bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of laboratory test conditions on the toxicity of silver to aquatic organisms
Authors: Erickson Russell J , Brooke Larry T , Kahl Michael D , Venter Fred Vende , Harting Sandra L , Markee Thomas P , Spehar Robert L 
Published: March 2010

Abstract
The effects of various chemical manipulations of test water on acute toxicity of silver to fathead minnows (Pimephales promelas) were investigated. Increases in hardness and organic carbon substantially reduced toxicity. Toxicity was also inversely related to pH and alkalinity when these parameters were jointly changed by addition of strong acid or base. The addition of 2 meq/L sodium sulfate had no significant effects, but the addition of 0.2 meq/L sodium chloride increased toxicity, perhaps related to the formation of the dissolved AgCl0 complex. We also evaluated the effects of static versus flow-through test conditions, feeding during exposure, and aging of test solutions before exposure on the acute toxicity of silver to fathead minnows and Daphnia magna. Static conditions and feeding reduced toxicity, likely as a result of accretion of organic carbon. Aging of test solutions had little effect. For both juvenile fathead minnows and D. magna, silver was much less toxic in water from the St. Louis River than in our normal laboratory water, presumably because of the much higher organic carbon content of the river water. This study identified some aspects of test conditions that are important in assessing the risk of silver to aquatic biota, but improved assessments will require information for more conditions, species, and endpoints. More importantly, if toxicity test results are to be extrapolated among waters with different chemistries, adequate characterization of the chemical speciation of silver and a better understanding of the mechanisms of silver toxicity and its relationship to silver speciation and other chemical factors are needed.
Impact of humic constituents on microbial dechlorination of polychlorinated dioxins
Authors: Barkovskii Andrei L , Adriaens Peter 
Published: March 2010

Abstract
We recently reported on the ability of a microbial consortium eluted from dioxin-contaminated Passaic River sediments to dechlorinate polychlorinated dibenzo-p-dioxins (PCDDs) through peridechlorination of 2,3,7,8-substituted hepta- to penta-CDDs resulting in the transient production of 2,3,7,8-tetra-CDD and through perilateral dechlorination pathway of non-2,3,7,8-substituted congeners. The dechlorination of PCDDs under combined reductive activities of the same microbial community and model humic constituents (MHCs) (resorcinol, 3,4-dihydroxybenzoic acid [3,4-DHBA], and catechol) was investigated. Model humic constituents alone caused reductive dechlorination of PCDDs, resulting in the production of hepta-, hexa-, and tetra-CDD congeners. Whereas abiotic MHC-stimulated dechlorination ceased at the tetra-CDD group of congeners, microbial activity caused further dechlorination to tri-, di-, and mono-CDDs. Combined with the microbial community, MHCs effected the appearance of a new profile of tetra through mono-CDD congeners that was distinguishable from either microbially or MHC-stimulated processes alone. An important overall trend could be discerned: the peridechlorination of PCDDs was promoted by MHCs, resulting in both a relative and an absolute (except for 3,4-DHBA) increase of 2,3,7,8-tetra-CDD relative to either microbially or MHC-stimulated dechlorination. This study indicates that, aside from direct deposition, the increase of 2,3,7,8-tetra-CDD concentrations in the environment may result from combined biotic and abiotic PCDD dechlorination.
Effects of soil type, prepercolation, and ageing on bioaccumulation and toxicity of zinc for the springtail Folsomia candida
Authors: Smit C Els , Van Gestel Cornelis A M 
Published: March 2010

