bluuebunny/crossref_metadata_2025_split huggingface dataset:
Toxicokinetics of PAHs in Hexagenia
Authors: Stehly Guy R. , Landrum Peter F. , Klemm Christina , Henry Mary G. 
Published: March 2010

Abstract
The accumulation kinetics of two waterborne polycyclic aromatic hydrocarbons (PAHs), benzo[a]pyrene (BAP) and phenanthrene (PHE), were studied in the mayfly nymph (Hexagenia limbata).
The uptake clearance decreased while the bioconcentration of BAP increased with an increase in weight of the H. limbata nymph. The relationship between uptake clearance and bioconcentration for PHE was variable, and bioconcentration was greater for the heavier animals.
Two kinetic models were used to evaluate the effect of nymph weight on disposition of PAHs: (a) the amount-uptake clearance model, similar to models most frequently used in environmental toxicology; and (b) a clearance-volume model, similar to models used in clinical pharmacology. The two models gave similar predictive results but were different in a few cases. These differences in common parameter estimation probably resulted from methodologies used and high data variability rather than the models themselves, since they are mathematically equal. Some of the parameters are unique to each of the models and are defined and described.
The clearance of oxygen from water is inversely and linearly related to the weight of the mayfly nymphs, but oxygen clearances were always much less than the uptake clearances of the PAHs. The high PAH uptake clearance compared to oxygen clearance implies a greater surface area or efficiency for PAH accumulation from water.
Bioaccumulation and biotransformation of polychlorinated dibenzo-p-dioxins and dibenzofurans in fish
Authors: Opperhuizen Antoon , Sijm Dick T. H. M. 
Published: March 2010

AbstractIn spite of their hydrophobicity, not all polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners accumulate significantly in fish or other aquatic organisms. This is found both in laboratory experiments and in organisms that are sampled in the natural environment. Hitherto, this congener-specific accumulation could not adequately be explained or predicted.Many PCDDs and PCDFs with four or more chlorine atoms, such as octachlorodibenzo-p-dioxin, are taken up very slowly, if at all, during aqueous exposure. Furthermore, the uptake rates after dietary exposure of these congeners are significantly less than those of other chlorinated aromatic hydrocarbons with comparable hydrophobicity, such as polychlorinated benzenes and biphenyls. A lack or a low rate of membrane permeation may help to explain this phenomenon.For several higher chlorinated congeners and for most of the lower chlorinated dioxins and furans, the rates of uptake after dietary and aqueous exposure are comparable to those of other hydrophobic aromatic hydrocarbons. The relatively low bioconcentration and biomagnification factors of these lower chlorinated PCDDs and PCDFs should thus be explained by high rates of excretion, probably by biotransformation. In several studies, polar metabolites have been identified. Furthermore, in fish in which the cytochrome P-450 system was inhibited with piperonylbutoxide, the bioconcentration factor of 2,8-dichlorodibenzo-p-dioxin was significantly higher than that in fish which were not pretreated with the blocking agent. These results support the hypothesis that biotransformation is of paramount importance for the bioaccumulation of several PCDDs and PCDFs.
5-Methyl deoxycytidine content of DNA from bluegill sunfish (Lepomis macrochirus) exposed to benzo[a]pyrene
Authors: Shugart Lee R. 
Published: March 2010

Abstract
The 5-methyl deoxycytidine (m5-dCyd) content of DNA from bluegill sunfish chronically exposed to benzo[a]pyrene at a concentration of 1 μg/L in their water for a period of 40 d was quantified by cation exchange chromatography. Hypomethylation, as measured by the loss of m5-dCyd from the DNA, occurred shortly after benzo[a]pyrene (BaP) exposure and continued even upon termination of exposure conditions. The onset and persistence of hypomethylation was found to be correlated with other types of DNA-damaging events such as strand breaks and DNA adduct formation. These observations suggest that changes in DNA integrity, including hypomethylation, are indicative of a biological response to genotoxic agents.
Determination of the ventilation rates of interstitial and overlying water by the clam Macoma nasuta
Authors: Winsor Martha H. , Boese Bruce L. , Lee Ii Henry , Randall Robert C. , Specht David T. 
Published: March 2010

