Assessment of soil heavy metal pollution and health risk in different functional areas of Shanghai City based on GIS

The contents of 8 heavy metals in 70 surface soil samples were determined, which were collected in Shanghai City, including six functional areas of parks, traffic areas, education areas, residential areas, industrial enterprises and farmlands. The pollution status and human exposure risk of heavy metals (HMs) in different functional areas were evaluated by pollution index evaluation method and health risk model. Meanwhile, the spatial distributions of HMs based on the geography information system (GIS) were plotted. The results showed that the average values of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn were 8.03, 0.22, 62.73, 35.52, 0.19, 33.67, 29.54 and 116.78 mg/kg, respectively. The contents of Cd, Cu, Hg, Pb and Zn were higher than the soil background values in Shanghai, the enrichment of Hg, Cd and Pb was obvious and the high values were concentrated in the center city. 10% of the soil samples were heavily polluted and 15.7% of the soil samples were moderately polluted. The areas with higher pollution index were mainly located in the urban areas, and the western and northeastern suburbs as well. From the perspective of different functional areas, the traffic areas and the enterprises were severely and moderately polluted, respectively, with a higher pollution index of Cu, Hg and Cd. Human health risk assessment results showed that the descending order of total carcinogenic risk in different functional areas was as follows: enterprises > traffic areas > residential areas > farmlands > education areas > parks, and As contributed the most to carcinogenic risk. High risk areas were concentrated in urban and the southern suburb. The total noncarcinogenic risks were found to be in descending order of residential areas > farmlands > education areas > traffic areas > enterprises > parks. As, Pb and Ni were the main pollutants affecting noncarcinogenic risk. The sampling sites exceeding the acceptable level were located in the eastern area. The study showed that under different assessment methods, heavy metals in urban soils displayed differentiated spatial distribution characteristics, with certain differences in terms of the relative pollution degree in each functional area.