Spatiotemporal variation of soil heavy metals in China: The pollution status and risk assessment

Soil heavy metal pollution has been a serious and widespread problem in China. Although more attention has been paid on soil pollution status of heavy metals in China, systematic reviews on the spatiotemporal distribution of soil heavy metals and their related health risk considering different land use types at a national scale are still lacking. In this review, we extracted concentrations of seven heavy metals in soils including lead (Pb), cadmium (Cd), mercury (Hg), chromium (Cr), arsenic (As), nickel (Ni), and copper (Cu), assessed the spatiotemporal distribution of soil heavy metal concentrations from studies carried out between 1977 and 2020, and estimated the ecological and human health risks on a national scale. Among the seven metals, associated risks posed by Pb and As are more serious compared to other metals. Based on the temporal trend of the geoaccumulation index of the seven heavy metals during 1977-2020, there is no further increasing trend. Among different land use types, mining areas showed higher risk compared to others. Totally, the pollution was more serious in southeast China than those in northwest. Children and adult females are identified as the priority group for protection. This paper presents a comprehensive ecological and health risk assessment of seven heavy metals in soils across China considering different land use types and spatiotemporal variation, and provides important evidence for policy makers to manage and reduce soil heavy metal pollution and related health risks.