Abstract
Soil properties are a major influence on the bioavailability and toxicity of metals and represent one of the important factors that complicate the extrapolation of results from laboratory tests to field situations. The influence of soil characteristics and way of contamination on the bioaccumulation and toxicity of zinc was investigated for the springtail Folsomia candida, and the applicability of chemical extraction techniques for the prediction of zinc uptake and toxicity was evaluated. Bioaccumulation of zinc in F. candida was related to water-soluble zinc concentrations, and uptake was dependent on the test soil used. Effects of zinc for F. candida could not be fully explained by bioaccumulation. This indicates that the existence of a fixed internal threshold concentration of zinc above which physiological functions are impaired is not likely for F. candida. In freshly contaminated soils, zinc toxicity was related to organic matter and clay content of the soil; however, the use of these soils overestimated the effects of zinc for F. candida by a factor of 5 to 8 compared to a test soil that was subjected to ageing under field conditions for 1.5 years. Equilibration of the zinc contamination by percolating the soils with water before use in the toxicity experiment strongly reduced the difference in zinc toxicity between laboratory-treated and aged soils. Water-soluble concentrations are most appropriate to predict effects of zinc on reproduction of F. candida in soils with unknown contamination histories. For laboratory toxicity tests, it is recommended to percolate soils with water after contamination and to include an equilibration period prior to use to achieve a more realistic exposure situation.
Mercury distribution in poplar creek, Oak Ridge, Tennessee, USA
Authors: Campbell Kym Rouse , Ford Clell J , Levine Daniel A 
Published: March 2010

Abstract
As a result of the lithium-isotope separation process used in the production of thermonuclear fusion weapons during the mid-1950s and early 1960s, 150 t of mercury were released into Poplar Creek (via East Fork Poplar Creek) in Oak Ridge, Tennessee, USA. This project was performed as part of a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) remedial investigation to define the nature and extent of mercury contamination in Poplar Creek. Ultraclean sampling techniques and ultrasensitive analytical methods were used to determine methylmercury and inorganic mercury concentrations in surface water, sediment, and pore water from Poplar Creek. Total methylmercury and inorganic mercury concentrations (0.08–0.7 ng/L and 0.4–560 ng/L, respectively) in surface water from reaches downstream from the East Fork Poplar Creek confluence were significantly higher (p &lt; 0.05) than the upstream reference reach (0.05–0.3 ng/L and 0.1–27 ng/L, respectively). Concentrations in surface water increased with distance downstream from the source (East Fork Poplar Creek), which was opposite of expected results. Sediment methylmercury and inorganic mercury concentrations also increased with the distance downstream from the source and were highest near the mouth of Poplar Creek (1.0–12 ng/g and 630–140,000 ng/g, respectively). High concentrations in surface water and sediment near the mouth of Poplar Creek appear to be a result of sediment deposition and resuspension, apparently caused by the stronger Clinch River current acting as a barrier and its backflow into Poplar Creek as a result of hydropower operations.
Determination of Henry's law constants by equilibrium partitioning in a closed system using a new in situ optical absorbance method
Authors: Allen John M , Balcavage Win X , Ramachandran B R , Shrout Anthony L 
Published: March 2010

Abstract
A new method for measurement of thermodynamic Henry's law constants (H) is reported. In this method, the optical absorbance of a dilute aqueous solution containing an organic compound is followed with time as the compound partitions into the air above the solution in a sealed vessel. The change in optical absorbance (i.e., change in concentration) and the vapor to liquid volume ratio of the vessel are then used to calculate the value for H. The concentration of the organic compound in the aqueous and vapor phases need not be known. This method allows the approach to equilibrium to be observed in real time so that attainment of equilibrium is readily apparent. This method works particularly well for water-soluble compounds having low vapor pressures. The applicability of this method is limited to compounds that exhibit significant optical absorbance in the ultraviolet and visible regions of the electromagnetic spectrum. Values for H and their temperature dependencies measured using this new method are reported for methacrolein, methyl vinyl ketone, benzaldehyde, and acetophenone. Values for H are also reported for benzene, toluene, and ethylbenzene at 298 K. All reported H data are compared with previously reported values.
Estimating the aqueous solubilities of individual chlorinated n-alkanes (C10–C12) from measurements of chlorinated alkane mixtures
Authors: Drouillard Ken G , Hiebert Tim , Tran Phuong , Tomy Gregg T , Muir Derek C G , Friesen Ken J 
Published: March 2010

