Accumulation of 14C-trinitrotoluene and related nonextractable (bound) residues in Eisenia fetida

To determine if trinitrotoluene (TNT) forms nonextractable residues in earthworms and to measure the relative degree of accumulation as compared to TNT and its deaminated metabolites, Eisenia fetida was exposed to ¹⁴C-TNT using dermal contact to filter paper or exposure to soil. Nonextractable residues made up 32-68% of total body burden depending on exposure media and depuration time. Parent TNT accounted for less than 3% of radioactivity, while ADNTs accounted for 7-38%. Elimination half-lives were 61-120 h for TNT, ADNTs, and DANTs, which was significantly lower than the half-lives found for nonextractable residues, 201-240 h. However, over 80% of the nonextractable residue was solubilized using weak acid (pH 2). Based on our findings that TNT accumulation occurs primarily as nonextractable residues, which have a longer half-life, and that nonextractable residues can be solubilized, we propose that nonextractable residues could be used as a selective biomarker for assessing TNT contamination.     

Hydrogen peroxide-assisted UV photodegradation of Lindane

Aqueous solutions of gamma-hexachlorocyclohexane (Lindane) were photolyzed (lambda=254 nm) under a variety of solution conditions. The initial concentrations of hydrogen peroxide (H(2)O(2)) and Lindane varied from 0 to 20 mM and 0.21 to 0.22 microM, respectively, the pH ranged from 3 to 11, and several concentration ratios of Suwannee River humic acid and fulvic acid were dissolved in the irradiated solutions. Lindane rapidly reacted, and the maximum reaction rate constant (9.7 x 10(-3) s(-1)) was observed at pH 7 and initial [H(2)O(2)]=1 mM. Thus, 90% of the Lindane is destroyed in approximately 4 min under these conditions. In addition, within 15 min, all chlorine atoms were converted to chloride ion, indicating that chlorinated organic by-products do not accumulate. The reactor was characterized by measuring the photon flux (7.04 x 10(-6) E s(-1)) and the cumulative production of *OH during irradiation. The cumulative *OH production during irradiation was fastest at an initial [H(2)O(2)]=5 mM (k=0.77 micro M s(-1)).     

Assessment of sediment concentration and nutrient loads in effluents drained from extensively managed fishponds in France

Expansion of aquaculture has increased concern over its environmental impact. The composition of effluents from intensive aquaculture is well documented, but few data on extensive aquaculture are available. During 12 draining operations, 523 water samples were collected downstream from six extensively-managed fishponds in northeastern France. Study ponds had surface areas of 2-620 ha and were managed for production of Cyprinids and Percids. Concentrations of total suspended solids, total phosphorus, and Kjeldahl nitrogen in effluents from the ponds were greatest during the final stage of draining. Loads of phosphorus were higher than those reported for effluents of more intensive aquaculture ponds in the USA, but the source of the potential pollutants was catchments and sediment rather than feeds and fertilizer. It will be necessary to reduce the water drawdown rate during the fishing stage and possibly implement other best management practices to prevent the TSS concentration from exceeding 1 g/L.     

Spatial Variability in Cost and Success of Revegetation in a Wyoming Big Sagebrush Community

The ecological integrity of the Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle and A. Young) alliance is being severely interrupted by post-fire invasion of non-native annual grasses. To curtail this invasion, successful post-fire revegetation of perennial grasses is required. Environmental factors impacting post-fire restoration success vary across space within the Wyoming big sagebrush alliance; however, most restorative management practices are applied uniformly. Our objectives were to define probability of revegetation success over space using relevant soil-related environmental factors, use this information to model cost of successful revegetation and compare the importance of vegetation competition and soil factors to revegetation success. We studied a burned Wyoming big sagebrush landscape in southeast Oregon that was reseeded with perennial grasses. We collected soil and vegetation data at plots spaced at 30?m intervals along a 1.5?km transect in the first two years post-burn. Plots were classified as successful (>5?seedlings/m(2)) or unsuccessful based on density of seeded species. Using logistic regression we found that abundance of competing vegetation correctly predicted revegetation success on 51?% of plots, and soil-related variables correctly predicted revegetation performance on 82.4?% of plots. Revegetation estimates varied from $167.06 to $43,033.94/ha across the 1.5?km transect based on probability of success, but were more homogenous at larger scales. Our experimental protocol provides managers with a technique to identify important environmental drivers of restoration success and this process will be of value for spatially allocating logistical and capital expenditures in a variable restoration environment.     

