bluuebunny/crossref_metadata_2025 huggingface dataset:
Intra- and intertreatment variability in reference toxicant tests: Implications for whole effluent toxicity testing programs
Authors: Moore Dwayne RJ , Warren-Hicks William , Parkhurst Benjamin R , Teed R Scott , Baird Rodger B , Berger Robert , Denton Debra L , Pletl James J
Published: March 2010

Wole effluent toxicity tests are used in permitting programs across the United States to determine whether effluents are potentially toxic to aquatic biota in receiving environments. In cases where whole effluent toxicity tests indicate unacceptable toxicity, corrective measures or further testing (e.g., field tests) may be required. To be consistent and fair to permit holders, whole effluent toxicity test outcomes (e.g., pass or fail) should not be strongly influenced by intra- and interlaboratory variability. In this study, we quantified intra- and interlaboratory variability for four species–data type combinations using the results of reference toxicant tests compiled from many laboratories in recent years. For each set of test results, we conducted a regression analysis using the generalized linear models framework. The results indicated that the coefficient of variation (CV) for intralaboratory 25% effective concentration (i.e., EC25) values varied from 15.7% for number of young of Ceriodaphnia dubia in laboratory CD4 to 122% for mortality of Menidia beryllina (inland silverside) in laboratory MB3. Interlaboratory variability was small for both mortality (CV = 17.3%) and number of young (CV = 13.4%) of C. dubia. Interlaboratory variability for mortality (CV = 65.8%) and biomass (CV = 117%) of M. beryllina, however, was very high. Our study shows that permit toxicity limits can be exceeded because of factors other than effluent toxicity, particularly when the limits are based on testing of M. beryllina.
Investigating the Incidence of type i errors for chronic whole effluent toxicity testing usingCeriodaphnia dubia
Authors: Moore Timothy F , Canton Steven P , Grimes Max
Published: March 2010

The risk of Type I error (false positives) is thought to be controlled directly by the selection of a critical p value for conducting statistical analyses. The critical value for whole effluent toxicity (WET) tests is routinely set to 0.05, thereby establishing a 95% confidence level about the statistical inferences. In order to estimate the incidence of Type I errors in chronic WET testing, a method blank-type study was performed. A number of municipal wastewater dischargers contracted 16 laboratories to conduct chronic WET tests using the standard test organism Ceriodaphnia dubia. Unbeknownst to the laboratories, the samples they received from the wastewater dischargers were comprised only of moderately hard water, using the U.S. Environmental Protection Agency's standard dilution water formula. Because there was functionally no difference between the sample water and the laboratory control/dilution water, the test results were expected to be less than or equal to 1 TUc (toxic unit). Of the 16 tests completed by the biomonitoring laboratories, two did not meet control performance criteria. Six of the remaining 14 valid tests (43%) indicated toxicity (TUc > 1) in the sample (i.e., no-observed-effect concentration or IC25 < 100%). This incidence of false positives was six times higher than expected when the critical value was set to 0.05. No plausible causes for this discrepancy were found. Various alternatives for reducing the rate of Type I errors are recommended, including greater reliance on survival endpoints and use of additional test acceptance criteria.
Effects of several variables on whole effluent toxicity test performance and interpretation
Authors: Markle Philip J , Gully Joseph R , Baird Rodger B , Nakada Kenneth M , Bottomley Jay P
Published: March 2010

Protocol changes and options contained within U.S. Environmental Protection Agency whole effluent toxicity tests represent variables that have the potential to affect bioassay performance and interpretation of results. Variables evaluated in this study include: the change in allowable age in the Pimephales promelas acute bioassay from up to 90 d to a maximum of 14 d, age-specific acute responses of P. promelas among the allowable ages of 1 to 14 d, change in the chronic growth endpoint definition from final mass to biomass, differences between hemacytometer and fluorometer measurements in the Selenastrum capricornutum protocol, and options for statistical interpretation of species sensitivity in multiple test/species screening bioassays. Clear age-related sensitivity and precision differences were observed in acute responses of P. promelas. Results obtained using the younger age classes were typically more variable in studies of both 1- to 14-d-old and 14- to 90-d-old P. promelas. In the experiments on 1-to 14-d-old organisms, larvae at 1 d of age were significantly less sensitive. In the tests on 14- to 90-d-old organisms, the 14-d-old organisms were significantly less sensitive. The change in endpoint definition in the P. promelas chronic bioassay resulted in an apparent increase in toxic response in the inhibition concentration (ICp) value for each bioassay, evaluated by the biomass method, with no general improvement in statistical intertest precision estimates and no predictable impact on the no-observed-effect concentration endpoint. Fluorometric scoring in the Selenastrum bioassay was significantly more precise and better capable of estimating counts than hemacytometer measurements. Discrepancies associated with commonly used statistical endpoints used to determine the most sensitive species were identified, and potential solutions were proposed.
Effect-based interpretation of toxicity test data using probability and comparison with alternative methods of analysis
Authors: Gully Joseph R , Baird Rodger B , Markle Philip J , Bottomley Jay P
Published: March 2010

