Solute geochemistry and groundwater quality for drinking and irrigation purposes: a case study in Xinle City, North China

Abstract

Xinle City is located in the upper reaches of the Daqing River basin, north China. Influenced by intense and extensive industrial and agricultural activities, sodium and nitrate pollution of the groundwater is becoming more and more serious in the study area. With an effort to quantitatively describe the present situation of groundwater and analyze the specific sources of the main ingredients, 32 well samples were collected and analyzed for understanding the hydrochemical characteristics and the suitability for drinking and irrigation purposes. Gibbs diagrams, Piper diagrams, solubility diagram, and ionic correlation analysis were used to assess the groundwater formation process. Drinking water quality index (DWQI) based on TDS, pH, K+, Ca2+, Na+, Mg2+, Cl−, HCO3−, SO42− and NO3− was used to evaluate the quality for drinking, while irrigation water quality index (IWQI) based on EC, Na%, permeability index (PI), sodium adsorption ratio (SAR), residual sodium bicarbonate (RSBC) and magnesium (MH) were used to assess the water quality for irrigation. The results demonstrated that the groundwater hydrochemical type in Xinle City is mainly dominated by the typical Ca∙Na-HCO3 and Ca-HCO3. Groundwater in the study area was found to be suitable for long-term drinking and irrigation. The abundances of ions are Ca2+>Na+>Mg2+>K+ for cations, and HCO3−>SO42−>NO3−>Cl−>F− for anions. The concentrations of Na+ and NO3− in groundwater are high in the study area. Particularly, the value of NO3− in some water samples far exceeds the WHO and Chinese standard limits. Na+ and NO3− are mainly of anthropogenic source, and they are from industrial pollution and agricultural pollution, respectively. Therefore, reducing the concentrations of Na+ and NO3− in groundwater is essential for the sustainable utilization of groundwater resources in the study area. The recommendations suggested in this research may provide insights for decision makers to make sound groundwater quality policies, and thus could be helpful to prevent further groundwater pollution in the study area.