期刊
GEOCHIMICA ET COSMOCHIMICA ACTA
卷 314, 期 -, 页码 1-15出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.gca.2021.09.003
关键词
Co-precipitation; Adsorption; Soil organic matter; Electron energy loss spectroscopy
资金
- NSF IGERT in Cross-Scale Biogeochemistry and Climate at Cornell University [1069193]
- Technical University of Munich Institute for Advanced Studies
- Andrew W. Mellon Foundation
- Cornell College of Agriculture and Life Sciences Alumni Foundation
- NSF [DMR-1654596]
- Packard Foundation
- National Science Foundation [DMR-1332208]
- NSF MRSEC [DMR-1719875]
- Canada Foundation for Innovation
- Natural Sciences and Engineering Research Coun-cil of Canada
- University of Saskatchewan
- Government of Saskatchewan
- Western Economic Diversification Canada
- National Research Council Canada
- Canadian Institutes of Health Research
- Direct For Education and Human Resources
- Division Of Graduate Education [1069193] Funding Source: National Science Foundation
The association of organic matter with mineral phases through co-precipitation is expected to be a common process in environments with high organic matter input and frequent mineral dissolution and re-precipitation. The study reveals that co-precipitation can lead to greater carbon accumulation and may cause spatial separation and transformation of both iron and carbon forms. Additionally, abiotic redox reactions between iron and carbon via substituted aromatic groups play a role in creating distinct co-precipitate composition, potentially impacting its mineralization.
Association of organic matter (OM) with mineral phases via co-precipitation is expected to be a widespread process in environments with high OM input and frequent mineral dissolution and re-precipitation. In contrast to surface area-limited adsorption processes, co-precipitation may allow for greater carbon (C) accumulation. However, the potential submicrometer scale structural and compositional differences that affect the bioavailability of co-precipitated C are largely unknown. In this study, we used a combination of high-resolution analytical electron microscopy and bulk spectroscopy to probe interactions between a mineral phase (ferrihydrite, nominally Fe2O3 center dot 0.5H(2)O) and organic soil-derived water-extractable OM (WEOM). In co-precipitated WEOM-Fe, nanometer-scale scanning transmission electron microscopy with electron energy loss spectroscopy (STEM-EELS) revealed increased Fe(II) and less Fe aggregation relative to adsorbed WEOM-Fe. Spatially distinct lower- and higher-energy C regions were detected in both adsorbed and co-precipitated WEOM-Fe. In co-precipitates, lower-energy aromatic and/or substituted aromatic C was spatially associated with reduced Fe(II), but higher-energy oxidized C was enriched at the oxidized Fe(III) interface. Therefore, we show that co-precipitation does not constitute a non-specific physical encapsulation of C that only affects Fe chemistry and spatial distribution, but may cause a bi-directional set of reactions that lead to spatial separation and transformation of both Fe and C forms. In particular, we propose that abiotic redox reactions between Fe and C via substituted aromatic groups (e.g., hydroquinones) play a role in creating distinct co-precipitate composition, with potential implications for its mineralization. (C) 2021 Elsevier Ltd. All rights reserved.
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