Showing papers in "Environmental Toxicology and Chemistry in 1991"

Technical basis for establishing sediment quality criteria for nonionic organic chemicals using equilibrium partitioning

Abstract: The purpose of this review paper is to present the technical basis for establishing sediment quality criteria using equilibrium partitioning (EqP). Equilibrium partitioning is chosen because it addresses the two principal technical issues that must be resolved: the varying bioavailability of chemicals in sediments and the choice of the appropriate biological effects concentration. The data that are used to examine the question of varying bioavailability across sediments are from toxicity and bioaccumulation experiments utilizing the same chemical and test organism but different sediments. It has been found that if the different sediments in each experiment are compared, there is essentially no relationship between sediment chemical concentrations on a dry weight basis and biological effects. However, if the chemical concentrations in the pore water of the sediment are used (for chemicals that are not highly hydrophobic) or if the sediment chemical concentrations on an organic carbon basis are used, then the biological effects occur at similar concentrations (within a factor of two) for the different sediments. In addition, the effects concentrations are the same as, or they can be predicted from, the effects concentration determined in water- only exposures. The EqP methodology rationalizes these results by assuming that the partitioning of the chemical between sediment organic carbon and pore water is at equilibrium. In each of these phases, the fugacity or activity of the chemical is the same at equilibrium. As a consequence, it is assumed that the organism receives an equivalent exposure from a water-only exposure or from any equilibrated phase, either from pore water via respiration, from sediment carbon via ingestion; or from a mixture of the routes. Thus, the pathway of exposure is not significant. The biological effect is produced by the chemical activity of the single phase or the equilibrated system. Sediment quality criteria for nonionic organic chemicals are based on the chemical concentration in sediment organic carbon. For highly hydrophobic chemicals this is necessary because the pore water concentration is, for those chemicals, no longer a good estimate of the chemical activity. The pore water concentration is the sum of the free chemical concentration, which is bioavailable and represents the chemical activity, and the concentration of chemical complexed to dissolved organic carbon, which, as the data presented below illustrate, is not bioavailable. Using the chemical concentration in sediment organic carbon eliminates this ambiguity. Sediment quality criteria also require that a chemical concentration be chosen that is sufficiently protective of benthic organisms. The final chronic value (FCV) from the U.S. Environmental Protection Agency (EPA) water quality criteria is proposed. An analysis of the data compiled in the water quality criteria documents demonstrates that benthic species, defined as either epibenthic or infaunal species, have a similar sensitivity to water column species. This is the case if the most sensitive species are compared and if all species are compared. The results of benthic colonization experiments also support the use of the FCV. Equilibrium partitioning cannot remove all the variation in the experimentally observed sediment- effects concentration and the concentration predicted from water-only exposures. A variation of approximately a factor of two to three remains. Hence, it is recognized that a quantification of this uncertainty should accompany the sediment quality criteria. The derivation of sediment quality criteria requires the octanol/water partition coefficient of the chemical. It should be measured with modern experimental techniques, which appear to remove the large variation in reported values. The derivation of the final chronic value should also be updated to include the most recent toxicological information.

Assessing the toxicity of freshwater sediments

Abstract: The science of sediment toxicology essentially began in the late 1970s. It was largely a product of dredging concerns and recognition of widespread contamination of sediments. During the past few years, sediment toxicity research activity has increased dramatically. Currently, most tests are of an acute nature with fewer available for determining sublethal endpoints of chronic toxicity. Test systems of single and multiple species have included most levels of biological organization in aquatic ecosystems and have been conducted in the laboratory on whole sediments, interstitial waters, elutriates, or other extractable fractions under a wide variety of conditions. Evaluations of methodological effects and comparisons with in situ toxicity using surrogate test species and indigenous communities have, on occasion, shown significant differences in test responses. These differences may be attributed to laboratory-controlled parameters (e.g., light, species, life stage, exposure conditions, test phase, spiking method); sampling and laboratory-induced disruption of sediment integrity; alteration of toxicant partitioning due to manipulations and temporal effects; and failure to recognize other influencing ecosystem variables (e.g., organism niche and life cycle, sediment partitioning and gradient dynamics, physicochemical and biological process integration, biotic and abiotic disturbances, micro- and macrobiota patches, food-web interactions). Optimizing and standardizing test methods will require further studies of these variables to improve inter-laboratory comparisons and ecosystem validity. Despite the many unknowns that exist, a variety of sediment toxicity tests have been effectively used in assessing toxicant contamination by measuring the bioavailable fraction of the in-place pollutants. The optimal assays vary with the study and its objectives. Intergrative studies using several chemical, community, and toxicity measures are currently the most effective at defining ecosystem perturbations.

