Groundwater metal pollution and health risk assessment in river valley heavy industrial cities of arid regions in China

Xining, a river valley city in China’s arid region, serves as an important industrial hub with a fragile ecological environment. While groundwater heavy metal pollution in this area has drawn increasing concern, the sources and associated human health risks remain inadequately understood. This study analyzed 144 shallow groundwater samples from urban Xining for 14 heavy metals (Fe, Al, B, Mn, Ba, Zn, Pb, Cr⁶⁺, Ni, Cu, Co, Sb, Cd, and As) using the Nemerow comprehensive pollution index, correlation analysis, and the USEPA health risk assessment model. Results identified Fe, Al, B, Mn, Ba, Pb, Cd, and As as the primary pollutants, especially concentrated in river valley plains. These contaminants primarily originate from natural sedimentary conditions and human activities such as industrial and agricultural development. The pollution indices for Al, Pb, Mn, and Fe exceeded clean water thresholds, indicating serious contamination and the need for enhanced regulation. Health risk assessments revealed that children face greater exposure risks than adults, with arsenic and nickel being the main contributors to carcinogenic risk. Sensitivity analysis further showed that As, Fe, and Cd posed the greatest non-carcinogenic and carcinogenic risks, particularly in human-impacted areas such as the Nanchuan and Beichuan valleys and Ganhegou. These findings provide essential insights for groundwater safety management in plateau river valley cities and similar vulnerable regions.