Hydrogeochemical Fingerprinting and Integrated Groundwater Quality Assessment in Northern Nansi Lake

Groundwater is essential for regional water supply, irrigation, and drinking safety. This study assessed groundwater quality around the northern Nansi Lake. Results show slightly alkaline water with HCO₃ ^- and Ca²⁺ as dominant ions. Hydrochemical types are mainly HCO₃·Ca·Mg and SO₄·Cl·Ca·Mg, controlled by rock weathering and cation exchange. Positive Matrix Factorization (PMF) analysis reveals industrial activities and evaporite dissolution prevail in dry season, while agricultural nitrate pollution intensifies in wet season. The evaluation of drinking water quality shows that overall water quality is good to excellent (better in the dry season), with 5% of samples unfit for drinking. Irrigation indicators indicate that most samples are suitable for irrigation. Health risk assessment shows children face higher risks from NO₃ ^- and F^- than adults. In wet season, children's mean HI is 1.62, with 37% of samples HI > 1, mainly near farmland and urban areas.