Soil type dependent toxicity of AgNM300K can be predicted by internal concentrations in earthworms

A continuous challenge in nanotoxicology is the interaction of nanoparticles with the soil components. In the present study, we compare the toxicity of silver nanoparticles (AgNM300K) on earthworms across 4 different soils, exploring which among the total-, soil solution-, or worm tissue-Ag-concentrations that enables the best prediction of toxicity across the soils. We exposed the earthworm Eisenia fetida to AgNM300K for 56 days to assess survival, reproduction, and bioaccumulation. These endpoints were related to measurements of Ag-ions and -nanoparticles in soil, soil solution, and in the worm tissue. Tested soils included the standard OECD, LUFA 2.2, Hygum, and RefSol 01A soils. Toxicity was strongly dependent on the soil type, highly correlated with the organic matter, clay, and Cation Exchange Capacity (CEC). CEC provided the best correlation with the internal silver concentrations across the soils. The soil solution did not provide useful predictions across the soils.