The efficient long-term inhibition of forsterite dissolution by common soil bacteria and fungi at earth surface conditions

Oelkers, Eric H.; Benning, Liane G.; Lutz, Stefanie; Mavromatis, Vasileios; Pearce, Christopher R.; Plümper, Oliver. 2015 The efficient long-term inhibition of forsterite dissolution by common soil bacteria and fungi at earth surface conditions. Geochimica et Cosmochimica Acta, 168. 222-235.

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This is the author’s version of a work that was accepted for publication in Geochimica et Cosmochimica Acta. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was will be published in Geochimica et Cosmochimica Acta 10.1016/j.gca.2015.06.004
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San Carlos forsterite was dissolved in initially pure H2O in a batch reactor in contact with the atmosphere for five years. The reactive fluid aqueous pH remained relatively stable at pH 6.7 throughout the experiment. Aqueous Mg concentration maximized after approximately two years time at 3x10-5 mol/kg, whereas aqueous Si concentrations increased continuously with time, reaching 2x10-5 mol/kg after 5 years. Element release rates closely matched those determined on this same forsterite sample during short-term abiotic open system experiments for the first 10 days, then slowed substantially such that the Mg and Si release rates are approximately an order of magnitude slower than that calculated from the short-term abiotic experiments. Post-experiment analysis reveals that secondary hematite, a substantial biotic community, and minor amorphous silica formed on the dissolving forsterite during the experiment. The biotic community included bacteria, dominated by Rhizobiales (Alphaproteobacteria), and fungi, dominated by Trichocomaceae, that grew in a carbon and nutrient-limited media on the dissolving forsterite. The Mg isotope composition of the reactive fluid was near constant after 2 years but 0.25‰ heavier in δ26Mg than the dissolving forsterite. Together these results suggest long-term forsterite dissolution in natural Earth surface systems maybe substantially slower that estimated from short-term abiotic experiments due to the growth of biotic communities on their surfaces.

Item Type: Publication - Article
Digital Object Identifier (DOI):
ISSN: 00167037
Date made live: 16 Jun 2015 09:18 +0 (UTC)

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