Pollution status, distribution, source analysis, and risk assessment of OCPs in soil from the Hexi Corridor in Northwest China

Since OCPs with different historical usage and atmospheric input may show varied environmental behaviors and risks to the local residents and relevant research on underdeveloped areas in the middle latitudes of China is lacking, it is essential to classify the contamination status and sources of OCPs from these middle latitudes areas and to evaluate the related health risks to humans. Fifty soil samples were collected and analyzed within five cities in the Hexi Corridor in Northwest China. The ranges of ∑24OCPs, ∑DDTs, and ∑HCHs concentrations in the soil samples were 23.1-393 ng/g, 4.96-167 ng/g, and 3.40-97.5 ng/g, respectively. The residual OCPs in soil were dominated by DDTs and HCHs, accounting for 38.7% and 16.1% of ∑24OCPs. Source analysis shows that the HCHs come from historical application and possible recent pesticide use, and DDTs are mainly from early application residues that formed in aerobic environments created by agriculture ploughing, which aerates the soil. The risk assessment showed that the soil in the Hexi Corridor may have a potential risk of residual OCPs, and the carcinogenic risk (CR) was 1.90 × 10-7-6.12 × 10-7 for adults and 5.6 × 10-7-1.8 × 10-6 for children, but the hazardous index (HI) was 0.0093 to 0.2817 for adults and 0.032 to 0.932 for children. Only a few samples showed values higher than the acceptable range for children. Therefore, in this study area, there is a low health risk to local residents. Nevertheless, our results provide a strong rationale for ongoing risk assessment and management and, hopefully, eradication of OCPs in the environment.