Heavy metal pollution and ecological risk assessment: A study on Linli County soils based on self-organizing map and positive factorization approaches

This study analyzed the pollution level, distribution, sources, and ecological impact of six heavy metals (As, Cd, Cr, Cu, Zn and Pb) in soil from Linli County, China. The concentration analysis showed that the concentration of Cd in all samples exceeded the background value, and the exceeding rate reached 100%, while the average concentrations of other elements were similar to the background value, and the exceeding rate was under 15%. The pollution level of Cd was the most severe according to geo-accumulation index and enrichment factor, while other elements were under mild pollution level. The results of self-organizing map (SOM) and positive matrix factorization (PMF) analysis showed that agricultural activities were one of the main sources of heavy metal elements in soil, and natural weathering and industrial pollution could also lead to soil pollution. Cd appeared to be the most significant pollutant element in the soil of Linli County, and it had the largest impact on the ecological environment. Overall, this study provides guidance for soil pollution control and related policies, aiming to reduce the pollution of heavy metal elements in soil and the hazards to the ecological system caused by agricultural production and industrial activities.