A methodology is described that incorporates the intra- and intertest variabilityand the biological effect of bioassay data in evaluating the toxicity of single and multiple tests for regulatory decision-making purposes. The single- and multiple-test regulatory decision probabilities were determined from t values (n − 1, one-tailed) derived from the estimated biological effect and the associated standard error at the critical sample concentration. Single-test regulatory decision probabilities below the selected minimum regulatory decision probability identify individual tests as noncompliant. A multiple-test regulatory decision probability is determined by combining the regulatory decision probability of a series of single tests. A multiple-test regulatory decision probability below the multiple-test regulatory decision minimum identifies groups of tests in which the magnitude and persistence of the toxicity is sufficient to be considered noncompliant or to require enforcement action. Regulatory decision probabilities derived from the t distribution were compared with results based on standard and bioequivalence hypothesis tests (t tests and no-observed-effect concentrations) using single- and multiple-concentration toxicity test data from an actual national pollutant discharge elimination system monitoring program. The analysis demonstrates that the use of regulatory decision probabilities effectively incorporated the precision of the effect estimate into regulatory decisions at a fixed level of effect. Also, probability-based interpretation of toxicity tests provides incentive to laboratories to produce, and permit holders to use, high-quality, precise data, particularly when multiple tests are used in regulatory decisions. These results are contrasted with standard and bioequivalence hypothesis tests in which the intratest precision is a determining factor in setting the biological effect used for regulatory decisions.
An empirical comparison of effective concentration estimators for evaluating aquatic toxicity test responses
Authors: Bailer A. John , Hughes Michael R , Denton Debra L , Oris James T
Published: March 2010

Aquatic toxicity tests are statistically evaluated by either hypothesis testing procedures to derive a no-observed-effect concentration or by inverting regression models to calculate the concentration associated with a specific reduction from the control response. These latter methods can be described as potency estimation methods. Standard U.S. Environmental Protection Agency (U.S. EPA) potency estimation methods are based on two different techniques. For continuous or count response data, a nominally nonparametric method that assumes monotonic decreasing responses and piecewise linear patterns between successive concentration groups is used. For quantal responses, a probit regression model with a linear dose term is fit. These techniques were compared with a recently developed parametric regression-based estimator, the relative inhibition estimator, RIp. This method is based on fitting generalized linear models, followed by estimation of the concentration associated with a particular decrement relative to control responses. These estimators, with levels of inhibition (p) of 25 and 50%, were applied to a series of chronic toxicity tests in a U.S. EPA region 9 database of reference toxicity tests. Biological responses evaluated in these toxicity tests included the number of young produced in three broods by the water flea (Ceriodaphnia dubia) and germination success and tube length data from the giant kelp (Macrocystis pyrifera). The greatest discrepancy between the RIp and standard U.S. EPA estimators was observed for C. dubia. The concentration–response pattern for this biological endpoint exhibited nonmonotonicity more frequently than for any of the other endpoint. Future work should consider optimal experimental designs to estimate these quantities, methods for constructing confidence intervals, and simulation studies to explore the behavior of these estimators under known conditions.
Using single-species toxicity tests, community-level responses, and toxicity identification evaluations to investigate effluent impacts
Authors: Maltby Lorraine , Clayton Sophie A , Yu Hongxia , McLoughlin Nathan , Wood Robert M , Yin Daqiang
Published: March 2010

Whole effluent toxicity (WET) tests are increasingly used to monitor compliance of consented discharges, but few studies have related toxicity measured using WET tests to receiving water impacts. Here we adopt a four-stage procedure to investigate the toxicity and biological impact of a point source discharge and to identify the major toxicants. In stage 1, standard WET tests were employed to determine the toxicity of the effluent. This was then followed by an assessment of receiving water toxicity using in situ deployment of indigenous (Gammarus pulex) and standard (Daphnia magna) test species. The third stage involved the use of biological survey techniques to assess the impact of the discharge on the structure and functioning of the benthic macroinvertebrate community. In stage 4, toxicity identification evaluations (TIE) were used to identify toxic components in the effluent. Receiving-water toxicity and ecological impact detected downstream of the discharge were consistent with the results of WET tests performed on the effluent. Downstream of the discharge, there was a reduction in D. magna survival, in G. pulex survival and feeding rate, in detritus processing, and in biotic indices based on macroinvertebrate community structure. The TIE studies suggested that chlorine was the principal toxicant in the effluent.
Bioequivalence approach for whole effluent toxicity testing
Authors: Shukla Rakesh , Wang Qin , Fulk Florence , Deng Chunqin , Denton Debra
Published: March 2010

Increased use of whole effluent toxicity (WET) tests in the regulatory arena has brought increased concern over the statistical analysis of WET test data and the determination of toxicity. One concern is the issue of statistical power. A number of WET tests may pass the current hypothesis test approach because they lack statistical power to detect relevant toxic effects because of large within-test variability. Additionally, a number of WET tests may fail the current approach because they possess excessive statistical power, as a result of small within-test variability, and detect small differences that may not be biologically relevant. The strengths and limitations of both the traditional hypothesis test approach and the bioequivalence approach for use in the National Pollutant Discharge Elimination System program were evaluated. Data from 5,213 single-concentration, short-term chronic WET tests with Ceriodaphnia dubia provided the database for analysis. Comparison of results between the current approach and the bioequivalence approach indicates that the current approach to WET testing is generally sound but that adopting the proposed bioequivalence approach resolves concerns of statistical power. Specifically, within this data set, applying the bioequivalence approach resulted in failure for tests with relatively large test variability and a pass for tests with relatively small within-test variability.
Adjusting for mortality effects in chronic toxicity testing: Mixture model approach
Authors: Wang Shin Cheng David , Smith Eric P
Published: March 2010

