James L. Lake

Origins of polycyclic aromatic hydrocarbons in estuarine sediments

Abstract In order to determine the origin of polycyclic aromatic hydrocarbons (PAHs) in sediments from Narragansett Bay, Rhode Island, the PAH assemblages from the sediments and from possible origin materials were analyzed by gas Chromatographic and gas chromatographic-mass spectrometric techniques. Analyses included determinations of: 1. (1) the relative content of non-alkylated PAH parent molecules i.e. parent compound distributions (PCDs); 2. (2) alkylation patterns of these PAH molecules, i.e. alkyl homolog distributions (AHDs); and 3. (3) phenanthrene/anthracene (P/A) ratios. Samples from the Narragansett Bay transect, which began at a sewage outfall for the City of East Providence, Rhode Island, and ended 20 km to the south, showed rapidly decreasing concentrations of PAH compounds with increasing distance from Providence. The PAH assemblages in transect sediment samples, and in other samples collected near piers, showed evidence for different origins. The sediments surrounding tarred piers were contaminated by coal tar used to coat the pilings. The close resemblance of PCDs from bay sediments and combustion products indicated that the PAHs in the transect sediments were predominantly combustion generated. While evidence for the input of PAHs from petroleum to bay sediments appeared in some AHDs of upper bay transect sediments, AHDs from the lower (less polluted) end of the transect showed less influence of petroleum PAH contamination. In general, the shapes of AHDs from transect sediments of Narragansett Bay appeared to be best explained by a combination of inputs of PAHs from petroleum and combustion processes, rather than by the solubility alteration of PAH assemblages on incoming airborne material.

Uptake and depuration of organic contaminants by blue mussels (Mytilus edulis) exposed to environmentally contaminated sediment

Experiments were designed to expose blue mussels (Mytilus edulis) to contaminated sediment collected from Narragansett Bay, Rhode Island, USA in 1982. Measurements were taken to allow comparisons of the uptake and depuration of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). In addition, concentration factors in the mussels were calculated separately against the dissolved and particulate phase concentrations and the results from the exposure and control systems were compared. Both PAHs and PCBs were rapidly accumulated by the mussels exposed to the contaminated sediment. After the mussels were transferred to control seawater, individual PAHs were depurated with half-lives ranging from 12 to 30 d. Individual PCBs showed depuration half-lives which ranged from 16 to 46 d. Concentration factors in the mussels calculated against the particulate phase concentrations were very different in the exposure and control systems. Concentration factors calculated using only the dissolved phase concentrations (bioconcentration factors) showed excellent agreement in the two systems, possibly an indication that the dissolved phase was the direct source of the contaminants accumulated by the mussels. The bioconcentration factors for PCBs were higher than those of PAHs when compounds with similar n-octanol/water partition coefficients were compared.

Comparisons of patterns of polychlorinated biphenyl congeners in water, sediment, and indigenous organisms from New Bedford Harbor, Massachusetts

Polychlorinated biphenyl patterns were compared in samples of water, surface sediment, and the indigenous organisms ribbed mussels (Modiolus demissus), grass shrimp (Paleomonetes pugio), mummichogs (Fundulus heteroclitis), and eels (Anguila rostrata) collected from 1991 through 1993 at two stations in the highly contaminated New Bedford Harbor, Massachusetts. Principal component analysis of analytical data showed groups of points that corresponded to individual species, but little separation between stations for the same species was found. Linear correlations showed a high level of agreement between PCB patterns in samples of the exposure environment (water and sediments) and two species of organisms (ribbed mussels and mummichogs). However, due to two separate metabolic alterations of PCBs, the patterns in both shrimp and eels showed poor agreement with patterns in water and sediment. Selective enrichment factors (SEFs), the ratios of individual coplanar or mono-ortho substituted congeners to the total PCBs, were used to compare the relative abundance of congeners in samples. Due to metabolic differences, the SEFs were lower in eels and higher in shrimp than those found in Aroclor® standards.

Using mussel isotope ratios to assess anthropogenic nitrogen inputs to freshwater ecosystems

