Using Isotopes (H, O, and Sr) and Major Ions to Identify Hydrogeochemical Characteristics of Groundwater in the Hongjiannao Lake Basin, Northwest China

Hongjiannao Lake is the largest desert freshwater lake in the Ordos Plateau, China, and the relict gull is an endangered species that uses the lake for its habitat, with the largest colonies being located there. Using hydrochemical parameters, stable hydrogen and oxygen isotopes, and strontium isotopes, we investigated the hydrogeochemical characteristics of groundwater. As a result, the major cations of the groundwater were found to be Ca2+ and Na+, the major anion was found to be HCO3-, and the hydrochemical facies were mainly found to be HCO3-Ca, HCO3-Na. and HCO3-Ca-Na. The hydrochemical formation of groundwater was controlled by both evaporation and water-rock interactions, and carbonate and sulfate minerals dissolved or precipitated in the groundwater. On the basis of isotope analysis, groundwater was affected by evaporation and delta O-18 enrichment, and the higher salinity of Hongjiannao Lake suffered from intensive evaporation. The higher Sr-87/Sr-86 ratio and lower concentrations of Sr2+ in the groundwater were derived from the dissolution of silicate minerals, whereas the opposite concentrations were due to the dissolution of carbonate and sulfate minerals. Based on this work, such results can be used to research groundwater recharge into the lake and to protect water quality.