Lakes on the Tibetan Plateau as Conduits of Greenhouse Gases to the Atmosphere

Lakes play an important role in the global carbon cycle, and littoral zones of lakes are potential hotspots of greenhouse gas production. In this study, we measured the partial pressures of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) in the littoral zones of 17 lakes on the Tibetan Plateau. The littoral zones of lakes on the Tibetan Plateau were supersaturated and acted as sources of CO₂, CH₄, and N₂O to the atmosphere. The average partial pressures of CO₂, CH₄, and N₂O in the surface lake water were 664.8 ± 182.5, 139.8 ± 335.6, and 0.3 ± 0.1 μatm, respectively. The average diffusive fluxes (and uncentainty intervals) of these three gases were 73.7 (0.9–295.3) mmol · m⁻² · day⁻¹, 5.2 (0.0008–45.9) mmol · m⁻² · day⁻¹, and 6.5 (0.07–20.9) μmol · m⁻² · day⁻¹, respectively. The diffusive fluxes of CO₂ in lakes were significantly correlated with dissolved organic carbon, dissolved organic nitrogen, salinity, and water temperature. The diffusive fluxes of N₂O were significantly correlated with lake water depth. However, no relationships were found between environmental factors and the CH₄ diffusive flux at the scale of this study. CO₂ exchange with the atmosphere from saline lakes was found to be higher than from freshwater lakes with equivalent CO₂ concentrations by a factor of 2.5 due to chemical enhancement of the gas transfer velocity. Therefore, further study with enhanced spatiotemporal resolution and breadth is needed to better understand the important role played by lakes on the Tibetan Plateau in both regional and global carbon cycles.