Hydrochemical and environmental isotope characteristics of groundwater in the Hongjiannao Lake Basin, Northwestern China

2021 
Understanding the hydrochemical and isotopic characteristics of groundwater and hydrogeochemical processes is crucial for groundwater resource development and environmental protection, especially in semiarid regions. To address this question, we collected and tested groundwater and river water samples form the Hongjiannao Lake Basin. The groundwater samples were took from a porous medium aquifer and a pore-fissure aquifer. We studied hydrochemical characteristics of groundwater from both aquifers using major element measurements, statistical calculations, and the use of Piper diagrams. The hydrogeochemical processes taking place in groundwater were identified using the Gibbs diagram, Gaillardet diagram, saturation index calculations, ratios of major ions, and chloro-alkaline indices. We also investigated the origin of groundwater using stable isotopes (D and 18O) and evaluated groundwater age on the basis of piston model of tritium isotope (3H) measurements. Groundwater–river water interactions are also identified using chemical and stable isotope characteristics. The results show that groundwater in both aquifers has a chemical composition dominated by are HCO3 anions that groundwater has a low total dissolved solids (TDS) content. An assessment of the analyzed groundwater chemical data suggests that feldspar dissolution, the dissolution/precipitation of carbonate minerals (dolomite and calcite), and cation exchange play an important role in the hydrochemical evolution of groundwater in the study area. The compositions of stable isotopes and tritium imply that groundwater in the porous medium and pore-fissure aquifers originate from modern and ancient precipitation sources, respectively. The groundwater recharge is influenced by evaporation as water infiltrates through the vadose zone. In addition, river, lake, and groundwater form an organic whole. This study provides effective guidance for groundwater resource development and environmental protection in a similar area.
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