Chronic toxicity tests, such as the Ceriodaphnia dubia 7-d test are typically analyzed using standard statistical methods such as analysis of variance or regression. Recent research has emphasized the use of Poisson regression or more generalized regression for the analysis of the fecundity data from these studies. A possible problem in using standard statistical techniques is that mortality may occur from toxicant effects as well as reduced fecundity. A mixture model that accounts for fecundity and mortality is proposed for the analysis of data arising from these studies. Inferences about key parameters in the model are discussed. A joint estimate of the inhibition concentration is proposed based on the model. Confidence interval estimation via the bootstrap method is discussed. An example is given for a study involving copper and mercury.
Toxicity of total dissolved solids associated with two mine effluents to chironomid larvae and early life stages of rainbow trout
Authors: Chapman Peter M , Bailey Howard , Canaria Edmund
Published: March 2010

Asessment of total dissolved solids (TDS) represents anintegrated measure of the concentrations of common ions (e.g., sodium, potassium, calcium, magnesium, chloride, sulfate, and bicarbonate) in freshwaters. Toxicity related to these ions is due to the specific combination and concentration of ions and is not predictable from TDS concentrations. Short-term chronic toxicity tests were conducted with larval chironomids and trout (eggs and swim-up fry) to assess their TDS tolerance relative to effluents from two Alaskan mines. Both effluents are characterized by high TDS content but differ with respect to concentrations of specific ions and alkalinity. The toxicity tests were conducted with synthetic effluents formulated to match the ionic composition of each mine discharge. No toxicity was observed at >2,000 mg of TDS/L with embryos or developing fry, but chironomids exhibited effects above 1,100 mg of TDS/L. These tests, together with information on the health of field populations (fish and benthic invertebrates), are appropriate and relevant for determining site-specific whole effluent TDS concentrations.
Insecticide-caused toxicity toCeriodaphnia dubia(CLADOCERA) in the Sacramento–San Joaquin River delta, California, USA
Authors: Werner Ingeborg , Deanovic Linda A , Connor Valerie , de Vlaming Victor , Bailey Howard C , Hinton David E
Published: March 2010

In recent years, populations of resident aquatic species in California's Sacramento–San Joaquin Delta, USA, have declined appreciably in numbers. The cause of these declines is not known, but has been attributed to a number of factors including water diversions, loss of habitat, introduced exotic organisms, and toxic compounds. To detect and characterize the spatial extent, severity, frequency, and causes of potential toxicity caused by anthropogenic pollutants, a monitoring study was conducted over a period of two years (1993–1995). Sites were monitored on a monthly basis using the standardized U.S. Environmental Protection Agency freshwater toxicity test with the zooplankton species Ceriodaphnia dubia. Twenty-four sites were sampled in 1993 to 1994. During the 1994 to 1995 sampling season, the number of sampling sites was restricted to 20, with special emphasis placed on back sloughs, delta island agricultural drains, and main-stem river sites. Significant mortality or reproductive toxicity in C. dubia was detected in 9.8% of 400 water samples tested. Ecologically important back sloughs had the largest percentage of toxic samples. Of 71 and 103 samples collected from back sloughs during 1993 to 1994 and 1994 to 1995, respectively, 14.1% and 19.6% were toxic. To determine the causative chemical(s), toxicity identification evaluations (TIEs) were conducted on 23 toxic samples. These included eight follow-up samples taken to determine whether toxicity at the respective site persisted. Organophosphate (chlorpyrifos, diazinon, malathion) and carbamate (carbofuran, carbaryl) pesticides were identified as primary toxicants. Chlorpyrifos was present at toxic concentrations in 87% of samples tested by TIE. Analysis of data from the follow-up samples suggested that toxicity may have persisted over periods of several days to weeks.
The role of calcium and sodium in toxicity of an effluent to mysid shrimp (Mysidopsis bahia)
Authors: Kline Edward R , Stekoll Michael S
Published: March 2010

The source of acute toxicity of an aged gold mill effluent to juvenile mysid shrimp (Mysidopsis bahia [Americamysis bahia]) was identified. Effluent osmolality was equivalent to that of 12 ppt seawater. At five effluent concentrations ranging from 4 to 100% (v/v), using 12 ppt seawater for dilution, the onset of responses was most rapid at 37% effluent. Simulated effluent was created by adding Na+, Ca2+, Mg2+, K+, Cl−, and SO42− to distilled water at concentrations equal to those measured in the effluent. The unusual finding of a more rapid onset of responses at 37% than at 100% effluent was duplicated with simulated effluent, demonstrating that responses of M. bahia to effluent were attributable to one or more of the six ions that were included in simulated effluent. Proportionally, excess Ca2+ and Na+ deficiency were among the greatest differences in the ionic composition of effluent relative to seawater. Manipulation of Ca2+ and Na+ concentrations in effluent and in simulated effluent, along with the results of the previous experiments, demonstrated that excess Ca2+ was the sole source of effluent toxicity and that Na+ deficiency, relative to the proportion in seawater, reduced Ca2+ toxicity.
Application of a fish DNA damage assay as a biological toxicity screening tool for metal plating wastewater
Authors: Choi Kyungho , Zong Moonshik , Meier Peter G
Published: March 2010

