bluuebunny/crossref_metadata_2025 huggingface dataset:
Avoidance of copper contamination by field populations of Daphnia longispina
Authors: Lopes Isabel , Baird Donald J. , Ribeiro Rui
Published: November 2004

Almost all terrestrial and aquatic assays that are accepted as standardized, or that have been proposed, involve the exposure of confined organisms to toxicants. If avoidance (sensu evasion, displacement) of contaminants occurs in real situations, then bioassays involving forced exposure severely underestimate pernicious effects of contamination. Two main objectives were achieved in this study: To verify the occurrence of avoidance of copper by cladocerans; to determine the association between avoidance and other toxicity endpoints (lethality and feeding depression), and therefore, to ascertain if fully acclimated individuals from a reference field population exhibited a genetically determined avoidance markedly different from those belonging to a historically metal-stressed population. Twelve cloned lineages of the cladoceran Daphnia longispina, collected from two field populations, were selected according to their lethal sensitivity to copper and acclimated to controlled conditions for more than 30 generations. A 1.1-m test chamber with five compartments was built, allowing the establishment of a dissolved toxicant gradient and the free movement of individuals. In the absence of any toxicant, juveniles from each cloned lineage distributed themselves randomly along the test chamber and furthermore, no significant differences were observed between the two replicates, attesting the repeatability of this novel assay. All lineages showed significant avoidance to copper when exposed to a gradient from 3 to 87 μg/L. The most sensitive lineages to lethal levels of copper began avoiding this metal earlier than resistant ones. An intense association was observed between other endpoints and avoidance; furthermore, avoidance was determined to be much more sensitive than lethality. Therefore, avoidance assays should be recommended as a complementary tool in ecological risk assessments and effluent biomonitoring because such assays can provide cost-effective and ecologically relevant information.
Contaminant effects on the teleost fish thyroid
Authors: Brown Scott B. , Adams Bruce A. , Cyr Daniel G. , Eales J. Geoffrey
Published: November 2004

Numerous environmentally relevant chemicals, including polychlorinated hydrocarbons, polycyclic aromatic hydrocarbons, organochlorine pesticides, chlorinated paraffins, organophosphorous pesticides, carbamate pesticides, cyanide compounds, methyl bromide, phenols, ammonia, metals, acid loads, sex steroids, and pharmaceuticals, exert acute or chronic effects on the thyroid cascade in the approximately 40 teleost fish species tested to date. Thyroid endpoints, therefore, serve as biomarkers of exposure to environmental pollutants. However, the mechanisms underlying thyroid changes and their physiological consequences are poorly understood because the thyroid cascade may respond indirectly and it has considerable capacity to compensate for abuses that otherwise would disrupt thyroid hormone homeostasis. Indeed, a xenobiotic-induced change in fish thyroid function has yet to be conclusively causally linked to decreased fitness or survival. Other complications in interpretation arise from the diversity of test conditions employed and the often indiscriminate use of numerous thyroid endpoints. Future work should be directed toward standardizing test conditions and thyroid endpoints and investigating causal links between thyroid changes and fish growth, reproduction, and development. Development may be particularly susceptible to thyroid disruption, and thyroid endpoints appropriate for early life stages need to be applied.
Particulate arsenic and iron during anoxia in a eutrophic, urban lake
Authors: Senn David B. , Hemond Harold F.
Published: November 2004

The bioavailability and transport of particle-reactive pollutants are influenced by their partitioning between dissolved and particulate phases. We explored the importance of particle complexation to the arsenic cycle in an urban lake (Upper Mystic Lake, eastern MA, USA) that experiences arsenic remobilization from contaminated sediments during seasonal hypolimnetic anoxia. Particle size distributions were measured using a new in situ serial filtration system that excludes oxygen and filters at low flow rates to minimize filtration artifacts. Despite anoxia, the majority of remobilized As was present as As(V), and typically 85 to 95% of total As was particle complexed, with 25 to 50% found in the size fraction between 0.4 and 0.05 μm. Iron was distributed similarly among these size classes (>95% of total Fe associated with particles larger than 0.05 μm, 30 to 50% between 0.4 μm and 0.05 μm), contrary to conventional expectation that the majority of Fe should be present as soluble Fe(II) in anoxic waters. By classical filtration (i.e., through a 0.4-μm filter), the colloidal fractions of both Fe and As would have been inaccurately classified as dissolved. Correlations between depth profiles of total As and particulate Fe as well as comparisons of measured arsenic sorption (i.e., total As > 0.05 μm) against predictions by surface complexation modeling of As on amorphous Fe(III) oxides argue that arsenic sorbed on Fe(III) oxides was the major As species present in this lake's hypolimnion throughout several months of anoxia.
Environmental risk assessment of six human pharmaceuticals: Are the current environmental risk assessment procedures sufficient for the protection of the aquatic environment?
Authors: Ferrari Benoǐt , Mons Raphael , Vollat Bernard , Fraysse Benoǐt , Paxēaus Nicklas , Giudice Roberto Lo , Pollio Antonino , Garric Jeanne
Published: November 2004

