bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bioavailability of labile and desorption-resistant phenanthrene sorbed to montmorillonite clay containing humic fractions
Authors: Lahlou Mohammed , Ortega-Calvo Jose Julio 
Published: March 2010

AbstractThe biodegradation of 14C-labeled phenanthrene in the presence of particles of montmorillonite and fulvic and humic acid–montmorillonite complexes was studied in a batch system. A mathematical model that takes into account the contribution to mineralization by the slowly desorbing compound was used to calculate the initial mineralization rates. Sorption of phenanthrene to the particles was determined in sorption isotherms, and desorption was measured during successive water extractions. Mineralization rates in equilibrated suspensions were higher than predicted from aqueous equilibrium concentrations, and in some cases, montmorillonite and fulvic acid–montmorillonite complexes stimulated the phenanthrene transformation rates. In contrast with the high bioavailability exhibited by phenanthrene sorbed as a labile form, biodegradation of the desorption-resistant phenanthrene occurred slowly and followed zero-order kinetics, which indicated a limitation caused by slow desorption. The results suggest that the mechanism of sorption may cause a differential bioavailability of the sorbed compound.
Bioavailability of freshly added and aged naphthalene in soils under gastric pH conditions
Authors: Jin Zhaowei , Simkins Stephen , Xing Baoshan 
Published: March 2010

Abstract
The bioavailability of hydrophobic organic chemicals decreases with aging in soil because of sequestration. However, assessments of the risk of exposure to contaminated soils are usually dependent on either chemical concentrations, which are measured using vigorous extraction methods, or models that assume an equilibrium without considering the actual conditions. The objective of this research was to determine the availability and desorption kinetics of freshly added and aged naphthalene from a peat and a mineral soil; naphthalene was desorbed into solutions with pH levels that approximate those found in different gastric regions. Soil and peat samples were spiked with radiolabeled and unlabeled naphthalene at 2 and 20 μg/g and were aged from 0 to 135 d. Desorption kinetics were determined using a simulated stomach solution (0.1 M NaCl, 0.1 M HCl, 0.01 M NH4Ac, pH = 1.0) and a neutral solution (0.2 M NaCl, pH = 6.7) that represented the pH of intestinal conditions and most soils. Peat sorbed much more naphthalene than did soil, and it allowed little desorption. Though both acidic and neutral extracting solutions could desorb naphthalene, little apparent effect of aging was observed in peat, whereas desorption from soil declined markedly with aging. In addition, the percentage of naphthalene that desorbed from soil was greater for the higher incubation concentration. The desorption of naphthalene from the peat and soil was higher into the neutral solution than into the gastric solution. These results suggest that aging, exposure conditions, concentration effect, and organic matter content should be taken into account in predictive models and risk assessments.
Membrane toxicity of linear alcohol ethoxylates
Authors: Müller Markus T , Zehnder Alexander JB , Escher Beate I 
Published: March 2010

Abstract
The membrane toxicity of linear alcohol ethoxylates (AEO/single reference compounds and technical mixtures) was investigated with an in vitro method based on time-resolved spectroscopy on energy-transducing membranes. The nonspecific membrane perturbation of narcotic chemicals can be quantified by the degree of disturbance of buildup and relaxation of the membrane potential in membrane preparations of the purple bacterium Rhodobacter sphaeroides. The effect concentrations obtained for this narcotic effect correlated well with the results from various toxicity tests on whole organisms. In addition, the effect concentrations at the target site, the biological membrane, were derived from the nominal effect concentrations using membrane-water partition coefficients. The test set of linear AEO comprised compounds with an alkyl chain length of 8 to 16 carbon units and 5 to 14 ethoxylate (EO) units covering more than four orders of magnitude of hydrophobicity (expressed as octanol–water partition coefficient). All AEO exhibited their toxic effect at concentrations well below the critical micelle concentration. When comparing aqueous effect concentrations, toxicity increased strongly with increasing length of the alkyl chain and showed a small parabolic dependence on the number of EO units with a maximum at eight EO units. With the toxic effect expressed in terms of membrane concentrations, all AEO exhibited similar activity in the concentration range typical for narcotic chemicals. The toxic membrane concentrations of AEO with 5 and ≥8 EO units were 200 and 60 mmol/kg lipid, which correspond to the critical body residues of nonpolar and polar narcotics in fish, respectively. In addition, the toxic effects of mixtures of AEO were measured and could be modeled as the sum of activities of the single constituents, confirming the concept of concentration additivity of compounds with the same mode of toxic action.
Enantioselective determination of two persistent chlorobornane congeners in sediment from a toxaphene-treated yukon lake
Authors: Vetter Walter , Bartha Richard , Stern Gary , Tomy Gregg 
Published: March 2010

