RESUMEN
The occurrence of some species listed under the United States' Endangered Species Act in agricultural landscapes suggests that their habitats could potentially be exposed to pesticides. However, the potential effects from such exposures on populations are difficult to estimate. Mechanistic models can provide an avenue to estimating the potential impacts on populations, considering realistic assumptions about the ecology of the species, the ecosystem it is part of, and the potential exposures within the habitat. In the present study, we applied a hybrid model of the Topeka shiner (Notropis topeka), a small endangered cyprinid fish endemic to the US Midwest, to assess the potential population-level effects of realistic exposures to a fungicide (benzovindiflupyr). The Topeka shiner populations were simulated in the context of the food web found in oxbow habitats that are the focus of ongoing habitat restoration efforts for the species. We applied realistic, time-variable exposure scenarios and represented lethal and sublethal effects to individual Topeka shiners using toxicokinetic-toxicodynamic models. With fish in general showing the highest sensitivity to the compound, direct effects on simulated Topeka shiner populations governed the population-level effects. We characterized the population-level effects of different exposure scenarios with exposure multiplication factors (EMFs) applied. The introduction of a vegetative filter strip (VFS; 15 ft; 4.6 m) between the treated area and the oxbow habitat was shown to be effective as mitigation because EMFs were 2 to 3 times higher than for the exposure scenario without VFS. Environ Toxicol Chem 2021;40:2615-2628. © 2021 SETAC.
Asunto(s)
Cyprinidae , Plaguicidas , Animales , Ecosistema , Especies en Peligro de Extinción , Cadena Alimentaria , Plaguicidas/toxicidad , Estados UnidosRESUMEN
Down-the-drain exposure models provide a valuable tool for estimating environmental exposure to substances which are treated and discharged by municipal wastewater-treatment plants (WWTPs). Microplastics may enter WWTPs from consumer activities and disposal. An exposure framework was developed using the iSTREEM® model, which estimates spatially explicit concentrations of substances in riverine systems across the United States and portions of Ontario, Canada. One hundred simulations covering a range of WWTP removal and instream loss rates (proxy for net sedimentation) were incorporated into a Web-based visualization tool for user exploration of relative concentrations across simulations. Surface water concentrations specific to user-supplied tonnage were examined via interactive heat maps and cumulative distributions. Exploring the spatial aspect of iSTREEM results showed that modeling 90% WWTP removal and no instream loss resulted in 8.5% of the mass entering WWTPs discharged to marine estuaries (7.4%) or Great Lakes (1.1%) environments, with the remainder of the mass discharged (1.5%) in inland sinks or exiting the United States via rivers. Modeling an example instream loss of k = 0.1 d-1 (i.e., half-life = 7 d), terminal river segments contained 3.3% of influent mass (2.3% marine estuaries, 1.0% Great Lakes). Varying instream loss rates had substantial impacts on the total mass exported. The Web-based tool provided a user-based mechanism to visualize relative freshwater concentrations of microplastics across a large geographic area by varying simplified particle fate assumptions. Environ Toxicol Chem 2019;39:210-219. © 2019 SETAC.