Hydro-geochemical evolution of groundwater and associated human health risk in River Sone subbasin of Middle-Gangetic floodplain, Bihar, India

Quality assurance of groundwater before drinking water supply is a major concern in South and South East Asia due to widespread presence of inorganic contaminants and their health implications. To investigate the groundwater quality and associated health risk, 65 groundwater samples were collected and analyzed for major ions along with Fe, As, and Mn. With 72.3% of the samples, Ca-HCO 3 is found as the major water type followed by Na-HCO 3 and Mg-HCO 3 water type. Silicate weathering, ion exchange, and dissolution and precipitation of aquifer minerals are found as the dominant factors responsible for groundwater quality. Of the samples, 88% and 65% are oversaturated with calcite and dolomite, respectively; however, all samples are under-saturated with respect to anhydrite, gypsum, halite, and fluorite minerals. Exceeding concentrations of F − , Fe, and Mn above WHO guidelines in 15.4%, 52.3%, and 24.6% samples, respectively, pose a significant public health concern. High F − is found along older alluvium with Na-HCO 3 water type and low Ca 2+ suggests dissolution of fluorite contributing F − ions in groundwater. F − is found as the major contribution on health indices (HI) followed by As > Mn > Fe. High HI > 1 that is found in 26.15% and 50.76% samples for adults and children indicates significant potential health risk. Higher HI value for children suggests higher health risk due to relatively lesser body weight. Proper management and quality assurance of groundwater is needed before its use.