Hydrogeochemical and health risk assessment of groundwater quality in the middle gangetic plains of Azamgarh, India

Groundwater quality degradation raises significant health concerns, particularly in agriculturally dominated regions of the Middle Gangetic Plains in India. The study investigated groundwater hydrogeochemistry, drinking water suitability, and fluoride-related non-carcinogenic health risks based on 12 physicochemical parameters of groundwater from the Azamgarh district, India. The result revealed that the groundwater was predominantly alkaline, with bicarbonate (HCO₃⁻) ion exceeding permissible limits in 95.23% of samples. The groundwater was found with elevated Mg 2 ⁺ (61.9%), with Ca-Mg-HCO 3 as the dominant hydrogeochemical facie. with bicarbonate (HCO₃⁻) exceeding permissible limits in 95.23% of samples. The groundwater was found with elevated Mg 2 ⁺ (61.9%), with Ca-Mg-HCO 3 as the dominant hydrogeochemical facie. Furthermore, rock weathering of silicates, cal-silicates, and dolomite governs the groundwater chemistry of the study area and is consistent with regional aquifer characteristics across the Middle Gangetic Plains. The WAWQI values ranged from 14.18 to 534.27, where 66.6% of samples fall under “good” quality, and 14.28% are unsuitable for drinking. It was also found that the region is primarily influenced by fluoride contamination in certain patches. In addition, the health risk assessment revealed greater vulnerability among children (HQ up to 5.66) than among adults (HQ up to 3.77). The findings highlight the critical role of geogenic processes in controlling groundwater chemistry, while localized fluoride enrichment poses significant health risks. Thus, targeted groundwater management and mitigation strategies are essential to ensure safe drinking water and protect vulnerable populations in the critical zones.