Hydrochemical Characterisation and Assessment of Groundwater Suitability for Drinking and Irrigation Purposes in Sângeorz-Băi Area, Bistrița-Năsăud County (Romania)

Groundwater quality is a key factor and a critical determinant of public health, agriculture, and socio-economic development, particularly in regions where private wells and mineral springs constitute the primary water sources. This study presents an integrated hydrochemical, radiological, and toxicological assessment of groundwater in the Sângeorz-Băi area, Romania, a spa region where mineral waters hold both therapeutic and economic significance. Samples from mineral springs, the municipal supply system, and private wells were analyzed to evaluate compliance with national and international standards and to assess their suitability for drinking, therapeutic, and agricultural purposes. The results reveal distinct hydrochemical contrasts between sources. Mineral springs are characterized by elevated salinity, hardness, and Na–HCO3 facies, whereas the municipal network and private wells are dominated by Ca–HCO3 facies. More than half of the private wells exceeded permissible limits for NO3−, NO2−, NH4+, Pb, and Fe, with one well posing a significant nitrite-related health risk. Trace metal analysis indicated localized enrichment in Cu, Fe, and Pb. Radon and radium activities generally complied with regulations, although radium occasionally exceeded the more stringent WHO guidelines. Seasonal variation was minimal, reflecting stable groundwater chemistry. Health risk and irrigation assessments suggest that municipal supply water is largely safe for consumption, while private wells require targeted monitoring and mitigation. Despite elevated Na+ and Cl−, mineral springs retain therapeutic value under controlled use. This study provides a replicable framework for groundwater quality assessment in spa regions and offers critical insights for public health protection, sustainable tourism, and agricultural resilience.