Stable nitrogen isotope ratios (δ15N) of freshwater mussels from a series of lakes and ponds wererelated to watershed land use characteristics to assess their utility in determining the source ofnitrogen inputs to inland water bodies. Nitrogen isotope ratiosmeasured in freshwater musselsfrom 19 lakes and ponds in Rhode Island, U.S.A., ranged from4.9–12.6‰ and were found tosignificantly correlate with the fraction of residential development in 100 and 200 m bufferzones around the ponds. Mussel δ15N values in 12 of the 19 ponds also showed significantcorrelation with average dissolved nitrate concentrations, which ranged from 23–327 μg L-1.These observations, in light of previous studies which link elevatedδ15N values of nitrogenderived from septic wastewater with those seen in biota, suggest that mussel isotope ratios mayreflect nitrogen source in freshwater ecosystems. We followed aniterative approach usingmultiple regression analysis to assess the relationship between musselδ15N and the land usecategories fraction residential development, fraction feedlotagriculture, fraction row-cropagriculture, and fraction natural vegetation in 100 and 200 m bufferzones and pond watersheds.From this we developed a simple regression model to predict musselδ15N from the fraction ofresidential development in the 200 m buffer zone around the pond.Subsequent testing with datafrom 16 additional sites in the same ecoregion led us to refine themodel by incorporating thefraction of natural vegetation. The overall average absolute differencebetween measured andpredicted δ15N values using the two-parameter model was 1.6‰. Potential sources of error inthe model include differences in the scale and categorization ofland-use data used to generate andtest the model, differences in physical characteristics, such asretention time and range ofresidential development, and exclusion of sources of enrichednitrogen such as runoff from feedlot operations or increased nitrogen loading from inefficient or failed septic systems.

An examination of dechlorination processes and pathways in New Bedford Harbor sediments

Abstract Estuarine sediments from upper New Bedford Harbor, Massachusetts, which were heavily contaminated with polychlorinated biphenyls (PCBs), showed considerable compositional alterations of PCB residues relative to mixtures of Aroclor 1242 and 1254 standards, and PCB distributions present in sediments from lower New Bedford Harbor and Black Rock Harbor, Connecticut. The compositional alterations, which presumably resulted from reductive dechlorinations by bacteria, became more extensive with increasing PCB concentration and decreasing distance from the suspected PCB source, an electrical capacitor manufacturing plant. Three pathways which removed chlorine substituents from specific locations on PCB molecules were responsible for most of the observed dechlorinations. Considerable differences were found in the extent of dechlorination within sediment cores and between sampling sites in upper New Harbor. The most extensively altered PCB distribution was found in the 15–17·5 cm deep section of a core from nearest to the plants outfall. In most cores, less altered PCB residues were found in the 0–2·5 and 5–7·5 cm core sections than in the 15–17·5 cm section. Large variations in estimates of dechlorination rates were found, depending on the sample and the congener. The dechlorination processes found may decrease the potential toxicity and bioaccumulation potential of the PCB residues in these sediments.

Contaminant Levels in Harbor Seals from the Northeastern United States

The concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzofurans (PCDF), polychlorinated dibenzo-p-dioxins (PCDD), and mercury (Hg) were determined in blubber and liver tissues of harbor seals (Phoca vitulina) collected along the northeast coast of the U.S. Average PCB concentrations in seal blubber (sum of congeners) were 12.0 μg/g (wet weight) with a range of 7.30 to 24.3 μg/g in 1980 and 6.66 μg/g (wet weight) with a range of 2.61 to 11.3 μg/g in 1990–1992. Comparisons between blubber data from this study and previous work indicated that the concentration of PCBs along the northeast coast of the U.S. may have decreased over the past twenty years.The average p,p′-DDE concentrations in seal blubber were 10.9 μg/g (wet weight) in 1980 with a range of 6.95 to 21.9 μg/g and 4.12 μg/g (wet weight) with a range of 1.83 to 7.84 μg/g in 1990–1992. Only trace amounts of PCDFs and PCDDs were found in a few blubber samples; levels in most tissues were below detection (3–5 pg/g) (wet weight). Trace amounts (<30 ng/g) of phenanthracene, anthracene, and alkylated MW-178 compounds were found in some seal samples; all other PAH compounds were below the detection level (5–15 ng/g).Toxic equivalents (TEQ) of selected coplanar and mono-ortho PCB congeners and relative toxic equivalents (RTE) (pg total TEQ/μg total PCB) were calculated, using recently proposed dioxin toxic equivalent factors (Ahlborg et al. 1994). The TEQs ranged from 41 to 315, and the RTEs ranged from 2.25 to 16.3. The RTEs for seal blubber indicated that the present values were in the midrange of those reported in the literature. Toxic equivalents calculated on the basis of the concentrations of the coplanar PCBs, PCDDs, and PCDFs indicated that coplanar PCBs, rather than PCDDs and PCDFs, may pose a more important toxic threat to harbor seals.Mercury levels in liver tissue averaged 70.0 μg/g (wet weight) and 44.1 μg/g (wet weight) in the 1991 and 1980 samples, respectively, and are similar to those found in relatively polluted waters of the British Isles.

