High methane emissions from thermokarst lakes on the Tibetan Plateau are largely attributed to ebullition fluxes

Lei Wang; Zhiheng Du; Zhiqiang Wei; Qian Xu; Yaru Feng; Penglin Lin; Jiahui Lin; Shengyun Chen; Yongping Qiao; Jianzong Shi; Cunde Xiao

doi:10.1016/j.scitotenv.2021.149692

High methane emissions from thermokarst lakes on the Tibetan Plateau are largely attributed to ebullition fluxes

Sci Total Environ. 2021 Dec 20:801:149692. doi: 10.1016/j.scitotenv.2021.149692. Epub 2021 Aug 19.

Authors

Lei Wang¹, Zhiheng Du², Zhiqiang Wei³, Qian Xu², Yaru Feng¹, Penglin Lin⁴, Jiahui Lin¹, Shengyun Chen², Yongping Qiao⁵, Jianzong Shi⁵, Cunde Xiao⁶

Affiliations

¹ State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China.
² State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
³ Zhuhai Branch of State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, at Zhuhai 519087, China.
⁴ College of Geography and Environmental Science, Northwest Normal University, Lanzhou 730070, China.
⁵ Cryosphere Research Station on the Qinghai-Tibet Plateau, State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resource, Chinese Academy of Sciences, Lanzhou, Gansu 730000, China.
⁶ State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China. Electronic address: cdxiao@bnu.edu.cn.

PMID: 34428650
DOI: 10.1016/j.scitotenv.2021.149692

Abstract

Ebullition has been shown to be an important pathway for methane (CH₄) emissions from inland waters. However, the CH₄ fluxes and their magnitudes in thermokarst lakes remain unclear due to limited research data, especially on the Tibetan Plateau (TP). The magnitude and regulation of two CH₄ pathways, ebullition and diffusion, were investigated in 32 thermokarst lakes on the TP during the summer of 2020. CH₄ emissions from thermokarst lakes on the TP showed significant spatiotemporal heterogeneity. Diffusion fluxes in lakes averaged 2.6 mmol m^-2 d^-1 (ranging from 0.003 to 48.4 mmol m^-2 d^-1), and ebullition fluxes in lakes averaged 6.6 mmol CH₄ m^-2 d^-1 (ranging from 0.002 to 140.0 mmol m^-2 d^-1). Together, these ebullition fluxes contributed 66.1 ± 24.9% (ranging 5.4 to 100.0%) to the total (diffusion + ebullition) CH₄ emissions, indicating the importance of ebullition as a major CH₄ transport mechanism on the TP. In general, thermokarst lakes with higher CH₄ diffusion fluxes and ebullition fluxes occurred in alpine meadows (2.5 ± 5.3 mmol m^-2 d^-1; 8.2 ± 20.6 mmol m^-2 d^-1), followed by alpine steppes (0.6 ± 5.3 mmol m^-2 d^-1; 0.7 ± 10.8 mmol m^-2 d^-1) and desert steppes (0.2 ± 0.2 mmol m^-2 d^-1; 0.6 ± 0.8 mmol m^-2 d^-1). The organic matter contents in water and sediment were found to be important factors influencing the seasonal variations in CH₄ diffusion fluxes. However, the ebullition CH₄ fluxes did not show a clear seasonal variation pattern. Our findings highlight the importance of considering the large spatiotemporal variations in ebullition CH₄ fluxes to improve the accuracy of large-scale estimations of CH₄ fluxes in thermokarst lakes on the TP. Greater insight into these aspects will increase the understanding of CH₄ dynamics in thermokarst lakes on the TP, which is essential for forecasting and climate impact assessments and to better constrain feedback to climate warming.

Keywords: Ebullition flux; Methane; Spatiotemporal variation; Thermokarst lakes; Tibetan Plateau; Vegetation.

MeSH terms

Lakes*
Methane* / analysis
Seasons
Tibet

Substances

Methane