Anthropogenic increase of heavy metals in soil from a heavily contaminated area of China

Evaluating the variation in heavy metal concentrations in soil caused by anthropogenic activities in heavily contaminated areas is of great significance. The degree of heavy metal pollution in soil is primarily assessed by different indices with different standards and reference elements. However, these methods cannot be used to evaluate the degree of heavy metal pollution caused by anthropogenic activities. In this study, Zhuzhou, China was selected as the contaminated area, and Yueyang, China was selected as the background area, where geological and climatic conditions are similar to those of Zhuzhou, China. The concentrations of As (6.6–23.6 mg/kg), Cd (0.125–0.757 mg/kg), Cu (33–75 mg/kg), Hg (0.032–0.202 mg/kg), Pb (17–108 mg/kg), and Zn (74–122 mg/kg) in the vertical soil profiles in the contaminated area were higher than those in the background area (ranging 1.7–20.7, 0.085–0.210, 21–47, 0.030–0.105, 17–38 and 32–88 mg/kg, respectively). K2O/Al2O3, SiO2/Al2O3, and the weathering leaching coefficient (ba) showed little difference, suggesting that the weathering degree of soil in these two areas was similar. The weathering degree of soil governs the geochemical behavior of heavy metals and reference elements. According to the prediction models for heavy metal concentrations and organic carbon, K2O/Al2O3, and SiO2/Al2O3 in the soil profiles from the background area, the increase in heavy metal concentrations in the topsoil in the contaminated area was depicted. The heavy metal concentrations in topsoil were obviously affected by anthropogenic activities. This study provides a case study for evaluating the impact of anthropogenic activities on heavy metals in soil.