Pumping methane out of aquatic sediments - ebullition forcing mechanisms in an impounded river
Pumping methane out of aquatic sediments - ebullition forcing mechanisms in an impounded river
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DOI：
10.5194/bg-11-2925-2014
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发表时间：
2014-01-01
期刊：
影响因子：
4.9
通讯作者：
Lorke, A.
中科院分区：
文献类型：
--
作者：
Maeck, A.;Hofmann, H.;Lorke, A.
淡水系统对全球大气甲烷收支有重大贡献。从淡水排放的甲烷中有很大一部分是通过沸腾来运输的。然而，由于其在空间和时间上的强烈变化，很难准确测量沸腾率;因此，其对全球预算的贡献的不确定性很大。在这里，我们分析了连续记录自动气泡陷阱在欧洲中部的一条蓄水河中的测量，并探讨了影响粘性沉积物中气泡释放的时间动态的机制。研究结果表明，压力变化是气泡释放的主要触发因素，主要来源于船闸引起的涌浪和船舶通道。对物理强迫的反应也受到以前释气的影响。从几分钟到几天的所有相关时间尺度上，沸腾率变化很大;因此，只能通过长时间连续采样来推断具有代表性的沸腾估计值。由于发现沸腾是间歇性的，几小时或几天的短期测量周期可能会低估沸腾率。因此，我们的研究结果表明，通量估计可能被严重低估（高达50%），如果正确的时间分辨率不使用数据收集过程中。
Freshwater systems contribute significantly to the global atmospheric methane budget. A large fraction of the methane emitted from freshwaters is transported via ebullition. However, due to its strong variability in space and time, accurate measurements of ebullition rates are difficult; hence, the uncertainty regarding its contribution to global budgets is large. Here, we analyze measurements made by continuously recording automated bubble traps in an impounded river in central Europe and investigate the mechanisms affecting the temporal dynamics of bubble release from cohesive sediments. Our results show that the main triggers of bubble release were pressure changes, originating from the passage of ship lock-induced surges and ship passages. The response to physical forcing was also affected by previous outgassing. Ebullition rates varied strongly over all relevant timescales from minutes to days; therefore, representative ebullition estimates could only be inferred with continuous sampling over long periods. Since ebullition was found to be episodic, short-term measurement periods of a few hours or days will likely underestimate ebullition rates. Our results thus indicate that flux estimates could be grossly underestimated (by up to similar to 50%) if the correct temporal resolution is not used during data collection.