Distribution characteristics and risk assessment of the heavy metals in agricultural land along the Yangtze River in the eastern suburbs of Nanjing City

To find out the heavy metal pollutant types and influence range of the agricultural land along the Yangtze River in the eastern suburbs of Nanjing City, 688 topsoil samples are collected to determine the pH values and contents of heavy metals such As As, Cd, Cr, Cu, Hg, Ni, Pb and Zn. The methods of single factor index, nemero comprehensive pollution index and potential ecological risk index are used to conduct the pollution risk assessment. The results show that compared with the background values of soil elements in Nanjing City, except Hg, 7 other heavy metals are all enriched. Cd is the main heavy metal pollution element in the area with the point exceeding rate of 36.4%, light pollution dominated. The Cd-contaminated areas are mainly distributed in neutral soil and acid soil. The Cd single factor potential ecological risk indexes indicate the risk areas above II level(moderate)account for 90% of the total area, and III level(high)risk areas occupy about 10%. Combined with the pollution risk of 8 heavy metals, most agricultural land are in the safe production level, with only a few farmlands in II and III risk levels. The potential ecological hazards of heavy metals in agricultural land is low on the whole.