A causation-based method developed for an integrated risk assessment of heavy metals in soil

A comprehensive and fact-based risk assessment of heavy metals in soils is paramount for defining strategies for environmental management. However, the risk assessment approaches of heavy metals in soils are often incomplete, in particular, causation-based pollution source apportionment is absent at present. Here, we developed a causation-based method framework of an integrated risk assessment of soil heavy metals. This method framework involves risk identification, causation-based source apportionment and an environmental sensitivity assessment. Dongtang Township in Guangdong Province, China was used as a case study. We found that air Cd, the background value and metallurgical industries (Danxia and Fankou plants) were identified as the major causes of soil Cd, and air and soil Cd as well as water Cd interacted causally. Danxia and Fankou plants, the mining area and background value were the major causes of soil Pb. The risk level and environmental sensitivity of the Danxia and Fankou plants were assessed. This is the first study to establish a causation-based method framework of an integrated risk assessment of soil heavy metals. This framework promotes systematic integration of risk assessment of soil heavy metals and expands traditional research on pollution source apportionment from a correlation-based approach to crucial insights into causation.