古元古代大氧化事件的生物学再认识
Rethinking the Paleoproterozoic Great Oxidation Event: A Biological Perspective
摘要：
竞争地球物理/地球化学假设地球表面如何成为氧化-有机碳埋藏，氢逃逸到太空，火山气体的氧化还原状态的变化-检查和一个更生物为基础的假设提供响应。有人认为，有机碳埋藏是次要的氧气的积累在一个主要缺氧的世界，有氧呼吸是不是全球性的显着。因此，对于大氧化事件（GOE）~ 2.4 Gyr ago，由于其生产的蓝细菌种群不断扩大的O2通量的增加被参数化为O2的主要来源。在太古代的大部分时间里，各种因素都会限制蓝藻的增殖和O2的产生，因此，蓝藻的出现和大气的氧化之间会有很长的延迟。通过甲烷氧化在大气中的O2破坏是一个主要的O2汇在太古代，和GOE的解释在很大程度上由产甲烷菌的人口和相应的甲烷通量，这反过来，主要是由于部分氧化的表面海洋的大幅下降。这些水的部分充氧状态也使得好氧甲烷氧化菌种群得以建立。这进一步导致了大气中CH 4通量的大幅减少，因为增加了从水柱较深的缺氧深度向上扩散的CH 4的消耗以及上层仍在产生的任何CH 4。CH 4通量的减少降低了CH 4对O2的氧化汇，同时变质和火山气体对O2的氧化汇也下降了。随着O2源的增加，从一个不断扩大的蓝细菌种群-触发了一个爆发的大陆形成约2.7-2.4 Gyr前-大气翻转，并成为永久含氧。
英文摘要：
Competing geophysical/geochemical hypotheses for how Earth's surface became oxygenated - organic carbon burial, hydrogen escape to space, and changes in the redox state of volcanic gases - are examined and a more biologically-based hypothesis is offered in response. It is argued that organic carbon burial is of minor importance to the accumulation of oxygen in a mainly anoxic world where aerobic respiration is not globally significant. Thus, for the Great Oxidation Event (GOE) ~ 2.4 Gyr ago, an increasing flux of O2 due to its production by an expanding population of cyanobacteria is parameterized as the primary source of O2. Various factors would have constrained cyanobacterial proliferation and O2 production during most of the Archean and therefore a long delay between the appearance of cyanobacteria and oxygenation of the atmosphere is to be expected. Destruction of O2 via CH4 oxidation in the atmosphere was a major O2 sink during the Archean, and the GOE is explained to a significant extent by a large decline in the methanogen population and corresponding CH4 flux which, in turn, was caused primarily by partial oxygenation of the surface ocean. The partially oxygenated state of these waters also made it possible for an aerobic methanotroph population to become established. This further contributed to the large reduction in the CH4 flux to the atmosphere by increasing the consumption of CH4 diffusing upwards from the deeper anoxic depths of the water column as well as any CH4 still being produced in the upper layer. The reduction in the CH4 flux lowered the CH4 oxidation sink for O2 at about the same time the metamorphic and volcanic gas sinks for O2 also declined. As the O2 source increased from an expanding population of cyanobacteria - triggered by a burst of continent formation ~ 2.7-2.4 Gyr ago - the atmosphere flipped and became permanently oxygenated.
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