bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of total polycyclic aromatic hydrocarbon concentrations in sediments and toxic units used for estimating risk to benthic invertebrates at manufactured gas plant sites
Authors: Hawthorne Steven B. , Miller David J. , Kreitinger Joseph P. 
Published: January 2006

Abstract
The U.S. Environmental Protection Agency's (U.S. EPA) narcosis model requires the measurement of 18 parent and 16 groups of alkyl polycyclic aromatic hydrocarbons (PAHs) (so-called 34 PAHs) in sediments to calculate the number of PAH toxic units (TU) available to benthic organisms. If data for the 34 PAHs are not available, the U.S. EPA proposes estimating the risk by multiplying the TU for 13 parent PAHs by 11.5 (95% confidence interval) based on data from 488 sediments. This estimate is overly conservative for PAHs from pyrogenic manufactured gas plant (MGP) processes based on the analysis of 45 sediments from six sites. Parent PAHs contributed approximately 40% of the total concentrations and TU for MGP sediments. In contrast, parent PAHs from diesel fuel and petroleum crude oil contributed only 2 and 1%, respectively, of the PAH concentrations and TU, compared to approximately 98 to 99% contributed by the alkyl PAHs. Statistical comparison of the TU based on the measured 34 alkyl and parent PAHs and those based on only 13 parent PAHs demonstrated that a factor of 4.2 (rather than 11.5) is sufficient to estimate total TU within a 95% confidence level for MGP sites. Similarly, measurement of parent PAHs is sufficient to accurately estimate the total 34 alkyl and parent PAH concentrations for MGP-impacted sediments.
Sorption of humic acids and α-endosulfan by clay minerals
Authors: Hengpraprom Sarunya , Lee Cindy M. , Coates John T. 
Published: January 2006

Abstract
Sorption of α-endosulfan by kaolinite and montmorillonite alone and in the presence of sorbed and dissolved humic acid (HA) was investigated (pH 8 and 25°C). Three types of HA, Elliot soil HA (EHA), Peat HA (PHA), and Summit Hill HA (SHHA), were used to represent typical humic substances found in soils. For sorption of HA by either mineral, Freundlich sorption coefficient (Kf) values appeared to decrease in the order of EHA &gt; PHA &gt; SHHA, which followed increasing polarity (expressed as the O/C atomic ratio) and decreasing percent-carbon content. For both clays, sorption of α-endosulfan by the HA mineral complex was greater than for sorption by the clay alone. Sorption of α-endosulfan by the HA mineral complexes followed the same order as the Kf of the HAs (EHA &gt; PHA &gt; SHHA). Based on the amount of HA adsorbed by each mineral, organic carbon partition coefficients (KOC) were determined for sorption of α-endosulfan by two of the HA mineral complexes. The value of KOC for α-endosulfan sorption was greater for kaolinite EHA than kaolinite SHHA. However, the opposite trend was found with the montmorillonite HA complexes. Montmorillonite appeared to sorb α-endosulfan and/or HA with higher affinity than kaolinite, which likely is due to its 2:1 layer structure and higher surface area. Sorption of endosulfan diol, a hydrolysis product, by the minerals was much less than the parent pesticide.
Effects of nitrate and atrazine on larval development and sexual differentiation in the northern leopard frog Rana pipiens
Authors: Orton Frances , Carr James A. , Handy Richard D. 
Published: January 2006

