This article deals with spatio-temporal changes in methane emission from the surface of the Mozhaisk reservoir. Seasonal changes in methane content and flux were revealed for different morphological areas of the reservoir, based on field observation data obtained in 2015–2018. In the low-flow Mozhaisk reservoir, the methane content in the boundary and bottom layers of the deep-water areas at the end of the summer stratification period may differ by three orders of magnitude. According to results from measuring with floating chambers in the central area of the reservoir from early June to the end of the period of direct stratification (August–September) the total methane flux increased from less than 1 to 16 mgC-CH4/(m2/hr). Time-coincident measurements with floating chambers of two types revealed characteristic values of the methane flux components and their change over the sampling period. It was found that at the period of stratification the diffusive flux predominates with the mean values 0.2 mgC-CH4/(m2/hr). A further increase in the total methane flux is associated with an increase of its bubble component. According to calculations, the diffusive flux reaches its maximum values in late summer in the shallow zone of the reservoir. It is established that a significant increase of the values of the total methane flux is observed when the upper boundary of the oxygen-free zone reaches the lower boundary of the epilimnion. The methane flux density reaches its largest values prior to destruction of the direct stratification. Comparison of field measurements with literature data showed that the magnitude of emission from reservoirs with a slow water exchange in the temperate zone can be underestimated in the evaluation of global methane emission.

中文翻译：

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莫扎伊斯克河谷型水库地表甲烷排放

本文讨论了莫扎伊斯克水库表面甲烷排放的时空变化。根据 2015-2018 年获得的现场观测数据，揭示了水库不同形态区域的甲烷含量和通量的季节性变化。在低流量莫扎伊斯克水库中，夏季分层末期深水区边界层和底层的甲烷含量可能相差三个数量级。根据 6 月初至直接分层期末（8-9 月）在水库中心区用浮舱测量的结果，甲烷总通量从小于 1 增加到 16小时）。两种类型的浮舱的时间重合测量揭示了甲烷通量成分的特征值及其在采样周期内的变化。发现在分层期间，扩散通量占优势，平均值为 0.2 mgC-CH4/(m2/hr)。总甲烷通量的进一步增加与其气泡成分的增加有关。根据计算，在储层浅层区域，扩散通量在夏末达到最大值。确定的是，当无氧区的上边界到达外层的下边界时，观察到的总甲烷通量值显着增加。在直接分层破坏之前，甲烷通量密度达到其最大值。