Characteristics and pollution risks of Cu, Ni, Cd, Pb, Hg and As in farmland soil near coal mines

Heavy metal (loid) pollution poses a serious threat to the health and habitability of ecosystems worldwide. This study aims to investigate the concentration, pollution degree, pollution sources, and health risks of heavy metal (loid)s (HMs) in soil of Shanxi Province, China. The concentrations of Cu, Ni, Cd, Pb, Hg and As were measured by ICP-MS in 146 soil samples collected from agricultural land. The pollution degree and ecological risks of HMs were analyzed by variety of indexes, and the human health risks were assessed using the USEPA model. Results showed the average concentrations of Cu, Cd, Pb, Hg and As were 1.08, 1.15, 1.44, 1.50 and 1.25 times higher than the background values in the soil of investigated areas, respectively. The contamination factors revealed moderate pollution of Hg, Pb, As, Cd and Cu in the investigated areas, and the pollution load index indicated considerable contamination. The Nemerow index revealed low to severe contamination with HMs. The potential ecological risk of HMs indicates that Hg and Cd pose a moderate risk threat to the soil ecology. Coal mining was the primary sources of soil HMs identified by ACPS-MLR. Soil As (75.1%) and Ni (62.3%) were mainly derived from coal mining, Pb (73.1%) was from traffic emissions, and Hg (38.6%) originated from coal combustion. The health risks associated with these HMs due to soil exposure were within the acceptable levels for adults. The As concentration imposes the strongest effect based on the non-carcinogenic risk analysis in different exposed populations. In conclusion, the higher concentration of soil HMs moderately threatens soil ecology, but there was no significant human health risk found in the study. Furthermore, this study reveals the potential risk and sources of HMs in Shanxi Province, which is helpful for managing contaminated soil in the region.