Abstract
The composition of toxaphene residuesand the enantiomeric ratios of the major congeners were studied in the top 10 slices (1935–1992) of a sediment core collected from Hanson Lake in the Yukon Territories (Canada). This lake was treated with toxaphene as a picsicide in July 1963. Electron-capture negative ion mass spectrometry and electron-capture detection were applied in combination with enantioselective gas chromatography using modified cyclodextrin columns. Of the 10 toxaphene peaks identified in each of the sediment slices, two congeners, 2-exo,3-endo,6-exo,8,9,10-hexachlorobornane (B6-923 or Hx-Sed) and 2-endo,3-exo, 5-endo,6-exo, 8,9,10-heptachlorobornane (B7-1001 or Hp-Sed), were the most abundant. Each of the three chiral stationary phases used in this study was successful at resolving the enantiomers in at least of one of the two congeners. Among them was permethylated β-cyclodextrin (Chirasil-Dex), which, up until now, has never been used for enantiomer separation of compounds of technical toxaphene. B6-923 and another less abundant, as of yet unknown, hexachlorobornane were racemic in all sediment core slices. For B7-1001, the latter eluting enantiomer was always more predominant. Furthermore, the enantiomeric ratio was found to consistently decrease with time from approximately 0.8 in the early slices (∼1950) to 0.7 in the slice representing 1992, implying that the first eluted B7-1001 enantiomer is less persistent than the second. B6-923 and B7-1001 are most likely metabolites of the more highly chlorinated congeners. A structural evaluation provided evidence that reductive dechlorination at carbons with geminal chlorine atoms is the primary microbial degradation pathway in sediments from Hanson Lake.
Thyroidal status of mummichogs (Fundulus heteroclitus) from a polluted versus a reference habitat
Authors: Zhou Tong , John-Alder Henry B , Weis Peddrick , Weis Judith S 
Published: March 2010

Abstract
Previous studies have demonstrated that mummichogs (Fundulus heteroclitus) collected from Piles Creek (PC), New Jersey, USA (a site polluted with heavy metals and organic materials), were sluggish and showed poorer prey capture and predator avoidance than those from a reference site (Tuckerton [TK], NJ, USA). We hypothesized that the behavioral dysfunction of the PC fish might be associated with thyroid impairment due to toxic exposures. In this preliminary study, we compared thyroid histology and thyroid hormones in the two populations and experimentally determined whether a polluted or an unpolluted environment could alter levels of thyroid hormones. In comparison to TK, PC fish had larger thyroid follicles and greater follicle epithelial cell heights and also contained significantly higher plasma thyroxine (T4) levels. However, no significant differences were found in levels of either plasma or tissue triiodothyronine (T3). The TK fish raised in a simulated PC environment contained higher plasma T4 and lower plasma T3 levels than those sampled from the field. The PC fish raised in clean water showed a reduction in both plasma T4 and T3 levels in comparison to field-sampled fish. In either case, no significant difference was found in tissue T3 content. The contaminants in PC may cause the differences in thyroid structure and function, which may be partly responsible for the behavioral differences between fish from the polluted PC and from the reference TK.
Effects of the agricultural pesticides atrazine, deethylatrazine, endosulfan, and chlorpyrifos on an estuarine microbial food web
Authors: DeLorenzo Marie E , Scott Geoffrey I , Ross Philippe E 
Published: March 2010

