Total Contaminant Concentrations Research Articles

A Biomonitor for Tracking Changes in the Availability of Lakewater Cadmium over Space and Time

ABSTRACT Determining the exposure of organisms to contaminants is a key component of Ecological Risk Assessments (ERAs). Effective estimates of exposure consider not only the total concentrations of contaminants in an organism's surroundings but also the availability of the contaminants to organisms. Contaminant availability can be inferred from mechanistic models and verified by measurements of contaminant concentrations in organisms. We evaluated the widespread lake-dwelling insect Chaoborus as a potential biomonitor for use in exposure assessments for three metals: cadmium (Cd), copper (Cu), and zinc (Zn). We show that larvae of this midge maintain constant their concentrations of the essential metals Cu and Zn and thus cannot be used to monitor them. In contrast, larval Cd concentrations varied widely both among lakes and in a given lake over time. We were able to relate these variations in biomonitor Cd to changes in lakewater Cd and pH using the Free Ion Activity Model (FIAM). Our results suggest that Chaoborus larvae could be used as an effective tool for estimating the Cd exposure of organisms in lakes for the purposes of ERAs.

Polycyclic aromatic hydrocarbons in ash: Determination of total and leachable concentrations

Before wood ash can be used as a soil fertilizer, concentrations of environmentally hazardous compounds must be investigated. In this study, total and leachable concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in four ash samples and one green liquor sludge. The ash sample with the highest carbon content also contained high levels of PAHs; three of the ash samples had total concentrations exceeding the limit permitted by the Swedish Forest Agency for recycling to forest soils. The leachable concentrations were higher for the non-stabilized samples; this was probably due to colloid-facilitated transport of the contaminants in these samples. However, the leachable concentrations were overall relatively low in all the samples studied. The amounts of PAHs introduced to forest soils by additions of stabilized, recyclable ash products will be determined primarily by the rate of weathering of the ash particles and the total concentration of contaminants.

PERFLUORINATED, BROMINATED AND CHLORINATED CONTAMINANTS IN A POPULATION OF LESSER BLACK-BACKED GULLS

Protein-bound perfluorinated compounds (PFCs) and lipid-soluble polybrominated diphenyl ethers (PBDEs) and organochlorines (OCs) were measured in whole blood from a large number (n = 83) of breeding lesser black-backed gulls (Larus fuscus) caught during two distinct sampling periods in a colony on the coast of northern Norway. We analyzed 14 PFCs (seven were detected in more than 75% of samples), 10 PBDEs (only BDE 47 was detected), and 27 OCs, including 12 polychlorinated biphenyl (PCB) congeners (14 OCs were detected). Median total PFC concentration was higher than median total OC concentration (43 vs 39 ng/g wet wt). Perfluorooctane sulfonate (PFOS) was the dominant PFC (mean relative contribution of PFOS to total contaminant concentration in blood [Sigmatotal contaminants] was 38%), whereas total PCB (26% of Sigmatotal contaminants) and p,p'-DDE (2,2-bis(4-chlorophenyl)-1,1-dichloroethene; 13% of Sigmatotal contaminants) were the dominant OCs. No covariability was found between protein-bound and lipid-soluble compounds; individuals with high concentrations of PFCs did not have high concentrations of OCs or BDE 47. The concentrations of PFCs were lower in birds caught during the late sampling period compared to those of the early period, and females had lower levels of some PFCs compared with males, suggesting that females sequester fluorinated substances into eggs. For lipid-soluble compounds, no significant sex or sampling period differences were found, except that trans-nonachlor, cis-nonachlor, and p,p'-DDE concentrations were lower in birds caught during the late sampling period. The pattern of PFC compounds (relative to PFOS) and lipid-soluble compounds (relative to PCB 153) differed between sampling periods in females but not in males. Finally, PFCs were distributed more uniformly within the population than the lipid-soluble compounds, for which the distributions were strongly negatively skewed.

