Large alpine deep lake as a source of greenhouse gases: A case study on Lake Fuxian in Southwestern China

• Published in: The Science of the total environment 2022-09, Vol.838 (Pt 2), p.156059-156059, Article 156059
• Main Authors: Miao, Yuqing, Meng, Henan, Luo, Wenlei, Li, Biao, Luo, Hao, Deng, Qi, Yao, Youru, Shi, Yinggui, Wu, Qinglong L.
• Format: Article
• Language: English
• Subjects: Alpine deep lake; CH4 flux; CO2 flux; Lake Fuxian; N2O flux
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.156059

Freshwater lakes are recognized as potential sources of greenhouse gases (GHGs) that contribute to global warming. However, the spatiotemporal patterns of GHG emissions have not been adequately quantified in large deep lakes, resulting in substantial uncertainties in the estimated GHG budgets in global lakes. In this study, the spatial and seasonal variability of diffusive GHG (CO2, CH4, and N2O) emissions from Lake Fuxian located on a plateau in Southwestern China were quantified. The results showed that the surface lake water was oversaturated with dissolved GHG concentrations, and the average concentrations were 24.25 μM CO2, 0.044 μM CH4, and 14.28 nM N2O, with diffusive emission rates of 8.82 mmol CO2 m−2 d−1, 31.94 μmol CH4 m−2 d−1, and 4.94 μmol N2O m−2 d−1, respectively. Diffusive CH4 flux exhibited high temporal and spatial variability similar to that in most lakes. In contrast, diffusive CO2 and N2O flux showed distinct seasonal variability and similar spatial patterns, emphasizing the necessity for increasing the temporal resolution in GHG flux measurements for integrated assessments. Water temperature and/or oxygen concentrations were crucial in regulating seasonal variability in GHG emissions. However, no limnological parameter was found to govern the spatial GHG patterns. The frequent advection mixing caused by wind-driven currents might be the reason for the low spatial heterogeneity in GHGs, in which the inconspicuous mechanism requires further research. It was recommended that at least 11 locations were needed for representative whole lake flux estimates at each sampling campaign. In addition, the maximum peak of CH4 in the oxycline from Lake Fuxian indicated that low CH4 oxidation occurred in oxic waters. Overall, this study suggests that, compared to other tropical and temperate lakes, this alpine deep lake is a minor CO2 and CH4 source, but a moderate N2O source, which are horizontally uniform. [Display omitted] •GHG concentrations and fluxes were reported in a large alpine deep lake in China.•Diffusive GHG fluxes exhibited high temporal variability in a large alpine deep lake.•Diffusive CO2 and N2O fluxes showed uniform spatial patterns.•Subsurface maximum CH4 concentration has been observed in the large deep lake.•The large alpine deep lake is a minor CO2 and CH4 source, but a moderate N2O source.