Bray, AW, Oelkers, EH, Bonneville, S et al. (4 more authors) (2015) The effect of pH, grain size, and organic ligands on biotite weathering rates. Geochimica et Cosmochimica Acta, 164. 127 - 145. ISSN 0016-7037
Abstract
Biotite dissolution rates were determined at 25 °C, at pH 2–6, and as a function of mineral composition, grain size, and aqueous organic ligand concentration. Rates were measured using both open- and closed-system reactors in fluids of constant ionic strength. Element release was non-stoichiometric and followed the general trend of Fe, Mg > Al > Si. Biotite surface area normalised dissolution rates (ri) in the acidic range, generated from Si release, are consistent with the empirical rate law: View the MathML sourceri=kH,iaH+xi where kH,i refers to an apparent rate constant, aH+aH+ designates the activity of protons, and xi stands for a reaction order with respect to protons. Rate constants range from 2.15 × 10−10 to 30.6 × 10−10 (molesbiotite m−2 s−1) with reaction orders ranging from 0.31 to 0.58. At near-neutral pH in the closed-system experiments, the release of Al was stoichiometric compared to Si, but Fe was preferentially retained in the solid phase, possibly as a secondary phase. Biotite dissolution was highly spatially anisotropic with its edges being ∼120 times more reactive than its basal planes. Low organic ligand concentrations slightly enhanced biotite dissolution rates. These measured rates illuminate mineral–fluid–organism chemical interactions, which occur in the natural environment, and how organic exudates enhance nutrient mobilisation for microorganism acquisition.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Editors: |
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Copyright, Publisher and Additional Information: | © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/). |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Earth Surface Science Institute (ESSI) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 01 Jun 2015 11:17 |
Last Modified: | 28 Jul 2015 17:19 |
Published Version: | http://dx.doi.org/10.1016/j.gca.2015.04.048 |
Status: | Published |
Publisher: | Elsevier |
Refereed: | Yes |
Identification Number: | 10.1016/j.gca.2015.04.048 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:86557 |