AbstractAricultural pesticide runoff is a critical issue for many southeasternestuaries. The estuarine microbial food web plays an important role in nutrient cycling and transfer of nutrients to higher trophic levels. The present study examined the effects of agricultural pesticides on the estuarine microbial food web. Polyurethane foam substrates were used to collect microbial communities from a reference tidal creek in the North Inlet National Estuarine Research Reserve (Georgetown, SC, USA). Colonized substrates were brought into the laboratory and exposed to the following commonly used agricultural pesticides: atrazine (and a metabolite, deethylatrazine), endosulfan, and chlorpyrifos. Chlorophyll a, phototrophic carbon assimilation, dissolved oxygen, and phototrophic biovolume were significantly reduced at concentrations of 50 and 250 μg/L atrazine and deethylatrazine. Generally, inhibition of the phytoplankton resulted in increased bacterial abundance and productivity, whereas heterotrophic ciliate and flagellate abundances were not affected. Total bacterial abundance, but not heterotrophic bacterial productivity, was significantly reduced with endosulfan treatments of 1 and 10 μg/L. Endosulfan was primarily found to target the cyanobacteria. Changes in biomass reflected compositional shifts in the phototrophs. The abundance of heterotrophic ciliates and flagellates was significantly reduced at 10 μg/L chlorpyrifos. Bacterial abundance and productivity increased, whereas phototrophic variables decreased. Agricultural pesticides were found to alter both functional and structural aspects of the estuarine microbial food web.
Genetic and demographic responses of mosquitofish (Gambusia holbrooki) populations exposed to mercury for multiple generations
Authors: Tatara Christopher Paul , Mulvey Margaret , Newman Michael C 
Published: March 2010

AbstractGenetic and demographic responses of mosquitofish were examined after multiple generations of exposure to mercury. Previous studies of acute lethal exposures of mosquitofish to either mercury or arsenic demonstrated a consistent correlation between time to death and genotype at the glucosephosphate isomerase-2 (Gpi-2) locus. A mesocosm study involving mosquitofish populations exposed to mercury for 111 d showed significant female sexual selection and fecundity selection at the Gpi-2 locus. Here the mesocosm study was extended to populations exposed to mercury for several (approx. four) generations. After 2 years, control and mercury-exposed populations met Hardy–Weinberg expectations and showed no evidence of genetic bottlenecks. The mean number of heterozygous loci did not differ significantly between the mercury-exposed and control populations. Significant differences in allele frequencies at the Gpi-2 locus were observed between the mercury-exposed and control populations. Relative to the initial and control allele frequencies, the Gpi-2100 allele frequency was lower, the Gpi-266 allele frequency increased, but the Gpi-238 allele frequency did not change in mercury-exposed populations. No significant differences were found in standard length, weight, sex ratio, or age class ratio between the control and mercury-exposed populations. Allele frequency changes at the Gpi-2 locus suggest population-level response to chronic mercury exposure. Changes in allele frequency may be useful as indicators of population response to contaminants, provided that the population in question is well understood.
Use of rainbow trout primary epidermal cell cultures as an alternative to immortalized cell lines in toxicity assessment: A study with nonoxynol
Authors: Dowling Kevin , Mothersill Carmel 
Published: March 2010

Abstract
Increased concern has centered around environmental contaminants that exert estrogenic effects. A class of nonionic surfactants, the nonylphenol ethoxylates (such as the compound nonoxynol), are an example of one such group of contaminants. We studied the effects of nonoxynol (α-(4-nonylphenyl)-ω-hydroxypoly-(oxy-1-ethanediyl)) on an epithelial primary culture. The culture system that was employed is a development of an in vitro technique for the culture of rainbow trout (Onchorynchus mykiss) epithelium, one that allows for the culture of both epithelial cells and goblet cells. The LC50 after 24 h was found to be 16.6 μmol/L. The LC50 after 48 h was 12.9 μmol/L. Nonoxynol was found to exhibit an acute lethal dose of 75 μmol/L. A decrease in the number of goblet cells present in the system was observed as exposure to nonoxynol increased. Nonoxynol was found to kill epithelial cells mainly by necrosis. A comparative study of the effects of nonoxynol on the epithelium papulosum cyprini cell line was also carried out. The LC50 of nonoxynol on this cell type was 4.1 μmol/L, with an acute lethal dose of 10 μmol/L.
Effects of a pulsed treatment with the herbicide afalon (active ingredient linuron) on macrophyte-dominated mesocosms. II. Structural responses
Authors: Van Geest Gerben J , Zwaardemaker Nathalie G , Van Wijngaarden René PA , Cuppen Jan GM 
Published: March 2010

