Toxicity of Selenium, Weathered and Aged in Soil, to the Collembolan Folsomia candida

Abstract : We investigated the toxicity of selenium (Se) to the soil invertebrate Folsomia candida using the Folsomia Reproduction Test (ISO 11267:1999). Studies were designed to generate ecotoxicological benchmarks for developing the ecological soil screening levels (Eco-SSLs) for risk assessments of contaminated soils. For this study, we selected aerobic upland soil, Sassafras sandy loam (SSL), with soil characteristics (low levels of clay and organic matter, soil pH adjusted high) that support high relative bioavailability of the anionic Se species that is typically found in aerobic soil. Se was amended into soil as sodium selenate, subjected to weathering-and-aging using 21 days of alternating cycles of air-drying/rehydration to 60 75% of the water-holding capacity of the SSL soil, under ambient greenhouse conditions. Effective concentration at 20 and 50% (EC20 and EC50) levels were 4.7 and 10.9 mg of Se/kg of soil, respectively, as determined on the basis of production of juveniles (reproduction) by F. candida exposed to Se weathered-and-aged in SSL soil. Toxicity benchmarks established in this study were submitted to the U.S. Environmental Protection Agency Eco-SSL Workgroup, and the EC20 value was used in developing soil invertebrate-based Eco-SSL for Se.