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

Abstract

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 (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) 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 CO 2 , CH 4 , and N 2 O to the atmosphere. The average partial pressures of CO 2 , CH 4 , and N 2 O 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 À2 · day À1 , 5.2 (0.0008-45.9) mmol · m À2 · day À1 , and 6.5 (0.07-20.9) μmol · m À2 · day À1 , respectively. The diffusive fluxes of CO 2 in lakes were significantly correlated with dissolved organic carbon, dissolved organic nitrogen, salinity, and water temperature. The diffusive fluxes of N 2 O were significantly correlated with lake water depth. However, no relationships were found between environmental factors and the CH 4 diffusive flux at the scale of this study. CO 2 exchange with the atmosphere from saline lakes was found to be higher than from freshwater lakes with equivalent CO 2 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.

Significant winter CO2 uptake by saline lakes on the Qinghai‐Tibet Plateau

“…The results in this study indicate that saline lakes are significant sinks of CO 2 from the atmosphere during ice-covered period and at the annual scale on the QTP (Figures 2 and 3), which contrasts the results from previous studies on the QTP and those on most fresh/saline lakes in other regions of the world (Duarte et al, 2008;Finlay et al, 2015;Hastie et al, 2018;Serikova et al, 2019;Yan et al, 2018). This difference is mainly attributed to the fact that winter/ice-covered periods are not included in annual C budgets.…”

“…Saline lakes, which cover approximately 44% of the volume and 23% of the area of all lakes on Earth (Messager et al, 2016; Wurtsbaugh et al, 2017), are usually considered C sources (Duarte et al, 2008; Yan et al, 2018). C processes in saline lakes are obviously different from those in freshwater lakes, CO 2 exchange between the air/saline water interface is controlled not only by meteorological variables but also by limnology, pH, salinity, and ice phenology in saline water (Duarte et al, 2008; Finlay et al, 2015).…”

“…(f) Sum of the multiyear average annual total CO 2 flux of 373 saline lakes on the QTP. The shadows and whiskers show the 0.5 standard deviation [Colour figure can be viewed at wileyonlinelibrary.com] magnitude of global lakes (−1.66−6.82 g C m −2 d −1 )(Duarte et al, 2008;Yan et al, 2018).…”

Unexpected large evasion fluxes of carbon dioxide from turbulent streams draining the world’s mountains

“…draining the inner Tibetan Plateau have low p CO 2 (median: 288 µatm; CI: 194 and 449 µatm) translating into a negative median ΔCO 2 of −56 mg C m –3 (CI: −105 and 23 mg C m −3 ). Similar CO 2 concentrations close to equilibrium were also reported by others for streams 42 and lakes 43 on the Tibetan Plateau. These gradients result in an overall negative areal CO 2 flux of −0.36 kg C m −2 yr −1 (CI: −4.29 and 0.87 kg C m −2 yr −1 ) (Supplementary Fig.…”

Variations in δ13CDIC and influencing factors in a shallow macrophytic lake on the Qinghai-Tibetan Plateau: implications for the lake carbon cycle

“…Carbon cycles have become one of the most extensively researched topics with regard to global climate change (Yang et al, 2021). Lakes, accounting for 3.7% of the global land area, are an important component of the inland water system, which regulate the carbon cycle by storing, transporting, and transforming carbon (Tranvik et al, 2009;Holgerson and Raymond, 2016;Cole et al, 1994;Holgerson & Raymond, 2016;Ran et al, 2017;Yan et al, 2018). For example, lake sediments can contain 0.03-0.07 Pg C a -1 (Molot & Dillon, 1996;Dean & Gorham 1998;Kortelainen et al, 2006), which is roughly equal to or higher than the carbon buried in marine sediments (Cole et al, 2007).…”