The utility of a fish DNA damage assay as a rapid monitoring tool was investigated. Metal plating wastewater was chosen as a sample because it contains various genotoxic metal species. Fish DNA damage assay results were compared to data generated from the conventional whole effluent toxicity (WET) test procedure. The Microtox® assay (Azur Environmental, Carlsbad, CA, USA) using Vibrio fischeri was also employed. Eleven samples from two metal plating companies were collected for this evaluation. For the fish DNA damage assay, 7-d-old fathead minnow larvae, Pimephalespromelas, were utilized. They were exposed to a series of dilutions at 20°C for 2 h. Whole effluent toxicity tests conducted in this study included two acute toxicity tests with Daphnia magna and fathead minnows and two chronic toxicity tests with Ceriodaphnia dubia and fathead minnows. The fish DNA damage assay showed good correlations with both the acute and chronic WET test results, especially with those obtained with fathead minnows. The kappa values, an index of agreement, between the fish DNA damage assay and WET tests were shown to be acceptable (kappa ≥ 0.55). These findings imply that this novel fish DNA damage assay has use as an expedient toxicity screening procedure since it produces comparable results to those of the acute and chronic fathead minnow toxicity tests.
Sporadic mortality in chronic toxicity tests using Pimephales promelas (rafinesque): Cases of characterization and control
Authors: Downey Patrick J , Fleming Kari , Guinn Richard , Chapman Norris , Varner Patricia , Cooney John D
Published: March 2010

In whole effluent toxicity tests, organisms are exposed to various effluent concentrations for a specific time period to estimate the potential effects of an effluent on a receiving stream. Laboratories typically have good success performing valid chronic toxicity tests. However, some difficulty in conducting valid chronic whole effluent toxicity tests with Pimephales promelas (fathead minnow) has been encountered as a result of sporadic control mortality. Some investigators report an interference that causes anomalous patterns of survival in chronic fathead minnow tests. This interference has been termed sporadic mortality phenomenon. Characteristics of sporadic mortality phenomenon include high variability among replicates, nonmonotonic dose responses, mortality beginning on or about day 4 of the test, and fungal growths often observed on the larvae. Histopathologic examinations often indicate bacterial and/or fungal infections on fish exhibiting symptoms of sporadic mortality phenomenon. The most plausible explanation of sporadic mortality phenomenon is a naturally occurring pathogen or pathogens that interfere with the test method. This interference may invalidate tests or falsely indicate toxicity. Sporadic mortality phenomenon can be reduced or eliminated by sample treatments intended to inactivate (heating, antibiotics, or ultraviolet light) or remove (filtration) pathogenic microorganisms. These methods must be used with forethought because of their potential to alter the toxicity of a sample.
Biokinetics of cesium in Perna viridis
Authors: Yu Peter K. N. , Lam Paul K S , Ng Ben K P , Li Ashley M Y
Published: March 2010

The biokinetics of Cs in four compartments in the green-lipped mussel Perna viridis, namely, gill, viscera, adductor muscle, and foot, were studied. First-order linear differential equations were set up for these four compartments, and their solutions were used to fit the experimental data. The parameters governing the biokinetics, which depend on the elimination rate from each compartment and the transfer coefficient between compartments, were found. These are useful in understanding the physiology of Perna viridis, in predicting the activity of cesium in each compartment of Perna viridis from a contamination history, or in using Perna viridis as a sentinel organism for surveying and monitoring radioactive contamination. The results showed that the viscera should be represented by more than one compartment. Concentration factors for the four compartments and for Perna viridis were also determined, and these agreed well with reported values in the literature.
Rapid mineralization of the endocrine-disrupting chemical 4-nonylphenol in soil
Authors: Topp Edward , Starratt Alvin
Published: March 2010

The persistence of the xenoestrogenic compound 4-nonylphenol in agricultural, noncultivated temperate, and Arctic soils was assessed in laboratory microcosm incubations. At 30°C, [ring-U-14C]4-nonylphenol was rapidly mineralized without a lag in six soils tested. A sandy loam agricultural soil was chosen for more detailed study. The 4-nonylphenol mineralization did not occur in autoclaved soil. The response of 4-nonylphenol mineralization to variation in temperature and moisture content was consistent with an aerobic biological mechanism of degradation. Mineralization of [ring-U-14C]4-nonylphenol was rapid in the concentration range of 1 to 250 mg/kg soil. Sludge solids did not inhibit 4-nonylphenol mineralization, although sewage sludge at high concentrations was inhibitory, apparently because of high biological oxygen demand. Gas chromatographic-mass spectrometric analyses of extracts prepared from soil incubated with commercial nonylphenol indicated that all detectable isomers were degraded. In summary, these results indicate that microorganisms that can metabolize 4-nonylphenol are found in a wide variety of soils, including two originating from the Canadian Far North, which presumably have not been exposed anthropogenically to this chemical. We conclude that 4-nonylphenol should be generally biodegradable in well-aerated arable soils.
In vitro kinetics of hepatic glutathione s-transferase conjugation in largemouth bass and brown bullheads
Authors: Allagher Evan P. G , Sheehy Karen M , Lame Michael W , Segall Henry J
Published: March 2010