Vertical distribution and water solubility of phosphorus and heavy metals in sediments of the St. Lucie Estuary, South Florida, USA

Accumulation and distribution of heavy metals and phosphorus in sediments impact water quality. There has been an increasing concern regarding fish health in the St. Lucie Estuary, which is related to increased inputs of nutrients and metals in recent decades. To investigate vertical changes of contaminants (P, Cd, Cr, Co, Cu, Ni, Pb, Zn, and Mn) in sediments of the St. Lucie Estuary in South Florida, 117 layer samples from six of the 210 to 420 cm depth cores were analyzed for their total and water-soluble P and heavy metals, clay, total Fe, Al, K, Ca, Mg, Na, and pH. Principal component analysis (PCA) was used in two sets of analytical data (total and water-soluble contaminant concentrations) to document changes of contaminants in each core of sediments. The PCA of total contaminants and minerals resulted in two factors (principal components). The first and second factors accounted for 61.7 and 17.2 % of the total variation in all variables, and contrast indicators associated with contaminants of P, Cd, Co, Cr, Ni, Pb, Zn, and Mn and accumulation of Fe and Al oxides, respectively. The first factor could be used for overall assessment of P and heavy metal contamination, and was higher in the upper 45–90 cm than the lower depths of each core. The concentrations of P and heavy metals in the surface layers of sediments significantly increased, as compared with those in the sediments deeper than 45–90 cm. The PCA of water-soluble contaminants developed two factors. The second factor (Cu–P) was higher in the upper than the lower depths of the sediment, whereas the highest score of the first factor (Cd–Co–Cr–Ni–Pb–Zn–Mn) occurred below 100 cm. The water-soluble Cu and P concentrations were mainly dependent on their total concentrations in the sediments, whereas the water-soluble Cd, Co, Cr, Ni, Pb, Zn, and Mn concentrations were mainly controlled by pH.

Bioremediation of contaminated soil and sediment by composting

There are many well-established bioremediation technologies applied commercially at contaminated sites. One such technology is the use of compost material. Composting matrices and composts are rich sources of microorganisms, which can degrade contaminants to innocuous compounds such as carbon dioxide and water. In this article, composting of contaminated soil and sediment was performed on a laboratory bench-scale pile. Fertilizer was added to increase the nutrient content, and the addition of commercial compost provided a rich source of microorganisms. After maintaining proper composting conditions, the feasibility of composting was assessed by monitoring pH, total volatile solids, total microbial count, temperature, and organic contaminant concentration. The entire composting process occurred over a period of five weeks and resulted in the degradation of contaminants and production of compost with a high nutritional content that could be further used as inocula for the treatment of hazardous waste sites. © 2006 Wiley Periodicals, Inc.

Comparison of Plants for Germination Toxicity Tests in Petroleum-Contaminated Soils

Pollution of soil by petroleum hydrocarbons is a serious environmental problem world-wide. Although total concentration of contaminants in soil and/or water is used for regulatory review, it also is beneficial to assess the potential for ecosystem impact through a series of bioassays. One commonly used bioassay is seed germination. In this test, seeds are placed in contaminated material, and seedlings enumerated after a specified incubation period. However, different plant species produce variability in response. In the research project reported here, lettuce (Lactuca sativa L.), millet (Panicum miliaceum), radish (Raphanus L.), red clover (Trifolium pratense L.), and wheat (Triticum aestivum) were tested for sensitivity to petroleum-contaminated soil in germination tests. While most plants appeared to show some sensitivity to the pollutant, only lettuce had a statistically significant difference in response to contaminated and uncontaminated soil. These results confirm that Latuca sativa L is the optimal plant choice for standard germination toxicity tests with petroleum-impacted soil.