Abstract
Outdoor mesocosms (experimental drainage ditches) were treated repeatedly with linuron at nominal concentrations of 0, 0.5, 5, 15, and 50 μg/L. After each of three treatments (with 4-week intervals), the systems were kept static for 1 week. Subsequently, they were flushed with nonpolluted surface water with a residence time of 5 d until the next treatment. Species composition and abundance of macrophytes, periphyton, phytoplankton, zooplankton, and macroinvertebrates were examined at prefixed time intervals. During the treatment periods, significant decreases in oxygen concentration and pH were observed, whereas the systems recovered during the flushing periods. The effects of the pulsed treatments on the structural endpoints (biota) were rarely significant and consistently were difficult to interpret. We conclude that under these experimental conditions, pulsed treatment with linuron causes only minor and negligible effects on the abundance of organisms in mesocosms, even when maximum permissible concentrations are exceeded by about 80 times. Risk assessment based on the more sensitive physiologic and functional endpoints suggested that the safety factor of 0.1 times the acute EC50 of the most sensitive standard alga (Scenedesmus acutus), as adopted in the Uniform Principles of the European Union, is sufficient to protect the community of the mesocosms in an exposure regime that was realistic for Dutch drainage ditches, using a photosynthesis inhibitor as the benchmark compound.
An evaluation of the seven-day toxicity test withAmericamysis bahia(formerlyMysidopsis bahia)
Authors: Lussier Suzanne M , Kuhn Anne , Comeleo Randy 
Published: March 2010

AbstractThe7-d test measuring survival, growth, and fecundity of Americamysis bahia (formerly Mysidopsis bahia) was developed for estimating the chronic toxicity of effluents and associated receiving waters for National Pollutant Discharge Elimination System permits. Currently, this test and its derivatives are also used in toxicity identification evaluation (TIE), risk assessment, and other applications. To evaluate the relative sensitivity of three measurement endpoints (survival, growth, and fecundity), we analyzed results from 115 tests with effluents, organic or inorganic chemicals, and receiving waters suspected of being toxic. Controls for 78 of these (68%) achieved acceptable survival and growth. Fifty of these 78 tests (64%, i.e., 43% of the total tests) also achieved acceptable control fecundity. In the 47 tests with significant effects, survival was the most sensitive response in 57%, fecundity in 30%, and growth in 30%. There was little duplication in responses. Improving pretest holding conditions by decreasing the maximum density from ∼20 to 10 animals/L and increasing the temperature from ∼26°C to a range of 26 to 27°C improved the growth and fecundity in controls. Although the percentage of tests achieving acceptable control survival (&gt;80%) and growth (&gt;0.20 mg) decreased from 93 to 86%, the percentage achieving acceptable fecundity in controls (&gt;50%) increased from 60 to 97%. Seasonal differences in fecundity were detected among control groups. Although variable, fecundity is often the most sensitive measure of response. The 7-d mysid test estimates the chronic toxicity of effluents most effectively when all three endpoints are used.
Determination of the sensitivity of macroinvertebrates in stream mesocosms through field-derived assessments
Authors: Dyer Scott D , Belanger Scott E 
Published: March 2010