In this study, exposure and ecotoxicity data of six human pharmaceuticals (carbamazepine, clofibric acid, diclofenac, ofloxacin, propranolol, and sulfamethoxazole) were collected, including our own experimental data and literature data. From this data collection, the two-tiered European draft guideline on the environmental risk assessment of human pharmaceuticals was tested. Measured environmental concentrations in effluents from France and in effluents and surface waters from Germany were compared to the predicted environmental concentrations (PECs) in both countries. In a similar manner, predicted no-effect concentrations (PNECs) derived from acute data and PNECs derived from chronic data were estimated for each pharmaceutical and corresponding PEC/PNEC ratios then were compared in both countries. Globally, results demonstrated that all environmental concentrations (predicted or measured) for each considered pharmaceutical exceeded the 10-ng/L cutoff value, which requires the implementation of the second-tier assessment based on ecotoxicity data. Moreover, the six pharmaceuticals showed a relatively limited acute toxicity, and carbamazepine and propranolol were inaccurately identified as having negligible risks under the current European draft procedure. Such results lead to discussion of the actual procedure on pharmaceuticals, especially on the need of appropriate ecotoxicity tests.
Dose-response relationships between herbicides with different modes of action and growth of Lemna paucicostata: An improved ecotoxicological method
Authors: Michel Albrecht , Johnson Robert D. , Duke Stephen O. , Scheffler Brian E.
Published: November 2004

Lemna species are widely used in ecotoxicological research to assess the phytotoxicity of environmental compounds. The purpose of the work described in this paper was to further refine the Lemna spp. bioassay, making it more robust and useful in comparing results between laboratories. A nondestructive image analysis method was used to measure growth as affected by herbicides during a time course. We tested 26 herbicides, with as many as 19 different modes of action, on leaf area growth of Lemna paucicostata to establish complete dose-response relationships. By using 3,5-dichlorophenol as a reference compound, different EC50 (concentration that inhibited growth by 50%) values of the herbicides can be compared. The EC50 values ranged from 0.003 μM for sulcotrione to 407 μM for asulam. Complete dose-response parameters were obtained that will better allow comparison of these results to those of other laboratories. These results should give useful information to anyone who works with Lemna species to address questions on herbicide residues in environmental compartments, screening of new herbicidal compounds, or the assessment of phytotoxic side effects of any compound.
Methylmercury uptake and distribution kinetics in sheepshead minnows, Cyprinodon variegatus, after exposure to CH3Hg-spiked food
Authors: Leaner Joy J. , Mason Robert P.
Published: November 2004

The distribution kinetics of methylmercury (CH3Hg[II]) was determined in sheepshead minnows (Cyprinodon variegatus) after a single dose of different CH3Hg(II)-spiked food to determine what factors influence the bioavailability, uptake, and redistribution of CH3Hg(II) to various organs of C. variegatus. The kinetics of CH3Hg(II) distribution was measured in the different organs during a period of 0.1 to 35 d after dosage. The CH3Hg(II) distribution kinetics in the different tissues was modeled using a simple multicompartmental pharmacokinetic model, which assumed that blood was the conduit linking the CH3Hg(II) exchange between the different organs. The CH3Hg(II) was taken up into the intestinal tissue within hours after feeding, followed by a slow release to the blood and the other organs of the body. Exchange between the blood and the visceral organs was relatively slow, with maximum CH3Hg(II) uptake in the liver and gill occurring at 1.5 d following dietary exposure. Subsequently, the majority of the CH3Hg(II) was channeled from the viscera to the rest of the body with a substantial lag time after feeding. However, the rate of transfer between tissues in the studies reported here were faster than those measured by others for larger fish.
Synergistic impacts of malathion and predatory stress on six species of North American tadpoles
Authors: Relyea Rick A.
Published: November 2004

The decline of many amphibian populations is associated with pesticides, but for most pesticides we know little about their toxicity to amphibians. Malathion is a classic example; it is sprayed over aquatic habitats to control mosquitoes that carry malaria and the West Nile virus, yet we know little about its effect on amphibians. I examined the survival of six species of tadpoles (wood frogs, Rana sylvatica; leopard frogs, R. pipiens; green frogs, R. clamitans; bullfrogs, R. catesbeiana; American toads, Bufo americanus; and gray tree frogs, Hyla versicolor) for 16 d in the presence or absence of predatory stress and six concentrations of malathion. Malathion was moderately toxic to all species of tadpoles (median lethal concentration [LC50] values, the concentration estimated to kill 50% of a test population, ranged from 1.25–5.9 mg/L). These values are within the range of values reported for the few amphibians that have been tested (0.2–42 mg/L). In one of the six species, malathion became twice as lethal when combined with predatory stress. Similar synergistic interactions have been found with the insecticide carbaryl, suggesting that the synergy may occur in many carbamate and organophosphate insecticides. While malathion has the potential to kill amphibians and its presence is correlated with habitats containing declining populations, its actual role in amphibian declines is uncertain given the relatively low concentration in aquatic habitats.
Water solubility and partitioning behavior of brominated phenols
Authors: Kuramochi Hidetoshi , Maeda Kouji , Kawamoto Katsuya
Published: November 2004