Bond contribution method for estimating henry's law constants

Abstract: Bond contribution values, used to estimate Henry's law constant (HLC) (air-to-water partition coefficient) from chemical structure, have been determined for 59 chemical bonds by a least-square analysis of known HLCs for 345 organic compounds. A correlation coefficient (r2) of 0.94 was determined for the relationship between known LWAPCs (log water-to-air partition coefficients) and bond estimated LWAPCs for the 345 compound data set. The correlation coefficient increases to 0.97 when quantified correction factors are applied to selected chemical classes. The ability of the bond method to estimate LWAPCs is demonstrated by a validation test set of 74 diverse and structurally complex compounds that were not included in the least-squares analysis. The correlation coefficient for the validation set is 0.96.

Acid-volatile sulfide as a factor mediating cadmium and nickel bioavailability in contaminated sediments

Abstract: The authors investigated the influence of sulfide, measured as acid-volatile sulfide (AVS), on the bioavailability of cadmium and nickel in sediments. Seventeen samples from an estuarine system heavily contaminated with cadmium and nickel were analyzed for AVS and simultaneously extracted metals (SEM) and tested in 10-d exposures with the amphipod Hyalella azteca and the oligochaete Lumbriculus variegatus. Molar SEM(cadmium + nickel)/AVS ratios in the sediments ranged from less than one to greater than 200, with several in the range of 1 to 10. Samples with SEM/AVS ratios greater than one were consistently toxic to Hyalella azteca, whereas sediments with ratios less than one were not. Lumbriculus variegatus was less sensitive to the test sediments than Hyalella azteca, which was consistent with their relative sensitivity to cadmium and nickel in water-only exposures. SEM/AVS ratios in the sediments also appeared to be important in determining bioaccumulation of metals by Lumbriculus variegatus. These results support other studies with metal-spiked samples in demonstrating the importance of AVS in determining metal bioavailability in sediments and suggest that AVS normalization is a reasonable means for assessing the hazard of some sediment-associated metals to aquatic ecosystems.

The hazard assessment of pulp and paper effluents in the aquatic environment: A review

Abstract: The hazard assessment of pulp and paper effluents in the aquatic environment is a complex task. Hundreds of individual compounds in pulping effluents and site-specific differences in processes, effluent treatment, and receiving ecosystems hinder hazard assessment. As a result, it is difficult to relate environmental effects with specific contaminants. Conventional parameters such as organic and nutrient loadings, solids deposition, and color complicate efforts to define chemical toxicants by causing environmental impacts at community and population levels. Reproduction is the most sensitive, consistent, and relevant end point tested to date in the laboratory, in mesocosms and experimental streams, and in field situations near some pulping discharges. Despite the application of a wide range of within-organism measurements, only the induction of mixed-function oxidase activities has been associated with exposure to particular effluent compounds in field situations. No complete mechanism of toxic action has been demonstrated that connects contaminant exposure, within-organism responses, whole-organism effects, and effects at the population and the community levels. Hazard assessments of pulping effluents require multidisciplinary efforts that integrate chemical, toxicological, and biological data at several organizational levels. Tiered or stepwise assessments are recommended that first clarify what adverse effects have occurred and then attempt to identify the responsible contaminants.

Predicting the toxicity of bulk sediments to aquatic organisms with aqueous test fractions: Pore water vs. elutriate

Abstract: The objective of this research was to evaluate the acute toxicity of bulk sediment vs. pore water or elutriate to fathead minnows (Pimephales promelas), cladocerans (Ceriodaphnia dubia), amphipods (Hyalella azteca), and oligochaetes (Lumbriculus variegatus). A total of 29 different samples from seven sites were used for this analysis. In most instances, pore water was more toxic than corresponding elutriate. Based on the results of these assays, pore water, but not elutriate, was an effective test fraction for predicting the presence of bulk sediment toxicity; however, there were a number of observations of pore water toxicity in the absence of bulk sediment toxicity. Data from this study concerning the sensitivity of Pimephales promelas, Hyalella azteca, and Lumbriculus variegatus to bulk sediment vs. pore water or elutriate suggest that upper-water-column species are inappropriate organisms for use in bulk sediment tests focused on evaluating in situ toxicity to benthic species. Hyalella azteca was the most sensitive and Lumbriculus variegatus the least sensitive species evaluated.

