Potential Risk Evaluation for Soil Environmental Quality Assessment in China Based on Spatial Multi-Criteria Decision-Making Theory

Soil environmental quality assessment traditionally focuses on a single objective. Therefore, related results only reflect the pollution of the assessment objective and ignore the interaction and relationships between soil, ecology, and human health. In this study, we collected and filtered data about heavy metal content (Cr, Pb, Cd, Hg, As, Cu, Zn, and Ni) in city soils from more than 1000 published papers. Spatial multi-criteria decision-making theory was used to establish the combined evaluation model of soil environmental quality using the geochemical accumulation, ecological risk, non-carcinogenic risk, and carcinogenic risk indexes. Our results showed that the pollution degree and elements causing most pollution were significantly different when these different methods were used for assessment. The proposed framework was able to unify the overall pollution trend in regional soil environmental quality assessment and could output more robust and reasonable assessment results of soil, ecology, and human health. The random forest model was used to analyze the potential sources for excessive accumulation of heavy metal elements in soils, and the results showed that the main potential sources were the proportion of secondary industry and urbanization rate, each with an average contribution ratio of 20%. This study provides comprehensive and specific information for the prevention and control of soil heavy metal pollution in China.