Abstract
Water solubilities of several chlorinated n-alkanes, with carbon chain lengths ranging from C10 to C12, were determined from simple synthetic mixtures because few of these compounds are available in pure form. The apparent solubilities (S′w) of several chlorinated n-decanes in the mixture were determined using the generator column technique. To assess the effect of the mixture on S′w, the aqueous solubility and activity coefficient (γorg) of a reference compound, 1,10-dichlorodecane, were determined as a function of its mole fraction in the same synthetic mixture. The mixture exhibited a cosolute effect on the solubility of dichlorodecane, with apparent solubilities decreasing linearly with decreasing mole fraction. The results were used to correct the apparent solubilities of terra- and pentachlorodecanes determined from the synthetic mixture, thereby providing estimates of the true subcooled-liquid aqueous solubilities of these compounds. The solubilities of polychlorinated decane, undecane, and dodecane congeners were also estimated using subcooled-liquid vapor pressures and Henry's law constants determined from previous experiments. The two methods yielded comparable estimates, within a factor of 1.5, of the true solubilities of polychlorinated decanes. Water solubilities for selected chlorinated n-alkane congeners among the three carbon chain lengths ranged from 22.4 to 975 μg/L and showed a trend of increasing solubility with increasing degree of chlorination to chlorine number five. The data, providing some of the first physical properties of individual isomers of C10 to C12 polychlorinated n-alkanes, may be useful in assessing the environmental behavior of chlorinated paraffins in general.
Assessment of metal inhibition of reductive dechlorination of hexachlorobenzene at a superfund site
Authors: Jackson W Andrew , Pardue John H 
Published: March 2010

Abstract
Laboratory studies were conducted to identify easily measured parameters that would predict the potential for metal inhibition in sediments co-contaminated by heavy metals and hexachlorobenzene (HCB) at the Petro Processors Superfund site. Metal inhibition was investigated using HCB-contaminated sediment and a range of added metal concentrations (1–1,000 mg/kg). Cadmium, Cu, Pb, and Zn all caused inhibition of HCB reductive dechlorination and methane production with inhibiting concentrations of Cd and Pb equivalent to those found in portions of the site. In the second phase of studies, laboratory experiments investigated the relationship between Cd and Pb availability on the kinetics of HCB degradation. Cadmium and Pb affected both dechlorination rates and lag times. In addition, Cd affected the appearance of lower chlorinated benzene metabolites. Inhibition of HCB dechlorination was well correlated to ratios of acid-volatile sulfide (AVS) to simultaneously extractable metals (SEM) and water-soluble Cd. Only treatments with a measurable concentration (&gt;6 μg/L) of free, uncomplexed Cd exhibited inhibition. Lead inhibited HCB dechlorination at all concentrations tested (10–1,000 mg/kg) and inhibition did not correlate to either water-soluble Pb concentrations or AVS/SEM ratios. For both Cd and Pb, methane production was less sensitive to metals than HCB dechlorination, making production of methane a poor indicator of inhibition. Measurement of free, uncomplexed Cd was the best predictor of Cd inhibition while no suitable indicators were found for Pb. These results demonstrate the importance of metal bioavailability on the inhibition of reductive dechlorination.
Volatile fractions of landfill leachates and their effect on Chlamydomonas reinhardtii: In vivo chlorophyll a fluorescence
Authors: Brack Werner , Rottler Horst , Frank Hartmut 
Published: March 2010

Abstract
A method for identification of toxic volatile constituents of landfill leachates is presented that combines bioassay-compatible sample preparation, chemical analysis, and a bioassay based on in vivo chlorophyll a fluorescence of the green alga Chlamydomonas reinhardtii. Two major pathways of toxicity were identified by comparing fluorescence patterns: specific toxicity of hydrogen sulfide, and narcotic action of nonreactive organic compounds. For quantification, the contributions of identified compounds were calculated using toxic units. The ecotoxicologic relevance of volatile fractions from hazardous waste leachates was shown.
Mechanistic approach for estimating bioconcentration of organic chemicals in earthworms (oligochaeta)
Authors: Jager Tjalling 
Published: March 2010

