Nitrate contamination in groundwater and its health risk assessment: a case study of Quanzhou, a typical coastal city in Southeast China

Nitrate contamination has become an ecological and health issue in Quanzhou, a typical coastal city in Southeast China. Hydrogeological surveys reveal that NO3- is a major factor influencing the groundwater quality in Quanzhou City, Fujian Province, China. To protect public health, this study explored the geographical spatial distribution, contamination level, contamination sources, and noncancer risks of nitrates in the plain area of Quanzhou. Key findings are as follows: (1) The groundwater in Quanzhou's plain area exhibits a high detection rate and over-limit ratio of NO3- -N of 99.3% and 57.86%, respectively. This result suggests that the groundwater in the area has been extensively contaminated by nitrates, with relatively severe nitrate contamination occurring in the Quanzhou Taiwanese Investment Zone, Jinjiang City, and Shishi City; (2) NO3- has become a major anion in groundwater in Quanzhou's plain area, leading to significant geochemical changes in some groundwater. 26.4% of the groundwater samples exhibited a hydrochemical type of nitric acid (also referred to as NO3- type water), with X(NO3-) >= 25%; (3) The primary nitrate contamination in groundwater in Quanzhou originates from the infiltration of domestic and industrial wastewater or landfill leachate; (4) 42.86%, 43.57%, and 67.14% of the samples posed health risks to adult males, adult females, and children, respectively when they were subjected to the prolonged exposure in a high-concentration nitrate environment. Additionally, the noncancer risks of nitrates principally stem from oral exposure for drinking water.