碳中和VS水体甲烷超量释放/甲烷悖论

Carbon neutrality vs excess methane release from water environments/the methane paradox

碳中和目前已成为国际共识,亦是我国政府的政治承诺.实现碳中和目标无疑需要人为努力,但自然界还存在着一些仍未完全被认知但又不可小觑的碳排放源.例如,地表水体中在常规水底沉积物厌氧产甲烷(CH4)现象之外还存在着一种非常规CH4释放现象(甲烷悖论),且这种非常规CH4释放量在某些地区甚至超过化石燃料使用、汽车尾气排放、管道泄漏等温室气体排放量总和.如果这种现象变得普遍,则有可能形成在21世纪中叶虽可实现碳中和目标,但在世纪末却难以完成控温<2℃的尴尬局面.因此,有必要了解甲烷悖论现象及过程机制,高度警惕甲烷悖论现象下的CH4超量释放现象,而不仅仅是以完成碳中和作为唯一目标.基于碳中和目的,首先简述水体底泥常规甲烷生成途径,并由此引出水体甲烷超量释放现象,即甲烷悖论.其次,综述现有甲烷悖论过程机理研究,揭示表层有氧水体过量释放甲烷现象的实质.最后,分析调控甲烷悖论有可能适用的技术策略.

Carbon neutrality has become an international consensus and also a political commitment of the China′s government.Achieving the goal of carbon neutrality undoubtedly requires our human efforts, but there are also other carbon emission sources in the nature, which have not been fully recognized and however cannot be underestimated.For example, there is the unconventional CH4 release phenomena(the methane paradox) in surface waters besides the conventional phenomena of anaerobic methane production(CH4) in water sediments, and moreover the unconventional CH4 release amount in some areas even exceeds the sum of greenhouse gas emissions from fossil fuel, automobile exhaust and pipeline leakage.If the phenomena become common, an embarrassing situation would emerged that the goal of carbon neutrality would even be achieved in the middle of this century but the controlled temperature below 2 ℃ by the end of this century would hardly be completed.For this reason, it is necessary to understand the phenomena of the methane paradox and the associated process mechanisms of highly alerting the over-released CH4 under the methane paradox, not only for paying attention to carbon neutrality as the only goal.Based on the purpose of carbon neutrality, the conventional methanogenic pathway from water sediments is briefly described, and the phenomena of excessive methane release from surface waters(the methane paradox) is introduced.Then, the mechanisms of the methane paradox are reviewed to reveal the essence of excessive methane production in surface aerobic waters.Finally, the possible technical strategies for controlling the methane paradox are analyzed.