Availability of O2 and H2O2 on Pre-Photosynthetic Earth
Availability of O2 and H2O2 on Pre-Photosynthetic Earth
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DOI：
10.1089/ast.2010.0572
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发表时间：
2011-05-01
期刊：
影响因子：
4.2
通讯作者：
Lee, Sukyoung
中科院分区：
文献类型：
--
作者：
Haqq-Misra, Jacob;Kasting, James F.;Lee, Sukyoung
一项新的研究恢复了关于在光合作用起源之前地球表面必须存在游离O-2的旧论点，该研究表明，有氧呼吸可以在溶解氧浓度比以前认为的低得多的情况下发生，可能低至0.05 nM，这相当于O-2的分压约为4 x 10（-8）bar。我们使用数值模式来研究是否这样的O-2浓度可能已经提供了大气光化学。结果表明，H_2O_2在表面附近的分解可能产生足够的O-_2来满足这一限制。另外，向极地运输的O-2从赤道平流层到极地夜间区域，然后在极涡向下运输，可能带来了O-2直接到表面。因此，我们的计算表明，这种“早期呼吸”的假设可能是合理的。
Old arguments that free O-2 must have been available at Earth's surface prior to the origin of photosynthesis have been revived by a new study that shows that aerobic respiration can occur at dissolved oxygen concentrations much lower than had previously been thought, perhaps as low as 0.05 nM, which corresponds to a partial pressure for O-2 of about 4 x 10(-8) bar. We used numerical models to study whether such O-2 concentrations might have been provided by atmospheric photochemistry. Results show that disproportionation of H2O2 near the surface might have yielded enough O-2 to satisfy this constraint. Alternatively, poleward transport of O-2 from the equatorial stratosphere into the polar night region, followed by downward transport in the polar vortex, may have brought O-2 directly to the surface. Thus, our calculations indicate that this ``early respiration'' hypothesis might be physically reasonable.