Thermal structure regulates the dynamics of carbon dioxide flux in alpine saline lake on the Qinghai-Tibet Plateau, China

Xin Liu; Xiaoyan Li; Fangzhong Shi; Zhigang Wang; Menglin Liu; Xia Zhang; Zhanfei Zhang

doi:10.1016/j.scitotenv.2024.172700

Thermal structure regulates the dynamics of carbon dioxide flux in alpine saline lake on the Qinghai-Tibet Plateau, China

Sci Total Environ. 2024 Apr 23:931:172700. doi: 10.1016/j.scitotenv.2024.172700. Online ahead of print.

Authors

Xin Liu¹, Xiaoyan Li², Fangzhong Shi³, Zhigang Wang¹, Menglin Liu⁴, Xia Zhang¹, Zhanfei Zhang¹

Affiliations

¹ State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China; School of Natural Resources, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China.
² State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China; School of Natural Resources, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China; Academy of Plateau Science and Sustainability, Qinghai Normal University, Xining 810016, China; College of Geographical Sciences, Qinghai Normal University, Xining 810016, China. Electronic address: xyli@bnu.edu.cn.
³ State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China; School of Natural Resources, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China; Research and Development Center for Watershed Environmental Eco-Engineering, Beijing Normal University at Zhuhai, Zhuhai 519085, China.
⁴ College of Geographical Sciences, Qinghai Normal University, Xining 810016, China.

PMID: 38657815
DOI: 10.1016/j.scitotenv.2024.172700

Abstract

Thermal stratification and mixing play important roles in the physicochemical composition of lakes and affect the geochemical cycle. However, the regulation of lake carbon exchange at the water-air interface by seasonal thermal structures remains unclear, especially for alpine saline lake on the Qinghai-Tibet Plateau (QTP). Based on continuous field sampling, carbon dioxide flux (FCO₂) at the water-air interface in Qinghai Lake during the ice-free period was quantitatively analyzed by thin boundary layer model, as well as the driving factors of the change in FCO₂ at the water-air interface. The findings revealed that the FCO₂ was -22.16 ± 11.73 mmol m^-2d^-1 during the stratification period, and - 45.32 ± 29.67 mmol m^-2d^-1 during the mixing period. We found that thermal stratification limits the matter-energy exchange between the upper and bottom water columns, and carbonate precipitation results in a higher FCO₂ than during mixing stage. However, the mixing process reduces the limiting effect of thermal stratification. During the carbonate process, water with higher salinity and pH at the bottom of the water column enters the upper part of the water column, reducing the partial pressure of carbon dioxide (pCO₂) in the water column and causing the absorption of CO₂ by the lake. Thermal stratification affects the vertical material-energy exchange and atmospheric CO₂ uptake of lake. The present study further explains the possible underlying regulation of CO₂ uptake in saline lake on the QTP involving the varied thermal structure.

Keywords: Alpine saline lake; CO(2) flux; Ice-free period; Qinghai-Tibet Plateau; Varying thermal structure.