高原湖泊溶解甲烷浓度空间异质性研究—以阳宗海秋季为例

以西南典型高原湖泊阳宗海为研究对象，于2020年11月应用新型快速水-气平衡装置（FaRAGE）及便携式温室气体分析仪，开展了表层水体和垂向剖面溶解CH₄浓度的高分辨率监测，揭示了溶解CH₄浓度空间分布特征及影响因素.结果表明，阳宗海表层水体溶解CH₄浓度为0.02~0.97μmol/L，表现为大气甲烷的源.空间上呈现出南北高、中部低的分布特征，与水生植物分布、入湖河流输出和水深等因素密切相关.湖泊不同区域垂向剖面溶解CH₄浓度分布较为一致，湖心区CH₄氧化消耗最为明显.自展分析表明，基于少量样点监测的CH₄排放估算具有较大不确定性，准确估算阳宗海CH₄扩散通量所需最小采样点数量约为3.7个/km²，高空间分辨率的监测对于湖库碳排放的准确估计十分必要.

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.