Abstract
Pollution from agrochemicals may be contributing to the global decline in amphibian populations. Environmentally relevant concentrations of nitrate and/or atrazine on anuran development and gonadal differentiation were tested. Four replicates of 20 tadpoles per tank (80/treatment) were exposed from Taylor–Kollros stage 2 to 3 to stage 23 to 34 to either 10 mg/L nitrate, 10 μg/L atrazine, a combined exposure of 10 mg/L nitrate plus 10 μg/L atrazine, or untreated controls. No treatment-dependent effects on weight, snout-vent or hind limb length, or time to forelimb emergence were observed. The proportions of females increased in all treatments compared to the controls, especially in the combined treatment (X2 = 17.90, df = 6, p = 0.0065, combined = 66.4% female, control = 41% female). The frequency of intersex was low in all treatments. No treatment-related effects on the total number of spermatogenic cells were observed, but the ratio of cell types differed in that testes from animals in the treated groups exhibited more spermatogonia, fewer spermatocytes, and more spermatids than the control (significantly different, Kruskal–Wallis, p &lt; 0.05). Ovaries from animals treated with nitrate or atrazine exhibited larger immature (previtellogenic) and mature (vitellogenic) follicles, but ovaries from the combined treatment had larger immature follicles only. Testicular oocytes were observed in the nitrate-only and atrazine-only treatments, and the control treatment, but not the combined treatment. Overall, this study has demonstrated changes in sex ratios that are more marked in response to combined nitrate/atrazine exposure than with these chemicals alone. Histological evidence suggests that premature maturation of gonad may occur as a result of nitrate and/or atrazine exposure during larval development.
Identification of mobile aliphatic sorptive domains in soil humin by solid-state 13C nuclear magnetic resonance
Authors: Simpson Myrna J. , Johnson Philippe C. E. 
Published: January 2006

Abstract
Many sorption studies aim to elucidate organic matter structure and contaminant sorption relationships. Through this pursuit, a great deal of insight has been gained about contaminant interactions with humic fractions, namely the fulvic and humic acid isolates. Comparatively, less is known about the structure and environmental reactivity of the humin fraction; however, researchers have reported that the humin fraction consistently produces higher sorption coefficients than the corresponding source material and other humic fractions. In this paper, we report on a study that uses solid-state 13C nuclear magnetic resonance (NMR) to characterize six humin samples extracted from soil. In addition, 1-naphthol sorption was measured for each whole-soil and humin sample. With the exception of the peat sample, the humin samples yielded significantly higher organic carbon–normalized sorption coefficients (Koc) compared with the whole-soil samples. The solid-state 13C NMR analysis reveals the presence of amorphous, polymethylene-rich domains in all of the humin samples. Other researchers have indicated that these domains exhibit a high affinity for hydrophobic organic contaminants. Consequently, we hypothesize that the concentration of amorphous, polymethylene-rich domains in soil humin is responsible for the high sorption coefficients reported here and by other researchers.
Interspecific relationships among soil invertebrates influence pollutant effects of phenanthrene
Authors: Cortet Jérôme , Joffre Richard , Elmholt Susanne , Coeurdassier Michael , Scheifler Renaud , Krogh Paul Henning 
Published: January 2006

Abstract
Five mesofauna communities varying in both structure and composition were exposed to phenanthrene in mesocosms for up to four months. Effects of phenanthrene were assessed on mesofauna population dynamics, fungal biomass (ergosterol concentrations), and litter decomposition (litter mass loss, nitrogen concentration). The effects of each community on the fate of phenanthrene were also assessed. We hypothesize that phenanthrene affects the population dynamics of mesofauna and soil biological functioning depending on exposure duration, type of community, or both. Results show that phenanthrene exerted an effect on mesofauna and that the effects on some species, like Folsomia fimetaria, were influenced by the species composition in the mesocosms, the soil layer, and the sampling date. However, the effects of phenanthrene on ergosterol content and organic matter decomposition were not significantly influenced by community composition. These results demonstrate that interspecific relationships are needed to assess the toxicity of pollutants and should be taken into account in ecotoxicological risk assessment. Furthermore, this work does not support the hypothesis of a direct link between toxic effects of organic pollutants on mesofauna species and soil biological functioning.
Ecotoxicological risk of pharmaceuticals from wastewater treatment plants in Korea: Occurrence and toxicity to Daphnia magna
Authors: Han Guk H. , Hur Hor G. , Kim Sang D. 
Published: January 2006