The kinetics of glutathione S-transferase (GST) catalysis were investigated in largemouth bass (Micropterus salmoides) and brown bullheads (Amerius nebulosus), two freshwater fish species found in a variety of polluted waterways in the eastern United States. The initial rates of hepatic GST activity toward four GST substrates, including 1-chloro-2,4-dinitrobenzene, ethacrynic acid, Δ5-androstene-17-dione, and nitrobutyl chloride, were significantly higher in brown bullheads than in largemouth bass. Hepatic GST activity toward 1,2-dichloro-4-nitrobenzene, a μ-class GST substrate in rodents, was not detectable in either species. Liver cytosolic GSTs were more efficient in bullheads than in bass at catalyzing 1-chloro-2,4-dinitrobenzene-reduced glutathione (CDNB-GSH) conjugation over a broad range of electrophile (CDNB) concentrations, including those representative of environmental exposure. In contrast, largemouth bass maintained higher ambient concentrations of GSH, the nucleophilic cofactor for GST-mediated conjugation, than brown bullheads. Biphasic kinetics for GST-CDNB conjugation under conditions of variable GSH concentration were apparent in Eadie-Hofstee plots of the kinetic data, suggesting the presence of at least two hepatic GST isozymes with markedly different Km values for GSH in both species. The GST-CDNB reaction rate data obtained under conditions of variable GSH were well fitted (R2 = 0.999) by the two-enzyme Michaelis-Menten equation. In addition, Western blotting experiments confirmed the presence of two different hepatic GST-like proteins in both largemouth bass and brown bullhead liver. Collectively, these findings indicate that largemouth bass and brown bullhead GSTs catalyze the conjugation of structurally diverse, class-specific GST substrates, and that brown bullheads exhibit higher initial rates of GST activity than largemouth bass. The relatively higher rates of in vitro liver GST activity at the low substrate concentrations relevant to environmental exposure is expected to protect brown bullheads from the toxic effects of sediment-associated electrophilic chemicals. The somewhat lower rates of GST activity in largemouth bass liver compared with brown bullhead liver, however, may be offset by maintenance of higher ambient hepatic GSH concentrations in largemouth bass.
Time-integrated, flux-based monitoring using semipermeable membrane devices to estimate the contribution of industrial facilities to regional polychlorinated biphenyl budgets
Authors: McCarthy John F , Southworth George R , Ham Kenneth D , Palmer Jennifer A
Published: March 2010

Passive monitoring of polychlorinated biphenyls (PCB) using semipermeable membrane devices (SPMD) was employed to evaluate the contribution of point and nonpoint sources to the flux of PCB in a drainage system encompassing three U.S. Department of Energy (U.S. DOE) industrial and research facilities in eastern Tennessee, USA. Polychlorinated biphenyls concentrations were highest at outfalls containing process waste from the DOE industrial facilities. The significance of these releases was evaluated by calculating the PCB flux (mass per unit time) at different monitoring locations. The flux was calculated from the time-integrated estimates of the aqueous concentrations of PCB and estimates of the volumetric flow rates of discharges and receiving streams during the deployment period. The DOE discharges accounted for most of the flux of PCB entering the Clinch River from the DOE drainage areas, but these sources constituted only 10% of the flux in the Clinch River about the DOE sources. Principal components analysis was helpful in attributing sources of PCB. In a stream receiving multiple inputs of PCB, congener profiles from upstream sources and discrete discharges were consistent with a mixture of those congener profiles in the downstream receiving water. In another stream with a single upstream source of PCB, changes in PCB flux and congener profiles suggested an apparent steady-state distribution between dissolved PCB and PCB adsorbed to organic matter on the streambed. The flux of dissolved PCB along different stream reaches reflected changes in the sediment organic content. Subtle alterations in congener profiles moving downstream suggested preferential desorption of less chlorinated congeners and sorption of more highly chlorinated congeners to sediment. Time-integrated, flux-based monitoring can be useful across a range of spatial scales for evaluating the significance of point and nonpoint contaminant sources and can help identify and prioritize feasible remedial alternatives.
Cadmium dynamics in estuarine sediments: Effects of salinity and lugworm bioturbation
Authors: Rasmussen Allan Dahl , Banta Gary Thomas , Andersen Ole
Published: March 2010

We investigated the effects of lugworm bioturbation on the fate of Cd added either to a thin layer at the sediment surface or homogeneously mixed throughout the sediment. In both situations, the Cd release to the overlying water was highest when lugworms were not present, most likely because bioturbation transported Cd-contaminated sediment away from the sediment surface. Also, irrigation transported water-borne Cd back into the sediment. When Cd was added to the sediment surface, a Cd peak emerged at the feeding depth of the worm within 1 d because of the transport of water-borne Cd down into the sediment by lugworm irrigation. In addition, the conveyor-belt feeding mode of the worm caused both burial of Cd by fecal casts and a gradual spreading of the Cd distribution within the sediment column. When Cd was added to the entire sediment column, bioturbation caused a net transport of Cd upwards, resulting in the surface layers having higher Cd concentrations than the deeper layers, indicating a net release of Cd from deeper sediments. The distribution of Cd in lugworms depended on the Cd exposure situation and suggested that worms were exposed mainly to water-borne Cd when Cd was added to the top of the sediment, whereas worms were exposed mainly by ingesting Cd-labeled sediment when Cd was mixed homogeneously throughout the sediment.
USE of outdoor freshwater pond microcosms: II. Responses of biota to pyridaben
Authors: Rand Gary M , Clark James R , Holmes Catherine M
Published: March 2010

