Site-Specific Soil Ecological Risk Assessment of a Metal Contaminated Area Based on the Triad Approach

Ecological risk assessment based on scientific data is crucial for understanding causal relationships between chemical pollution and environmental risk. Simultaneously, a balance is required between socioeconomic factors and scientific evidence. The TRIAD approach, which incorporates three lines of evidence (LoE)—chemical (Chem-LoE), ecotoxicological (Ecotox-LoE), and ecological (Eco-LoE)—was applied in five sites of an abandoned mine for site-specific soil ecological risk assessment (SERA). The Chem-LoE comprised total metal concentrations, 0.43 M HNO3, and water extractable metal concentrations. Ecotox-LoE comprised eleven bioassays for soil and soil extract, and Eco-LoE comprised collembolan abundance, vegetation survey, and bait-lamina assay. High risk sites were prioritized based on the TRIAD approach results. In all sites, the Chem-LoE contributed higher integrated risk values than Ecotox-LoE and Eco-LoE. This suggests that a balance of the three LoE is important for site-specific SERA. In this study, additional diverse bioassays and field investigations were performed to reduce uncertainty about SERA; thus, the priority list of the organisms that can cost-effectively reflect ecological risks could be inferred. The results provide information to support effective decision making for risk management to protect the soil ecosystem. Moreover, these findings will be useful in establishing policies and priorities for soil risk management