Characterization of the hydrochemistry of water resources of the Weibei Plain, Northern China, as well as an assessment of the risk of high groundwater nitrate levels to human health.

This study aimed to evaluate the hydrochemistry of the water resources of the Weibei Plain, Northern China, as well as the risks posed by high groundwater nitrate concentrations to human health. Groundwater and surface water samples numbering 168 and 14, respectively, were collected during the dry and wet seasons. Water in the study area was weakly alkaline, falling into a hard-fresh or hard-brackish category. The groundwater chemical types were mainly SO4·Cl-Ca·Mg (59.5%) and HCO3-Ca·Mg (28.6%), whereas the dominant chemistry type of surface water was SO4·Cl-Na (78.6%). Groundwater showed relatively high concentrations of NO3-, with average dry and wet season concentrations of 212 mg·L-1 and 223 mg·L-1, respectively, whereas surface water had a low NO3- content. The major processes affecting water chemistry were determined to be rock weathering, such as silicate weathering and evaporative dissolution, as well as cation exchange. NO3- in groundwater was found to mainly originate from anthropogenic inputs such as agricultural production and domestic sewage. The entropy-weight water quality index (EWQI) assessment showed that although the quality of surface water was generally good, more than half of the groundwater samples failed drinking water standards, with NO3- identified as being the most problematic parameter affecting the water quality evaluation. Risk assessment of high groundwater nitrate concentrations indicated that long-term domestic use of groundwater in the study area can put the health of residents at great risk. Totals of 81% and 75% of the groundwater samples exceeded the acceptable limit for non-carcinogenic risk (HI = 1) to infants during the dry and wet seasons, respectively, whereas 75% and 71.3% of samples exceeded the acceptable limit for children, respectively. Future management of water in the Weibei Plain should prioritize the control groundwater nitrate pollution.