Inland waters are important sources of greenhouse gases(GHGs)to the atmosphere that may partially offset the terrestrial carbon sink.However,GHG emissions from high altitude saline lakes on the Tibetan Plateau are cur...Inland waters are important sources of greenhouse gases(GHGs)to the atmosphere that may partially offset the terrestrial carbon sink.However,GHG emissions from high altitude saline lakes on the Tibetan Plateau are currently poorly constrained.In this study,we measured methane(CH_(4))and carbon dioxide(CO_(2))concentrations and their carbon stable isotope(δ13C),and calculated diffusive water-to-air fluxes from two saline high-altitude lakes,Qinghai Lake and Hala Lake,located in northeast Tibetan Plateau in October 2020.The two lakes were mostly supersaturated in CH_(4)(89.8%-4623.9%sat)and acted as sources of CH_(4) to the atmosphere.Conversely,more than 96%investigated area of Qinghai Lake and all investigated area of Hala Lake was a sink of CO_(2).The average diffusive fluxes of CH_(4) and CO_(2) in the surface waters of Qinghai Lake were 34.51μmol m−2 d−1 and−1.29 mmol m−2 d−1,while diffusive fluxes of CH_(4) and CO_(2) in Hala Lake averaged 5.48μmol m−2 d−1 and−5.24 mmol m−2 d−1,respectively.Salinity(Sal),fluorescent dissolved organic matter(fDOM),temperature(Temp)and dissolved oxygen(DO)are key factors for diffusive CH_(4) and CO_(2) flux in Qinghai Lake and Hala Lake.CH_(4) diffusive fluxes across water-air interface from Qinghai Lake and Hala Lake were found to be significantly lower than other freshwater lakes,likely due to their saline nature.A simple isotope mixing model(Miller-Tans plots)revealed a distinctly different isotopic source values of CO_(2) and CH_(4) in Qinghai Lake and Hala Lake.The CH_(4) production pathway of Qinghai Lake was mainly by the acetate fermentation,while that of Hala Lake was mainly by the CO_(2) reduction.The results show that the continuous measurement can help capture the spatial variability of GHGs fluxes in saline lakes.展开更多
基金We thank Yanbin Cai for helping with the rice treatments. The work was supported by the National Natural Science Foundation of China （41103042）, the Field Frontier Project of Insti- tute of Geochemistry. Chinese Academy of Sciences （2045200295）. the Training Program for the Top Young Talents of Zhejiang Agri- cultural and Forestry University （2034070001）. and the Program for the Distinguished Young and middle-aged Academic Leaders of Higher Education Institutions of Zhejiang Province （PD2013240）.
基金funded by the National Natural Science Foundation of China(41801054)Beijing Normal University Talent Introduction Project(12807-312232101)+1 种基金Youth Innovation Promotion Association,CAS(2020419)Scientific Research Foundation of the Key Laboratory of Cryospheric Sciences(SKLCSZZ-2021).
文摘Inland waters are important sources of greenhouse gases(GHGs)to the atmosphere that may partially offset the terrestrial carbon sink.However,GHG emissions from high altitude saline lakes on the Tibetan Plateau are currently poorly constrained.In this study,we measured methane(CH_(4))and carbon dioxide(CO_(2))concentrations and their carbon stable isotope(δ13C),and calculated diffusive water-to-air fluxes from two saline high-altitude lakes,Qinghai Lake and Hala Lake,located in northeast Tibetan Plateau in October 2020.The two lakes were mostly supersaturated in CH_(4)(89.8%-4623.9%sat)and acted as sources of CH_(4) to the atmosphere.Conversely,more than 96%investigated area of Qinghai Lake and all investigated area of Hala Lake was a sink of CO_(2).The average diffusive fluxes of CH_(4) and CO_(2) in the surface waters of Qinghai Lake were 34.51μmol m−2 d−1 and−1.29 mmol m−2 d−1,while diffusive fluxes of CH_(4) and CO_(2) in Hala Lake averaged 5.48μmol m−2 d−1 and−5.24 mmol m−2 d−1,respectively.Salinity(Sal),fluorescent dissolved organic matter(fDOM),temperature(Temp)and dissolved oxygen(DO)are key factors for diffusive CH_(4) and CO_(2) flux in Qinghai Lake and Hala Lake.CH_(4) diffusive fluxes across water-air interface from Qinghai Lake and Hala Lake were found to be significantly lower than other freshwater lakes,likely due to their saline nature.A simple isotope mixing model(Miller-Tans plots)revealed a distinctly different isotopic source values of CO_(2) and CH_(4) in Qinghai Lake and Hala Lake.The CH_(4) production pathway of Qinghai Lake was mainly by the acetate fermentation,while that of Hala Lake was mainly by the CO_(2) reduction.The results show that the continuous measurement can help capture the spatial variability of GHGs fluxes in saline lakes.