Comparison of selected non-exhaustive extraction techniques to assess PAH availability in dissimilar soils

Recently, it has become apparent that the use of total contaminant concentrations as a measure of potential contaminant exposure to plants or soil organisms is inappropriate and that bioavailability of contaminants is a better measure of potential exposure. In light of this, non-exhaustive extraction techniques are being investigated to assess their appropriateness in determining bioavailability. In this study, phenanthrene extractability using hydroxypropyl-β-cyclodextrin (HPCD) and desorption kinetics using butan-1-ol (BuOH) were determined in three dissimilar spiked soils. The soils were extracted after 1 d, 40 d and 80 d of soil-compound contact time. The amount of phenanthrene extracted by HPCD was compared to the rapidly desorbed fraction removed by BuOH. Further experiments using the same soils and extraction methods to assess the relative extractability of phenanthrene, pyrene and benzo( a)pyrene were conducted. Overall, the extraction methods used in this study had different extraction efficiencies. Results suggest that as compound hydrophobicity increased, BuOH became a more exhaustive extractant with respect to HPCD, especially for soils with high clay and organic matter content. These results are important as they highlight differences between two contrasting non-exhaustive extraction techniques both of which have been suggested to be appropriate in the assessment of bioavailability.

Modelling partitioning and distribution of micropollutants in the lagoon of Venice: a first step towards a comprehensive ecotoxicological model

The model presented in this paper integrates a large amount of recent and ad hoc collected data concerning environmental contamination from micropollutants in the lagoon of Venice. This model represents the first step in setting up of an ecotoxicological model for the Venice lagoon, to simulate fate of contaminants from abiotic matrices to organisms. Distribution and partitioning of organic and inorganic contaminants are modelled by a two-dimensional model, based both on deterministic and empirical submodels and adapted to a large spectrum of different substances (polychlorinated dibenzo-dioxins/polychlorinated dibenzo-furans (PCDD/F), polychlorinated biphenyls (PCBs), heavy metals). The model was successfully calibrated on a wide set of experimental data. Sensitivity analysis showed that the model is generally not very sensible to parameters values but it is sensible to external conditions (e.g., pollutants loads). Distribution of dissolved and total concentrations of contaminants was obtained for a series of PCDD/F and PCBs congeners and for eight heavy metals. These distributions represent integrated information on ecosystem health, complementary to monitoring data and they are useful to be used for comparisons with various water quality criteria. Simulation scenarios under different external conditions are proposed as examples of use of the model for management purposes.

Chemistry — More than a One-Line Item

Research into water and sediment quality assessment is a multidisciplinary exercise involving chemists and biologists. During these exercises, it is not uncommon to hear my ecotoxicologist and ecologist colleagues refer to ‘the chemistry’ of waters or sediments, as if it was a one-line or even onenumber parameter categorizing the sample, that can be used in conjunction with their biological studies. This simplistic view fails to acknowledge that a sample’s (or system’s) chemistry is not just a single measurement of one or more chemical components, but embraces an understanding of the dynamics, persistence, reactivity, degradation, transformation, and speciation of these components and their products. Why is this important? Clearly concentration alone will be insufficient to describe or predict the effects of a contaminant on an ecosystem. Rather, the effects will be determined by the exposure dose which is controlled by the behaviour of the contaminant in that environment and its chemical speciation, as modified by the chemistry and physics of the associated water, sediment, or soil system. In many cases, we have a very simplistic understanding of the fundamental chemical processes that are taking place in environmental systems. For example, there are many cases (for example diffusion-limited or reaction-limited systems) in which chemical speciation will only play a minor role and contaminant mobility or reactivity will be much more important. Here, evaluations of total concentrations (potential supply) may be much more important than those that take chemical speciation into account. Environmental effects are increasingly being addressed from a risk perspective. This allows appropriate prioritization of management actions. The risk-assessment paradigm uses the chemistry and dose information as part of an ‘exposure characterization’, whereas the ‘effects characterization’ deals with the organism’s/ecosystem’s responses to this exposure. Simple approaches for screening risk assessment use measurements of total contaminant concentrations, but such crude chemistry has the potential to grossly overestimate the risk. Management, based on this low level of information, could waste money on expensive but unnecessary remediation or waste treatment. Full risk assessments require a more comprehensive evaluation of the chemistry that answer such questions as: • What is the chemical form of the contaminant (e.g. free, bound), and how is this altered by other parameters such as pH, Eh, etc? • What is the physical form of the contaminant? • What is the persistence of the compound in the environmental compartment? • What are its transformation products, dominant transformation pathways, and the rates of transformation?