Toxicokinetics and toxicity of a mixture of sediment-associated polycyclic aromatic hydrocarbons to the amphipod Diporeia sp

Abstract: Amphipods, Diporeia sp., were exposed to a reference sediment dosed with two radio- labeled polycyclic aromatic hydrocarbons (PAHs) and sediments dosed with a mixture of PAHs at four concentrations: 21.4, 41.0, 119.6, and 327.0 nmol g-I dry sediment, as the molar sum of the PAH congeners. Diporeia sp. were sampled for mortality and toxicokinetics for up to 26 d. Signif- icant sediment avoidance was observed at the highest dose out to 6 d of exposure. The toxicity for the mixture was 38 * 3% after 19 d of exposure at the highest dose, 327 nmol g-I dry sediment as the molar sum of the PAHs. The measured organism concentration required to produce the mor- tality at day 19 was 2.9 pmol g-I as the sum of the bioaccumulated PAHs. The uptake clearance (g dry sediment g-' organism h-I) from sediments for the radiotracers increased with dose to an apparent plateau. Uptake clearance is the conditional constant relating the contaminant flux into the organism to the contaminant concentration in the referenced environmental compartment, in this case the sediment. This enhanced bioavailability with dose occurred even in the absence of overt effects and in the absence of changes in the measured partition coefficients for phenanthrene (273 + 98) and pyrene (540 + 212), between the freely dissolved radiotracers in interstitial water and the sediment particles. These changes in bioavailability with changes in PAH concentration suggest that predictions of bioaccumulation of PAH congeners from sediments under different field con- centration conditions will not be possible with standard partitioning relationships.

The role of acid-volatile sulfide in determining cadmium bioavailability and toxicity in freshwater sediments

Abstract: The objective of this study was to determine if the acid-volatile sulfide (AVS) content of freshwater sediments was important in limiting the bioavailability and toxicity of cadmium. Five different concentrations of cadmium were spiked into sediments with three different AVS concentrations, and 10-d exposures with the oligochaete Lumbriculus variegatus and the snail Helisoma sp. were conducted. Concurrent water-only cadmium exposures were also conducted. When the cadmium-to-AVS ratios were ≤1, toxicity was not observed. At ratios ≤1, mean whole-body cadmium residue concentrations of organisms were approximately equal to or less than the maximum residues obtained in survivors of the cadmium exposures in water only. These results corroborated the results of a previous experiment conducted with saltwater sediments and indicate that metal/AVS relationships could be used to establish numeric sediment quality criteria for use in the protection of aquatic life.

Effects of dissolved organic carbon on accumulation and acute toxicity of fenvalerate, deltamethrin and cyhalothrin to Daphnia magna (straus)

Abstract: The effects of dissolved organic carbon (DOC) in the form of Aldrich humic acid on the accumulation and acute toxicities of three synthetic pyrethroids — fenvalerate, deltamethrin, and cyhalothrin—to Daphnia magna in laboratory experiments were investigated. Concentrations of DOC as low as 2.6 mg/L, 3.2 mg/L, and 3.1 mg/L for deltamethrin, fenvalerate, and cyhalothrin, respectively, resulted in a significant decrease in bioaccumulation. Acute toxicities of all three pyrethroids were found to decrease as DOC concentrations increased; e.g., at a DOC concentration of 15.5 mg/L, the acute toxicity of fenvalerate was reduced by a factor of 17. The percentages of deltamethrin and fenvalerate bound to DOC increased as DOC concentrations increased after 2-h and 24-h contact times. At low concentrations of DOC (e.g., 1.7 mg/L), as much as 40% of fenvalerate and 20% of deltamethrin were found sorbed to the dissolved material. After 24-h contact times, 76.4 and 80.8% of fenvalerate and deltamethrin, respectively, were bound to DOC. Reverse-phase partition coefficients (Krp) for both fenvalerate and deltamethrin were found to vary with DOC concentrations and were in the range 1.0 to 4.8 × 105 L/kg for fenvalerate and 0.9 to 5.6 × 105 L/kg for deltamethrin.

The acute toxicity of selected metals to the freshwater mussel, Anodonta imbecilis

Abstract: The mussel fauna of many North American waters is declining, probably due to a combination of factors. The factors may include channelization and impoundment of rivers where the mussels once thrived, as well as the influx of pesticides and metal pollution from surrounding watersheds. Much is known about the effects of metal pollution on zooplankton and aquatic insects, but little is known about the response of freshwater mussels. With more and more species of mussels being listed as threatened or endangered, it is important that we begin to determine their range of sensitivity to pollutants so we can better protect them. Mussels have been labeled insensitive to metals because they can survive while containing high body burdens. However, almost no direct measurement of metal toxicity has been reported for unionid mussels. What little we do know has come from tests with adult mussels. In response to the need for such information, a series of laboratory toxicity tests were performed to assess the sensitivity of Anodonta imbecilis to six metals, a metal-containing effluent and four metal mixtures. Acute toxicity tests were performed on juvenile mussels reared in the laboratory. Overall, mussels were found to be as sensitive to metals as zooplankton and more sensitive than commonly tested fish and aquatic insects.