Abstract
The extrapolation of no observed effect concentrations derived from experimental ecosystem tests (mesocosms) to the field assumes low assessment factors, i.e., the test system is sensitive and serves as a good surrogate for the field. We tested this assumption by comparing the responses of dominant invertebrate taxa exposed to municipal effluent in Procter&Gamble's experimental stream facility (ESF) to those of the same taxa found in routine field samples collected by the Ohio Environmental Protection Agency (1,112 sites). The index of community sensitivity was used as the basis for comparison of mesocosm responses to field-collection data. Control ESF responses corresponded to the 75th and 80th percentiles, whereas most effluent responses corresponded to between the 22nd and 30th percentiles. These analyses support the use of a low assessment factor for the ESF.
Growth and fertility ofCaenorhabditis elegans(nematoda) in unpolluted freshwater sediments: Response to particle size distribution and organic content
Authors: Höss Sebastian , Haitzer Markus , Traunspurger Walter , Steinberg Christian EW 
Published: March 2010

AbstractThe nematode Caenorhabditis elegans (Maupas) was exposed in a sediment bioassay to 26 different unpolluted freshwater sediments varying in particle size distribution (2.5–18% clay, 25.7–68.2% silt, 18.7–70.9% sand) and organic content (2.5–77.1%). We examined the variation of the test endpoints body length, eggs per worm, and percentage of gravid worms. Caenorhabditis elegans tolerated all investigated sediments, with at least 80% (total mean 96.6%) of the worms reaching the stage of reproductive adults. Variation in body length was small (total mean 1,235 ± 97.8 μm), but significant differences among the various sediments were found. We found a weak correlation of body length with particle size distribution, indicating that the nematodes grew better in coarser sediments. The number of eggs per worm showed relatively high variation among treatments (total mean 12.4 ± 4.8) and also within treatments (mean ± 5–95%). C. elegans is a suitable test organism for freshwater sediment bioassays, using body length and percentage of gravid worms as test endpoints.
Whole effluent toxicity testing—usefulness, level of protection, and risk assessment
Authors: Chapman Peter M 
Published: March 2010

AbstractThe general status of whole effluent toxicity (WET) tests is assessed relative to their generally accepted purpose of identifying, characterizing, and eliminating toxic effects of effluents on aquatic resources. Although WET tests are useful, they are not perfect tools (no perfect tools exist). Imperfections include the innate variability of these tests, due both to biotic and anthropogenic factors; the reality of species differences both between the laboratory and the field and within the field; and differences between the laboratory and the receiving environment. Whole effluent toxicity tests may be overprotective (because of their conservative nature, the absence of environmental and ecological processes that could ameliorate exposure, and sensitivity to noncontaminant effects), underprotective (because the most sensitive species cannot be tested, multiple stresses tend to be present in the receiving environment, and failure to account for food chain effects or all possible endpoints), or offer an uncertain level of protection (intermittent doses and mixtures in the environment, adaptations, and hormesis). The implication of hormesis and inverted U-shaped dose responses for WET testing are reviewed in particular detail. Comparisons to field conditions indicate that WET tests are not reliable predictors of effects or lack of effects in the receiving environment. Whole effluent toxicity tests are only the first stage in a risk assessment and as such identify hazard, not risk. Identification of risk requires discarding the concept of independent applicability. The appropriate use of WET tests is identified in the context of their advantages and disadvantages.
Applications and statistical properties of minimum significant difference-based criterion testing in a toxicity testing program
Authors: Wang Qin , Denton Debra L , Shukla Rakesh 
Published: March 2010

Abstract
As a follow up to the recommendations of the September 1995 SETAC Pellston Workshop on Whole Effluent Toxicity (WET) on test methods and appropriate endpoints, this paper will discuss the applications and statistical properties of using a statistical criterion of minimum significant difference (MSD). We examined the upper limits of acceptable MSDs as acceptance criterion in the case of normally distributed data. The implications of this approach are examined in terms of false negative rate as well as false positive rate. Results indicated that the proposed approach has reasonable statistical properties. Reproductive data from short-term chronic WET test with Ceriodaphnia dubia tests were used to demonstrate the applications of the proposed approach. The data were collected by the North Carolina Department of Environment, Health, and Natural Resources (Raleigh, NC, USA) as part of their National Pollutant Discharge Elimination System program.