Effect of Geologically Constrained Environmental Parameters on the Atmosphere and Biosphere of Early Earth


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Ralph.Lehmann [ at ] awi.de

Abstract

The Great Oxidation Event (GOE) about 2.3 gigayears ago denotes the first major rise of atmospheric molecular oxygen (O2) in Earth’s history. As a consequence, the planet experienced the emergence of widespread habitability and complex life. Recently, there has been a revolution in improved methods for constraining geological data for atmospheric pressure, composition, and ocean temperature of the early Earth. We investigate the effect of this revised data upon processes which drove the GOE. Results suggest that increasing Archean carbon dioxide (CO2) produces increased O 2 with height due to enhanced CO2 photolysis. This is counterbalanced by stronger O2 destruction as a result of enhanced carbon monoxide (CO) (from increased CO2) and nitrogen oxides (NOx) (from decreased hydroxyl via increased CO). Pre-GOE atmospheres with low O2 yet high CO2 could counteract O2 accumulation. For low surface pressures of 0.5 bar, O2 decreases between 0.5 to 0.005 bar. This arose mainly from O2 destruction via hydrogen oxides from enhanced water from higher temperatures for p < 0.01 bar and weaker O2 production via less ultraviolet radiation that initiates ozone production via CO2 photolysis. Shortly before the GOE, ∼20% lower net primary productivity (NPP) can maintain comparable O2 as for a 1 bar atmosphere and, hence, the accumulation of O2 produced by a photosynthetic biosphere is supported. We identify new O2 production and destruction pathways with NOx containing species for Archean Earth for high CO2 atmospheres and low/high surface pressure. On increasing ocean temperatures, NPP is reduced due to lower O2 solubility before the GOE. This facilitates atmospheric O2 accumulation.



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ISI/Scopus peer-reviewed
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Published
Eprint ID
49424
DOI 10.1021/acsearthspacechem.8b00088

Cite as
Gebauer, S. , Grenfell, J. L. , Lehmann, R. and Rauer, H. (2018): Effect of Geologically Constrained Environmental Parameters on the Atmosphere and Biosphere of Early Earth , ACS Earth and Space Chemistry, 2 (11), pp. 1112-1136 . doi: 10.1021/acsearthspacechem.8b00088


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