The water solubility (Sw) in the temperature range from 283 to 308 K and 1-octanol/water partition coefficient (Kow) for the nonionic form of brominated phenols (BPhs) of varying bromine content (4-bromophenol, 2,4-dibromophenol, 2,4,6-tribromophenol, and pentabromophenol) were measured by the generator-column or shake-flask method and by the high-performance liquid chromatography method, respectively. The temperature dependence of Sw, namely enthalpy of solution (ΔHsolution), was calculated using the van't Hoff Equation. To determine the activity coefficients in water (γw) of BPhs from the Sw data, enthalpy of fusion (ΔHfusion) and melting point (Tm) were measured by a differential scanning calorimetry method. The γw was used for evaluating data consistency as well as for predicting other physico-chemical properties, such as the Henry's law constant (Hw). The present work systematically reports, to our knowledge for the first time, the experimental values of Sw, Kow, ΔHsolution, ΔHfusion, Tm, and γw for BPhs with one to five bromines, and it discusses the effects of bromine content on these physico-chemical properties. Finally, the overall physico-chemical characteristics of BPhs are compared with those of polychlorinated phenols, polycyclic aromatic hydrocarbons, and brominated benzenes with the same solubility level as BPhs.
Using Biowin™, Bayes, and batteries to predict ready biodegradability
Authors: Boethling Robert S. , Lynch David G. , Jaworska Joanna S. , Tunkel Jay L. , Thom Gary C. , Webb Simon
Published: November 2004

Wether or not a given chemical substance is readily biodegradable is an important piece of information in risk screening for both new and existing chemicals. Despite the relatively low cost of Organization for Economic Cooperation and Development tests, data are often unavailable and biodegradability must be estimated. In this paper, we focus on the predictive value of selected Biowin™ models and model batteries using Bayesian analysis. Posterior probabilities, calculated based on performance with the model training sets using Bayes' theorem, were closely matched by actual performance with an expanded set of 374 premanufacture notice (PMN) substances. Further analysis suggested that a simple battery consisting of Biowin3 (survey ultimate biodegradation model) and Biowin5 (Ministry of International Trade and Industry [MITI] linear model) would have enhanced predictive power in comparison to individual models. Application of the battery to PMN substances showed that performance matched expectation. This approach significantly reduced both false positives for ready biodegradability and the overall misclassification rate. Similar results were obtained for a set of 63 pharmaceuticals using a battery consisting of Biowin3 and Biowin6 (MITI nonlinear model). Biodegradation data for PMNs tested in multiple ready tests or both inherent and ready biodegradation tests yielded additional insights that may be useful in risk screening.
Estimation of microbial reductive transformation rates for chlorinated benzenes and phenols using a quantitative structure–activity relationship approach
Authors: Tebes-Stevens Caroline L. , Jones W. Jack
Published: November 2004

A set of literature data was used to derive several quantitative structure–activity relationships (QSARs) to predict the rate constants for the microbial reductive dehalogenation of chlorinated aromatics. Dechlorination rate constants for 25 chloroaromatics were corrected for the effects of hydrophobic partitioning and adjusted for the observed distribution of product species. A number of physicochemical properties and molecular parameters were considered for inclusion in the QSARs. Multivariate statistical analyses were used to select the optimal set of descriptors to minimize multicollinearity between the descriptors, as well as to minimize the p-value of the regression coefficients. The final QSAR included four descriptors: The logarithm of the octanol–water partition coefficient (Kow), the summation of the Hammett sigma constants, and the sigma induction constants in the ortho and meta positions relative to the transformation reaction center. The predictive ability of this QSAR was evaluated using 24 site-specific rate constants that were measured in five separate studies and were not used to derive the expression. The peer-reviewed literature was screened carefully to ensure that all rate constant data were representative of environmentally relevant conditions.
Distribution of atrazine into three chemical fractions: Impact of sediment depth and organic carbon content
Authors: Smalling Kelly L. , Aelion C. Marjorie
Published: November 2004

The fate and transport of organic contaminants in aquatic sediments are impacted largely by microbial degradation and sorption to organic matter. Atrazine, a pre-emergent herbicide, has the potential to contaminate groundwater because of its slight water solubility, long half-life, and sorption to organic matter. Mineralization and distribution of 14C-atrazine into three chemical fractions were monitored over time in surface and subsurface coastal aquatic sediments of different land use. Sediments were extracted with an organic solvent followed by an alkali hydrolysis, and 14C activity was measured in the aqueous, solvent, and basic fractions (representing nonsorbed compounds, loosely sorbed compounds, and humic or fulvic acid bound compounds, respectively). Limited mineralization of atrazine occurred (<4%). The 14C activity in the aqueous and basic fractions increased over time, was greater in surface versus subsurface sediments, and was positively correlated with sediment organic carbon (SOC) content, indicating greater biological and chemical activity. Total 14C recovered ranged from 50 to 90%, was less in surface versus subsurface sediments, and was not correlated with SOC after 80 d. These results suggest that in native aquatic surface sediments, atrazine sorption plays a major role, whereas in subsurface sediments atrazine may be available for degradation and transport to shallow groundwater.
Effects of dietary zinc exposure on the life history of the parthenogenetic springtail Folsomia candida (Collembola: Isotomidae)
Authors: Smit C. Els , Stam Ed M. , Baas Nicolette , Hollander Ronald , van Gestel Cornelis A. M.
Published: November 2004