The effects of pyridaben, an insecticide-miticide on zooplankton, macroinvertebrates, and fish were studied in outdoor freshwater microcosms using an analysis of variance design with three chemical concentrations (0.34, 3.4, 34.0 μg/L) and one untreated control randomized among 24 tanks. Each treatment was replicated six times. Monitoring was conducted during an 11-month baseline phase followed by a total of three months for treatment and posttreatment phases. Two applications of a wettable powder formulation were sprayed directly below the water surface with a 30-d interval between treatments. Copepoda adult abundance was significantly reduced at 34.0 μg/L but recovery occurred within 6 weeks after application. Abundance of copepoda nauplii was significantly reduced at 3.4 and 34.0 μg/L, after applications one and two; effects were more severe at 34.0 μg/L and recovery was more rapid at 3.4 μg/L. Abundance of Rotifera was reduced at 34.0 μg/L, after applications one and two, and recovery occurred within 8 weeks for all groups except Polyarthra and Keratella. Of the most abundant Cladocera, abundance of Alona was not significantly affected and abundance of Latonopsis was significantly reduced at 34.0 μg/L, after applications one and two, but recovery occurred within 6 weeks. Abundance of Latonopsis also was significantly reduced at 3.4 μg/L, after applications one and two, but recovery occurred within 2 weeks. A significant decrease occurred in the abundances of Cnidaria, Insecta, and Hydracarina at 34.0 μg/L, only after application one. Pyridaben was toxic to bluegill at 34.0 μg/L, but was not acutely toxic at the laboratory 96-h LC50 concentration (∼3.4 μg/L).
Effects of exposure source, worm density, and sex on DDT bioaccumulation and toxicity in the marine polychaeteNeanthes arenaceodentata
Authors: Lotufo Guilherme R , Farrar J Daniel , Bridges Todd S
Published: March 2010

The influence of exposure source, worm density, and sex on the bioaccumulation and toxicity of 14C-labeled DDT was evaluated for Neanthes arenaceodentata. Emergent juvenile worms were exposed to DDT-spiked sediment (SED), DDT-spiked supplemental food (TetraMarin; TM), or a combination of both (SEDTM) in 28-d toxicity experiments. The DDT concentrations in the sediment and in the food were equal on an organic carbon basis. Higher body residues were attained under the TM exposure compared to SED, indicating the importance of nonsedimentary organic matter as a source for contaminant uptake. The DDT was more bioavailable when associated with TetraMarin compared to sediment, indicating that factors other than sorption to organic carbon can influence contaminant bioavailability. Body residues as high as 0.5 mol/g wet weight were not associated with decreased survival, suggesting general narcosis as the mode of lethal toxicity of DDT to N. arenaceodentata. Most of the body burden was DDT unmetabolized compound (∼70%). Reduced growth, observed under all exposures, was significant at lower concentrations when worms were fed DDT-spiked food (TM and SEDTM). Neanthes arenaceodentata may have detected the presence of DDT in the TetraMarin and decreased their feeding rate, at the cost of reduced growth. The influence of worm density on DDT toxicity and bioaccumulation was examined by exposing one or five worms per beaker (74 and 370 worms/m2, respectively) to spiked sediment. Although higher body residues were attained under low density, worms exposed in groups of five were significantly more sensitive to the effects of DDT on growth. Sex also had a large influence on DDT uptake kinetics. In sediment exposures (SED) to a trace concentration, the uptake clearance rate (mgoc/g lipids/h) was two times more efficient and the elimination rate was five times faster in mature males than in mature females.
Applying species-sensitivity distributions in ecological risk assessment: Assumptions of distribution type and sufficient numbers of species
Authors: Newman Michael C , Ownby David R , Mézin Laurent C A , Powell David C , Christensen Tyler R L , Lerberg Scott B , Anderson Britt-Anne
Published: March 2010

Species-sensitivity distribution methods assemble single-species toxicity data to predict hazardous concentrations (HCps) affecting a certain percentage (p) of species in a community. The fit of the lognormal model and required number of individual species values were evaluated with 30 published data sets. The increasingly common assumption that a lognormal model best fits these data was not supported. Fifteen data sets failed a formal test of conformity to a lognormal distribution; other distributions often provided better fit to the data than the lognormal distribution. An alternate bootstrap method provided accurate estimates of HCp without the assumption of a specific distribution. Approximate sample sizes producing HC5 estimates with minimal variance ranged from 15 to 55, and had a median of 30 species-sensitivity values. These sample sizes are higher than those suggested in recent regulatory documents. A bootstrap method is recommended that predicts with 95% confidence the concentration affecting 5% or fewer species.
Dechlorination of substituted trichloromethanes by an iron(II) porphyrin
Authors: Larson Richard A , Cervini-Silva Javiera
Published: March 2010

