Microbial, Plant, and Invertebrate Test Methods in Regulatory Soil Ecotoxicology

Standard tests have been used in soil ecotoxicology for about 40 years, but there is still room for improvement, such as (1) increased use of such tests because of regulatory requirements, in particular for the risk assessment of chemicals (mainly pesticides) and, to a lesser extent, of contaminated soils; (2) increased efforts regarding the standardization of ecotoxicological methods, handled either by OECD (Organization for Economic Cooperation and Development) prospectively for individual chemicals or by ISO (International Organization for Standardization) retrospectively for contaminated soils; (3) increased inclusion of ecological aspects, i.e., by performing higher-tier tests under semi-field and field conditions. However, until quite recently, nominal concentrations of the stressors are used, meaning that their bioavailability was not taken into account. We are providing an overview on currently required and/or proposed ecotoxicological effect tests, covering OECD and ISO methods for main soil organism groups (microbes, invertebrates, and plants). Based on this overview, we discuss how the current set of test methods could be improved, trying to capture ecological reality by addressing issues such as different soils, species, endpoints, and exposure (i.e., bioavailable instead of nominal/total concentrations). The TRIAD approach is highlighted as an example how bioavailability could be implemented in soil quality regulations.