Groundwater Quality for Drinking and Non-Carcinogenic Risk of Nitrate in Urban and Rural Areas of Fereidan, Iran

Determining the controlling factors of groundwater quality can help decision-makers in preparing optimal management plans for a sustainable supply of water for drinking. In this research, the hydrogeochemical parameters of 126 groundwater samples in the Fereidan region, central Iran have been analyzed to determine the drinking water quality, investigate the mechanisms controlling the chemical composition of groundwater, identify the sources of nitrate (NO3), and assess the non-carcinogenic health risk of NO3. Inverse geochemical modeling has been used to calculate the saturation indices of 21 species. Mechanisms controlling the chemical composition of groundwater such as evaporation, cation exchange, and water-rock interaction have been investigated using an optimized Gibbs diagram and ionic ratios. The entropy-weighted water quality index (EWQI) has been used to determine drinking water quality. The ratios of NO3/Na vs. Cl/Na and NO3/Cl vs. Cl have been used to identify the sources of NO3 in groundwater. The results show that the interaction of water with carbonate formations and the reverse cation exchange are the main geogenic factors affecting the chemical composition of groundwater. About 98% of the samples have excellent to moderate quality. Chemical fertilizers and sewage are the most important sources of NO3 concentration. The non-carcinogenic health risks of NO3 show that about 31, 39, 72, and 80% of the samples are safe for drinking, respectively, for infants, children, teenagers, and adults. The results of this study can help policymakers better understand the hydrogeochemical status of groundwater, thus facilitating safe drinking water management.