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首页> 外文期刊>Aquatic Sciences >Spatial variations in surface water methane super-saturation and emission in Lake Lugano, southern Switzerland
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Spatial variations in surface water methane super-saturation and emission in Lake Lugano, southern Switzerland

机译：瑞士南部卢加诺湖地表水甲烷过饱和和排放的空间变化

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We measured methane concentrations in the surface water of the northern basin of Lake Lugano in spring (May 2012) and autumn (October 2011, 2012), and calculated turbulent diffusive methane fluxes to the atmosphere. Surface water methane concentrations were highly variable in space and time but always exceeded atmospheric equilibrium. Methane concentrations were significantly lower in spring (on average 16 nmol L-1) than during the autumn sampling campaigns (on average 57 nmol L-1 in 2011 and 45 nmol L-1 in 2012). This suggests methane accumulation in the surface mixed layer during the summer productive season. The origin of the methane in the lake's surface waters requires further assessment, but the observed concentration profiles indicate that the excess methane originates from a near-surface source, rather than from the large deep-water methane pool in the anoxic monimolimnion. As a consequence of the higher surface water methane concentrations and increased buoyancy turbulence caused by autumnal cooling of the surface boundary layer, diffusive fluxes were much higher in October (average similar to 97 mu mol m(-2) day(-1), compared to 7 mu mol m(-2) day(-1) in May 2012). The increase in methane concentration in the surface water between spring and autumn suggests links between methane accumulation and the annual biological cycle, yet seasonal changes in wind and temperature forcing of methane emission likely play an important modulating role. While the relative importance of biological versus physical controls on methane emission in Lake Lugano awaits further investigations, our study underscores that lakes can act as an important source of methane to the atmosphere, even when the lake-internal microbial methane filter in the water column seems to work efficiently.
机译：我们在春季（2012年5月）和秋季（2011年10月，2012年10月）测量了卢加诺湖北部盆地地表水中的甲烷浓度，并计算了向大气中的湍流扩散甲烷通量。地表水中甲烷的浓度在时间和空间上变化很大，但始终超过大气平衡。春季的甲烷浓度（平均为16 nmol L-1）明显低于秋季的采样活动（2011年为平均57 nmol L-1和2012年为45 nmol L-1）。这表明在夏季生产季节甲烷在表面混合层中积累。湖泊地表水中甲烷的来源需要进一步评估，但是观察到的浓度分布图表明，过量的甲烷来自近地表来源，而不是来自缺氧一氧化氮的大型深水甲烷库。由于较高的地表水甲烷浓度和由表面边界层的秋季冷却引起的浮力湍流增加，十月份的扩散通量要高得多（平均与97μmol m（-2）天（-1）相比）到2012年5月达到7 mol mol m（-2）day（-1）。春季和秋季之间地表水中甲烷浓度的增加表明甲烷的积累与年度生物周期之间存在联系，但是风的季节变化和强迫甲烷排放的温度可能起着重要的调节作用。尽管卢加诺湖沼气的生物控制与物理控制相对重要，尚待进一步研究，但我们的研究强调，即使水柱内部的湖泊内部微生物沼气过滤器看来，湖泊也可以作为大气中甲烷的重要来源。有效地工作。

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