The effect of zinc on growth and reproduction of the springtail Folsomia candida has been determined for individual animals exposed to contaminated food. Zinc caused a decrease in growth of the springtails, which resulted in a decrease in the estimated final fresh weight at the highest exposure level (20 mg/g dry food). Other effects were observed from 5 mg/g dry food and included an increase of the juvenile period, an increase of development time, a reduction in first-clutch size and egg viability, and a reduction in the number of individuals reaching the reproductive state. The effect of these changes on the population growth rate was evaluated using an estimated value for mortality in the field. In the present analysis, the juvenile period was the most sensitive variable.
Kinetics of toluene sorption and desorption in Ca- and Cu-montmorillonites investigated with Fourier transform infrared spectroscopy under two different levels of humidity
Authors: Shih Yang-Hsin , Wu Shian-Chee
Published: November 2004

Clays in soils or groundwater aquifer materials play roles in the sorption of organic pollutants. The intrinsic sorption kinetics of toluene in dry and humid clay films was investigated by tracking the change of infrared absorbance. Under the humid condition, similar toluene-sorbed intensities were found in Ca- and Cu-montmorillonites. However, a higher intensity of sorbed toluene was found in the Cu-form than in the Ca-form under the dry condition, which indicates a stronger interaction occurring in dry Cu-montmorillonite. The general time scale of sorption of toluene on clays is around 100 s. In both forms of montmorillonite, some portion of toluene was desorbed at an extremely slow rate under the dry condition. Some newly identified peaks were persistent against desorption from montmorillonites, suggesting the existence of irreversibly sorbed species and the possibility of toluene transformation occurring in clay systems.
Linking metal bioaccumulation of aquatic insects to their distribution patterns in a mining-impacted river
Authors: Cain Daniel J. , Luoma Samuel N. , Wallace William G.
Published: November 2004

Although the differential responses of stream taxa to metal exposure have been exploited for bioassessment and monitoring, the mechanisms affecting these responses are not well understood. In this study, the subcellular partitioning of metals in operationally defined metal-sensitive and detoxified fractions were analyzed in five insect taxa. Samples were collected in two separate years along an extensive metal contamination gradient in the Clark Fork River (MT, USA) to determine if interspecific differences in the metal concentrations of metal-sensitive fractions and detoxified fractions were linked to the differences in distributions of taxa relative to the gradient. Most of the Cd, Cu, and Zn body burdens were internalized and potentially biologically active in all taxa, although all taxa appeared to detoxify metals (e.g., metal bound to cytosolic metal-binding proteins). Metal concentrations associated with metal-sensitive fractions were highest in the mayflies Epeorus albertae and Serratella tibialis, which were rare or absent from the most contaminated sites but occurred at less contaminated sites. Relatively low concentrations of Cu were common to the tolerant taxa Hydropsyche spp. and Baetis spp., which were widely distributed and dominant in the most contaminated sections of the river. This suggested that distributions of taxa along the contamination gradient were more closely related to the bioaccumulation of Cu than of other metals. Metal bioaccumulation did not appear to explain the spatial distribution of the caddisfly Arctopsyche grandis, considered to be a bioindicator of metal effects in the river. Thus, in this system the presence/absence of most of these taxa from sites where metal exposure was elevated could be differentiated on the basis of differences in metal bioaccumulation.
A bayesian approach to parameter estimation for a crayfish (Procambarus spp): Bioaccumulation model
Authors: Lin Hsin-I , Berzins David W. , Myers Leann , George William J. , Abdelghani Assaf , Watanabe Karen H.
Published: November 2004

Bioaccumulation models are used to describe chemical uptake and clearances by organisms. Averaged input parameter values are traditionally used and yield point estimates of model outputs. Hence, the uncertainty and variability of model predictions are ignored. Probabilistic modeling approaches, such as Monte Carlo simulation and the Bayesian method, have been recommended by the U.S. Environmental Protection Agency to provide a quantitative description of the degree of uncertainty and/or variability in risk estimates in ecological hazards and human health effects. In this study, a Bayesian analysis was conducted to account for the combined uncertainty and variability of model parameters in a crayfish bioaccumulation model. After a 5-d exposure in the LaBranche Wetlands (LA, USA), crayfish were analyzed for polycyclic aromatic hydrocarbon concentrations and lipid fractions. The posterior distribution of model parameters were derived from the joint posterior parameter distributions using a Markov chain Monte Carlo approach and the experimental data. The results were then used to predict the distribution of chrysene concentration versus time in the crayfish to compare the predicted ranges at the different study sites.
Quantitative structure-activity relationship modeling of acute toxicity of quaternary alkylammonium sulfobetaines to Daphnia magna
Authors: Davies Joanna , Ward Robert S. , Hodges Geoffrey , Roberts David W.
Published: November 2004