Spatial variability in Mussels used to assess base level nitrogen isotope ratio in freshwater ecosystems

Freshwater mussels have been used to establish base level nitrogen isotope ratio values (δ15N) used in trophic position and food web studies in freshwater ecosystems. In this study, we assess the variability introduced when using unionid mussels in this manner by investigating the spatial variation in δ15N values in mussels from different locations in shallow freshwater ponds, and also differences in δ15N in different tissue types in the mussels. Results from the analysis of adductor, foot and a section of the mantle tissues from mussels across all ponds showed that adductor tissue was consistently enriched by about 1‰ versus the mantle and foot. The foot showed the least variability which, coupled with ease in obtaining consistent samples, led us to select this tissue type for subsequent analysis. The six ponds included in the study had average mussel δ15N values ranging from 4.9‰ to 11.9‰. Four of the six ponds showed no significant within pond differences between δ15N values from mussels collected at different sampling sites. The range of mussel δ15N values obtained from within ponds showed that using data from a single mussel to assess baseline δ15N values would result in the introduction of a maximum error of 0.56 of a trophic level to subsequent trophic position calculations.

Predicting bioaccumulation: Development of a simple partitioning model for use as a screening tool for regulating ocean disposal of wastes

Simple bioconcentration models and relatively complex food chain models have been used to predict the accumulation of resistant organic compounds in aquatic organisms. Other models based on fugacities have been used to estimate distributions of compounds in idealized environments including organisms. Selection of a model depends on the availability of input data and the objectives of the study. The accuracy of the model prediction, however, depends upon (1) the accuracy of the input variables; (2) the validity of the model for predicting the modeled process; and (3) limitations in the range of applicability of the model including, for environmental studies, the importance of the process that is modeled in determining the total bioaccumulation in the organism.

PCBs and other chlorinated organic contaminants in tissues of Juvenile Kemp's Ridley Turtles (Lepidochelys kempi)

Concentrations of PCBs (polychlorinated biphenyls) and chlorinated pesticides were measured in liver and body fat samples of juvenile Kemps ridley sea turtles (Lepidochelys kempi). These turtles were killed in the fall or early winter by rapid seasonal temperature drops and were collected on the eastern shores of Long Island from 1980 to 1989. These endangered organisms contained average PCB concentrations (on a wet weight basis) ranging from 655 ng/g in 1980 to 272 ng/g in 1989 in the liver samples, and 1250 ng/g in 1985 to 476 ng/g in 1989 in body fat. The average liver concentrations were four to ten times higher than those found in the livers of other sea turtles. The highest PCB concentration found in a Kemps ridley turtle was more than a factor of 20 below those reported to cause reproductive effects in snapping turtles (Chelydra serpentina) from freshwater environments. Average yearly concentrations of other compounds in the tissues of Kemps ridley turtles ranged from 137 to 386 ng/g (wet weight) for p,p′-DDE and from 27.5 to 129 ng/g (wet weight) for trans-nonachlor. Strong correlations were found between liver and body fat concentrations for PCBs (r2 = 0.90), p,p′-DDE (r2= 0.80) and trans-nonachlor (r2= 0.93) which suggested that either tissue may be used for monitoring these contaminants in Kemps ridley turtles.

Mercury and stable isotopes of carbon and nitrogen in mink

Total Hg concentrations and values of stable isotopes (delta(15)N, delta(13)C) in tissues of mink (Mustela vison) captured in Rhode Island (USA) during winters of 1999 to 2004 were statistically distinct based on location. Mink captured in salt marsh environments (salt marsh group mink [SMGM]) had significantly lower mean Hg concentrations in liver and muscle tissue, and significantly higher delta(15)N and delta(13)C values in muscle, than those in corresponding samples of mink from upland freshwater locations (upland group mink [UPGM]). Stomach content samples obtained from the mink carcasses showed that fish, frogs, and crayfish were the dominant food items in UPGM, but in SMGM, fish predominated. Significant correlations were found for total Hg concentrations and stable isotope values between stomach contents and tissues. Comparisons of increases in Hg concentrations and delta(15)N values from stomach contents to muscle tissue showed nonsignificant differences between UPGM and SMGM for Hg concentrations (SMGM, factor of 4.2; UPGM, factor of 3.9) and delta(15)N values (SMGM, difference of 3.9 per thousand; UPGM, difference of 3.1 per thousand). These results suggest that the length of the trophic step and the extent of accumulation of Hg were approximately equal in both mink groups despite the differences in dietary composition and possible differences in accumulation of organic and inorganic Hg. The correspondence of stable isotope values and Hg concentrations between mink tissues and their stomach contents indicates that use of stomach content analysis to identify major prey items, followed by collection and analysis of appropriate field prey, may represent an approach for estimating Hg exposure to mink.