Heavy metals and couple fecundity, the LIFE Study

The effect of heavy metals at environmentally relevant concentrations on couple fecundity has received limited study despite ubiquitous exposure. In 2005-2009, couples (n = 501) desiring pregnancy and discontinuing contraception were recruited and asked to complete interviews and to provide blood specimens for the quantification of cadmium (μg L⁻¹), lead (μg dL⁻¹) and mercury (μg L⁻¹) using inductively coupled plasma-mass spectrometry. Couples completed daily journals on lifestyle and intercourse along with menstruation and pregnancy testing for women. Couples were followed for 12 months or until pregnant. Fecundability odds ratios (FORs) and 95% confidence intervals (CIs) were estimated adjusting for age, body mass index, cotinine, and serum lipids in relation to female then male exposures. FORs <1 denote a longer time to pregnancy. In adjusted models, reduced FORs were observed for both female cadmium (0.78; 95% CI 0.63-0.97) and male lead (0.85; 95% CI 0.73-0.98) concentrations. When jointly modeling couples’ exposures, only male lead concentration significantly reduced the FOR (0.82; 95% CI 0.68, 0.97), though the FOR remained <1 for female cadmium (0.80; 95% CI 0.64, 1.00). This prospective couple based cohort with longitudinal capture of time to pregnancy is suggestive of cadmium and lead’s reproductive toxicity at environmentally relevant concentrations.     

Hexavalent chromium reduction kinetics in rodent stomach contents

Reduction of hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) in the stomach prior to absorption is a well-recognized detoxification process thought to limit the toxicity of ingested Cr(VI). However, administration of high concentrations of Cr(VI) in drinking water cause mouse small intestinal tumors, and quantitative measures of Cr(VI) reduction rate and capacity for rodent stomach contents are needed for interspecies extrapolation using physiologically-based toxicokinetic (PBTK) models. Ex vivo studies using stomach contents of rats and mice were conducted to quantify Cr(VI) reduction rate and capacity for loading rates (1-400 mg Cr(VI) L⁻¹ stomach contents) in the range of recent bioassays. Cr(VI) reduction was measured with speciated isotope dilution mass spectrometry to quantify dynamic Cr(VI) and Cr(III) concentrations in stomach contents at select time points over 1 h. Cr(VI) reduction followed mixed second-order kinetics, dependent upon concentrations of both Cr(VI) and the native reducing agents. Approximately 16 mg Cr(VI)-equivalents of reducing capacity per L of fed stomach contents (containing gastric secretions, saliva, water and food) was found for both species. The second-order rate constants were 0.2 and 0.3 L mg⁻¹ h⁻¹ for mice and rats, respectively. These findings support that, at the doses that caused cancer in the mouse small intestine (?20 mg Cr(VI) L⁻¹ in drinking water), the reducing capacity of stomach contents was likely exceeded. Thus, for extrapolation of target tissue dose in risk assessment, PBTK models are necessary to account for competing kinetic rates including second order capacity-limited reduction of Cr(VI) to Cr(III).     

Potential sources of methylmercury in tree foliage

Litterfall is a major source of mercury (Hg) and toxic methylmercury (MeHg) to forest soils and influences exposures of wildlife in terrestrial and aquatic ecosystems. However, the origin of MeHg associated with tree foliage is largely unknown. We tested the hypothesis that leaf MeHg is influenced by root uptake and thereby related to MeHg levels in soils. Concentrations of MeHg and total Hg in deciduous and coniferous foliage were unrelated to those in soil at 30 urban and rural forested locations in southwest Ohio. In contrast, tree genera and trunk diameter were significant variables influencing Hg in leaves. The fraction of total Hg as MeHg averaged 0.4% and did not differ among tree genera. Given that uptake of atmospheric Hg(0) appears to be the dominant source of total Hg in foliage, we infer that MeHg is formed by in vivo transformation of Hg in proportion to the amount accumulated.     