The logarithm of the octanol/water partition coefficient has been widely used as the sole physicochemical property to define various types of biological activity, such as aquatic toxicity. In the present study, we derive a quantitative structure–activity relationship (QSAR) equation for the prediction of acute aquatic toxicity (48-h median effective concentration) of quaternary alkylammonium sulfobetaines to the aquatic invertebrate Daphnia magna Straus. The single-parameter approach described is also based on the hydrophobicity parameter, log P. The 17 zwitterionic compounds were considered for QSAR development. They have the general formula RN+(CH3)2(CH2)nSO3−, where n = 2 to 4, and were synthesized by reacting the corresponding N,N-dimethylamines with either sodium-2-chloroethanesulfonate (n = 2), 1,3-propanesultone (n = 3), or 1,4-butanesultone (n = 4). The R group was either a C6 to C12 alkyl chain, a phenylalkyl unit bearing a C1 to C4 chain, or a phenylpropyl unit with a C4 to C6 para-substituted alkyl group. Octanol/water partition coefficients were experimentally determined via a conventional stir-flask procedure, which was quantified using a reverse-phase, high-performance liquid chromatographic technique coupled with either an ultraviolet or an electrospray ionization mass spectrometry detection system. Median effective concentration values were also determined experimentally via a standard acute immobilization test recommended by Organisation for Economic Cooperation and Development (Paris, France) Guideline 202. The established QSAR equation for such zwitterionic compounds is consistent with the standard equation that normally defines the polar narcosis mode of toxic action.
A field test and comparison of acute and chronic sediment toxicity tests with the estuarine amphipod Leptocheirus plumulosus in Chesapeake Bay, USA
Authors: McGee Beth L. , Fisher Daniel J. , Wright David A. , Yonkos Lance T. , Ziegler Gregory P. , Turley Steven D. , Farrar J. Daniel , Moore David W. , Bridges Todd S.
Published: November 2004

A 28-d partial life-cycle test with the estuarine amphipod Leptocheirus plumulosus was developed in response to the need for an assay to mimic chronic exposure to sediment-associated contaminants. To ensure that toxicity tests have environmental relevance, it is essential to evaluate the relationship between laboratory responses and field measures of contamination. Consequently, one objective of the study was to compare the results of the chronic sediment toxicity test with L. plumulosus to gradients of sediment contamination and the in situ benthic community in its native Chesapeake Bay. Chronic tests were conducted by two laboratories, the Army Corps of Engineers Waterways Experiment Station ([WES]; Vicksburg, MS, USA) and the University of Maryland ([UM] College Park, MD, USA) using different feeding regimes, providing the opportunity to evaluate the effect of this variable on response sensitivity. A second objective was to compare the relative sensitivity of acute and chronic tests with L. plumulosus with field-collected sediments. Overall, there was good agreement between the toxicological response of acute and chronic tests with L. plumulosus and field measures of contamination. Survival in the acute test and chronic test conducted by WES was negatively correlated with concentrations of sediment-associated contaminants. Survival in acute exposures was significantly reduced in sediments from 8 of 11 stations. Indigenous L. plumulosus were found only at two of the three stations that did not exhibit acute toxicity. An unexpected finding was the difference in responsiveness of the two chronic tests. Survival in tests conducted by UM and WES was significantly reduced in sediments from 4 and 6 of 11 stations, respectively. No additional sublethal toxicity was detected in the UM chronic test, but the WES test detected reproductive effects at two additional stations. We believe the observed differences were related to the test diet used. Partly as a result of our findings, the recommended diet for the L. plumulosus chronic test was changed in the final methods document.
Effects of the pesticides captan, deltamethrin, isoproturon, and pirimicarb on the microbial community of a freshwater sediment
Authors: Widenfalk Anneli , Svensson Jonas M. , Goedkoop Willem
Published: November 2004

In three microcosm experiments, we exposed microbial communities of a natural sediment to environmentally relevant concentrations of the fungicide captan, the herbicide isoproturon, and the insecticides deltamethrin and pirimicarb. Exposure concentrations were estimated negligible concentrations (NCs), maximum permissible concentrations (MPCs), and 100 times MPC (100MPC). Experimental endpoints were microbial community respiration and biomass, bacterial activity, and denitrification. All four pesticides inhibited bacterial activity by 20 to 24% at MPC, which corresponded to concentrations in the range of μg/kg dry-weight sediment. Treatments with deltamethrin and isoproturon showed inhibiting effects on bacterial activity at NC exposures. Surprisingly, for captan, deltamethrin, and isoproturon, this inhibiting effect was not observed at 100MPC treatments. Microbial biomass was negatively effected in MPC treatments with deltamethrin and in NC treatments with isoproturon. The tested pesticides did not affect community respiration and denitrification rates. These results show that exposure to the tested pesticides may induce toxic responses in sediment microbial communities at concentrations that are predicted to be environmentally safe.
Influence of soot on hydrophobic organic contaminant desorption and assimilation efficiency
Authors: Lamoureux Elizabeth M. , Brownawell Bruce J.
Published: November 2004

Soot, soot-amended sediment, and unamended sediment spiked with hydrophobic organic contaminants (HOC) were subjected to laboratory desorption and assimilation efficiency experiments in an effort to assess and compare the importance of soot in controlling HOC desorption and deposit-feeder assimilation efficiency. Three contaminants, naphthalene (NAP), benzo[a]pyrene (BaP), and hexachlorobenzene (HCB) were sorbed to sediments, sediments amended with soot (2–4% dry wt), and soot for a period of 34 d. Desorption of all three contaminants into seawater from the three prepared sorbates was then monitored, and Nereis succinea assimilation efficiency experiments on the BaP- and HCB-contaminated sorbates were conducted. Both NAP and BaP desorption rates for soot and soot-amended sediments were reduced by at least a factor of two relative to unamended sediment. Hexachlorobenzene desorption rates were similar for both the soot-amended and the unamended sediments. Results of N. succinea assimilation efficiency experiments indicate a trend similar to the desorption experiments: higher assimilation of BaP from unamended relative to soot-amended sediment and little difference in assimilation between treatments for HCB. However, soot was more effective in reducing BaP desorption than assimilation efficiency, which would be consistent with the hypothesis that the gut fluid dissolution by deposit feeders may partially decouple biological availability from chemical availability.
Role of source matrix in the bioavailability of polycyclic aromatic hydrocarbons to deposit-feeding benthic invertebrates
Authors: Rust Aaron J. , Burgess Robert M. , McElroy Anne E. , Cantwell Mark G. , Brownawell Bruce J.
Published: November 2004