AbstractEarthworms (Oligochaeta) represent an important food source for many vertebrates and as a result, predators may encounter toxic effects via the food chain (secondary poisoning) from consumption of contaminated worms. Therefore, including an assessment of secondary poisoning in risk assessment procedures is advisable. In this study, a mechanistic model is presented for estimating bioconcentration of organic chemicals in earthworms. It is assumed that bioconcentration can be described by a thermodynamic partitioning between soil solids, soil water, and the resident organism's tissues. For most chemicals, the lipid phase is the dominant site for sorption in the earthworm, but for more hydrophilic compounds, the water phase may also play a role. Model predictions are compared to literature data that were derived from experiments with earthworms in water, laboratory experiments with various soils, and from field experiments. Without calibration, the model was able to accurately predict bioconcentration factors (BCFs) from experiments in water, indicating the applicability of this theoretical approach. However, BCFs in soil were consistently overestimated by the model (on average a factor of 5.6), which may be due to the absence of true equilibrium conditions in the soil-pore water-earthworm system. The collected experimental data reveal no net influence of uptake via soil ingestion, growth dilution, or sorption to dissolved organic carbon. Field data were more variable, but were generally consistent with the model. Nevertheless, before field data can be accurately predicted, the influences of chemical sorption, sorption kinetics, and earthworm behavior must be quantified under field conditions.
An environmental risk assessment profile of two synthetic polymers
Authors: Guiney Patrick D , Woltering Daniel M , Jop Krzysztof M 
Published: March 2010

Abstract
A number of environmental fate and effects studies on two distinctly different polycarboxylates were conducted as part of a product stewardship program. These studies led to the development of an environmental risk assessment for the two materials. Polymer emulsion (PE) is a typical anionic, styrene-acrylic polymer (MW 50,000–60,000) used in coating applications. Resin polymer (RP), insoluble at neutral pH but increasingly soluble at pH ≥8, is a neutral-charged, styrene-acrylic polymer (molecular weight 4,500–9,000) used primarily for graphic arts products. Some amount of both materials will enter the environment given their use and disposal patterns. Their environmental fate is driven by physical-chemical characteristics. Both polymers demonstrated low biodegradation and bioaccumulation potential and strong sorption to soils, sludge, and sediments in laboratory and/or field studies. Ecotoxicity test results on a variety of plant and animal species indicated a very low order of acute and chronic toxicity. The environmental risk assessment included characterization of exposure in relevant environmental matrices, characterization of adverse effects or hazards to receptors for which there are complete exposure pathways, and characterization of risk by comparison of predicted exposure levels to adverse effect threshold levels. Based on conservative exposure assumptions, the safety margins established in this assessment indicate that the use of PE and RP, in both commercial and household applications, presents a very low risk to aquatic organisms in the water column and sediments, as well as to terrestrial plants, invertebrates, and wildlife. These polymers are also compatible with wastewater and solid waste treatment systems.
Community level analysis of ecotoxicological field studies: I. Biological monitoring
Authors: Kedwards Timothy J , Maund Stephen J , Chapman Peter F 
Published: March 2010

Abstract
A number of multivariate techniques including nonmetric clustering, nonmetric multidimensional scaling, and principal components analysis were used to analyze data from a farm pond study in which the pyrethroid insecticide cypermethrin was aerially applied adjacent to the water body. The techniques were used to investigate the effects upon benthic and emerging macroinvertebrate communities prior to, during, and following application. Hydrosoil cypermethrin residue was strongly correlated with changes in community composition, and Diptera were found to be most affected by the perturbation. However, any deleterious effect upon chironomid communities was transient, with Chironomidae larvae rapidly recovering after application. The study illustrates how multivariate techniques can aid in the interpretation of biological monitoring studies in which an adequate control pond is unlikely to be available.
Pilot plant study to assess the fate of two volatile methyl siloxane compounds during municipal wastewater treatment
Authors: Parker Wayne J , Shi Jichun , Fendinger Nicholas J , Monteith Hugh D , Chandra Grish 
Published: March 2010