Abstract
The overall ecotoxicological effect of pharmaceutically active compounds (PhACs) detected in the effluents of Korean wastewater treatment plants (WWTPs) to Daphnia magna was investigated using biological and chemical analyses. The bioassay results showed median lethal concentrations and no-observed-effect concentrations ranging from a few to tens of ppm levels for nine PhACs in 48-h acute and 21-d chronic tests. The mixture effects of pharmaceuticals also were examined by other acute and chronic tests, which showed no significant toxicity despite a slightly increased combined effect of approximately twofold. The residual concentrations of nine PhACs were analyzed at concentrations ranging from 10 ng/L to 89 μg/L in the influents and from 10 ng/L to 11 μg/L in the effluents from four metropolitan cities in South Korea between January and November of 2004. Through repeated investigations of the influents and the effluents from different WWTPs, relatively higher removal efficiencies (23.9–91.3%) compared with those of previous surveys performed in other countries were observed for most pharmaceuticals, with the exception of acetaminophen (8.7%). The present study showed no significant risk effects of the effluents from WWTPs containing pharmaceuticals (i.e., hazard quotient &lt; 1), even at the 95th percentile contamination range, although a risk assessment factor of 1,000 was applied. Therefore, it can be concluded that the potential risk of pharmaceuticals should be monitored carefully with more bioassay data, because many uncertainties still exist in the determination and toxicity of metabolites in water environments. No significant risk was observed, however, from the selected PhACs in the effluents from WWTPs discharged into surface waters.
Deriving effects onChironomuspopulation carrying capacity from standard toxicity tests
Authors: Péry Alexandre R. R. , Babut Marc P. , Mons Raphaël , Garric Jeanne 
Published: January 2006

AbstractTranslating effects from individual to population level is a crucial issue in ecological risk assessment of bed sediments. We first propose a modeling package to tackle this question for the species Chironomus riparius with biology- and ecology-based models to deduce effects on chironomid production per generation or per year. However, this approach requires the performance of many toxicity tests. Currently, the information available to perform this scaling is limited to a few data from standardized tests, mainly growth and survival after a certain period of time and sometimes emergence after 28 d. We propose here to simplify our model to make it able to deal with only data from standardized tests. The daily death rate is assumed to be constant throughout each instar, the effects on growth to be independent of time, and the effects on reproduction to be negligible. The reliability of this approach is first tested by comparing the population effects on organisms exposed to copper-spiked sediments calculated with the simple model and the more exhaustive one from which it was derived. The simple model just slightly underestimated the effects at the population level. Second, data from tests performed either with unpolluted sediment or with field sediment with different degrees of contamination are used to propose an effect threshold for populations. It appears that control sediments lead to less than 20% effects at population level, which may help define a natural variability range. For polluted sediments, we could find effects up to 42%. Implications of these findings are discussed in a sediment risk assessment perspective.
Estrogenic endpoints in fish early life-stage tests: Luciferase and vitellogenin induction in estrogen-responsive transgenic zebrafish
Authors: Bogers Rinus , Mutsaerds Esther , Druke Jeanette , De Roode Daphne F. , Murk Albertinka J. , Van Der Burg Bart , Legler Juliette 
Published: January 2006

AbstractThis study incorporated specific endpoints for estrogenic activity in the early life-stage (ELS) test, as described in Guideline 210 of the Organization for Economic Cooperation and Development and traditionally used for toxicity screening of chemicals. A transgenic zebrafish model expressing an estrogen receptor–mediated luciferase reporter gene was exposed to ethi-nylestradiol (EE2), and luciferase activity as well as vitellogenin (VTG) was measured. Concentrations of EE2 were tested at 1, 3, or 10 ng/L for 30 d from fertilization or during only the last 4 d with dimethylsulfoxide (DMSO) as presolvent (0.01%). Exposure to EE2 induced no toxic effects. Mean body weights were significantly higher in groups exposed for 30 d in the presence of DMSO, but condition factors were not affected. Significant luciferase and VTG induction occurred following 30-d exposure (3 and 10 ng EE2/L), while only VTG levels were affected in the 4-d exposure (10 ng EE2/L). This study demonstrated the usefulness of incorporating estrogenic endpoints in the OECD ELS test, fitting the requirements for screening estrogenic activity of chemicals. Quantitative measurement of both VTG and luciferase activity proved to be rapid and sensitive. Additional value of using transgenic zebrafish lies in combining VTG measurement with the more mechanistic approach of luciferase induction in one experiment.
A simulation study comparing different experimental designs for estimating uptake and elimination rates
Authors: Bell Bryan R. , Bailer A. John , Wright Stephen E. 
Published: January 2006