The bioavailability of polycyclic aromatic hydrocarbons (PAHs) to benthic organisms is complicated by the variety of ways that they are introduced to coastal waters (dissolved, as nonaqueous phase liquids, and tightly bound to soot, coal, tire rubber, and eroded shale). In order to better understand the controlling variables that affect chemical and biological availability of PAHs, a study was conducted in which three deposit-feeding infaunal benthic invertebrate species (Cirriformia grandis, Clymenella torquata, and Macoma balthica) were exposed to sediments amended with PAH-rich materials (coal dust, tire rubber, diesel soot, creosote, crude oil, and fuel oil). Lipid and organic carbon normalized bioaccumulation factors (BAFlocs) were calculated after 20 d of exposure and PAH bioavailability from the different treatments was assessed. Bioaccumulation of coal-derived PAHs usually was too low to be measured, though PAHs associated with soot and tire rubber showed significant accumulation in organism tissues. Polycyclic aromatic hydrocarbons from the fuel oil, creosote, and crude oil treatments were more bioavailable than PAHs bound in solid carbonaceous matrices (soot, coal, and tire rubber). Desorption of PAHs from the amended sediments into seawater also was measured using XAD resin. As was observed with bioaccumulation, PAHs in coal were desorbed the least; tire rubber and diesel soot were intermediate; and creosote, fuel oil, and crude oil desorbed to the greatest extent. In only one out of the three species evaluated was PAH bioaccumulation related to extent of desorption after 20 d. Decoupling between biological and chemical availability may be due to species-specific factors such as surfactant-mediated solubilization in the guts of some deposit-feeding organisms. A significant finding of this work was the demonstration that PAHs associated with soot and tire rubber in their native state (rather than experimentally added) are available to some benthic biota.
Influence of soot carbon on the bioaccumulation of sediment-bound polycyclic aromatic hydrocarbons by marine benthic invertebrates: An interspecies comparison
Authors: Rust Aaron J. , Burgess Robert M. , McElroy Anne E. , Cantwell Mark G. , Brownawell Bruce J.
Published: November 2004

The sorption of polycyclic aromatic hydrocarbons (PAHs) to soot carbon in marine sediments has been hypothesized to reduce PAH bioavailability. This hypothesis was tested for eight species of marine benthic invertebrates (four polychaete worms, Clymenella torquata, Nereis virens, Cirriformia grandis, and Pectinaria gouldii, and four bivalve mollusks, Macoma balthica, Mulinia lateralis, Yoldia limatula, and Mya arenaria) that span a wide range of feeding behavior, ability to metabolize PAHs, and gut chemistry. Organisms were exposed for 20 d to two PAH-spiked sediments, one with soot and one without soot. The soot treatment generally resulted in lower bioaccumulation than the no soot treatment, though the differences between treatments were not significant for all species. All but one species accumulated significant PAH concentrations in their tissues from the soot treatment, indicating that soot-bound PAH cannot be dismissed as unavailable to infaunal benthic biota. Bioaccumulation factors were correlated negatively to both the organisms' ability to metabolize PAHs and the gut fluid contact angle, supporting the hypotheses that high PAH metabolism results in lower bioaccumulation factors and bioavailability of PAHs may be limited partially by PAH solubilization in the gut lumen. The variability in bioaccumulation due to the soot treatment was much less than the variability between species and between PAH analytes. Comparatively low bioaccumulation was observed in Nereis virens, a species commonly used in bioaccumulation tests. These results suggest that more effort is needed in understanding the salient characteristics of species present in a threatened environment, rather than focusing solely on the sediment geochemistry (e.g., soot and organic carbon content) and contaminant characteristics when predicting ecological risk of PAH-contaminated sediments.
Overview and comparison of lipid-containing semipermeable membrane devices and oysters (Crassostrea gigas) for assessing organic chemical exposure
Authors: Huckins James N. , Prest Harry F. , Petty Jimmie D. , Lebo Jon A. , Hodgins Maureen M. , Clark Randal C. , Alvarez David A. , Gala William R. , Steen Alexis , Gale Robert , Ingersoll Christopher G.
Published: November 2004

