Hydrogeochemistry and δ13CDIC and δ18OH2O composition of three Chinese Tibetan Plateau lakes
2018
Wang, Xiaodan | Li, Shijie | Liu, Cong-Qiang | Mostofa, Khan M. G. | Zhao, Zhiqi | Luo, Rongqin
This study established the hydrochemistry and stable isotope variations in three lakes, namely brackish Zigetang Co, freshwater Cona and Ranwu lakes located in the central and southeastern Tibetan Plateau of China. Vertical profile fluctuations in the water column, such as temperature and dissolved oxygen (DO) concentration, displayed significant differences which were linked to the thermocline. The hydrochemistry of the three lakes showed that as the dominant anion, whereas Na⁺ is the main cation in Zigetang Co and Cona lake and Ca²⁺ is the prevailing cation in Ranwu lake. In Zigetang Co, K⁺ and Na⁺ concentrations decreased by 42 % from 1999 to 2012, caused by the enlargement of the lake area, documented by field investigations carried out in 1998, 2002, 2006 and 2012. The δ¹³CDIC and δ¹⁸OH₂O values analysed from the three lakes varied from −6.0 to 2.0 ‰, and from −14.8 to −6.4 ‰, respectively. The closed Zigetang lake showed higher δ¹³CDIC and δ¹⁸OH₂O values compared to those of the rivers, the semi-closed Cona and open Ranwu lakes. The δ¹³CDIC values of lake water in Zigetang Co were mainly controlled by CO₂ exchange between lake water and atmosphere; the δ¹⁸OH₂O values were dominated by the evaporation/freshwater input ratios.
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