Manganese toxicity in soil for Eisenia fetida, Enchytraeus crypticus (Oligochaeta), and Folsomia candida (Collembola)

The U.S. Environmental Protection Agency is developing Ecological Soil Screening Level (Eco-SSL) benchmarks for ecological risk assessment (ERA) of contaminants at Superfund sites. Eco-SSLs are developed from published values whenever sufficient quantity and quality of data exist. Because insufficient information was available to generate an Eco-SSL for Mn, standardized toxicity testing was undertaken to fill the data gaps. Tests included the earthworm (Eisenia fetida) cocoon production test, the enchytraeid (Enchytraeus crypticus) reproduction test, and the collembolan (Folsomia candida) reproduction test, all conducted in Sassafras sandy loam soil that supports a relatively high bioavailability of metals. Weathering and aging of manganese-amended soil were carried out to more closely simulate exposure effects at Superfund sites on soil invertebrates. Data were analyzed by nonlinear regression to determine EC20 and EC50 values based on concentration–response relationships. The toxicity order for manganese in Sassafras sandy loam was E. crypticus>E. fetida>F. candida, with EC20 values of 116, 629, and 1209 mg kg−1, respectively. The Eco-SSL requirement for the testing of multiple representative species is well justified. All study results will be submitted to the Eco-SSL Task Group for quality control review prior to inclusion in the Eco-SSL database.