Spatio-Temporal Analysis and Health Risk Assessment of Heavy Metals in Water from the Fuhe River, South China

With rapid developments in society and economy, the concentrations of heavy metals in surface water in South China have increased significantly, which poses a serious threat to the regional water security. In this study, the Fuhe River watershed in South China was selected as the study area to analyze physicochemical characteristics and heavy metal (Cu, Zn, Pb, Cd and Cr) concentrations in river water in the dry and rainy seasons, in 2019, with the purpose of exploring their spatial–temporal variations and main influences and assessing the potential health risks of heavy metals. The pH value of river water varied from 5.82 to 7.97, and it fluctuated less overall in the dry season, but it oscillated greatly in the rainy season and was lower, especially in the lower reach of the Fuhe River. The electrical conductivity (EC) value changed between 33 μS/cm and 128 μS/cm and increased and fluctuated along the river flow in the two periods. The concentrations of Cd, Cr, Cu, Pb, and Zn in river water showed obvious differences between the two periods. The concentrations of Cd and Cu were lower with the ranges from 0.001 μg/L to 0.67 μg/L and from 1 μg/L to 12 μg/L, respectively, in the dry season than in the rainy season, while there were inverse cases for other heavy metals. Along the river flow, the Cr concentration was stable, whereas other heavy metals showed increasing trends. It was noted that the concentrations of heavy metals in the Fuhe River were, on average, lower than the Chinese drinking standard values, with the concentration of Pb in the dry season significantly higher than the drinking standard value of the World Health Organization (WHO). Principal component analysis and correlation analysis showed that rock weathering and anthropogenic inputs were the main controlling factors of Cu and Zn in the Fuhe River, and human activities were mainly responsible for Pb, Cr, and Cd concentrations. The health risk assessment results showed that the non-carcinogenic risk (HQingestion) value of Pb was greater than 1 in most sampling points in the middle and lower reaches in the dry season, suggesting a significant non-carcinogenic risk for adults and children by direct ingestion. The minimum carcinogenic risk (CRingestion) value of Cr was more than 10−4 in the rainy and dry seasons, and the CRingestion value of Cd in some sampling points was more than 10−4 in the rainy season, indicating significant cancer risks to adults and children. For areas with significant pollution and health risks in the Fuhe River watershed, it is urgent to strengthen the controls of industrial, agricultural, and urban wastewater discharge