Environmental isotopic and hydrochemical study of groundwater in the Ejina Basin,northwest China |
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| Authors: | Y H Su G F Zhu Q Feng Z Z Li F P Zhang |
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| Institution: | (1) Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, 730000 Lanzhou, China;(2) The School of Mathematics, Physics and Software Engineering, Lanzhou Jiaotong University, 730000 Lanzhou, China;(3) Institute of Bioinformatics, School of Mathematics and Statistics, Lanzhou University, 730000 Lanzhou, China;(4) School of Mathematics and Information Sciences, Henan University, 475001 Kaifeng, China |
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| Abstract: | The study investigates the groundwater evolution and its residence time in the Ejina Basin, northwest China according to isotope
and hydrochemical analyses results. The groundwater chemistry is mainly controlled by the dissolution of halite, Glauber’s
salt, gypsum, dolomite and calcite, also influenced by other processes such as evaporation, ion exchange, and deposition.
Based on tritium content in atmospheric precipitation and by adopting a model with exponential time distribution function,
the mean residence time of the unconfined aquifer groundwater with fairly high tritium activities (21–49 TU) is evaluated.
The results show that these groundwaters have low residence time (5–120 years) and are renewable. In contrast, the deep confined
groundwaters are tritium-free and radiocarbon values range from 18.3 to 26.7 pmc. According to the most commonly used 14C correction models, the radiocarbon groundwater ages were calculated which yield ages of approximately 4,087–9,364 years
BP. Isotopic signatures indicate formation of deep confined groundwaters in a colder and wetter climate during the late Pleistocene
and Holocene. It is suggested that long-term, rational water usage guide should be set up for the Heihe River Basin as a whole
to permit a considerable discharge to the Ejina Basin. |
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| Keywords: | Ejina Basin Environmental isotope Hydrochemistry Arid regions Groundwater age |
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