Spatial distribution, origin, and health risk assessment of nitrate in groundwater of Cenozoic basalts in Zhangbei county, Hebei Province

[Objectives] In order to identify nitrate sources and health risks in groundwater of Cenozoic basaltic rock in Hebei province.[Methods] The basalt distribution region in Zhangbei county is selected as a typical study area. Based on hydrochemistry and isotopes data of 45 groups groundwater samples, the distribution characteristics and origin of nitrate in basalt groundwater were studied, the health risk of nitrate in groundwater was evaluated using the health risk assessment model.[Results]The results showed that the average concentration of nitrate in the groundwater of the study area was 86.08 mg·L^-1, The nitrate concentration of 26.6% of the sampling sites exceeded the limit value of the III grade groundwater quality in GB/T 14848-2017《The Quality standard of Underground Water》 (20 mg·L^-1);The nitrate pollution of different land use types varied greatly, and the content of nitrate in urban areas was the highest, followed by irrigated land,with forests、grasslands or dry land not exceeding the standard.The sources of nitrate in groundwater was mainly manure and domestic sewage, and the next was chemical fertilizer leaching;The health risks of nitrate exposure through skin contact among the population in the study area were at acceptable levels, while the health risk of nitrate intake from drinking water was higher, and the contribution rate of nitrate intake from drinking water accounted for 99.23% of the total risk, which was much higher than that from skin contact route.The health risks of drinking water intake and skin contact in children were significantly higher than those of adults.The health risks of groundwater nitrates to children in 75.55% of the sampling sites exceeded acceptable levels.[Conclusions] From the perspective of water supply safety, it is recommended to increase water purification equipment in high-risk areas to reduce human health risks