Spatial distribution of metal pollution of soils of Chinese provincial capital cities.

This work describes the spatial distribution of metal concentrations, resulting environmental quality, and potential ecological risks using ArcGIS. The data were based on collecting the soil background and baseline values of eight metal elements (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in 31 Chinese provincial capital cities (PCCs) from published literatures 2005-2017. The following results were obtained in accordance with the integrated pollution index and the total potential ecological risk index: (1) The average concentrations of metals varied in relatively low degree in Chinese PCCs, while 10 and six PCCs were classified as having "severe" contamination and "moderate" risk, respectively. (2) Cd, Hg, Cu, Pb, and Zn were chosen as priority control metals; Beijing, Chengdu, Tianjin, Changsha, Shijiazhuang, Shenyang, Ji'nan, Changchun, and Xi'an were chosen as priority control PCCs, due to their higher pollution level and ecological risk of soils in comparison to other metals or PCCs. (3) A clear southeast/northwest boundary marked the urban soil metal pattern, which was aligned with the famous demographic, geological, and economic boundary known as the "Hu-line." This finding suggests that metal contamination in urban soil was caused by both geochemical background and human activities. These results provide basic information that can assist to avoid further degradation of soil by preventing and monitoring metal contamination in China's PCCs. The study suggests that more attention should be focused on developing cities in western China and "The Belt and Road" when pursuing economic development.