Spatial variation of metals and acid volatile sulfide in floodplain lake sediment

In risk assessment of aquatic sediments, much attention is paid to the immobilizing effect of acid volatile sulfide (AVS) on trace metals. The difference of AVS and simultaneously extracted metals (SEM) gives an indication of metal availability. In floodplain sediments, where changing redox conditions occur, AVS may play a major role in determining variation in metal availability. The importance of spatial heterogeneity has been recognized in risk assessment of trace-metal-polluted sediments. However, little is known about spatial variation of available metal fractions. We studied spatial variability of sediment, environmental conditions, total contaminant concentrations, and available metals (as SEM-AVS or SEM-AVS/f(oc)) in a floodplain lake. The top 5 cm of sediment was sampled at 43 locations. Data were analyzed with correlation and principal component analysis as well as with geostatistical methods. Trace metal and SEM concentrations and most sediment characteristics were more or less constant within 10%. In contrast, AVS concentrations were much more variable and showed a strong spatial dependence due to differences in lake depth, total sulfur pools, and redox potential (E(h)), which resulted in crucial differences in trace-metal availability within the lake. The spatial pattern of SEM-AVS deviates from total or normalized trace-metal patterns. This particularly has implications for risk assessment of sediments prone to dynamic hydrological conditions, where AVS concentrations are also variable in time.

Polychlorinated dibenzo‐p‐dioxins and dibenzofurans and dioxinlike polychlorinated biphenyls in sediments and mussels at three sites in the lower Great Lakes, North America

Levels of contaminants including polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), non-ortho-substituted and mono-ortho-substituted dioxinlike polychlorinated biphenyls (DLPCBs) were determined in sediments and freshwater mussels (Dreissena spp. and Elliptio complanata) at three sites in the lower Great Lakes (North America). Impacts of mussel colonization on sediment quality were investigated by comparing contaminant levels in colonized sediment with levels in sediment in the same area that was not colonized, but exposed to similar environmental conditions. Significant impacts on contaminant levels of colonized sediment, compared to noncolonized sediment, were observed at two sites exhibiting high mussel population densities (Fort Erie, eastern Lake Erie, ON, Canada, 2.2 kg/m2 dry wt biomass, and Port Dalhousie, western Lake Ontario, Ontario, Canada, 6.1 kg/m2 dry wt biomass); these differences were not observed at a site with lower mussel densities (Bay of Quinte, eastern Lake Ontario, Ontario, Canada, 0.7 kg/m2). Total organic carbon and contaminant concentrations were statistically significantly greater in colonized sediment, compared to noncolonized sediment, at the two impacted sites. Areal estimates of PCDD/PCDF and DLPCB toxicity equivalents (TEQs) in mussel biomass at the three sites averaged 0.16% and 3.3%, respectively, of the TEQs in the top 3 cm of sediment, indicating that the sediments were the primary sink for contaminants. The observed differences between colonized and noncolonized sediment suggest that Dreissena are capable of influencing the chemical properties of sediment they colonize.

Availability of polychlorinated biphenyls (PCBs) and lindane for uptake by intestinal Caco-2 cells.

Children may ingest contaminated soil from hand to mouth. To assess this exposure route, we need to know the oral bioavailability of the contaminants. Two determining steps in bioavailability of soil-borne contaminants are mobilization from soil during digestion, which is followed by intestinal absorption. The first step has been investigated in previous studies that showed that a substantial fraction of PCBs and lindane is mobilized from soil during artificial digestion. Furthermore, almost all contaminants are sorbed to constituents of artificial human small intestinal fluid (i.e., chyme), whereas only a small fraction is freely dissolved. In this study, we examine the second step using intestinal epithelial Caco-2 cells. The composition of the apical exposure medium was varied by addition of artificial chyme, bile, or oleic acid at similar or increasing total contaminant concentrations. The uptake curves were described by rate constants. The uptake flux seemed to be dose-dependent. Furthermore, different exposure media with similar total contaminant concentrations resulted in various uptake rates. This can be attributed to different freely dissolved concentrations and carrier effects. In addition, the large fractions of contaminants in the cells indicate that PCBs and lindane sorbed to bile, oleic acid, and digestive proteins contributed to the uptake flux toward the cells. These results can be extrapolated qualitatively to in vivo conditions. Because the sorbed contaminants should be considered available for absorption, the first step of mobilization from soil is the most important step for oral bioavailability of the presently investigated soil-borne contaminants.