Abstract
The ventilation rates of interstitial and overlying water for the deposit-feeding, tellinid clam Macoma nasuta (Conrad) were determined using two water-soluble dyes to differentiate between the two water sources. A unique exposure chamber, the clambox, was used to separate the inhalant and exhalant siphons of the clam, allowing measurements of dye fluxes and total water ventilated. The results suggested that interstitial water constituted very little (4%) of the total amount of water ventilated by this clam. Factors that could affect the importance of interstitial water as a pollutant uptake route and how these might vary among pollutants or infaunal species are discussed.
Ground water transport of hydrophobic organic compounds in the presence of dissolved organic matter
Authors: Kan Amy T. , Tomson Mason B. 
Published: March 2010

Abstract
The effects of dissolved organic matter (DOM) on the transport of hydrophobic organic compounds in soil columns were investigated. Three compounds (naphthalene, phenanthrene and DDT) that spanned three orders of magnitude in water solubility were used. Instead of humic matter, molecularly well-defined DOM represented by Triton X-100, a nonionic industrial detergent, and bovine serum albumin protein were used. In batch isotherm studies, the sorption of naphthalene to both model DOMs appeared to be hydrophobic in nature and quantitatively similar to the binding to humic materials. Equations were derived to model the enhanced transport of organic compounds by DOM based on octanol/water partition coefficients, Kow. For a specific soil and DOM level, it was shown theoretically and experimentally that all organic compounds with Kow values above a specific value should move at the same rate in ground water. In some situations, DOM can increase the movement of highly hydrophobic compounds, such as DDT, by a factor of a thousand or more. This enhanced transport in the presence of DOM can either be a problem, as with ground water contaminant spreading, or a benefit, as with contaminated aquifer cleanup.
QSARs based on statistical design and their use for identifying chemicals for further biological testing
Authors: Tosato Maria Livia , Marchini Silvia , Passerini Laura , Pino Anna , Eriksson Lennart , Lindgren Fredrik , Hellberg Sven , Jonsson Jörgen , Sjöström Michael , Skagerberg Bert , Wold Svante 
Published: March 2010

Abstract
The paper provides an overview of how quantitative structure-activity relationship (QSAR) studies may represent a tool for predictions of toxic/ecotoxic effects of chemicals and identification of potentially hazardous ones. The paper is divided into two parts: theory and application. In the first part, the issues discussed are: the philosophy of QSAR, the conditions that must be fulfilled for constructing sound models and a strategy to establish priorities for further toxicological testing. In the second part, illustrations are reported regarding how a number of environmentally significant chemicals is distributed into chemical classes that meet QSAR criteria for modeling and how QSAR studies are carried out. For this latter purpose, four classes of chemicals are considered and emphasis is placed on the selection of the training sets and the validation of the models.
Characterization of the reducing properties of anaerobic sediment slurries using redox indicators
Authors: Tratnyek Paul G. , Lee Wolfe N. 
Published: March 2010

Abstract
The reduction of six redox indicators in anaerobic sediment slurries was studied by observing the disappearance of the color of the oxidized forms. The reaction kinetics were first-order in concentration of the oxidized form of the indicator and the reducing agents were sediment associated. The rate of indicator reduction reflects the standard potential of the indicator couple, the structure of the indicator moiety reduced and the potential and capacity of reducing agents in the sediment slurry. The relative reduction rates of the indicators suggest that anaerobic sediment systems contain concentrations of mild reducing agents that are available to react rapidly with substrates that are easily reduced. However, more refractory substrates require strong reducing agents that are gradually produced, probably as a result of microbial metabolism.
Adsorption of dodecyltrimethylammonium chloride (C12TMAC) to river sediment
Authors: Hand Vincent C. , Rapaport Robert A. , Wendt Richard H. 
Published: March 2010

