Evidence linking calcium to increased organo-mineral association in soils

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Version: Final published version
License: CC BY 4.0
Serval ID
serval:BIB_1327FC0BC500
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Evidence linking calcium to increased organo-mineral association in soils
Journal
Biogeochemistry
Author(s)
Rowley M. C., Grand S., Spangenberg J. E., Verrecchia E. P.
ISSN
0168-2563
1573-515X
Publication state
Published
Issued date
04/2021
Peer-reviewed
Oui
Volume
153
Number
3
Pages
223-241
Language
english
Abstract
Geochemical indicators are emerging as important predictors of soil organic carbon (SOC) dynamics, but evidence concerning the role of calcium (Ca) is scarce. This study investigates the role of Ca prevalence in SOC accumulation by comparing otherwise similar sites with (CaCO3-bearing) or without carbonates (CaCO3-free). We measured the SOC content and indicators of organic matter quality (C stable isotope composition, expressed as δ13C values, and thermal stability) in bulk soil samples. We then used sequential sonication and density fractionation (DF) to separate two occluded pools from free and mineral-associated SOC. The SOC content, mass, and δ13C values were determined in all the fractions. X-ray photoelectron spectroscopy was used to investigate the surface chemistry of selected fractions. Our hypothesis was that occlusion would be more prevalent at the CaCO3-bearing site due to the influence of Ca on aggregation, inhibiting oxidative transformation, and preserving lower δ13C values. Bulk SOC content was twice as high in the CaCO3-bearing profiles, which also had lower bulk δ13C values, and more occluded SOC. Yet, contrary to our hypothesis, occlusion only accounted for a small proportion of total SOC (< 10%). Instead, it was the heavy fraction (HF), containing mineral-associated organic C, which accounted for the majority of total SOC and for the lower bulk δ13C values. Overall, an increased Ca prevalence was associated with a near-doubling of mineral-associated SOC content. Future investigations should now aim to isolate Ca-mediated complexation processes that increase organo-mineral association and preserve organic matter with lower δ13C values.
Keywords
Soil organic carbon, Density fractionation, Carbon stable isotopes, X-ray photoelectron spectroscopy, Rock-Eval® pyrolysis
Web of science
Open Access
Yes
Funding(s)
University of Lausanne
Swiss National Science Foundation
Create date
03/05/2021 11:54
Last modification date
16/12/2022 6:51
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