We performed 20-d, flow-through exposures of lipid-containing semipermeable membrane devices (SPMDs) and Pacific oysters (Crassostrea gigas) to three concentrations (nominally 10, 100, and 250 ng/L) of a diverse mixture of polycyclic aromatic hydrocarbons (PAHs). Exposure water was seawater free of particulates larger than 0.1 μm. The results of these controlled laboratory studies demonstrated that SPMDs and oysters concentrate the same chemicals but that the relative amounts accumulated are different. For oysters, the 20-d mean (across treatments) concentration factors (CFs) of test compounds with log Kow ≤ 4.8 were much lower (4.0- to 20-fold lower) than those of the same compounds in SPMDs. In contrast, the 20-d CFs of PAHs with log Kow ≥ 5.6 in oysters from the low-level treatment were higher than the corresponding CFs for SPMDs. The CFs of these compounds in oysters from the low-level treatment ranged from approximately 3.0- to 13-fold higher than those in oysters from the high-level treatment. This physiologically mediated difference in oyster CFs appears to be linked to active feeding in the low-level treatment and to apparent toxicity-induced cessation of feeding (i.e., valve closure) in the high-level treatment. Because CFs for these compounds in oysters were not independent of exposure concentrations, it follows that tissue levels were not proportional to exposure concentration. However, both sampling approaches have advantages and disadvantages, and the appropriateness of their use depends on the goals of a given study.
Effects of vertebrate hormones on development and sex determination in Daphnia magna
Authors: Kashian Donna R. , Dodson Stanley I.
Published: November 2004

Daphnia (Crustacea) are extensively used as model organisms in ecotoxicology; however, little is known regarding their endocrine system. This study examines Daphnia vulnerability to vertebrate hormones. Twelve natural or synthetic vertebrate hormones were screened for activity on developmental and reproductive processes in Daphnia magna. Natural hormones tested included: β-estradiol, gonadotropin, hydrocortisone, insulin, melatonin, progesterone, somatostatin, testosterone, and thyroxine at concentrations ranging from 1 to 100 μg/L. Synthetic hormones tested included diethylstilbestrol (estrogenic), R-1881 (androgen), and ICI-182,780 (antiestrogen); all hormones were screened with a 6-d assay. Additionally, progesterone, insulin, testosterone, and thyroxine were screened for 25 d. Diethylstilbestrol decreased D. magna growth rate while thyroxine increased it. Short-term testosterone exposure reduced D. magna fecundity; however, long-term exposure did not, potentially indicating testosterone hydroxylation with long-term exposure. Hormones commonly considered sex-hormones (estrogens and androgens) in vertebrates do not appear to control sexual differentiation in D. magna; however, several vertebrate hormones do affect reproduction and development in D. magna making D. magna a potentially useful tool in monitoring for the presence of these hormones or compounds that mimic them.
The long-term fate of polychlorinated biphenyls in San Francisco Bay (USA)
Authors: Davis Jay A.
Published: November 2004

A simple one-box mass budget model is presented as a first step toward a quantitative understanding of the long-term fate of polychlorinated biphenyls (PCBs) in San Francisco Bay (USA). Sensitivity analysis indicated that the most influential input parameters were degradation half-life in sediment, Kow, outflow, average PCB concentration in sediment, and depth of the active sediment layer. Moderately influential parameters included organic carbon content of suspended solids, sediment burial mass transfer coefficient, and Henry's law constant. If external loading could be eliminated entirely, the mass of PCBs in the bay is predicted to drop to half of the present value in 20 years. The model predicts that sustained loading of 10 kg year−1 would prevent the total PCB mass in the bay from ever dropping below 10% of the present mass. With a sustained loading of 20 kg year−1, the model predicts that the total PCB mass would never fall below about 25% of the present mass. The half-lives in the bay for the individual PCB congeners evaluated in this report ranged from four years for PCB 18 to 30 years for PCB 194.
Use of cyclodextrin and calcium chloride for enhanced removal of mercury from soil
Authors: Wang Xiaojiang , Yolcubal Irfan , Wang Weizi , Artiola Janick , Maier Raina , Brusseau Mark
Published: November 2004

The use of solutions containing carboxymethyl-β-cyclodextrin (CMCD) or CaCl2 for enhancing the removal of Hg from a sandy soil was investigated using batch and column experiments. The retention of Hg appeared to be controlled by specific adsorption reactions, which greatly constrained Hg removal when using water (KNO3 solution) to flush columns packed with contaminated soil. The results showed that the two reagents did enhance the removal of Hg from the soil. For example, 81% and 60% of Hg was recovered after 50 pore volumes of flushing with 50 mM CaCl2 and 2 mM CMCD, respectively, compared to 24% recovery for a 10 mM KNO3 solution. However, significant tailing and delayed recovery of Hg during the elution process occurred in the presence of all reagents, indicating that the removal of Hg from the soil was rate limited.
Baseline toxicity of a chlorobenzene mixture and total body residues measured and estimated with solid-phase microextraction
Authors: Leslie Heather A. , Hermens Joop L. M. , Kraak Michiel H. S.
Published: November 2004

Body residues of compounds with a narcotic mode of action that exceed critical levels result in baseline toxicity in organisms. Previous studies have shown that internal concentrations in organisms also can be estimated by way of passive sampling. In this experiment, solid-phase microextraction (SPME) fibers were used as a tool to estimate the body residues, which were then compared to measured levels. Past application of SPME fibers in the assessment of toxicity risk of samples has focused on separate exposure of fibers and organisms, often necessitated by the amount of agitation needed in order to achieve steady state in the fibers within a convenient time period. Uptake kinetic studies have shown that in SPME fibers with thin coatings, equilibrium concentrations can be reached without agitation within the time frame of a toxicity test. In contrast to toxicity experiments to date, the SPME fibers in the current study were exposed concomitantly to the test water with the organisms, ensuring an exposure under the exact same conditions. Fibers and two aquatic invertebrate species were exposed to a mixture of four chlorobenzenes with a narcotic mode of action. The total body residue of these compounds in the organisms was determined, as was the acute toxicity resulting from the accumulation. The total body residues of both species were correlated to the total concentrations in SPME fibers. It was concluded that toxicity could be predicted based on total body residue (TBR) estimates from fiber concentrations.
Monitoring polynuclear aromatic hydrocarbons in aqueous environments with passive low-density polyethylene membrane devices
Authors: Carls Mark G. , Holland Larry G. , Short Jeffrey W. , Heintz Ron A. , Rice Stanley D.
Published: November 2004