Abstract
Adsorption distribution ratios for [14C]-dodecyltrimethylammonium chloride (C12TMAC) to sediment have been measured at realistic environmental concentrations. As observed by investigators of hydrophobic organic and metal sorption, the distribution ratio was found to be inversely related to the sediment concentration. The value of the distribution ratios varied from 440 L/kg at a sediment concentration of 248,000 mg/L up to 251,000 L/kg at a sediment concentration of 230 mg/L. Data can be fit to Freundlich isotherms with slopes ≤1. Data are consistent with an ion-exchange mechanism.
Effect, uptake and disposition of nitrobenzene in several terrestrial plants
Authors: Farlane C. Mc , Pfleeger T. , Fletcher J. 
Published: March 2010

Abstract
Eight species of plants were exposed to nitrobenzene in a hydroponic solution. Four species experienced no depression of either transpiration or photosynthetic rates, while one was rapidly killed and the other three were temporarily affected but recovered from the treatment. Uptake of nitrobenzene was passive and was shown to be proportional to the rate of water flux in each species. The transpiration stream concentration factor (TSCF) was 0.72. The root concentration factor (RCF) was variable between the species and was higher than expected, presumably due to deposits of insoluble metabolic products. All of the species examined displayed a capacity to chemically alter nonpolar nitrobenzene into both polar and insoluble products. Volatilization of nitrobenzene from the leaves was a major route of chemical loss.
Leaching and transformation of glufosinate-ammonium and its main metabolite in a layered soil column
Authors: Behrendt H. , Matthies M. , Gildemeister H. , Görlitz G. 
Published: March 2010

Abstract
Results from a long-term study on leaching and transformation of the herbicide glufosinate-ammonium (ammonium-DL-homoanalin-4-yl (methyl)phosphinate) in a layered soil column were compared with model calculations. Soil columns with layers of loamy sand and sand were treated with 3 kg/ha glufosinate-ammonium, applied to the soil surface. The soils were irrigated and the leachate was monitored for glufosinate-ammonium and the main metabolite 3-methylphosphinico-propionic acid during a period of 256 d. Calculations for glufosinate-ammonium and the metabolite were performed with the soil column model EXSOL. Linear equilibrium sorption coefficients (Kd) and first-order half-lives were used for fitting effluent curves for both the herbicide and the metabolite. Sorption coefficients were compared with those values estimated from a relation to the clay content derived from batch studies. Fitted half-lives were compared with the results from die-away and 14CO2 evolution studies of both the parent and the daughter compound. The observed leaching of glufosinate-ammonium could be well simulated using Kd (0.5 cm3/g) and half-life (11.2 d). The half-life fitted for the metabolite (10–30 d) was a factor 2 to 3 smaller than that measured with batch degradation experiments. This may be the result of using degradation data estimated by 14CO2 evolution, which only indirectly indicates the disappearance of the compound.
Evaluation of intact soil-core microcosms for determining potential impacts on nutrient dynamics by genetically engineered microorganisms
Authors: Fredrickson J. K. , Bolton H. , Mcfadden K. M. , Li S. W. , Voris P. Van. , Bentjen S. A. 
Published: March 2010

Abstract
Nutrient export from intact soil-core microcosms in leachate or by plant uptake was evaluated as a means to assess the ecosystem impacts from the environmental release of genetically modified root-colonizing bacteria. Intact cores of two soil types, a Burbank sandy loam and a Palouse silt loam, were excavated for use as microcosms, seeded with corn and wheat, respectively, and inoculated with Azospirillum lipoferum transposon Tn5 mutants. Microcosms were leached at 33 d and 67 d after seeding and the leachate analyzed for sulfate, phosphate, ammonium, nitrite, nitrate, dissolved organic carbon and inorganic carbon. Statistically significant differences in leachate nutrient concentrations between treatments were due to differences in soil types, rather than inoculation with the bacteria. The high variation in the concentrations of nutrients in the leachates from replicate microcosms, attributed to real field variation, suggest that the measurement of nutrient export in leachate from microcosms may not be a sensitive indicator of ecosystem impacts. One exception was dissolved organic carbon (and total carbon). A statistically significant difference (p ≥ 0.05) was observed between the microcosms receiving live inoculum and those receiving heat-killed cells for leachate organic carbon concentration. Plant uptake of N, P, S, B, Cu, Fe, Mg, Mn and Zn was not affected by inoculation but the coefficients of variation were considerably lower than for the leachate analyses. It is suggested that, although the leaching of organic carbon from microcosms may be used as a holistic indicator of ecosystem impacts from the release of genetically engineered microorganisms (GEMs), measurements of plant assimilation of nutrients and specific rates of microbial transformation of nutrients may provide more sensitive effects end points.
Survival of the fattest: Implications for acute effects of lipophilic chemicals on aquatic populations
Authors: Lassiter Ray R. , Hallam Thomas G. 
Published: March 2010

