Hydrogeochemical evolution processes of water resources across the campus, groundwater quality, and non-carcinogenic risk assessment of groundwater in terms of human health (Van Yüzüncü Yıl University- Zeve Campus)

In the study area, including the Van Yüzüncü Yıl University (YYÜ) campus, drinking water samples were collected from campus sources, while groundwater and irrigation water samples were obtained from boreholes in the Karasu and Morali River sub-basins. The study aimed to evaluate the hydrogeochemical characteristics and water quality of groundwater and surface water resources. Water samples were analyzed for physicochemical parameters and compared with WHO (2011), and TSE-266 (2005) drinking water standards. Groundwater temperatures ranged from 3.70 to 14.60 °C, with pH values between 6.96 and 8.96, while surface waters were slightly alkaline. Redox potential values indicated predominantly reducing conditions, affecting the mobility of redox-sensitive elements such as As, Fe, and Mn. Electrical conductivity and total dissolved solids were higher in the Morali River sub-basin. The waters were generally moderately hard, dominated by Ca²⁺ and Na⁺ cations and HCO₃⁻ and SO₄²⁻ anions. Piper diagram results showed that water chemistry was controlled by silicate and carbonate weathering, ion exchange, and evaporation. Ca–HCO₃-type waters dominated in the Karasu River, whereas Ca–HCO₃–SO₄-type waters prevailed in the Morali River sub-basin. Entropy-weighted water quality index results indicated that most groundwater samples were of "good" to "excellent" drinking water quality. Irrigation water assessments showed that most waters were suitable for irrigation; however, high TDS levels and intense evaporation limited the use of Morali River waters. Groundwater arsenic concentrations ranged from 0.011 to 0.122 mg/L and exceeded drinking water standards in all samples. Elevated arsenic levels were associated with low redox potential and slightly alkaline alluvial and paleo–fluvial–lacustrine deposits. Eh-pH diagrams showed that As (V) dominated in approximately 100% of the samples. Health risk assessments indicated that arsenic-related risks were higher in chil-dren than in adults and increased during the dry season. As a result, the groundwater in the study area poses a serious environmental and public health risk due to its high ar-senic content and the predominance of the As (V) species. Continuous monitoring and effective treatment strategies were therefore critical for regional water security.