Fate of the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in soil and bioaccumulation in bush bean hydroponic plants

Abstract: Soils amended with [[sup 14]C]hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) were sampled over 60 d and subjected to exhaustive Soxhlet extraction followed by HPLC analysis. RDX was the only radiolabeled compound observed in soil extracts. Emission of volatile organics and [sup 14]CO[sub 2] from soil accounted for only 0.31 % of the amended radiolabel. Mass balance for RDX-amended soil was better than 84% throughout the two-month study. The analytical method developed for plants involved acid hydrolysis, solvent extraction, fractionation on Florisil adsorbent and separation by HPLC. The described methodology allowed for RDX recovery of 86 [+-] 3% from fortified bush bean leaf tissue. Further experiments were conducted with bush bean plants maintained on RDX-containing hydroponic solutions. Hydroponic plants did not emit detectable amounts of [sup 14]CO[sub 2] or radiolabeled volatile organics. Analysis of the plant tissue indicated bioaccumulation of RDX in the aerial tissues of hydroponic plants exposed for either 1 or 7 d. Metabolism of RDX to polar metabolites was observed in plants exposed for 7 d.

A sediment bioassay using the tubificid oligochaete worm tubifex tubifex

Abstract: A new technique using the tubificid oligochaete Tubifex tubifex as a standard sediment bioassay is described. The various factors affecting quality assurance and control have been examined, such as the appropriate number of replicates; the sensitivity, discriminatory power, and repeatability of the test; and the effects of temperature, animal size, organic content, density, and duration on the test. The proposed bioassay is simple and straightforward and can be done with readily available and inexpensive equipment. It utilizes reproduction, the most ecologically relevant and sensitive life stage, as an end point and has been shown in the laboratory to be both repeatable and discriminatory. The technique can be recommended for further investigation in field trials and for consideration as part of a suite of assays for use in sediment assessment.

Evaluation of selected lipid methods for normalizing pollutant bioaccumulation

Abstract: - Current environmental models use organism lipid concentrations to estimate maximum pollutant bioaccumulation potentials. This collaborative study has shown that significantly different lipid concentrations (3.5~) are found when using common, but different, extraction solvents and methods. Based on these variable lipid values, models that estimate tissue pollutant concentrations normalized to lipid will give significantly different bioaccumulation estimates. To reduce that vari- ability, a standard lipid method needs to be developed or adopted. Keywords - Lipid Bioaccumulation Lipid analysis Bioaccumulation modeling INTRODUCTION Tissue residues of neutral organic pollutants such as polychlorinated biphenyls (PCBs) and 1,1, I-tri- chloro-2,2-bis-( pchloropheny1)ethane (DDT) are correlated with lipid concentrations in both fish and invertebrates 11-31. As a result of this association of hydrophobic neutral organics with lipids, lipid concentration has been used to normalize tissue residues

Long‐term neurobehavioral effects of perinatal polychlorinated biphenyl (PCB) exposure in monkeys

Abstract: In recent years, there has been growing concern about the potential long-term neurobe-havioral effects of perinatal polychlorinated biphenyl (PCB) exposure. We have addressed this issue in a series of studies at the Harlow Primate Laboratory. Offspring of rhesus monkeys (Macaca mulatto) exposed to commercial PCB mixtures (Aroclor 1016 or Aroclor 1248) were tested on two-choice discrimination-reversal learning at 1.5 years of age and on delayed spatial alternation, a spatial learning and memory task, at four to six years of age. Deficits in performance were observed on both tasks. The deficit observed on delayed spatial alternation in Aroclor 1248-exposed monkeys was quite dramatic. The monkeys were tested for 80 test sessions, but were never able to achieve control levels of performance. This effect was observed when the monkeys were four to six years of age (young adulthood), even though they had not been exposed to PCBs since they were weaned at four months of age. The pattern of effects on both discrimination-reversal learning and delayed spatial alternation was suggestive of damage to the prefrontal cortex.

Abiotic and biotic factors influencing in situ trace metal levels in macroinvertebrates in freshwater ecosystems

Abstract: We examined the potential of a multiple regression model, including both biotic and abiotic variables, to predict trace metal levels (Cd, Pb, Cu and Zn) in benthic invertebrate communities from various aquatic habitats in The Netherlands. Variables included in the regression model and their relative contribution to the predictive power appeared to be highly element-specific. Sediment- and water-related abiotic variables were especially important for the prediction of Cd, Pb and, to a lesser extent, Zn. For the essential trace metals, the biotic variables such as the presence of hemocyanin (in the case of Cu) and trophic level (Zn) appeared to have a dominant influence. Species-body weight showed a negative log-linear relationship with trace metal levels of Pb and, to a lesser extent, Cu and Cd. For all metals, significant coefficients of multiple correlation were observed. The variance in invertebrate trace metal levels explained by the model ranged from 25% for Zn to 37% for Cd and Cu. For all trace metals, the introduction of biotic variables resulted in a significant increase in predictive power (p < 0.02), compared to the use of only abiotic predictors. Marked differences in predictive power of the model were observed among various species or taxonomic categories. For several species remarkably significant relationships were revealed, indicating the potential usefulness of the organisms for biological monitoring and further modeling studies.

