Heavy metal pollution status, children health risk assessment and source apportionment in farmland soils in a typical polluted area, Northwest China

Sewage irrigation solves rural water problems, pollutants in wastewater are retained in agricultural soils and enter the human body through crops, jeopardizing human health. Here, contamination features, source apportionments, and associated health risks from agricultural soils were systematically investigated in the Dongdagou Watershed. According to descriptive statistics and heavy metal evaluation, Dongdagou Watershed were mainly polluted by Cd, Cu, Pb, Zn, and As, to different degrees. Health risk assessment results showed that the total hazard indices (THI) for preschool children were 3.20-4.11 and the total carcinogenic risks (TCR) were 9.09 x 10(-5) to 1.38 x 10(-4). Monte Carlo simulation showed that THI values of 83.16-92.87% of children were > 1 and TCR values of 4.36-13.69% of children exceeded 10(-4), indicating the HI risk to preschool children is unacceptable, and the carcinogenic risk could not be ignored. Positive matrix factorization analysis showed that Cd, Zn, and Cu in the soil are primarily from industrial activity, such as sewage irrigation (75.6%); Pb is primarily from atmospheric deposition; and Mn, Ni, and Hg are mainly derived from natural historical pollution sources. The source-oriented health risk assessment showed that sewage irrigation was the most important anthropogenic health risk source for children.