBs) were examined in surface and suspended sediments collected between 1994 and 2018 from over twenty nearshore stations on the Canadian side of Lake Ontario and the St. Lawrence River. In 2018, PCB concentrations ranged over an order-of-magnitude in surface (<10 ng/g?357 ng/g) and suspended sediments (<10 ng/g–330 ng/g), illustrating the presence of legacy hotspots as well as diffuse urban inputs. PCB concentrations in both surface and suspended sediments were consistently highest in Hamilton Harbour, but were also elevated at other stations around the perimeter of the Niagara basin as well as near Trenton and Kingston, Ontario. Generally, higher PCB concentrations were found in surface sediment relative to paired suspended sediment samples suggesting temporal improvements in nearshore sediment quality. However, many stations demonstrated temporal variability in PCB concentrations, a likely factor in the lack of an overall nearshore declining trend. Given that PCBs are listed as a consumption-limiting contaminant for all fish sampling blocks in the Canadian waters of Lake Ontario and are responsible for 78% of restricted advisories, sediment quality benchmarks that account for bioaccumulation potential should be considered over toxicologically-derived guidelines to gauge severity of PCB contamination of nearshore sediments. Relatively higher TOC-normalized PCB concentrations in the western end of Lake Ontario suggests additional research on PCB bioavailability from nearshore sediment would be beneficial in understanding basinwide trends of PCBs in fish, and that an adaptive approach to sediment management may be needed in the context of consumption advisories.     

Anomalous Concentrations and Chlorination of Polychlorinated Biphenyls in Sediment Downwind of Lake Ontario

Relatively high concentrations (up to 98.5 ng/g dry wt) of polychlorinated biphenyls (PCBs) have been found in two cores penetrating fluvial sands east of Lake Ontario. One core was taken from the upper Salmon River reservoir on the Tug Hill Plateau and the other from Rice Creek near the lake at Oswego. In both instances, portions of the cores containing PCBs and other organochlorines (OCs) lack excess radiogenic ²¹⁰Pb and ¹³⁷Cs, implying depositional ages predating widespread OC commercial production, use, and release. Within each core there is little vertical variation in PCB composition and highly chlorinated congeners dominate the pattern. In addition, the PCB signature is analytically indistinguishable between cores despite collection over 50 km apart. This argues against local sources, and implies deposition and accumulation by processes operating over a substantial area and time period. Transport and introduction of a residual fraction of colloidal-bound PCBs to the sands via tannin-rich riverine waters is proposed.The PCB congener-specific pattern of air samples collected during the spring and summer of 1999 downwind of the lake at two locations (Rice Creek and Sterling) are similar to the sediments and display anomalous concentrations and chlorination with respect to other air sampling localities in the Great Lakes. A link between the residual fraction of PCBs observed in the sediment and air patterns via volatilization from the terrestrial surface is proposed. Elevated PCB concentrations and chlorination in non radiogenic fluvial sands and air may reflect regional accumulation and weathering processes operating over many decades and/or enhancement of contaminant deposition and partitioning downwind of the lake related to lake-effect precipitation.     

Spatial Patterns in PCB Concentrations of Lake Michigan Lake Trout

Most of the PCB body burden in lake trout (Salvelinus namaycush) of the Great Lakes is from their food. PCB concentrations were determined in lake trout from three different locations in Lake Michigan during 1994–1995, and lake trout diets were analyzed at all three locations. The PCB concentrations were also determined in alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax), bloater (Coregonus hoyi), slimy sculpin (Cottus cognatus), and deepwater sculpin (Myoxocephalus thompsoni), five species of prey fish eaten by lake trout in Lake Michigan, at three nearshore sites in the lake. Despite the lack of significant differences in the PCB concentrations of alewife, rainbow smelt, bloater, slimy sculpin, and deepwater sculpin from the southeastern nearshore site near Saugatuck (Michigan) compared with the corresponding PCB concentrations from the northwestern nearshore site near Sturgeon Bay (Wisconsin), PCB concentrations in lake trout at Saugatuck were significantly higher than those at Sturgeon Bay. The difference in the lake trout PCB concentrations between Saugatuck and Sturgeon Bay could be explained by diet differences. The diet of lake trout at Saugatuck was more concentrated in PCBs than the diet of Sturgeon Bay lake trout, and therefore lake trout at Saugatuck were more contaminated in PCBs than Sturgeon Bay lake trout. These findings were useful in interpreting the long-term monitoring series for contaminants in lake trout at both Saugatuck and the Wisconsin side of the lake.     

The Effect of a Large Resuspension Event in Southern Lake Michigan on the Short-term Cycling of Organic Contaminants

In January and March, 1998, a series of intense, northerly wind-driven storms suspended sediment over the entire coastline of the southern basin of Lake Michigan. The effect of large scale resuspension on organic contaminant cycling was investigated using a two-pronged sample collection strategy that included analysis of settling sediment trap material and discrete air and water samples collected before and after a major resuspension event. It was found that major resuspension events result in a large flux of contaminants. For example, 6.2 ng/cm² ΣPCB (sum of 89 congener peaks) and 175 ng/cm² ΣPAHs (sum of 31 compounds) fell through the water column in the southern basin between November and May but almost half of that occurred in the month of March after a series of intense storms induced a largescale resuspension event in that month. Assuming the concentration of contaminants in settling sediments is similar throughout the basin, the March event brought ∼400 kg of ΣPCBs and ∼13,000 kg ΣPAHs into the water column. Furthermore, the data indicate that concentrations of dissolved phase ΣPCB and ΣPAHs declined significantly (α = 0.05) after the event and after resuspended sediment had settled from the surface waters. As a result of the depressed dissolved concentrations at the surface, the potential for gas-phase input to the lake increases on the southwestern coastal region near Chicago, IL and Gary, IN. The potential input of gas-phase contaminants was 8 kg for ΣPCBs and 2,200 kg for ΣPAHs over the 40-day lifetime of the near-shore event.     

Bioaccumulation Potential of Sediment-Associated Polychlorinated Biphenyls (PCBs) in Ashtabula Harbor,Ohio

Ashtabula Harbor, Ohio is designated as a Great Lakes Area of Concern contaminated by PCBs. Information on the bioaccumulation of PCBs from sediments is important for sediment management strategies such as dredging to restore navigable depths in the harbor. To ascertain the bioaccumulation of these PCBs, the aquatic earthworm Lumbriculus variegatus was exposed in the laboratory to contaminated sediments collected from 15 areas in the harbor. Data from these bioaccumulation experiments were used to determine the bioaccumulation potential of PCBs through the calculation of Biota- Sediment Accumulation Factors (BSAFs). The results showed that the mean values of the experimentally derived BSAFs for individual harbor areas ranged from 0.27 to 1.69. The median BSAF for sediments in the lower river sector of the harbor (0.38) was significantly lower than that for upper river sediments (1.34), indicating that the high adsorptive properties of coal soot particles constrained PCB bioavailability in the lower river sediments. These results indicate that the origin of total organic carbon (TOC) has a major influence on the bioavailability of total PCBs in harbor sediments. Moreover, the empirical BSAFs were well below the 4.0 default BSAF value recommended in joint USEPA/USACE protocols that are used to evaluate the Theoretical Bioaccumulation Potential, or bioavailability, of neutral organic chemicals in Great Lakes sediments. These empirical values should be used to more precisely predict the bioavailability of total PCBs in Ashtabula Harbor sediments.