Source analysis of soil selenium and evaluation of soil environmental quality and safety in the eastern area of Zichuan District, Shandong Province.

Zichuan District is a selenium (Se)-rich area discovered in Shandong Province. This study analyzed the source of soil Se in the eastern area of Zichuan District with using multivariate statistical analysis methods and considering the contribution of exogenous input for the first time. Additionally, the environmental quality of soil was evaluated using single factor index methods and comprehensive evaluation methods. Finally, the safety of crops and the health risks of human ingestion were assessed. The results showed that: the background value of Se in the study area was 0.43 mg/kg, significantly higher than that in Shandong Province and Chinese soil (Layer A). The F1 of R-type factor analysis revealed that the black sedimentary parent material was the material basis and initial source of soil Se enrichment, while pedogenic geochemical processes and the properties of Se contribute to the continuous accumulation of soil Se, but the exogenous input was low. Cd, Hg, and Pb exhibited the most severe pollution levels in soils. Most soils in the area were none or slightly polluted, but a small portion showed moderate or intense pollution. The MPI of 45 wheat grains was all below 1, confirming the absence of heavy metal (HM) contamination. However, the Hazard Index (HI) of HMs in 3 out of the 45 wheat grains was greater than 1, indicating potential health risks from ingestion. In contrast, the Hazard Quotient (HQ) of Se in crops was all less than 1, suggesting no harm to human health.