Assessment of Potential Heavy Metal Contamination in the Peri-urban Agricultural Soils of 31 Provincial Capital Cities in China

To obtain a general understanding of heavy metal contamination in peri-urban agricultural soils in China, this study investigates the concentrations of eight heavy metals, i.e., Cd, Pb, Zn, As, Cu, Cr, Hg, and Ni, in the peri-urban agricultural soils of 31 provincial capital cities in China. The data were obtained via exhaustive literature searches in both the Web of Science and China National Knowledge Infrastructure (CNKI) as well as from statistical yearbooks published in China. To evaluate the pollution status of each city and identify a variety of potential sources, various contamination indexes, e.g., the enrichment factor (EF), geoaccumulation index (I-geo), and integrated pollution index (IPI), were calculated based on the peri-urban agricultural soil dataset. The results of the analysis of the heavy metal concentrations, EF values and I-geo values showed that the peri-urban agricultural soils were enriched in most heavy metals, and Cd and Hg concentrations greatly exceeded the Chinese Environmental Protection Administration (CEPA) guidelines. The IPI results showed that 15 of the 31 cities, i.e., 48%, exhibited varying extents of heavy metal pollution. Although the mean IPI value for peri-urban agricultural soils in all cities (0.83) was slightly lower than that for urban soil (0.9), the IPI values for peri-urban agricultural soils from 65% of the cities were greater than those for urban soils, indicating that peri-urban agricultural soils are more polluted than urban soils in these large cities. These results are important for guiding future research on heavy metal pollution in peri-urban agricultural soils of presently expanding Chinese cities.