Distribution Characteristics and Health Risk Assessment of Metal Elements for Groundwater in the Ningxia Region of China

Abstract

To explore the distribution characteristics of metal elements in groundwater and evaluate the health risks they pose to the population in the Ningxia region of China, a total of 210 groundwater samples were collected, and eight metal elements (As, Cr, Al, Cu, Pb, Mn, Fe, and Sr) in the water samples were analyzed. The pollution characteristics, distribution, and health risks of the metals in the groundwater were revealed by a comprehensive pollution assessment, multivariate statistical analysis, and health risk assessment model, respectively. The results revealed that the mean mass concentrations of metal elements in groundwater from the study area were in the following order:ρ(Sr) > ρ(Al) > ρ(Mn) > ρ(Cu) > ρ(Pb) > ρ(Cr) > ρ(As) > ρ(Fe). The ρ(Sr) content of 75.24% of the samples exceeded that from drinking natural mineral water[0.2 mg·L-1of ρ(Sr)] as per China's standard. The maximum ρ(As) 76.60 μg·L-1, ρ(Cr) 145.01 μg·L-1, ρ(Pb) 59.93 μg·L-1, and ρ(Mn) 734.67 μg·L-1 exceeded the corresponding standard limits. Compared with the natural control, the As and Pb pollution in the study area was more serious, showing a planar distribution. Mn and Cr pollution were relatively concentrated, mainly distributed in the northern Yellow River and southeast, respectively. Other metals were lightly polluted. The results of the multivariate statistical analysis showed that the concentrations of As and Pb pollution may be caused by natural factors, industrial activities, and the use of pesticides. Mn pollution may be caused by irrigation with the Yellow River. Cr pollution may be caused by mining for oil. The health risk assessment showed that the health risk to children was higher than that to adults, and the risk of drinking water exposure was higher than that of skin infiltration exposure. The non-carcinogenic health risk (HI) was mainly caused by As through the drinking water pathway. Due to the pollution of As and Cr, the carcinogenic risk through the drinking water and skin penetration pathways to children and adults in the study area was higher than the safety level (5.0×10-5). The contribution rate of Cr to the carcinogenic risk through the two pathways was greater than 80%. For drinking water safety, the concentrations of As and Cr should be controlled before drinking.