AbstractSimple assumptions for individual toxic response, exchange of toxicant with environmental concentrations and body composition are used in a model to evaluate the effect of lipid variation on toxic response in a subpopulation of similarly sized individuals. This model represents the internal distribution of a chemical such that more hydrophobic chemicals preferentially move into body lipid. Thus, for exposures of equal chemical activity, both increasing body fat and greater hydrophobicities increase the exposure duration that can be withstood without effect. In simulated 96 h bioassays the effect of increased tolerance to higher hydrophobicities was apparent for chemicals whose KOW exceeded 104. These simulations are compared to published observations. Simulations are also compared to other published data for longer-term bioassays. The effect of interspecies gill morphology on toxic response is also explored. It is concluded that variation in lipid can account for much variation in tolerance in a subpopulation of similarly sized individuals; that gill morphology is another variable influencing toxic response; and that, in general, for similarly exposed organisms, the fattest survives the longest.
Toxicant-induced mortality in models of daphnia populations
Authors: Hallam Thomas G. , Lassiter Ray R. , Li Jia , Mckinney William 
Published: March 2010

Abstract
A method to determine the mortality effects of a hydrophobic chemical on a population is proposed. The ecotoxicological protocol is based on individual organism response and is derived from the static theory of “survival of the fattest.” This study, focusing upon effects of mortality and the effects of toxicant stress on population succession, examines the static assessment survival of the fattest in a dynamic population model. A premise in this approach is that risk assessment should not be based solely upon chemical properties of the toxicant and that the biology of the exposed organisms is an important factor in the determination of effects.
Solubility and toxicity of eight phthalate esters to four aquatic organisms
Authors: Defoe David L. , Holcombe Gary W. , Hammermeister Dean E. , Biesinger Kenneth E. 
Published: March 2010

Abstract
Solubility values for eight phthalate esters investigated ranged from 0.020 to 121 mg/L. Acute toxicity tests were conducted with fathead minnows (Pimephales promelas) and all eight phthalate esters. Acute and chronic tests were conducted with rainbow trout (Oncorhynchus mykiss) and Japanese medaka (Oryzias latipes) using di-2-ethylhexylphthalate. In addition, the chronic toxicity of the three di-n-butylphthalates and a mixture of these three phthalates was examined using daphnids (Daphnia magna). Fathead minnow 96-h LC50 values for di-n-butyl-ortho-phthalate, di-n-butyl-tere-phthalate, di-n-butyl-iso-phthalate and α, w-butylene di[o-(4-hydroxybutoxycarbonyl)-benzoate] were 1.1, 0.61, 0.90 and 121 mg/L, respectively. Di-n-octyl-ortho-phthalate, di-n-octyl-iso-phthalate and di-n-octyl-tere-phthalate were not acutely toxic to fathead minnows at concentrations that exceeded the water solubility estimates for each phthalate. Di-2-ethylhexyl-phthalate was not acutely toxic to any tested species at the highest tested concentrations. No significant adverse effects were observed on hatchability, survival or growth of rainbow trout exposed to a mean di-2-ethylhexylphthalate concentration of 0.502 mg/L (the highest concentration tested) in a 90-d embryo-larval test. However, exposure to a mean di-2-ethylhexylphthalate concentration of 0.554 mg/L significantly reduced the growth of Japanese medaka during a 168-d larval test. Significant adverse effects on reproduction occurred in 21-d chronic tests with D. magna at concentrations of 1.91, 0.20 and 0.64 mg/L for di-n-butyl-ortho-phthalate, di-n-butyl-iso-phthalate and di-n-butyl-tere-phthalate, respectively. A daphnid mixture test with these three phthalates showed complete additivity, which suggests a similar mode of toxic action.
Biodehalogenation: Oxidative and reductive metabolism of 1,1,2-trichloroethane by Pseudomonas Putida—Biogeneration of vinyl chloride
Authors: Castro C.E. , Belser N.O. 
Published: March 2010

