Factors influencing heavy metal availability and risk assessment of soils at typical metal mines in Eastern China.

China exemplifies the serious and widespread soil heavy metal pollution generated by mining activities. A total of 420 soil samples from 58 metal mines was collected across Eastern China. Total and available heavy metal concentrations, soil physico-chemical properties and geological indices were determined and collected. Risk assessments were applied, and a successive multivariate statistical analysis was carried out to provide insights into the heavy metal contamination characteristics and environmental drivers of heavy metal availability. The results suggested that although the degrees of pollution varied between different mine types, in general they had similar contamination characteristics in different regions. The major pollutants for total concentrations were found to be Cd and As in south and northeast China. The availability of Zn and Cd is relatively higher in south China. Soil physico-chemical properties had major effect on metal availability where soil pH was the most important factor. On a continental scale, soil pH and EC were influenced by the local climate patterns which could further impact on heavy metal availability. Enlightened by this study, future remediation strategies should be focused on steadily increasing soil pH, and building adaptable and sustainable ecological system to maintain low metal availabilities in mine site soils.