Iron(II)porphyrins complex with many organochlorinecompounds and oxidizebydechlorinating them. For a series of trichloromethyl derivatives, CCl3R (R = NO2, CHCl2, CN, Cl, COO−, CH3, H, C(O)NH2, and CH2OH), heme oxidation occurred in two consecutive steps: heme-CCl3R complexation, and (usually slower) inner-sphere electron transfer. Stability of the intermediate CCl2R radical, which is strongly correlated with the ability of the R group to delocalize electron density, governed the overall electron transfer rate.
Structure–activity relationships for acute and chronic toxicity of alcohol ether sulfates
Authors: Dyer Scott D , Stanton David T , Lauth John R , Cherry Donald S
Published: March 2010

Acoholethersulfates(AES)areanionicsurfactantscommonlyusedinconsumerproducts. Commercial AES alkyl chain lengths range from C12 to C18, with ethoxylate (EO) units ranging from 1 to 5. Alkyl sulfate is a special case of AES with no EO units. Acute and chronic toxicity tests using Ceriodaphnia dubia via a novel flowthrough method were conducted with 18 AES compounds to derive SARs for effects assessment. In general, acute toxicity (48-h LC50) increased with increased alkyl carbon chain length and decreased with increased numbers of EO units. Parabolic structure–chronic (7-d) toxicity relationships were observed for endpoints such as the no-observed-effect concentration, lowest-observed-effect concentration, maximum acceptable toxicant concentration, EC20, and EC50. A linear relationship of the fractional negative-charged surface area (FNSA-3) with acute toxicity was also determined. FNSA-3 refers primarily to the polar head group of AES and secondarily to the alkyl chain. Seventy percent of the variance in the chronic data was addressed with a quadratic equation relating toxicity to alkyl chain length and EO units. Alternatively, the molecular descriptors FNSA-3 and S3P (3χp, which is the simple, third-order path index) were also found to address most of the data nonlinearity. A chronic test conducted with a mixture of four AES components indicated additivity, leading to the support of the performance of an effects assessment of AES as a mixture.
Acute toxicity ofpara-nonylphenol to saltwater animals
Authors: Lussier Suzanne M , Champlin Denise , LiVolsi Joseph , Poucher Sherry , Pruell Richard J
Published: March 2010

para-Nonylphenol (PNP), a mixture of alkylphenols used in producing nonionic surfactants, is distributed widely in surface waters and aquatic sediments, where it can affect saltwater species. This article describes a database for acute toxicity of PNP derived for calculating a national saltwater quality criterion. Using a flow-through exposure system with measured concentrations, we tested early life stages of four species of saltwater invertebrates and two species of fish. Static 96-h tests were also conducted on zoeal Homarus americanus, embryo-larval Mulinia lateralis, and larval Pleuronectes americanus. The number of organisms surviving the flow-through test was measured at 2, 4, 8, and 12 h and daily through day 7. Mortality for most species plateaued by 96 h. The ranked sensitivities (96-h 50% lethal concentrations, measured in micrograms per liter) for the species tested were 17 for Pleuronectes americanus, 37.9 (48-h 50% effective concentration) for Mulinia lateralis, 59.4 for Paleomonetes vulgaris, 60.6 for Americamysis bahia (formerly Mysidopsis bahia), 61.6 for Leptocheirus plumulosos, 70 for Menidia beryllina, 71 for Homarus americanus, 142 for Cyprinodon variegatus, and > 195 for Dyspanopius sayii. Values for the seven most sensitive of these species ranged over a factor of only 4.2. The narrow range of responses for PNP implies that exceeding a threshold concentration would endanger a large proportion of the aquatic community.
Kinetics of waterborne strontium uptake in the common carp, Cyprinus carpio, at different calcium levels
Authors: Chowdhury Mohammed J , Van Ginneken Luc , Blust Ronny
Published: March 2010

The uptake kinetics of strontium in the commoncarp(Cyprinus carpio) were characterized in vivo, exposing preac-climated fish to a wide range of Sr2+ (0.27 μM–10.0 mM) and Ca2+ (10 μM–10 mM) concentrations in water; 85Sr, 45Ca, and 47Ca were used as tracers in determining the uptake, and the possibility of adsorption of the tracers to the exterior of the fish were verified. The uptake rates were determined in the whole body, gills, and blood of the fish after an exposure period of 3 h and were analyzed as a function of the free-ion activity of strontium and calcium in water. With the increase of Sr2+ concentration in the exposure water, Sr2+ uptake did not increase linearly but displayed Michaelis–Menten saturation kinetics, and with the increase of Ca2+ concentration, Sr2+ uptake decreased significantly in the whole body, gills, and blood. The competitive inhibition model fitted to the pooled data for whole-body uptake explains about 94% of the variation in Sr2+ uptake and 71% in Ca2+ uptake, indicating a competitive type of interaction during the transport of these metal ions across the biological interfaces. The maximum uptake rate of Sr2+ (JmaxSr) was estimated to be 243.0 μmol/kg/h and that of Ca2+ (JmaxCa) 119.4 μmol/kg/h. The apparent Km for Sr2+ uptake increased greatly with the increase of Ca2+ concentration in water (186, 789, and 5,515 μM for 35, 348, and 3,480 μM Ca2+, respectively). Estimation of the true Km for Sr2+ uptake (KmSr) and its inhibitor constant for Ca2+ (KiCa) yielded the values of 96.3 and 28.5 μM, respectively. These values are very close to those obtained for Ca2+ uptake (KmCa = 24.9 and KiSr = 100.9 μM). This model provides a mechanistic description of the effect of calcium on strontium uptake from water and, vice versa, in carp.
Organochlorine exposure and bioaccumulation in the endangered Northwest Atlantic right whale (Eubalaena glacialis) population
Authors: Weisbrod Anne V. , Shea Damian , Moore Michael J , Stegeman John J
Published: March 2010

