Groundwater hydrogeochemical characterization and quality assessment based on integrated weight matter-element extension analysis in Ningxia, upper Yellow River, northwest China

Abstract

• Groundwater chemistry and quality were analyzed in the Ningxia region. • NO 3 − , NH 4 + and NO 2 − are related to human pollution. • Water quality was assessed using an integrated weight matter-element extension model. • High health risks of F − , NO 3 − , NH 4 + , and NO 2 − were found, especially for children. Assessing groundwater quality and identifying pollutant risks are essential for managing groundwater resources in arid and semi-arid regions. An analysis of the hydrochemical characteristics, controlling factors, and pollutant characteristics of the groundwater in the upper Yellow River region is presented to understand the overall groundwater quality and identify the risk to human health in this region. Traditional hydrochemical analysis methods, integrated weight matter-element extension analysis, and health risk models were used in this study. A total of 210 groundwater samples were collected from the wells for physical and chemical analyses. Results showed that groundwater in the study area was weakly alkaline, with the predominant hydrochemical types of groundwater being SO 4 ·Cl-Ca·Mg, SO 4 ·Cl-Na, and HCO 3 -Ca·Mg. The hydrochemical composition of the groundwater is controlled by rock dominance, evaporation dominance, and cation exchange. Nitrogen pollution of groundwater is caused by industrial activities and fertilizers; fluorine pollution is caused by fluorite dissolution. To reasonably evaluate the groundwater quality, the groundwater evaluation method based on an integrated weight matter-element extension analysis was optimized. The method effectively avoids defects of G1 and entropy weight methods in determining weights and thoroughly considers the fuzziness and uncertainty of the water quality grade. The overall quality groundwater assessment results showed that 96.19% of the overall water quality in the study area was good and could be used in many ways. Land irrigated with groundwater is mainly exposed to salinity hazards. Health risk assessment results showed that 57% and 21% of the samples posed unacceptable health risks to children and adults, respectively. Therefore, more attention should be paid to real-time, continual monitoring of pollutants in groundwater management. The results help decision makers make wise decisions on identifying groundwater purposes to avoid further water quality deterioration and increase in pollutants, ensuring the cleanliness of groundwater resources in the upper Yellow River..