Hydrochemical Controls, Source Apportionment, and Health Risks of Groundwater Nitrate in Rural Areas of the Huaibei Plain, China

Groundwater quality remains insufficiently characterized in the rural agriculture–residential interface of the Huaibei Plain, particularly with respect to nitrate (NO3−) occurrence, hydrochemical controls, source contributions, and population-specific health risks. In this study, multivariate statistical analysis, source apportionment models, and health risk assessment models were applied to investigate the hydrochemical characteristics of groundwater and related non-carcinogenic risks to different populations. NO3− content exceeded the World Health Organization (WHO) guidelines for drinking water in 60.0% and 62.5% of wet- and dry-season groundwater, respectively. Groundwater NO3− was mainly influenced by agricultural non-point inputs and domestic sewage, whereas major-ion composition was primarily governed by water–rock interactions. Our deterministic health risk assessment model reveals that the hazard index (HI) exceeded the acceptable threshold of 1.0 in 76.25%, 65.00%, 66.25%, and 56.25% of groundwater samples for infants, children, adult females, and adult males, respectively. These results indicate that continuous monitoring, improved sewage collection, and more controlled nitrogen management are required in the rural agricultural–residential interface of the Huaibei Plain with regard to shallow domestic groundwater.