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

However, the spatiotemporal patterns of GHG emissions have not been adequately quantifled 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 quantifled. The results showed that the surface lake water was oversaturated with dissolved GHG concentrations, and the average concentrations were 24.25 mu M CO2, 0.044 mu M CH4, and 14.28 nM N2O, with diffusive emission rates of 8.82 mmol CO2 m-2 d-1, 31.94 mu mol CH4 m-2 d-1, and 4.94 mu mol 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

Automated summary

This study quantifies the spatial and seasonal variability of diffusive greenhouse gas (GHG) emissions from Lake Fuxian in southwestern China. The results show significant variations in GHG emissions, highlighting the importance of increasing temporal resolution in GHG flux measurements. Water temperature and oxygen concentrations were found to regulate seasonal variability in emissions.