Availability of Polychlorinated Biphenyls (PCBs) and Lindane for Uptake by Intestinal Caco-2 Cells

Children may ingest contaminated soil from hand to mouth. To assess this exposure route, we need to know the oral bioavailability of the contaminants. Two determining steps in bioavailability of soil-borne contaminants are mobilization from soil during digestion, which is followed by intestinal absorption. The first step has been investigated in previous studies that showed that a substantial fraction of PCBs and lindane is mobilized from soil during artificial digestion. Furthermore, almost all contaminants are sorbed to constituents of artificial human small intestinal fluid (i.e., chyme), whereas only a small fraction is freely dissolved. In this study, we examine the second step using intestinal epithelial Caco-2 cells. The composition of the apical exposure medium was varied by addition of artificial chyme, bile, or oleic acid at similar or increasing total contaminant concentrations. The uptake curves were described by rate constants. The uptake flux seemed to be dose-dependent. Furthermore, different exposure media with similar total contaminant concentrations resulted in various uptake rates. This can be attributed to different freely dissolved concentrations and carrier effects. In addition, the large fractions of contaminants in the cells indicate that PCBs and lindane sorbed to bile, oleic acid, and digestive proteins contributed to the uptake flux toward the cells. These results can be extrapolated qualitatively to in vivo conditions. Because the sorbed contaminants should be considered available for absorption, the first step of mobilization from soil is the most important step for oral bioavailability of the presently investigated soil-borne contaminants.

Use of semipermeable membrane devices (SPMDs)

Triolein-containing semipermeable membrane devices (SPMDs) were employed as passive samplers to provide data on the bioavailable fraction of organic, waterborne, organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polynuclear aromatic hydrocarbons (PAHs) in streams flowing through a highly polluted industrial area of Bitterfeld in Saxony-Anhalt, Germany. The contamination of the region with organic pollutants originates in wastewater effluents from the chemical industry, from over one-hundred years of lignite exploitation, and from chemical waste dumps. The main objective was to characterise time-integrated levels of dissolved contaminants, to use them for identification of spatial trends of contamination, and their relationship to potential pollution sources. SPMDs were deployed for 43 days in the summer of 1998 at four sampling sites. The total concentration of pollutants at sampling sites was found to range from a low of 0.8 microgram/SPMD to 25 micrograms/SPMD for PAHs, and from 0.4 microgram/SPMD to 22 micrograms/SPMD for OCPs, respectively. None of the selected PCB congeners was present at quantifiable levels at any sampling site. A point source of water pollution with OCPs and PAHs was identified in the river system considering the total contaminant concentrations and the distribution of individual compounds accumulated by SPMDs at different sampling sites. SPMD-data was also used to estimate average ambient water concentrations of the contaminants at each field site and compared with concentrations measured in bulk water extracts. The truly dissolved or bioavailable portion of contaminants at different sampling sites ranged from 4% to 86% for the PAHs, and from 8% to 18% for the OCPs included in the estimation. The fraction of individual compounds found in the freely dissolved form can be attributed to the range of their hydrophobicity. In comparison with liquid/liquid extraction of water samples, the SPMD method is more suitable for an assessment of the background concentrations of hydrophobic organic contaminants because of substantially lower method quantification limits. Moreover, contaminant residues sequestered by the SPMDs represent an estimation of the dissolved or readily bioavailable concentration of hydrophobic contaminants in water, which is not provided by most analytical approaches.

Effect of zinc chloro complexes to photoluminescent bacteria: dependence of toxicity on metal speciation.