Application of toxicity identification evaluation procedures to the ambient waters of the colusa basin drain, California

Abstract: Pesticides are applied to the rice fields in the Sacramento Valley to prevent the growth of plants, algae and insects that reduce rice yields. Following the pesticide application, field water is released into agricultural drains that in turn discharge into the Sacramento River and delta. Rice irrigation is the largest single use of irrigation water in the Sacramento Valley, and because the irrigation water (or rice return) flows are the primary source of drain effluent during the spring and summer (up to 33% of the total flow), these discharges can significantly affect drain water quality and resident aquatic organisms. Acute and chronic toxicity to freshwater organisms (Ceriodaphnia dubia) was observed in the drain water during the period that coincides with the initial draining of the fields in 1986, 1987 and 1988. In 1988, a toxicity identification evaluation (TIE) was conducted using Ceriodaphnia dubia in an effort to identify the cause of toxicity. Both methyl parathion and carbofuran were identified as possible toxicants. Mixture tests and chronic toxicity tests indicated that the concentrations of methyl parathion and carbofuran in the water sample account for the toxicity observed in Ceriodaphnia dubia.

The contribution of ammonia, metals and nonpolar organic compounds to the toxicity of sediment interstitial water from an illinois river tributary

Abstract: Toxicity of Illinois River bulk sediment, sediment interstitial (pore) water and elutriates to the oligochaete Lumbriculus variegatus, fathead minnow (Pimephales promelas) and the amphipod Hyalella azteca was compared to determine the most representative aqueous fraction for toxicity identification evaluation (TIE) studies. Toxicity of pore water corresponded better than elutriates to bulk sediment toxicity. Subsequent TIE procedures conducted with the cladoceran Ceriodaphnia dubia indicated that ammonia, metals and nonpolar organic compounds (nonylphenols, polycyclic aromatic hydrocarbons, benzenes, long-chain hydrocarbons) were responsible for toxicity of the sediment pore water. Results of TIE manipulations also suggested that methods for recovering pore water that include filtration may eliminate, a priori, a major component of the sediment contaminants responsible for toxicity.

Routes of uptake and their relative contribution to the toxicologic response of Northern bobwhite (Colinus virginianus) to an organophosphate pesticide

Abstract: Ingestion of contaminated food is considered the primary route of exposure in birds to agricultural chemicals. Routes of exposure other than ingestion are not often considered in risk assessments of agricultural chemicals to avian wildlife. However, recent studies demonstrated anorexic or avoidance behaviors in birds exposed to organophosphate (OP) insecticides. These behaviors would tend to limit exposure if ingestion alone were considered. The contribution, if any, of dermal, preening, and respiratory pathways to the exposure of birds to pesticides under field conditions is unknown. In addition, oral exposures are currently assessed in artificial environments that do not reflect real-life exposure scenarios. To determine the relative contribution of these pathways and to assess exposures under ecological conditions, 270 northern bobwhite (Colinus virginianus) were exposed to simulated aerial crop applications of methyl parathion in an environmentally controlled wind tunnel. The wind tunnel environment consisted of a 25-cm cotton plant canopy, a 5-cm-thick floor of silt-loam, a temperature of 25°C, 50% RH, UV intensity similar to summer sunlight, and a wind speed of 3.2 km/h. Inhalation, preening, and dermal routes were isolated in groups of birds exposed to each application. Five birds from each group were collected at 1, 4, 8, 24, and 48 h post-spray to determine cholinesterase (ChE) response to the exposures. Contaminated and uncontaminated darkling beetle (Tenebrio molitar) larvae were presented to free-ranging sprayed birds in the wind tunnel to assess oral uptake. ChE response was determined at 4, 8, 24, and 48 h postspray. All exposures were replicated. All four routes contributed to the inhibition of brain ChE at different post-spray periods. Dermal uptake and preening were major contributors to the overall dose and toxic response of birds to methyl parathion. Inhalation was the major route of exposure at 1 h post-spray. At 4 h post-spray, uptake through preening caused the greatest inhibition of brain ChE activity. Oral ingestion resulted in less than 20% inhibition of brain ChE during the test. Routes of uptake in order of contribution to toxicologic response from 8 to 48 h post-spray were dermal > preening ≥ oral > inhalation.

