Spatial heterogeneity of dissolved methane in a plateau lake: a case study in Yangzonghai Lake in autumn

Near-surface and vertical profiles of dissolved CH4 concentrations were measured at a high resolution using the new fast-response automated gas equilibrator (FaRAGE) connected to a greenhouse gas analyzer at Yangzonghai Lake in November 2020, to investigate the spatial pattern of dissolved CH4 and its driving factors. Results showed that dissolved CH4 concentrations of surface water ranged between 0.02 and 0.97μmol/L, indicating a net source of atmosphere CH4. The dissolved CH4 was relatively higher in the north and south parts of the lake, but lower in the middle area, which was mainly influenced by aquatic plants distribution, discharge from inflow rivers and topographical conditions. Vertical profiles of dissolved CH4 at different spots of the lake exhibited relatively consistent pattern, while CH4 was more significantly oxidized in the middle section. The bootstrap analysis suggested that estimates of CH4 emission derived from fewer measurements were subjected to potentially large biases, and the minimum number of sampling sites that guaranteed an accurate estimation of diffusive CH4 flux at Yangzonghai Lake was 3.7per km2. It was necessary to perform high-resolution observations of CH4 concentration for an accurate estimation of carbon emission from lakes or reservoirs. © 2022, Editorial Board of China Environmental Science. All right reserved.