Risk assessment and source analysis of soil heavy metal pollution in Xuanzhou District, Anhui Province

Based on 1∶250 000 geochemical survey data of land quality in Xuancheng City of Anhui Province, the authors assessed the risk of soil contamination by heavy metals and analyzed the source of heavy metals. The overall risk of heavy metal contamination was relatively low: the soils with low and controllable risks of contamination account for 74.64％ and 25.04％ respectively, and their major concern contaminants are Cd and As, followed by Cu, Hg, Pb and Zn. The soils with higher risk of contamination account for 0.32％, and the major concern is Cd. Form analysis of the heavy metals indicated that the ecological risk of Cd and Pb was higher than that of As and Hg in the soils, and As and Hg were the highest in residual form, Cd is the highest in the form of ion exchange, and Pb is higher in residual form and Fe-Mn oxide. Through the correlation analysis between the contents of a heavy metal in the top soil and that in deep soil, it is suggested that the heavy metals in the soils mainly came from the parent materials of the soils, and the high contents of Hg, Cd, Cu, Zn, As and Pb in some local areas mainly migrated from mining, animal husbandry and other human activities.