Peatlands account for a large fraction of global methane (\(\mathrm {CH_4}\)) emissions. These environments exchange \(\mathrm {CH_4}\) with the atmosphere via three main mechanisms: diffusion through the peat and water, plant-mediated diffusion, and sporadic release of \(\mathrm {CH_4}\) bubbles. While rapid advances have been made in measuring \(\mathrm {CH_4}\) fluxes above peatlands on sub-daily time scales, partitioning \(\mathrm {CH_4}\) fluxes into ebullition and background diffusion remains a formidable challenge. Such partitioning is becoming necessary for future projection of methane concentration as atmospheric, hydrologic, and edaphic drivers of these two types of methane releases may differ significantly. Using surface renewal theory, a framework for partitioning measured methane fluxes based on the mass transfer mechanism is introduced with the overall objective of characterizing the intermittency of \(\mathrm {CH_4}\) source and its strength at the ground. This approach is tested using a large dataset of measured turbulent air velocity and multiple scalar concentrations (including heat, water vapour, and carbon dioxide) for flow above a boreal peatland in Finland. The transport efficiencies of different gas transfer mechanisms are then evaluated for scalars characterized by background diffusion (e.g., water vapour) or by intermittent sources (e.g., methane). Whether environmental variables such as water-table levels and atmospheric conditions have a signature on the occurrence of \(\mathrm {CH_4}\) hotspots is then investigated. Building upon the classical surface renewal theory, this work introduces a novel approach for inferring the intermittent nature of scalar sources at the ground and for exploring how non-homogeneity affects the efficiency of gas turbulent transport in the atmospheric surface layer.

泥炭地占全球甲烷（\(\mathrm {CH_4}\)）排放的很大一部分。这些环境通过三种主要机制与大气交换\(\mathrm {CH_4}\)：通过泥炭和水的扩散、植物介导的扩散和\(\mathrm {CH_4}\)气泡的零星释放。虽然在亚日时间尺度上测量泥炭地上方的\(\mathrm {CH_4}\)通量取得了快速进展，但分区\(\mathrm {CH_4}\)沸腾和背景扩散的通量仍然是一项艰巨的挑战。这种划分对于未来预测甲烷浓度变得必要，因为这两种甲烷释放的大气、水文和土壤驱动因素可能有很大不同。使用表面更新理论，引入了基于传质机制划分测量甲烷通量的框架，其总体目标是表征\(\mathrm {CH_4}\)源及其在地面的强度。使用测量湍流空气速度和多个标量浓度（包括热量、水蒸气和二氧化碳）的大型数据集对芬兰北方泥炭地上方的流动进行了测试。然后针对以背景扩散（例如水蒸气）或间歇源（例如甲烷）为特征的标量评估不同气体传输机制的传输效率。地下水位、大气条件等环境变量是否对\(\mathrm {CH_4}\)然后调查热点。在经典地表更新理论的基础上，这项工作引入了一种新方法来推断地面标量源的间歇性，并探索非均匀性如何影响大气表层中气体湍流传输的效率。