Source Apportionment and Health Risk Assessment of Heavy Metals in Groundwater Around Typical Karst Region of the Lower Yellow River, China

The Pingyin-Changqing section of the Yellow River serves as an important groundwater recharge area in the lower reaches of the Yellow River, and its groundwater quality safety holds significant importance for the regional ecology and the health of its residents. This study systematically collected groundwater samples from this area, detected concentrations of six heavy metals (Mn, Zn, Ni, Pb, As, and Cd), and comprehensively applied mathematical statistics, spatial mapping analysis, source apportionment, and health risk assessment methods to systematically investigate the characteristics, distribution patterns, source mechanisms, and health risks of groundwater heavy metals in the region. The results indicate that (1) the mean concentrations of heavy metals in groundwater of the study area, in descending order, are Mn > Zn > Ni > Pb > As > Cd; compared against the Class III standard limits of the National Standard for Groundwater Quality, Mn shows the highest exceedance rate, followed by Pb, with exceedance rates of 18% and 5%, respectively; (2) heavy metal concentrations exhibit considerable spatial variability, with Mn exceedance points uniformly distributed in upstream and downstream areas on both banks of the Yellow River, while Pb concentrations demonstrate higher values downstream than upstream, with exceedance points mainly concentrated in the junction of Qihe and Dong'e; (3) sources of groundwater heavy metal pollution are identified as follows: Zn, Ni, and Cd primarily originate from different industrial sources, Pb mainly from traffic sources, As primarily from agricultural sources, and Mn predominantly from natural sources; (4) groundwater ingestion was identified as the dominant exposure pathway. Pb was the major contributor to noncarcinogenic risk, whereas As was the primary contributor to carcinogenic risk. Children exhibited higher noncarcinogenic risk levels than adults, reflecting their greater susceptibility to heavy metal exposure. Although both carcinogenic and noncarcinogenic risks remained within acceptable limits overall, relatively elevated risk values were concentrated at the junction of Changqing, Pingyin, Dong'e, and Qihe. Through the technical route of "pollution identification-spatial mapping-source apportionment-risk assessment," this study provides a scientific basis for groundwater safety protection in the Yellow River Basin. It is recommended to strengthen dynamic monitoring of Pb pollution and implement comprehensive prevention and control measures in high-risk areas of this region.