Abstract
The design of ecotoxicological studies requires decisions about the number and spacing of exposure groups tested, the number of replications, the spacing of sampling times, the duration of the study, and other considerations. For example, geometric spacing of sampling times or toxicant concentrations is often used as a default design. Optimal design methods in statistics can suggest alternative spacing of sampling times that yield more precise estimates of regression coefficients. In this study, we use a computer simulation to explore the impact of the spacing of sampling times and other factors on the estimation of uptake and elimination rate constants in an experiment addressing the bioaccumulation of a contaminant. Careful selection of sampling times can result in smaller standard errors for the parameter estimates, thereby allowing the construction of smaller, more precise confidence intervals. Thus, the effort invested in constructing an optimal experimental design may result in more precise inference or in a reduction of replications in an experimental design.
Anodic stripping voltammetry measures copper bioavailability for sea urchin larvae in the presence of fulvic acids
Authors: Lorenzo J. Ignacio , Nieto Oscar , Beiras Ricardo 
Published: January 2006

Abstract
Copper speciation in the presence of fulvic acids (FAs) was studied in chemically defined seawater by square wave anodic stripping voltammetry (SQWASV). A simple complexation model assuming a single type of ligand and a 1:1 reaction stoichiometry successfully explained the measured data. A conditional stability constant of 5.80 ± 0.07 and a complexing capacity of 610 ± 80 μmol Cu/g FAs were obtained. This conditional stability constant would correspond to 7.23 on a free copper ion basis. The complexation kinetics was easily followed by anodic stripping voltammetry (ASV) measurements, and complexation equilibria were not reached until approximately 12 h. Coupled to speciation studies, the toxicity of copper in the presence of FAs was studied with the sea urchin Paracentrotus lividus embryogenesis bioassay. A clear protective effect of FAs was observed on Cu toxicity, and this effect could be accurately explained by SQWASV Cu speciation measurements. Additional experiments in the presence of high Cu and FA concentrations were performed, and no extra toxicity of Cu–FA complexes was observed. These results are in agreement with metal bioavailability models and also underline the usefulness of ASV for determining copper bioavailability in the presence of natural organic matter.
Comparative toxicity of cadmium, zinc, and mixtures of cadmium and zinc to daphnids
Authors: Shaw Joseph R. , Dempsey Thomas D. , Chen Celia Y. , Hamilton Joshua W. , Folt Carol L. 
Published: January 2006

AbstractInvestigations were conducted to determine acute (48-h) effects of cadmium and zinc presented individually and in combination on Ceriodaphnia dubia, Daphnia magna, Daphnia ambigua, and Daphnia pulex. Toxicity tests were conducted with single metals to determine lethal effects concentrations (lethal concentrations predicted for a given percent [x] of a population, LCx value). These were used to derive metal combinations that spanned a range of effects and included mixtures of LC15, LC50, and LC85 values calculated for each metal and species. In single-metal tests, 48-h LC50 values ranged from 0.09 to 0.9 μmol/L and 4 to 12.54 μmol/L for cadmium and zinc, respectively. For each metal, D. magna was most tolerant and showed a different pattern of response from all others as determined by slope of concentration–response curves. In the combined metal treatments, all daphnids showed a similar pattern of response when LC15 concentrations were combined. This trend continued with few exceptions when LC15 concentrations of cadmium were combined with LC50 or LC85 values for zinc. However, when this treatment was reversed (LC15, zinc + LC50 or LC85, cadmium), responses of all species except D. magna indicated less-than-additive effects. For C. dubia, a near complete reduction in toxicity was observed when the LC15 for zinc was combined with LC85 for cadmium. Multimetal tests with D. magna did not differ from additive. Collectively, these studies suggest that D. magna may not be representative of other cladocerans.
Composition and production of thiol constituents induced by cadmium in the marine microalga Tetraselmis suecica
Authors: Pérez-Rama Mónica , Vaamonde Enrique Torres , Alonso Julio Abalde 
Published: January 2006