Degradation of toluene and p‐xylene in anaerobic microcosms: Evidence for sulfate as a terminal electron acceptor

Abstract: The degradation of aromatic hydrocarbons (benzene, toluene, ethylbenzene, p-xylene, o-xylene, 1,3,5-trimethylbenzene, and naphthalene) under anaerobic conditions was studied in column microcosms developed with aquifer material from the vicinity of a gasoline spill at Seal Beach, California. In one column, which did not receive any electron acceptors other than those naturally present (sulfate and carbon dioxide), more than 60% of the toluene was oxidized to CO2. The other six added substrates were not degraded when the toluene supply was constant. In another column, the addition of toluene was discontinued after 126 d, which coincided with the onset of p-xylene degradation. Addition of sulfate, the only electron acceptor that was detected, stimulated the transformation of toluene in batch experiments.

Predicting chemical reactivity by computer

Abstract: Mathematical models for predicting the fate of pollutants in the environment require reactivity parameter values —that is, the physical and chemical constants that govern reactivity. Although empirical structure-activity relationships have been developed that allow estimation of some constants, such relationships generally hold only within limited families of chemicals. Computer programs are under development that predict chemical reactivity strictly from molecular structure for a broad range of molecular structures. A prototype computer system called SPARC (SPARC Performs Automated Reasoning in Chemistry) uses computational algorithms based on fundamental chemical structure theory to estimate a variety of reactivity parameters (e.g., equilibrium/rate constants, UV-visible absorption spectra, etc.). This capability crosses chemical family boundaries to cover a broad range of organic compounds. SPARC does not do “first principles” computation, but seeks to analyze chemical structure relative to a specific reactivity query in much the same manner in which an expert chemist would do so. Molecular structures are broken into functional units with known intrinsic reactivity. This intrinsic behavior is modified for a specific molecule in question with mechanistic perturbation models. To date, computational procedures have been developed for UV-visible light absorption spectra, ionization pKa, hydrolysis rate constants, and numerous physical properties. This paper describes the logic of the approach to chemistry prediction and provides an overview of the computational procedures. Additional papers are in preparation describing in detail the chemical models and specific applications.

Degradation and bound residue formation of atrazine in a Western Tennessee soil

Abstract: Biological and physical degradation, and metabolite and soil-bound residue formation, of [U-ring-14C]atrazine (2-chloro-4-[ethylamino]-6-[isopropylamino]-1,3,5-triazine) were characterized in a western Tennessee soil using laboratory and field assays. Biological mineralization of [14C]atrazine was examined in the laboratory using intact surface soil cores in sealed microcosms. Physical mineralization was determined using gamma-radiation-sterilized soil microcosms. Metabolites measured were deethylatrazine (DEA), deisopropylatrazine (DIA), dealkylatrazine (DAA) and hydroxyatrazine (HYA). Atrazine was applied at a rate of 2.2 kg/ha (˜ 5.6 μg/g soil) to soil microcosms in two studies and 3.2 kg/ha to the field. Evolution of 14CO2 from [14C]atrazine in nonirradiated soil microcosms increased to 12 and 28% of the radiolabel added after 180 d incubation. Irradiated soil microcosms evolved less than 0.07% of the radiolabel as 14CO2 for both studies after the same period. The concentrations of metabolites throughout the laboratory and field studies were: HYA > DEA > DIA > DAA. The highest concentration of HYA detected during microcosm and field studies was approximately 0.5 μg/g soil. Atrazine dissipation rates and metabolite production in nonirradiated microcosms were comparable to field results. Atrazine concentrations after 180 d in nonirradiated microcosm and field samples were lower than HYA, and either equivalent to or greater than DEA. The DAA was not detected throughout microcosm or field studies. Rates of dissipation for atrazine followed first-order kinetics. Atrazine half-life, based on extractable residues, was approximately 21 d in the microcosm studies, compared to 14 d in surface field soil. Extractable 14C residues sampled from nonirradiated microcosms decreased in concentration during the incubation period. Soil-bound 14C residues increased and, at the termination of the two studies, accounted for 39 and 43% of the radioactivity added to nonirradiated microcosms. Bound 14C residues in irradiated microcosms accounted for 49 and 48% of the activity after 180 d. Similarity of results between microcosm and field studies suggests that those microcosms may be useful for predicting the fate of atrazine in surface soil.