An introduction to decision science for conservation

Biodiversity conservation decisions are difficult, especially when they involve differing values, complex multidimensional objectives, scarce resources, urgency, and considerable uncertainty. Decision science embodies a theory about how to make difficult decisions and an extensive array of frameworks and tools that make that theory practical. We sought to improve conceptual clarity and practical application of decision science to help decision makers apply decision science to conservation problems. We addressed barriers to the uptake of decision science, including a lack of training and awareness of decision science; confusion over common terminology and which tools and frameworks to apply; and the mistaken impression that applying decision science must be time consuming, expensive, and complex. To aid in navigating the extensive and disparate decision science literature, we clarify meaning of common terms: decision science, decision theory, decision analysis, structured decision-making, and decision-support tools. Applying decision science does not have to be complex or time consuming; rather, it begins with knowing how to think through the components of a decision utilizing decision analysis (i.e., define the problem, elicit objectives, develop alternatives, estimate consequences, and perform trade-offs). This is best achieved by applying a rapid-prototyping approach. At each step, decision-support tools can provide additional insight and clarity, whereas decision-support frameworks (e.g., priority threat management and systematic conservation planning) can aid navigation of multiple steps of a decision analysis for particular contexts. We summarize key decision-support frameworks and tools and describe to which step of a decision analysis, and to which contexts, each is most useful to apply. Our introduction to decision science will aid in contextualizing current approaches and new developments, and help decision makers begin to apply decision science to conservation problems.     

Geochemical parameters influencing tungsten mobility in soils

The biogeochemistry of tungsten and its effects on mobility have recently gained attention due to the existence of human cancer clusters, such as in Fallon, NV. Tungsten exists in many environmental matrices as the soluble and mobile tungstate anion. However, tungsten can polymerize with itself and other anions, creating poly- and heteropoly-tungstates with variable geochemical and toxicological properties. In the present work, geochemical parameters are determined for tungstate species in a model soil that describe the potential for tungsten mobility. Soluble tungsten leached from a metallic tungsten-spiked soil after six to twelve months aging reached an equilibrium concentration >150 mg/L within 4 h of extraction with deionized water. Partition coefficients determined for various tungstate and polytungstate compounds in the model soil suggest a dynamic system in which speciation changes over time affect tungsten geochemical behavior. Partition coefficients for tungstate and some poly-species have been observed to increase by a factor of 3 to 6 over a four month period, indicating decreased mobility with soil aging.     

In vitro cytotoxicity assessment of a West Virginia chemical spill mixture involving 4-methylcyclohexanemethanol and propylene glycol phenyl ether

Thousands of gallons of industrial chemicals, crude 4-methylcyclohexanemethanol (MCHM) and propylene glycol phenyl ether (PPh), leaked from industrial tanks into the Elk River in Charleston, West Virginia, USA, on January 9, 2014. A considerable number of people were reported to exhibit symptoms of chemical exposure and an estimated 300,000 residents were advised not to use or drink tap water. At the time of the spill, the existing toxicological data of the chemicals were limited for a full evaluation of the health risks, resulting in concern among those in the impacted regions. In this preliminary study, we assessed cell viability and plasma membrane degradation following a 24-h exposure to varying concentrations (0–1000 μM) of the two compounds, alone and in combination. Evaluation of different cell lines, HEK-293 (kidney), HepG2 (liver), H9c2 (heart), and GT1-7 (brain), provided insight regarding altered cellular responses in varying organ systems. Single exposure to MCHM or PPh did not affect cell viability, except at doses much higher than the estimated exposure levels. Certain co-exposures significantly reduced metabolic activity and increased plasma membrane degradation in GT1-7, HepG2, and H9c2 cells. These findings highlight the importance of examining co-exposures to fully understand the potential toxic effects.