Abstract
Resting cell suspensions of the camphor-grown soil organism Pseudomonas putida PpG-786, ATCC culture 29607, dehalogenate 1,1,2-trichloroethane by two pathways under aerobic conditions. The dominant pathway (85%) is oxidative (kox, 4 × 10−19 L/org/sec) and leads in sequence to chloroacetic acid and glyoxylic acid. A competitive reductive pathway (15%) (kred, 0.7 × 10−19 L/org/sec) occurs simultaneously and yields vinyl chloride exclusively. Glucose-grown cells are ineffective in these reactions, and carbon monoxide completely inhibits these transformations. These findings implicate cytochrome P-450 cam as the responsible enzyme in vivo. Overall rates of conversion of 1,1,2-trichloroethane by the organism and the isolated enzyme correspond to those obtained previously with ethylene dibromide.
The results suggest that reductive microbial dehalogenation can occur in the environment even under aerobic conditions.
Relationship between bioavailability and hydrophobicity: Reduction of the uptake of organic chemicals by fish due to the sorption on particles
Authors: Schrap S. Marca , Opperhuizen Antoon 
Published: March 2010

Abstract
The uptake of five chlorinated benzenes and three polychlorinated biphenyls by guppies (Poecilia reticulata) from a sediment suspension has been investigated. To examine the availability of these chemicals, the uptake from water has been compared to that from a sediment suspension. In the two experiments, i.e., with and without sediment being present, the total amount of the test compounds was the same. The only difference was that the chemicals were purely dissolved in the water in one system and partly sorbed on the sediment in the other.
For all five chlorobenzenes bioconcentration factors are found to be reduced when fish are exposed in a sediment suspension. The reduction increased with increasing hydrophobicity of the compounds. A relationship is found between the amount sorbed on the sediment and the reduction of the bioconcentration factor. The same relationship was found from results of studies reported in the literature.
This study also showed that small amounts of sediment can be present in the intestines of the fish when the fish are exposed in a sediment suspension. Depending on the affinity of the chemical for the sediment, the concentrations of the test compounds measured in the whole fish can be significantly influenced.
Acute toxicity of a complex mixture of synthetic hexachloroethane (HC) smoke combustion products: II. Determination of component toxicity
Authors: Fisher Daniel J. , Burton Dennis T. , Paulson Robert L. 
Published: March 2010

Abstract
Synthetic hexachloroethane (HC) smoke combustion products are a complex mixture containing Zn, Cd, As, Pb, Al, CCl4, C2Cl4, C2Cl6, C6Cl6 and HCl. The dissolved components of the synthetic HC smoke combustion products mixture are quite toxic to a number of freshwater species, especially a green alga, rainbow trout and water flea. Acute 48-h static bioassays were conducted with neonate Daphnia magna to assess the toxicity of various individual components and mixtures of components of the synthetic HC smoke combustion products mixture. These tests showed that the metals, zinc in particular, were the major toxic component of the mixture. When the chlorinated organics were tested as a group, they caused only minimal toxicity to the daphnids.
New method for determining effluent toxicity using duckweed (Lemna Minor)
Authors: Taraldsen James E. , Norberg-King Teresa J. 
Published: March 2010

AbstractDuckweed (Lemna minor), a small vascular plant, grows rapidly, is sensitive to a wide variety of toxicants and is easy to culture. A method is described that measures duckweed frond growth and chlorophyll levels as indicators of growth inhibition. The method requires a small testing volume (15 ml) of reconstituted test medium that is prepared by using commercial grade soil to promote frond and chlorophyll production.A variety of single toxicants, industrial effluents and wastewater treatment plant effluents were tested. For most chemicals, the duckweed was as sensitive as other frequently used test species. The comparative toxicities to Ceriodaphnia dubia and fathead minnows (Pimephales promelas) with various effluents indicates that, for some industrial effluents, duckweed was the most sensitive indicator used.