In situ and laboratory sediment toxicity testing with ceriodaphnia dubia

Abstract: Ecological assessments of sites containing hazardous wastes are improved by field testing. In situ exposures of Ceriodaphnia dubia were conducted in a stream impacted by several effluents, a combined sewer overflow and a creosote treatment operation. Sediments contained high levels of metals and polynuclear aromatic hydrocarbons. Fish and macroinvertebrate community indices were depressed. Ceriodaphnia dubia were placed in sediment exposure chambers in the stream for 48 h and also exposed to sediments that were simultaneously collected in the laboratory. Percent survival was generally higher in situ as compared to static laboratory exposures; however, overlying water toxicity was lower in laboratory assays. Average survival rates in elutriate fractions were slightly higher than interstitial or solid-phase exposures, and filtration reduced both elutriate and interstitial fraction toxicity. In situ sediment exposures proved to be sensitive indicators of both degraded and nondegraded stream conditions. Results show traditional sample collection and laboratory toxicity test methods may alter the water and sediment toxicity that occurs in situ. This highlights the importance of laboratory validation and in situ testing in aquatic safety assessments.

Effects of sediment‐bound endosulfan on survival, reproduction and larval settlement of meiobenthic polychaetes and copepods

Abstract: Endosulfan-contaminated muddy sediments were collected from a tidal creek bottom after rain runoff from an agricultural watershed and tested for their effects on larval settlement/growth, survival and reproduction of cultured meiobenthic polychaetes and copepods. Endosulfan (ES) strongly inhibited larval colonization and early juvenile growth of the cosmopolitan, euryhaline polychaete Streblospio benedicti. In laboratory microcosms, ES concentrations as low as 50 μg·kg−1 sediment significantly reduced the number of larval colonists by >50% relative to ES-free control sediments. Higher concentrations closer to actual field levels suppressed Streblospio benedicti colonization completely. Early growth of newly metamorphosed juveniles was depressed 36 and 40% relative to controls at ES concentrations of 50 and 100 μg·kg−1, respectively. In contrast, when the common benthic harpacticoid copepod Pseudobradya pulchella was chronically exposed to sediment ES as high as 200 μg·kg−1, survival and egg production were unaffected despite many examples of high ES toxicity to other crustaceans. Of more than 1,600 Pseudobradya pulchella tested, more than 95% survived ES concentrations of at least 200 μg·kg−1, and over 98% of 1,200 females produced normal clutches of eggs. Similarly, survival of another common benthic copepod, Nannopus palustris, was not significantly affected below a threshold concentration of 200 μg·kg−1 ES. At 200 μg·kg−1, however, Nannopus palustris' survival was significantly reduced relative to control and 50-μg·kg−1 ES treatments.

The lethal and sublethal responses of gammarus pulex to stress: Sensitivity and sources of variation in an in situ bioassay

Abstract: The feeding rate and mortality of the freshwater amphipod Gammarus pulex L., a common benthic detritivore, were measured during four trials of an in situ bioassay. The Gammarus pulex were deployed in a factorial experiment designed to assess the effects of water quality (three stations), test population (two sources), and test operator (two laboratories). Stations were selected above and below a domestic sewage treatment works, a sewage treatment works processing domestic and industrial waste, a quarry, and a pulp mill. Feeding rate appeared to have potential as an indicator of water quality, but the source of the test population and the laboratory performing the measurements both significantly influenced the results.

Toxicity to aquatic organisms of off‐target deposition of endosulfan applied by aircraft

Abstract: Aerial drift from pesticide spray applications can result in contamination of nontarget environments such as aquatic systems In this study, the off-target deposit of aerially applied endosulfan was collected on flat plate samplers and in containers of water placed at various distances downwind of the treated area The water contaminated by that deposit was subsequently used to conduct 24-h lethal bioassays in a nearby temporary laboratory, using threespine stickleback (Gasterosteus aculeatus), water boatmen (Sigara alternata), caddisfly larvae (Limnephilus spp), bivalve molluscs (Pisidium spp), bloodworms (Chironomiidae spp), and water fleas (Daphnia magna) Three different spray events were sampled, all of which occurred at times when meteorological conditions were within regulatory constraints Chemical analysis of deposit collectors and exposed water indicated that deposit decreased in an exponential manner with distance downwind and ranged from 82 mg/m3 and 17 mg/L for plates and waters within the target site to 0051 mg/m3 and 0004 mg/L for plates and waters at 200 m downwind After 24-h exposure to spray-drift contaminated water, no mortalities that could be attributed to the pesticide were observed for bivalve molluscs, bloodworms, or water fleas, even within the treated area Water boatmen, caddisfly larvae, and threespine stickleback, on the other hand, suffered levels of mortality that varied directly with distance downwind from the treated area The distances at which 50% mortality was measured in water boatmen and caddisfly larvae tests were 50 m and 10 m, respectively Threespine stickleback were the most sensitive species tested, having a mortality of up to 90% at a distance of 200 m downwind These results demonstrate the extreme risk to aquatic organisms from drift deposit of aerially applied endosulfan and indicate the need for similar assessments of other popular pesticides

