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 mu atm, respectively. The average diffusive fluxes (and uncentainty intervals) of these three gases were 73.7 (0.9-295.3) mu mol . m(-2) . day(-1), 5.2 (0.0008-45.9) mu mol . m(-2) . day(-1), and 6.5 (0.07-20.9) mu mol . 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.