Exposure to toxicants is one factor hypothesized to influence population growth of the northern right whale. Organo-chlorines in right whale skin, feces, and prey were measured and used to identify factors influencing exposure and bioaccumulation. Concentrations of 30 polychlorinated biphenyls (PCBs) (5.7 ± 8.9 μg/g lipid) and 20 pesticides (11.4 ± 15.4 μg/g lipid) in skin biopsies were consistent with other baleenopterids. Concentrations in feces and prey were two orders of magnitude less than in biopsies. In principal component analysis, organochlorines in biopsies matched those from Bay of Fundy, Canada, zooplankton, whereas feces were like Cape Cod, USA, copepods. Year of biopsy collection was the principal factor associated with differential accumulation of nonmetabolizable PCBs, 4,4′-DDE, and dieldrin. Biopsies collected during winter had lower concentrations of lipid and metabolizable compounds than biopsies collected during summer. Concentrations of metabolizable PCBs increased with age in males. The bioaccumulation patterns implied that blubber burdens change annually because of the ingestion of different prey or prey from distinct locations and the release of some organochlorines stored in blubber during lipid depletion in winter. Because biopsy concentrations were lower than those found in marine mammals affected by PCBs and DDTs, we do not have evidence that the endangered whales bioaccumulate hazardous concentrations of organochlorines.
Toxic effects of cadmium and zinc on ectomycorrhizal colonization of scots pine (Pinus sylvestris L.) from soil inoculum
Authors: Hartley-Whitaker Jeanette , Cairney John W G , Meharg Andrew A
Published: March 2010

Scots pine seedlings colonized by ectomycorrhizal (ECM) fungi from natural soil inoculum were exposed to a range of Cd or Zn concentrations to investigate the effects of metals on ECM fungi–Scots pine associations in a realistic soil environment. Experiments focused on the relationship between the sensitivity of ECM fungi and their host plants, the influence of metals on ECM community dynamics on Scots pine roots, and the effects of metal exposure on ECM colonization from soil-borne propagules. Ectomycorrhizal colonization was inhibited by Cd and Zn, with a decrease in the proportion of ECM-colonized root tips. Shoot and root biomass, total root length, and total root-tip density, however, were unaffected by Cd or Zn. A decrease in the diversity of ECM morphotypes also occurred, which could have a negative effect on tree vigor. Overall, colonization by ECM fungi was more sensitive than seedling growth to Cd and Zn, and this could have serious implications for successful tree establishment on metal-contaminated soils.
Responses of a macroinvertebrate community from a pristine, southern British columbia, Canada, stream to metals in experimental mesocosms
Authors: Richardson John S , Kiffney Peter M
Published: March 2010

Metal contamination is one of the most widespread impacts onsurface waters. Experimental flumes receiving water and aquatic invertebrates from an undisturbed, forested stream were used to determine the impact of metals in a low-conductivity stream. The experimental flumes were exposed to a gradient of doses maintaining a constant ratio of metals (1995: Cu, Zn, Mn, and Pb; 1996: Cu and Zn) for 6 d. Benthos and emigration were sampled from each of the 16 troughs. The overall densities of benthos declined, but not significantly, as the dose of metals increased. On the basis of the slopes of the concentration–response curve, Baetis, Ameletus, and Paraleptophlebia were the most sensitive taxa present. Other taxa (e.g., Nemouridae and Oligochaeta) were mildly affected by high metal concentrations. Chironomidae showed no significant decrease in densities with increasing dose. Chironomids made up >80% of the benthos and is the primary reason for no significant dose effect on overall densities. No treatment effect was observed on either algal standing crop or bacterial respiration rates. The invertebrate genera most affected by exposure to metals in this study were also absent or rare in nearby urban streams with high metal concentrations.
Characterizing aquatic ecological risks from pesticides using a diquat dibromide case study. I. Probabilistic exposure estimates
Authors: Ritter Amy M , Shaw Jennifer L , Williams W Martin , Travis Kim Z
Published: March 2010

Diquat dibromide (6,7-dihydrodipyrido[1,2-a:2′,1′-c] pyrazinediium dibromide; diquat) is one of the few herbicides registered for direct application to water systems in the United States to control noxious aquatic weeds. The dissipation of diquat dibromide in aquatic environments is highly dependent on the hydrodynamic and physicochemical characteristics of the receiving water body. Computer simulations (EXAMSII) were conducted to evaluate the variability of diquat cation dissipation in farm ponds, lakes, and canals following applications to control aquatic weeds across the United States. Within each scenario, probabilities were assigned to varying values for physical properties (velocity, dispersion, suspended sediment concentrations, bed sediment properties, and plant biomass) using a joint probability method, and the results were expressed as spatially and temporally explicit cumulative probability distributions by water-body type on a regional scale. The results showed that the dissipation of diquat cation in water was very rapid, with the highest exposure concentrations (90th percentile) predicted to be 0.194 mg/L diquat cation 1 h after treatment and typically reaching 0.01 mg/L by 96 h.