Environmental problems are multifold and complex, especially those arising from the disposal of hazardous materials. Therefore, a pressing requirement at present is to identify and assess the toxicity of such substances. Classically, chemical analyses have been the only technique used to identify contaminants in a water ecosystem. Sensitive analytical methodologies are available for determining total concentration of many contaminants and interpretation of the concentration data is relatively straightforward. However, these analysis have some important limitations when employed alone to assess the potential for toxicity. Traditionally, toxicant levels in water effluents and other sources have been estimated by bioassays employing micro and macrovertebrates. Lately, there has been an increased tendency to use microbial systems for screening toxicants as an alternative to tests with animals. Microbial assays are simple, rapid, inexpensive and reproducible. Of all the microbial systems, the Microtox test developed by (Bulich et al. 1981) is the most widely applied. Because the general presence of metals in our environment, studies of their toxicity have become important. In this context, the Microtox® assay has been used to screen the toxicity of some metallic salts (Rib6 et al. 1989; Hinwood and McCormick 1987; Dutka and Kwan 1981). In this method toxicity is measured in a 2% NaCl medium using the luminescent marine Vibrio fischeri When the bacteria are exposed to a toxic sample the emitted light is reduced in relation to the potency of the sample. The EC50, the effective concentration of toxicant that causes a light reduction of 50%, can be calculated.

Performance of Birch Seedlings Replanted in Heavily Polluted Industrial Barrens of the Kola Peninsula, Northwest Russia

AbstractIndustrial barrens replacing coniferous forests around the Severonikel smelter in the Kola Peninsula, northwestern Russia, have recently expanded over 3000 ha or more. Total concentrations of metal contaminants in the upper soil layers approach 3000–5000 μg/g, and maximum hourly concentrations of sulphur dioxide in ambient air exceed 1000 μg/m3. To monitor possibilities for vegetation recovery in the denuded landscapes continuously affected by industrial emissions, we conducted several experiments with 4‐ to 15‐year‐old (1–25 cm tall) seedlings of Betula pubescens ssp. czerepanovi (mountain birch), replanted to two barren sites. Specifically, we investigated the effects of wind‐sheltering, watering, and fertilization on seedling performance in the polluted sites. Sheltered and watered seedlings had more symmetrical leaves than control seedlings, suggesting less environmental stress. Consistently, sheltering and (to a lesser extent) watering improved the survival of seedlings compared with controls. The beneficial effects of watering and sheltering were most pronounced the first 2–4 weeks following planting and were greatest in the most polluted site. We conclude that the revegetation of industrial barrens can be significantly promoted by inexpensive treatments such as wind sheltering and watering, even under current emissions.

Temporal and Spatial Trends in Biogeochemical Conditions at a Groundwater−Surface Water Interface: Implications for Natural Bioattenuation

The biogeochemical effects of a large surface water on a contaminated anaerobic groundwater at the groundwater−surface water interface (GSI) were evaluated using spatially discretized multilevel arrays and interpreted in light of natural bioattenuation mechanisms. Groundwater samples, collected during a 5-month evaluation period with increasing storm activity, were evaluated to determine the effect of lake activity on the oxidation capacity and contaminant distribution within the plume. Our analyses indicate that concentrations of methane and chloroethene decreased as the groundwater became increasingly oxidized along the GSI in shallow sample points impacted by infiltration of oxygenated lake water. cis-1,2-Dichloroethene remained unchanged or slightly increased at the same locations, indicating that the decrease in methane and chloroethene was not due to dilution effects. Moreover, negative correlation of chloroethene and methane data with oxygen suggest that chloroethene is co-oxidized by methane-oxidizing bacteria in the shallow zone of the plume. Contrary to oxidative processes in the shallow zone, reductive dechlorination of contaminants remained the predominant bio-transformation process in the deep zones of the GSI with chloroethene and ethene being the major contributors to total contaminant concentration. This study is the first to evaluate the effects of seasonal changes on a chlorinated ethene-contaminated plume at the GSI in spatial and temporal detail.

