Photochemical production of methane in natural waters: implications for its present and past oceanic source.

Bange, Hermann W. and Uher, Günther (2005) Photochemical production of methane in natural waters: implications for its present and past oceanic source. Chemosphere, 58 (2). pp. 177-183. DOI 10.1016/j.chemosphere.2004.06.022.

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Abstract

We conducted irradiation experiments with riverine, estuarine, and marine water samples to investigate the possibility of photochemical methane (CH4) formation. CH4 photoproduction was undetectable under oxic conditions or in the absence of methyl radical precursors indicating that its photochemical formation is negligible in the present ocean. Significant photochemical CH4 production was observed in the presence of a methyl radical precursor such as acetone under strictly anoxic conditions. Our results indicate an indirect formation mechanism with coloured dissolved organic matter acting as photosensitizer. We suggest that photochemical CH4 formation might have occurred in the anoxic ocean surface layer of the Archean prior to the onset of O2 accumulation in the atmosphere at around 2300 million years ago. Oceanic CH4 photoproduction via methyl radical (CH3) precursors and its subsequent release to the atmosphere may have contributed to high CH4 mixing ratios in the Archean atmosphere.

Document Type: Article
Keywords: Methane; Coloured dissolved organic matter; North Sea; Aquatic photochemistry; Archean
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.chemosphere.2004.06.022
ISSN: 0045-6535
Date Deposited: 17 Mar 2010 12:30
Last Modified: 11 Dec 2017 11:32
URI: http://oceanrep.geomar.de/id/eprint/5700

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