Source analysis of heavy metals in groundwater of centralized drinking water sources and seasonal variations of health risks in Wuzhou City, Pearl River Delta, China

Groundwater serves as a critical source for centralized drinking water, particularly in rapidly urbanizing regions, yet its quality is increasingly threatened by heavy metals (HMs) pollution. Systematic assessments that integrate source apportionment with seasonal health risks in such settings remain limited, hindering the development of targeted protection strategies. To assess the pollution characteristics and potential health risks of HMs in groundwater in Wuzhou City, Pearl River Delta, a total of 198 groundwater samples were collected for systematic analysis during the wet season and dry season in this study. The results show that the average concentrations of Mn, Fe and Zn are the highest in the two seasons, and Mn, Fe and As often exceed the Class III water limit. Overall, the pollution level of HMs is relatively high during the dry season. Three sources of HMs were identified by principal component analysis and the absolute principal component score - multiple linear regression model: geological background (28.67 % in the dry season and 21.45 % in the wet season), mining activities (22.70 % in the dry season and 26.52 % in the wet season), and agricultural activities (24.08 % in the dry season and 32.23 % in the wet season). The calculation results of the HMs pollution index show that the average HMs pollution index during the dry season and the wet season are 18.0 and 16.1 respectively, further confirming that groundwater pollution is more prominent during the dry season. Health risk assessment and Monte Carlo simulation indicate that the non-carcinogenic risk of children is slightly higher than that of adults. The spatial distribution characteristics indicate that the health risks in the northwest of the study area are more severe. Based on the comprehensive pollution characteristics and risk assessment results, Mn, Fe and As were identified as characteristic pollutants that need to be prioritized for control. The results of this study can provide scientific support for the precise control and treatment of heavy metal pollution in groundwater in Wuzhou City, Pearl River Delta, and at the same time offer an important reference for the formulation of drinking water safety guarantee strategies in similar urbanized areas. • Multi-seasonal, multi-parameter monitoring revealed seasonal heavy metals pollution differences. • Absolute principal Component score - multiple linear regression identified three main sources of heavy metals. • Deterministic and uncertain analyses of health risks were conducted. • It is determined that the heavy metals that need to be prioritized for control are Mn, Fe and As.