Chemical Factors Influencing Colloid-Facilitated Transport of Contaminants in Porous Media

The effects of colloids on the transport of two strongly sorbing solutesa hydrophobic organic compound, phenanthrene, and a metal ion, Ni2+were studied in sand-packed laboratory columns under different pH and ionic strength conditions. Two types of column experiments were performed as follows: (i) sorption/mobilization experiments where the contaminant was first sorbed in the column under conditions where no colloids were released and mobilized under conditions where colloids were released as a result of ionic strength reduction in the influent; and (ii) transport experiments where the contaminant, dissolved or sorbed on colloids, was injected into columns packed with a strongly sorbing porous medium. In the first type of experiment, contaminant mobilization was significant only when all releasable colloids were flushed from the column. In all other cases, although high colloid particle concentrations were encountered, there was no marked effect on total contaminant concentrations. In the second type of ...

Use of a 3H-labeled substrate to measure microbial biodegradation in marine waters

A method is described in which a high specific activity (SA) 3H-labeled substrate was used to measure microbial biodeegradation of p-cresol in coastal marine waters. [2,6- 3H] p-cresol with a SA of 11 Ci mmol −1 was added to marine waters collected off Souther California. After short incubations of 12 h, subsamples were filtered to collect bacterial cells, respired 3H 2O and 3H-labeled biodegradation intermediates were collected, and residual [2,6- 3H] p-cresol was isolated using C 18 solid phase extraction columns. Activity in each of these fractions was used to calculate biodegradation kinetics. Filter effects, substrate adsoption, and extraction efficiency were determined with formalin treated abiotic controls. The method has broad applicability and since 3H-labeled substrates are commercially available with about three orders of magnitude greater SA than for 14C-labeled compounds, the method can detect biodegradation rates at extremely low levels of target organics. Also, the methods allows for use of smaller sample volumes and, as a result, smaller amounts of radioactive waste are produced. In environments where contamination is present and its concentration can be determined, isotopic dilution can be calculated and radioactivity can be related to total contaminant concentration. The method has broad applicability for assessing the kinetics of p-cresol (and other 3H-labeled phenols) biodegradation in areas of contamination.

The Role of the Zebra Mussel, Dreissena polymorpha, In Contaminant Cycling: II. Zebra Mussel Contaminant Accumulation from Algae and Suspended Particles, and Transfer to the Benthic Invertebrate, Gammarus fasciatus

To determine the contribution of ingested material to zebra mussel contaminant accumulation, contaminant assimilation efficiencies (fraction of the total contaminant exposure that is accumulated into tissue, AE) from spiked algae and suspended sediment particles were measured for benzo(a)pyrene, the insecticide DDT, and selected polychlorinated biphenyl (PCB) congeners. Contaminant transfer from zebra mussel feces to the benthic invertebrate, Gammarus fasciatus, was determined by measuring AE from PCB contaminated mussel feces to gammarids. Further, mussel contaminant AE values coupled with physiological and environmental parameters were used in a steady-state model to examine the relative importance of the algal, suspended sediment, and water-borne exposure routes for a representative organochlorine compound, hexachlorobiphenyl (HCBP). The relative accumulation via the fecal and water exposure routes were modeled for gammarids. Mussel AE values for contaminant accumulation were greater from algae than from suspended sediments. Model estimates indicated that when contaminant concentrations in the water were near detection limits, dietary exposure was the primary route of contaminant accumulation (61.5% of the total contaminant concentration). Water was the most important route of contaminant exposure (89.5% of the total contaminant concentration) when contaminant concentrations in water were 10 times greater than the compound detection limit. Suspended sediment was the major dietary source of contaminants at all water concentrations. % AE for zebra mussel feces to gammarid transfer were high—79.0 and 89.4% for hexachlorobiphenyl and tetrachlorobiphenyl respectively—but not statistically different. Model estimates indicated that the dietary route of exposure was the primary source of PCB exposure for gammarids and indicated a potential for PCB biomagnification in the mussel-based detrital food chain. Results suggest that zebra mussels have the potential to change contaminant cycling in the Great Lakes by rerouting dissolved and paniculate bound contaminants through zebra mussel food chains with possible biomagnification in upper trophic levels.