Uptake and elimination kinetics of organophosphorous pesticides in the guppy (poecilia reticulata): Correlations with the octanol/water partition coefficient

Abstract: Bioconcentration factors, uptake rate constants and elimination rate constants of a series of organophosphorous pesticides were determined in the guppy (Poecilia reticulata). The results of these three toxicokinetic parameters were related to measured octanol/water partition coefficients (Kow). A simple one-compartment model fitted the uptake and elimination characteristics of the chemicals. A biphasic relationship was observed between log k1 (uptake rate constant) and log Kow, whereas elimination rate constants were inversely related to Kow. For some of the test compounds substantially higher elimination rates were found, compared to isolipophilic chlorobenzenes, which resulted in lower bioconcentration factors. This divergent behavior is discussed in view of possible biotransformation reactions for these compounds.

Cytochrome P450E (P450IA) induction and inhibition in winter flounder by 3,3′,4,4′-tetrachlorobiphenyl: Comparison of response in fish from georges bank and narragansett bay

Abstract: Induction of liver microsomal cytochrome P450 by 3,3′,4,4′-tetrachlorobiphenyl (TCB) was evaluated in winter flounder from two different sites, one offshore (Georges Bank) and one coastal (Narrow River, Narraganseti, Rhode Island). Immunoblot analysis of liver microsomes with monoclonal antibody 1–12–3 to scup P450E (P450IA1) revealed P450IA protein content of 0.01 nmol/mg in Georges Bank fish that were not treated with TCB. By comparison, untreated Narrow River fish had an 80-fold greater content of immunodetected P450IA protein, indicating a strong environmental induction in these fish. In Georges Bank fish the total (spectrophotometrically measured) microsomal P450 content and the content of P450IA protein were induced progressively by intraperitoneal doses of TCB ranging from 0.1 to 10.0 mg/kg. Ethoxyresorufin-O-deethylase (EROD) specific activity (activity per mg protein) was also progressively induced, but the catalytic efficiency or turnover number (i.e., activity/nmol P450IA) was less in fish given the greater doses of TCB. In Narrow River fish TCB treatment resulted in no significant change (at P ≤ 0.05) in total microsomal P450 content or in P450IA protein content, although they tended to be less (total P450) or greater (P450IA) in fish given the greater doses. The EROD activity per mg protein was less in Narrow River fish given greater TCB doses than it was in control fish. EROD activities per nmol of P4501A protein in control Narrow River fish were less than those in any treatment group of Georges Bank fish and tended to diminish even further with TCB treatment. The results show that 3,3′,4,4′-TCB induces P450IA in winter flounder and that TCB acts in vivo to inhibit the activity of P450IA enzyme by mechanisms not yet known. The lower catalytic efficiency of P450IA enzyme in Narrow River fish than in Georges Bank fish indicates that P450IA inhibition, whether caused by TCB or some other agent, does occur in the environment. The data also indicate that prior condition, including existing environmental induction, can strongly influence the responses of P450IA protein to additional chlorobiphenyl exposure.

Evaluation of effects associated with an oil platform, using the sediment quality triad

Abstract: The Sediment Quality Triad concept, which incorporates components of sediment chemistry, toxicity (= bioassay tests) and benthic community structure, was applied to the area immediately surrounding a commercial oil and gas production site in the Gulf of Mexico The results of this study indicated that stations within a 25-m radius of a central platform and at a remote platform had high levels of sediment chemical enrichment and high toxicity, as determined in laboratory sediment toxicity tests Benthic community structure at those stations was different from that at more distant stations, where chemical enrichment and toxicity were low; the differences included some examples of greater taxa richness, total abundance and specific taxa abundance in the vicinity of the platforms There was no evidence of depauperate fauna near the platforms, such as might be expected if significant adverse effects were manifest in situ Although chemical enrichment from the platforms had the potential to cause adverse environmental effects within the immediate vicinity of source (the 25-m stations in the present study), this potential was not manifest in the benthos, possibly due to offsetting factors that could have included the physical habitat provided by the platforms, grain-size effects and adaptation

The european system of standardized legal tests for assessing the biodegradability of chemicals

Abstract: A brief overview is given of the approach to biodegradation testing adopted by the European Economic Community (EEC) as part of the legislation on new chemicals. The tiered system of screening and simulation tests is outlined and the various tests are discussed briefly. It is concluded that the test strategy is logical and cost-effective, but that ongoing work to further harmonize and revise screening tests for ready biodegradability must be completed before these tests perform satisfactorily. The principles governing simulation tests should be further developed, and, in particular, the importance of the applied concentration of test chemical should be addressed.