Fluoride and nitrogen contamination and potential health risks in the groundwater of a typical agricultural region

Fluoride and nitrogen contamination is a global concern and has been a serious problem in agricultural areas. This study aims to identify the source of fluoride and nitrogen in the groundwater and assess groundwater quality and human health risks in the Guanzhong Plain, northwest China. The results showed that the concentrations were 0.15-4.74 mg/L for F^-, 0.02-89.89 mg/L for NO₃^--N, and BDL-2.40 mg/L for NH₄⁺-N in groundwater. Distinct area-dependent distributions of fluoride and nitrogen were observed in the study region. Higher F^- and NO₃^--N concentrations in groundwater were detected in the northern part, and higher NH₄⁺-N levels were observed in the southern part. Water-rock interaction and agricultural activities were the controlling factors for fluoride and nitrogen distribution in groundwater. About 80% of samples are considered to have good water quality with WQI < 100. Exposure to fluoride and nitrogen through drinking should require more attention. The total non-carcinogenic risks through oral ingestion of groundwater were 0.22-3.19 for adults and 0.51-7.44 for children, respectively. The order of pollutants in the groundwater in terms of their hazard to residents was F^- > NH₄⁺-N > NO₃^--N > NO₂^--N. The findings of this study could provide more insights into groundwater management.