[Source Determination and Health Risk Assessment of Heavy Metals in Groundwater of Guangzhou]

Heavy metal pollution in groundwater seriously threatens human health and the sustainable development of the ecological environment. With the rapid urbanization, heavy metal pollution in groundwater is becoming an increasingly serious issue. Guangzhou, as the core engine of the Guangdong-Hong Kong-Macao Greater Bay Area, has high economic vitality and holds an important position in the development of the country. In order to understand the groundwater situation in Guangzhou, 87 groundwater samples were collected during the wet and dry seasons, and the concentration and spatial distribution characteristics of seven heavy metal elements (Cr, Fe, Cu, Zn, Cd, Pb, and As) were analyzed. The sources of heavy metals in groundwater were then determined through correlation analysis and the absolute principal component analysis-multiple linear regression model. Finally, the health risk model and Monte Carlo simulation were used to evaluate the different health risks associated with these heavy metals. The results showed that the average values of Fe and As exceeded the limit of Class Ⅲ of the National Groundwater Quality Standard, and the excess rate of Fe was the highest, which was the top priority for the prevention and control of heavy metals in the future. There were obvious spatial differences in the concentrations of heavy metals in groundwater in the study area, with concentrations of most elements in the central and southern regions higher than those in the northern regions. There were four pollution sources in both the wet and dry seasons, namely agricultural, mixed natural and agricultural, industrial, and traffic sources. In both the wet and dry seasons, the non-carcinogenic risk of heavy metals in groundwater in the study area was at an acceptable level, except for Cr and As, which were exposed to a higher carcinogenic risk. During wet seasons, priority should be given to the regulation of agricultural activities, while during dry seasons, control should be focused on industrial activities.