Abstract
Time course of intracellular levels of different thiols (phytochelatins, desglycyl-phytochelatins, glutathione, γ-glutamylcysteine [γ-Glu-Cys], and cysteine) were studied in the microalga Tetraselmis suecica exposed to different cadmium concentrations for 8 d. The cadmium concentrations assayed were 3, 7.9, 15, and 30 mg/L. Contents of thiol compounds synthesized by this microalga changed with cadmium concentration and with time of exposure. Cysteine concentrations increased significantly compared with those of γ-Glu-Cys and glutathione in cultures containing 7.9, 15, and 30 mg/L. The increase in the amount of glutathione was significant only in cells exposed to the higher cadmium concentrations (15 and 30 mg/L). Nevertheless, in all the cadmium concentrations assayed, γ-Glu-Cys levels were constant. A rapid increase in phytochelatins was observed with increased cadmium concentration during the first days of culture. The type of phytochelatins (number of subunits) also was dependent on the concentration of cadmium. The rate of (γ-Glu-Cys)3-Gly accumulation was higher than those of other types of phytochelatins throughout the culture in cells exposed to 3, 15, and 30 mg/L. However, in cultures treated with 7.9 mg/L, (γ-Glu-Cys)4-Gly increased substantially after 8 d of culture, exceeding the amount of (γ-Glu-Cys)3-Gly. Cultures exposed to the higher cadmium concentrations (15 and 30 mg/L) showed a decrease in phytochelatins after 4 and 3 d of culture, respectively, whereas an increase in cysteine and glutathione occurred at the same time. A rapid decrease in phytochelatins also was measured when cells were placed into cadmium-free medium. This decrease is consistent with a degradation of the phytochelatins.
The use and misuse of biomarkers in ecotoxicology
Authors: Forbes Valery E. , Palmqvist Annemette , Bach Lis 
Published: January 2006

AbstractSubstantial efforts have been devoted to developing and applying biomarkers for use in ecotoxicology. These efforts have resulted partly from a desire for early warning indicators that respond before measurable effects on individuals and populations occur and partly as an aid to identifying the causes of observed population- and community-level effects. Whereas older biomarkers focused on measures of organism physiology or biochemistry, advances in molecular biology are extending the biomarker philosophy to the level of the genes (i.e., ecotoxicogenomics). However, the extent to which biomarkers are able to provide unambiguous and ecologically relevant indicators of exposure to or effects of toxicants remains highly controversial. In the present paper, we briefly discuss the application of biomarkers in ecotoxicology and ecological risk assessment, and we provide examples of how they have been applied. We conclude that although biomarkers can be helpful for gaining insight regarding the mechanisms causing observed effects of chemicals on whole-organism performance and may, in some cases, provide useful indicators of exposure, individual biomarker responses should not be expected to provide useful predictions of relevant ecological effects—and probably not even predictions of whole-organism effects. Suites of biomarkers are only likely to provide increased predictability if they can be used in a comprehensive mechanistic model that integrates them into a measure of fitness. Until this can be achieved, biomarkers may be useful for hypothesis generation in carefully controlled experiments. However, because the aims of environmental monitoring and ecological risk assessment are to detect and/or predict adverse chemical impacts on populations, communities, and ecosystems, we should be focusing our efforts on improving methods to do this directly. This will involve developing and testing models of appropriate complexity that can describe real-world systems at multiple scales.
Effects of atrazine and iridovirus infection on survival and life-history traits of the long-toed salamander (Ambystoma macrodactylum)
Authors: Forson Diane , Storfer Andrew 
Published: January 2006

Abstract
Environmental contaminants and emerging infectious diseases are implicated as factors contributing to global amphibian declines. However, few studies have tested the interaction of these factors. We exposed six-week-old, larval long-toed salamanders (Ambystoma macrodactylum) to Ambystoma tigrinum virus (ATV; 0 or 103.5 plaque-forming units/ml) and sublethal concentrations of atrazine (0, 1.84, 18.4, and 184 μg/L) in a 4 × 2 factorial design for 30 d. We tested the effects of atrazine and virus on mass and snout-vent length (SVL) at metamorphosis and larval period as well as on rates of mortality and viral infectivity. We confirmed ATV transmission to A. macrodactylum via polymerase chain reaction, but infection rates were lower than expected, consistent with the theory predicting lower pathogen transmission to nonnative hosts. Larvae exposed to both atrazine and ATV had lower levels of mortality and ATV infectivity compared to larvae exposed to virus alone, suggesting atrazine may compromise virus efficacy. The highest atrazine level (184 μg/L) accelerated metamorphosis and reduced mass and SVL at metamorphosis significantly relative to controls. Exposure to ATV also significantly reduced SVL at metamorphosis. The present study suggests moderate concentrations of atrazine may ameliorate effects of ATV on long-toed salamanders, whereas higher concentrations initiate metamorphosis at a smaller size, with potential negative consequences to fitness.