Phytoestrogens and mycotoxins in Iowa streams: an examination of underinvestigated compounds in agricultural basins

This study provides the first broad-scale investigation on the spatial and temporal occurrence of phytoestrogens and mycotoxins in streams in the United States. Fifteen stream sites across Iowa were sampled five times throughout the 2008 growing season to capture a range of climatic and crop-growth conditions. Basin size upstream from sampling sites ranged from 7 km2 to > 836,000 km2. Atrazine (herbicide) also was measured in all samples as a frame-of-reference agriculturally derived contaminant. Target compounds were frequently detected in stream samples: atrazine (100%), formononetin (80%), equol (45%), deoxynivalenol (43%), daidzein (32%), biochanin A (23%), zearalenone (13%), and genistein (11%). The nearly ubiquitous detection of formononetin (isoflavone) suggests a widespread agricultural source, as one would expect with the intense row crop and livestock production present across Iowa. Conversely, the less spatially widespread detections of deoxynivalenol (mycotoxin) suggest a more variable source due to the required combination of proper host and proper temperature and moisture conditions necessary to promote Fusarium spp. infections. Although atrazine concentrations commonly exceeded 100 ng L(-1) (42/75 measurements), only deoxynivalenol (6/56 measurements) had concentrations that occasionally exceeded this level. Temporal patterns in concentrations varied substantially between atrazine, formononetin, and deoxynivalenol, as one would expect for contaminants with different source inputs and processes of formation and degradation. The greatest phytoestrogen and mycotoxin concentrations were observed during spring snowmelt conditions. Phytoestrogens and mycotoxins were detected at all sampling sites regardless of basin size. The ecotoxicological effects from long-term, low-level exposures to phytoestrogens and mycotoxins or complex chemicals mixtures including these compounds that commonly rake place in surface water are poorly understood and have yet to be systematically investigated in environmental studies.     

Effectiveness of zerovalent iron and nickel catalysts for degrading chlorinated solvents and n-nitrosodimethylamine in natural groundwater.

Laboratory batch experiments were performed to evaluate the effectiveness of nickel catalysts, nanoscale zerovalent iron (nZVI) doped with palladium, and microscale ZVI for treatment of tetrachloroethene, trichloroethene, and n-nitrosodimethylamine (NDMA) in soil-groundwater slurries. Results indicated that the presence of NDMA inhibited degradation of chlorinated solvents. Although both the nickel catalyst and nZVI were able to degrade NDMA in deionized water, neither of these metals was effective at degrading NDMA in the soil-groundwater system evaluated in this study. The effectiveness of the nickel catalyst and nZVI, with respect to treatment of the chlorinated solvents, also appeared to be highly dependent on the groundwater geochemical conditions. Overall results of this study suggest that the degradation mechanisms involving nickel catalysts and nZVI in natural soil/groundwater systems are not well-understood, and addition of metal catalysts to ZVI may not necessarily enhance observed degradation rates in natural systems.     

How accurately do semi-permeable membrane devices measure the bioavailability of polycyclic aromatic hydrocarbons to Daphnia magna?

Semi-permeable membrane devices (SPMDs) are passive samplers that have been designed to sample the bioavailable fractions of hydrophobic organic compounds in aquatic ecosystems. This study aims at evaluating the ability for SPMD to sample polycyclic aromatic hydrocarbons (fluoranthene, pyrene and benzo[a]pyrene) that are actually bioavailable to Daphnia magna. For that purpose, the SPMD-available fraction and the bioavailable fraction to D. magna are compared in controlled media with Dissolved Organic Matters (DOMs) from various origins and at different concentrations. The presence of all but one DOM reduces the accumulation of PAHs in SPMD or in D. magna. Moreover, this comparative laboratory study shows that in 10 cases on 13, the SPMD-available fraction is close to the available fraction to D. magna. When significant differences are observed between SPMD-available and bioavailable fractions, they remain less than 50% at DOM concentrations below 10 mg/l DOC, which corresponds to a maximum DOC concentration usually found in temperate rivers. This study confirms the suitability of the SPMD technique to monitor readily bioavailable hydrophobic contaminants in aquatic environments containing DOM from various origins and characteristics.     

Alternative strategies in avian scavengers: how subordinate species foil the despotic distribution

Trade-offs in species’ traits can mediate competition and enable coexistence. A key challenge in ecology is understanding the role of species’ trade-offs in maintaining diversity, and evolutionary trade-offs between the abilities of competing species are best understood by considering how competitive advantages change along an environmental gradient. Previous studies of such trade-offs are generally limited to two-species systems and a single trade-off. In this study, I consider the effect of trade-offs in search efficiency and competitive abilities on habitat use patterns among a diverse avian scavenger guild. I hypothesize that species’ dominance status and search efficiency will both be correlated with patch quality. Using counts of searching birds in areas that vary in habitat quality in terms of both wildlife and human settlement density and observations at experimental carcasses, I assess the competitive ability, search efficiency, and habitat use of seven avian scavenger species in Masai Mara National Reserve, Kenya. Findings support the hypothesis with Bateleurs, a species with high search efficiency, and Ruppell’s, Lappet-faced, and White-backed vultures, species with high individual or social dominance, preferentially exploiting habitats of high quality, while Tawny eagles and Hooded vultures, species with low search efficiency and competitive ability, prefer habitats of low quality. This paper demonstrates the importance of considering multiple strategies for assessing the effect of competition on habitat use within complex communities.     

Developing environmental quality standards for various pesticides and priority pollutants for French freshwaters

The French Ministry of the Environment and Water Agencies have derived environmental quality standards following the existing French framework called SEQ-Eau, for 28 pesticides and seven priority substances listed in the Water Framework Directive. Like other existing frameworks, SEQ-Eau relies upon the use of standard toxicity test results and assessment factors. This approach made it possible to derive the desired quality standards, but due to the lack of chronic toxicity data many of the standards are only provisional. In addition, emerging issues such as endocrine disruption should be taken into account in this framework. Depending on the available data, more flexible derivation approaches, such as the statistical distribution of NOECs, are recommended for future versions of SEQ-Eau. A comparison is made using SEQ-Eau and the methodology currently being discussed in Europe to develop environmental quality standards, showing that the European approach is more conservative. Conversely, the proposed approach under the Water Framework Directive does not cover the entire range of required quality classes.     

Reactivity of sulfate radicals with natural organic matters

Advanced oxidation processes based on sulfate radicals (SO ₄ ^·? ) are capable of efficiently degrade organic pollutants from ground, surface and wastewaters. However, this degradation may be limited by aqueous natural organic matter (NOM). Here we measured the absolute rate constants of reaction of SO ₄ ^·? with four types of organic matter: two fulvic acids and two lake organic matter. We used laser flash photolysis technique to monitor the SO ₄ ^·? decay and the formation of the transients from organic matters. Reaction rate constants comprised between 1530 and 3500 s^?1 mgC^?1 L were obtained by numerical analysis of differential equations and the weighted average of the extinction coefficient of the generated organic matters radicals between 400 and 800 M^?1 cm^?1.