Distribution Characteristics and Pollution Evaluation of Heavy Metals in Greenbelt Soils of Nanjing City

Abstract

Concentrations and the spatial distribution of heavy metals (Cr, Cu, Zn, Pb, and Cd) in greenbelt soils in the main areas of Nanjing City, Jiangsu Province, were investigated and pollution levels were assessed using the single factor pollution index (SFPI), Nemerow integrated pollution index (NIPI), and potential ecological risk coefficient (PERC). The results showed that the average concentrations of heavy metals in greenbelt soils exceeded their background values, with the SFPI results ranked Cd > Pb > Cr > Cu > Zn, and the mean NIPI was 2.72 indicating that the greenbelt soils are moderately polluted. The PERC of each heavy metal (Cr, Cu, Zn, and Pb) was less than 10, indicating that the greenbelt soils present a slight ecological risk, while the PERC of Cd reached 97.32, indicating a strong ecological risk. The composite PERC of all heavy metals was less than 150, indicating a slight ecological risk overall. The five heavy metals showed a patchy spatial distribution, with high concentrations of Cr, Cu, Zn, and Pb in the greenbelt soils of northeast areas, and high concentrations of Cd in the southwest and northwest. Based on the results of study, Cd pollution in greenbelt soils in main areas of Nanjing City is relatively serious, which requires further attention.