Analysis of Heavy Metal Sources in Groundwater and Assessment of Health Risks: An Example from the Southwest Sub-basin of the Shiqi River

Abstract

In order to explore the sources of pollution and health risk profile of heavy metal elements in groundwater, 41 sets of representative groundwater samples from the southwest sub-basin of the Shiqi River were examined for 10 heavy metal elements (As, Cr, Cd, Al, Cu, Zn, Ni, Co, Mn, and Hg), and correlation analysis and principal component analysis were used to resolve the possible sources of heavy metal contamination in groundwater in the study area. The concentration characteristics and health risk levels of the 10 heavy metals were assessed using the single-factor contamination index (Pi), the Nemerow comprehensive contamination index (PN), and the health risk model. The results showed that:① the average values of heavy metal elements of the groundwater in the study area all met the limit of the class Ⅲ water standard in the quality standard for groundwater (GB/T 14848-2017); only the maximum value of Al was exceeded, followed by a large variation in the concentrations of Al, Mn, and Cr. The heavy metal element with the largest average contribution was Al (65.74%). ② The results of the single-factor contamination index evaluation showed that only the heavy metal element Al exceeded the cleaning level, and the results of the Nemerow comprehensive contamination index evaluation showed that the study area was basically at low pollution levels, and the quality of groundwater was good. ③ The results of the multivariate statistical analysis showed that Zn, Co, and Mn were from mixed sources consisting of geological formation and domestic waste; Al, As, and Cu were from agricultural sources; Cd, Cr, and Ni were from industrial sources; and Hg came from long-range atmospheric transport. ④ The health risk values for all heavy metals in the study area were within acceptable limits, with higher health risk values for children than for adults from the drinking water route, lower health risk values than in adults from the dermal route, and higher health risk values for heavy metals from the drinking water route than those from the dermal route, indicating that the drinking water route was the main route of exposure to heavy metals.