Multidimensional Groundwater Quality Assessment and Source Apportionment in the Guyuan Region, Ningxia
Groundwater is a vital drinking and irrigation source in the loess regions of northwestern China. In Guyuan, a densely populated area in southern Ningxia, systematic assessments of groundwater pollution risks are lacking. This study collected 60 groundwater samples and employed the Nemerow index, heavy metal pollution index (HPI), and health risk assessment models to evaluate pollution levels and health risks of eight elements including Cr, As, and Hg. Results show that the groundwater is generally Class IV quality, with a mean TDS of 1350.9 mg·L−1. Average concentrations of As, Cr, and Mn are 4.39, 29.87, and 45.77 μg·L−1, respectively. The Nemerow index indicates moderate pollution. The mean HPI is 10.56, but a local sample (PS1-51-下) reaches 36.15, indicating severe pollution. Health risk assessment reveals that carcinogenic risks from Cr and As for adults and children are 8.037×10−6 a−1 and 3.863×10−6 a−1, respectively, below US EPA limits but above recommended levels by Swedish and Dutch agencies, with children at higher risk. Hydrogen and oxygen isotopes and principal component analysis suggest that groundwater is primarily recharged by atmospheric precipitation. Cr, Zn, and Mn mainly originate from regional copper ore belts, coal mining, and agricultural activities. This study fills a gap in multidimensional groundwater assessment in populated loess areas, identifies pollution characteristics distinct from typical loess regions, and provides a scientific basis for regional water resource risk management and sustainable development.