Source apportionment and assessment of risk to human health of soil heavy metals: a high-density sampling survey in the Dan River Basin, Shandong Province, China

Purpose The rapid development of industry, mining, and agriculture in recent years has led to heavy metal enrichment in the soil in the Dan River Basin, which has greatly threatened the land quality in this area. However, little is known regarding the sources and risks of soil heavy metal pollution in the Dan River Basin. Materials and methods This study conducted high-density soil sampling in the Dan River Basin. The sources and potential risks of soil heavy metals to human health were investigated through the use of fuzzy synthetic evaluation (FSE), index evaluation, spatial analysis, the absolute principal component scores multiple linear regression (APCS-MLR) model, and the health risk assessment model. Results and discussion The variation coefficients of heavy metals are relatively high. The monitoring results indicated the study area to be slightly to moderately polluted, with contamination concentrated in the south and parts of the east and west. It needs to bring a high attention to Ni and Cr pollution caused by excessive content and Cd pollution caused by its high toxicity. Soil heavy metals posed a low level of comprehensive ecological risk. The sources of soil heavy metals could be placed into two categories: (1) Cu, Zn, Ni, Cr, and Cd mainly originated from industry and agriculture; (2) Pb and Hg could be attributed to transportation and mining. Ingestion represented the main route that topsoil heavy metals enter the body. While the risk of ingestion was high for both adults and children, the latter were at higher risk. Risks to adults and non-carcinogenic risks to children were negligible, whereas the carcinogenic risks posed by heavy metals to children are higher. Conclusions The concentration of heavy metals in soil in the study area was influenced by anthropogenic activities. Heavy metal pollution could be mainly attributed to Ni and Cr. Cd posed a moderate to considerable ecological risk in most areas. More attention is needed on the carcinogenic risk to children by Cr produced through manufacturing. This study provides information for regional soil pollution source apportionment and can guide efforts to mitigate pollution and protect human health.