Low-density polyethylene membranes, typically filled with triolein, have been previously deployed as passive environmental samplers designed to accumulate nonpolar hydrophobic chemicals from water, sediments, and air. Hydrocarbons in such samplers, known as semipermeable membrane devices (SPMDs), diffuse through pores in the membranes and are trapped in the central hydrocarbon matrix, mimicking uptake by living organisms. Here, we describe laboratory and field verification that low-density polyethylene membrane devices (PEMDs) without triolein provide reliable, relatively inexpensive, time-integrated hydrocarbon sampling from water. For comparison, polynuclear aromatic hydrocarbon (PAH) uptake in SPMDs and pink salmon eggs also was studied. Total concentrations of PAH accumulated by PEMDs were highly correlated with concentrations in water (r2 ≥ 0.99) and linear over the range tested (0–17 μg/L). Higher-molecular-mass PAH preferentially accumulated in PEMDs and in pink salmon eggs, but the source of oil in PEMDs remained identifiable. Accumulations of PAH were highly similar to those in SPMDs. The PEMDs retained approximately 78% of accumulated total PAH for 40 d in clean water. Thus, a simple plastic membrane can be conveniently used for environmental monitoring, particularly during situations in which contaminant concentrations are low (in the parts-per-billion range), variable, and intermittent.
A historical record of mercury contamination in southern florida (USA) as inferred from avian feather tissue: Contribution R-09888 of the Journal Series, Florida Agricultural Experiment Station
Authors: Frederick Peter C. , Hylton Becky , Heath Julie A. , Spalding Marilyn G.
Published: November 2004

During the late 1980s, the upper trophic-level biota of the Everglades (FL, USA) was recognized as being highly contaminated with mercury (Hg). However, the timing and pattern of that increase is poorly known, and no information is available about mercury contam ination in Everglades wildlife prior to 1974. We measured methylmercury concentrations in feathers of white ibises (n = 33), great egrets (n = 7), anhingas (n = 21), and great blue herons (n = 12) from museum specimens collected from 1910 through 1980 and combined them with more recent feather samples collected from live birds (1985–2000, n = 98, 37, 49, and 7, respectively). We found no evidence of contamination of museum samples with inorganic mercuric preservatives (0.01–0.28% of total Hg in feathers). All species showed relatively low concentrations of mercury through the 1970s (<5 μl/L dry wt for anhingas, ibises, and egrets, <10 μl/L for herons). Samples from all species taken during the 1990s showed a large and significant increase (4–5X) in MeHg concentration. This evidence suggests that most of the increase in Hg deposition during the 20th century in south Florida occurred during the last two to three decades, which is consistent with information about local source deposition. Contamination levels prior to the 1970s appear to have been associated with normal reproduction in these birds, suggesting partial evidence for a threshold of reproductive impairment.
Soil-air relationships for toxaphene in the southern United States
Authors: Bidleman Terry F. , Leone Andi
Published: November 2004

Volatilization of toxaphene residues from agricultural soil was investigated at farms in the southern United States by collecting air samples 40 cm above the soil. The concentration of total toxaphene ranged over several orders of magnitude, from <3 to 6,500 ng g−1 dry weight in soil, and <0.3 to 42 ng m−3 in air. A log-log plot of total toxaphene concentrations in soil and overlying air showed a significant (p < 0.001) positive relationship, with r2 = 0.73. The soil/air fugacity ratio (FR) for 26 events ranged from 0.4 to 238, exceeded FR = 1.0 (soil/air equilibrium) in 24 events, and exceeded FR = 10 in 17 events. This indicates that toxaphene in air sampled at 40 cm generally was not at equilibrium but undersaturated with respect to the soil. Compared to a technical toxaphene standard, chromatographic profiles of toxaphene residues in soil and air showed alterations due to preferential degradation and volatilization of the components. Peaks matching the retention times of labile octachlorobornanes B8–531 and B8–806 + B8–809 were depleted in both soil and air relative to the more recalcitrant B8–1413 + B8–1945 and B8–2229. For each event, log-log plots were made of the dimensionless soil/air concentration quotient (Q) versus liquid-phase vapor pressure (PL, Pa) for 10 toxaphene components (peaks containing coeluting congeners) that spanned the volatility range of hepta- to nonachlorobornanes. Statistically significant linear relationships were obtained with r2 values for most events ranging from 0.54 to 0.96. Slopes for all but one event ranged from −1.01 to −1.53 and averaged −1.28 ± 0.20. When regressions were carried out for only components one to nine, which cover the vapor pressure range of most components reported in ambient air, the average slope was reduced to −1.02 ± 0.15. Previous models of toxaphene emission, transport, and deposition have considered only total toxaphene. These results provide a basis for modeling soil/air exchange on the basis of single congeners or groups of congeners having similar volatilities.