Abstract
The environmental fate ofoctamethylcyclotetrasiloxane(D4) and decamethylcyclopentasiloxane (D5) during municipal wastewater treatment has been investigated in an activated sludge pilot plant by continuously dosing the influent with exagerated amounts of the compounds and measuring their emissions in the off-gas, effluent, and sludge streams. The total removal was found to be 86.4 ± 3.9% for D4 and 95.8 ± 1.5% for D5 (±1 SD statistical uncertainty). However, low overall mass balances were found for both compounds in the pilot system. In order to elucidate the detailed removal mechanisms for these two compounds, the model TOXCHEM was used to simulate their removal and analyze their mass balances in the pilot system. Experimental and model results indicated that the low mass balances were caused by the significant underestimation of the primary sludge removal by the grab sampling method used for sludge analyses. This underestimation may be due to the high variability of the primary influent suspended solids concentration and hence inhomogeneity in the primary sludge underflow. When this underestimation was taken into account, primary sludge removal and volatilization in the aeration basin were found to contribute approximately equally to the removal of D4 and D5 in the pilot plant system. The present results are useful for the environmental risk assessment of these two siloxane compounds in the unlikely event of their point source discharge into municipal wastewater systems.
Reproductive success and biochemical effects in tree swallows (Tachycineta bicolor) exposed to chlorinated hydrocarbon contaminants in wetlands of the great lakes and st. lawrence river basin, USA and Canada
Authors: Bishop Christine A , Mahony Nancy A , Trudeau Suzanne , Pettit Karen E 
Published: March 2010

Abstract
Reproduction and biochemical indicators (vitamin A, ethoxyresorufin-O-deethylase [EROD], highly carboxylated porphyrins) of contaminant effects, and concentrations of organochlorine residues were measured in tree swallows from wetlands within the watersheds of the Great Lakes and the St. Lawrence River, USA and Canada. To assess the vitamin A sources in the tree swallow diets, insects were collected, by ligature, from nestlings at four of these sites. Diet samples were analyzed for retinol and α- and β-carotene. Marked differences were found in chlorinated hydrocarbon residues in eggs and nestlings among sites; however, we did not find any significant differences in hatching or fledging success. The maximum polychlorinated biphenyl (PCB) concentration found was 11.1 μg/g in eggs from Akwesasne Reserve, New York, USA, on the St. Lawrence River, whereas the highest p, p′-DDE concentration of 2.57 μg/g was found in eggs from Mud Creek, Ontario, Canada, in the Lake Erie watershed. Concentrations of other organochlorine pesticides and chlorobenzenes were low and not variable among sites. Significant differences in hepatic EROD activity, retinol and retinyl palmitate, and uroporphyrin in nestling birds existed among sites. Ethoxyresorufin O-deethylase activity was highest and retinol and retinyl palmitate were lowest at Cornwall Island, Ontario, Canada, in the St. Lawrence River, whereas porphyrins were highest at Toronto and Hamilton harbors, Ontario, Canada, in Lake Ontario. Ethoxyresorufin O-deethylase induction was significantly and negatively correlated with nestling hepatic retinol concentrations, whereas uroporphyrin concentrations were positively correlated with PCB congener 118 in nestlings. In contrast, few differences occurred in vitamin A concentrations in diet samples among sites. Together, these findings suggest that depressed hepatic vitamin A and elevated highly carboxylated porphyrin concentrations are strongly associated with sites with the highest organochlorine exposure in tree swallows.
Solid-phase genotoxicity assay for organic compounds in soil
Authors: Alexander Renee R , Chung Namhyun , Alexander Martin 
Published: March 2010

Abstract
A genotoxicity assay was developed for samples from environments in which toxic organic compounds are largely sorbed. The assay entails measurement of the rate of mutation of a strain of Pseudomonas putida to rifampicin resistance. The ratio of induced to spontaneous mutants was a function of the concentration of a test mutagen in soil. In studies of the utility of the assay in samples amended with 2-aminofluorene as a test mutagen, the ratio of induced to spontaneous mutants declined with time. The decline paralleled the disappearance of extractable 2-aminofluorene from the soil. The ratio of induced to spontaneous mutants also fell in four other soils with dissimilar properties. We suggest that this solid-phase assay is more appropriate for the estimation of genotoxicants sorbed in soil than assays involving extractants or suspensions of soil or sediment samples.