Abstract
Soil environmental assessment is a great importance for the protection of soil biodiversity. Environmental risk of dioxins on earthworm and soil microorganism was evaluated to propose a new soil risk assessment standard. The proposed approach in this study may be a useful tool for precautionary approach and management for soil and ground water contamination in Japan. The procedure consists of exposure assessment, effects assessment and risk evaluation. In the exposure assessment, Predicted Environmental Concentration (PEC) for soil, hereby PECsoil, was calculated. In the effects assessment, Predicted non-Effects Concentration (PNEC) for soil invertebrate and microorganisms, hereby PNECsoil and PNECsoilmicroorg, were calculated. Risk Characterization Ratio (RCR; ratio of PECsoil and PNECsoil, and PEC soil and PNECsoilmicroorg.) for dioxins were applied to quantify the level of risk. Under the assumption that RCR is 1, the risk-based soil concentration limits (allowance levels) were calculated to be up to 885 pg-TEQ/g for earthworm and to be 998,000 pg-TEQ/g soil for soil microorganism. This means that the risk level to representative soil invertebrates and microorganisms could be tolerable when the soil concentration was below these values. We propose this risk assessment method as one of measures to investigate, estimate and evaluate the soil biodiversity so that proper risk management measures are conducted and then biodiversity is preserved forever.
