A comparative assessment of groundwater and surface water quality in the Yangtze River Delta.

Water resources are essential for the development of Yangtze River Delta. Thus, the investigations and evaluations of water quality are of great importance. In this study, 40 groups of surface water and groundwater samples from Nantong City, a coast city located in the northern Yangtze River Delta were collected and thoroughly analyzed. The Water Quality Index (WQI) and Health Risk Assessment (HRA) methods were employed to evaluate water quality and health risks of nitrate. Results indicated that 15% and 5% of groundwater samples were slightly and heavily polluted, respectively. Only 5% of surface water samples were slightly polluted, showing better water quality than groundwater. Moreover, the concentrations of nitrate in 32.5% groundwater samples exceeded the World Health Organization (WHO) guideline of 50 mg/L, with the highest concentration reaching 403.02 mg/L. Surface water samples, on the other hand, showed no significant nitrate pollution. The health risk assessments of groundwater demonstrated that there is a certain level of nitrate health risk in the groundwater within some region of research area, with children, followed by adult females and males, facing the highest risks due to increased nitrate exposure, underlining a significant public health issue. This study bridges the knowledge gap in groundwater and surface water quality and nitrate health risk assessments in the Yangtze River Delta. It also provides a valuable case study comparing spatial patterns of water quality at the regional scale and offers important insights for sustainable water resource management in deltaic regions.