Interannual Variability of Methane Storage and Emission During Autumn Overturn in a Small Lake
Interannual Variability of Methane Storage and Emission During Autumn Overturn in a Small Lake
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DOI：
10.1029/2021jg006388
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发表时间：
2021-11
期刊：
影响因子：
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通讯作者：
R. B. Ragg;F. Peeters;J. Ingwersen;P. Teiber-Siessegger;H. Hofmann
中科院分区：
文献类型：
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作者：
R. B. Ragg;F. Peeters;J. Ingwersen;P. Teiber-Siessegger;H. Hofmann
来自淡水系统，特别是来自小湖泊的甲烷排放，是自然产生的大气甲烷的重要来源。在小型温带湖泊中，储存通量，即在水体季节性翻转期间储存在缺氧沃茨中的甲烷的扩散排放，可以贡献年度甲烷排放的很大一部分。在这里，我们使用广泛的现场数据集来量化缺氧深水中的甲烷储存，并确定和量化这种甲烷的来源和损失。在一个小的温带湖泊（Illmensee）4年的测量结果的比较表明，甲烷储存量可以有很大的不同。在2012年和2018年，整个水体中储存的甲烷的年最大值（5，350和5，822公斤）是2013年和2017年（2，722和2，295公斤）的两倍左右。甲烷质量平衡的方法表明，甲烷储存在缺氧水之间的变化是不是由缺氧-好氧水界面的甲烷通量造成的，而是与缺氧沉积物中甲烷来源的变化有关。沉积物通量的年际差异不能用沉积物温度来解释，而是由有机质的不同供应。我们的研究结果表明，浮游植物水华促进甲烷储存在同一年内，从而导致在秋季翻转排放的年际变化。
Methane emissions from freshwater systems, and especially from small lakes, source a significant proportion of naturally produced atmospheric methane. In small temperate lakes, storage flux, that is, the diffusive emission of methane that was stored in anoxic waters during the seasonal overturn of the water column, can contribute a large fraction of annual methane emissions. Here, we use an extensive field data set to quantify methane storage in anoxic deep water and identify as well as quantify the sources and losses of this methane. The comparison of measurements from 4 years in a small temperate lake (Illmensee) shows that methane storage can differ substantially between years. In 2012 and 2018, the annual maximum of the methane stored in the entire water column was around twice as high (5,350 and 5,822 kg) as in 2013 and 2017 (2,722 and 2,295 kg). A methane mass balance approach suggests that the variability of methane storage in the anoxic water between the years was not caused by the methane flux at the anoxic–oxic water interface, but rather was related to changes in the methane source from the anoxic sediments. The interannual differences in sediment flux could not be explained by sediment temperature, but rather by the differing supply of organic matter. Our findings suggest that phytoplankton blooms promote methane storage within the same year and thus cause interannual variability in emissions during autumn overturn.