Biogeochemical modeling of CO2 and CH4 production in anoxic Arctic soil microcosms
Soil organic carbon turnover to CO 2 and CH 4 is sensitive to soil redox potential and pH conditions. However, land surface models do not consider redox and pH in the aqueous phase explicitly, thereby limiting their use for making predictions in anoxic environments. Using recent data from incubation...
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ftcopernicus:oai:publications.copernicus.org:bg51378 2023-05-15T14:59:52+02:00 Biogeochemical modeling of CO2 and CH4 production in anoxic Arctic soil microcosms Tang, Guoping Zheng, Jianqiu Xu, Xiaofeng Yang, Ziming Graham, David E. Gu, Baohua Painter, Scott L. Thornton, Peter E. 2018-09-27 application/pdf https://doi.org/10.5194/bg-13-5021-2016 https://www.biogeosciences.net/13/5021/2016/ eng eng doi:10.5194/bg-13-5021-2016 https://www.biogeosciences.net/13/5021/2016/ eISSN: 1726-4189 Text 2018 ftcopernicus https://doi.org/10.5194/bg-13-5021-2016 2019-12-24T09:52:00Z Soil organic carbon turnover to CO 2 and CH 4 is sensitive to soil redox potential and pH conditions. However, land surface models do not consider redox and pH in the aqueous phase explicitly, thereby limiting their use for making predictions in anoxic environments. Using recent data from incubations of Arctic soils, we extend the Community Land Model with coupled carbon and nitrogen (CLM-CN) decomposition cascade to include simple organic substrate turnover, fermentation, Fe(III) reduction, and methanogenesis reactions, and assess the efficacy of various temperature and pH response functions. Incorporating the Windermere Humic Aqueous Model (WHAM) enables us to approximately describe the observed pH evolution without additional parameterization. Although Fe(III) reduction is normally assumed to compete with methanogenesis, the model predicts that Fe(III) reduction raises the pH from acidic to neutral, thereby reducing environmental stress to methanogens and accelerating methane production when substrates are not limiting. The equilibrium speciation predicts a substantial increase in CO 2 solubility as pH increases, and taking into account CO 2 adsorption to surface sites of metal oxides further decreases the predicted headspace gas-phase fraction at low pH. Without adequate representation of these speciation reactions, as well as the impacts of pH, temperature, and pressure, the CO 2 production from closed microcosms can be substantially underestimated based on headspace CO 2 measurements only. Our results demonstrate the efficacy of geochemical models for simulating soil biogeochemistry and provide predictive understanding and mechanistic representations that can be incorporated into land surface models to improve climate predictions. Text Arctic Copernicus Publications: E-Journals Arctic Biogeosciences 13 17 5021 5041 |
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Copernicus Publications: E-Journals |
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ftcopernicus |
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English |
description |
Soil organic carbon turnover to CO 2 and CH 4 is sensitive to soil redox potential and pH conditions. However, land surface models do not consider redox and pH in the aqueous phase explicitly, thereby limiting their use for making predictions in anoxic environments. Using recent data from incubations of Arctic soils, we extend the Community Land Model with coupled carbon and nitrogen (CLM-CN) decomposition cascade to include simple organic substrate turnover, fermentation, Fe(III) reduction, and methanogenesis reactions, and assess the efficacy of various temperature and pH response functions. Incorporating the Windermere Humic Aqueous Model (WHAM) enables us to approximately describe the observed pH evolution without additional parameterization. Although Fe(III) reduction is normally assumed to compete with methanogenesis, the model predicts that Fe(III) reduction raises the pH from acidic to neutral, thereby reducing environmental stress to methanogens and accelerating methane production when substrates are not limiting. The equilibrium speciation predicts a substantial increase in CO 2 solubility as pH increases, and taking into account CO 2 adsorption to surface sites of metal oxides further decreases the predicted headspace gas-phase fraction at low pH. Without adequate representation of these speciation reactions, as well as the impacts of pH, temperature, and pressure, the CO 2 production from closed microcosms can be substantially underestimated based on headspace CO 2 measurements only. Our results demonstrate the efficacy of geochemical models for simulating soil biogeochemistry and provide predictive understanding and mechanistic representations that can be incorporated into land surface models to improve climate predictions. |
format |
Text |
author |
Tang, Guoping Zheng, Jianqiu Xu, Xiaofeng Yang, Ziming Graham, David E. Gu, Baohua Painter, Scott L. Thornton, Peter E. |
spellingShingle |
Tang, Guoping Zheng, Jianqiu Xu, Xiaofeng Yang, Ziming Graham, David E. Gu, Baohua Painter, Scott L. Thornton, Peter E. Biogeochemical modeling of CO2 and CH4 production in anoxic Arctic soil microcosms |
author_facet |
Tang, Guoping Zheng, Jianqiu Xu, Xiaofeng Yang, Ziming Graham, David E. Gu, Baohua Painter, Scott L. Thornton, Peter E. |
author_sort |
Tang, Guoping |
title |
Biogeochemical modeling of CO2 and CH4 production in anoxic Arctic soil microcosms |
title_short |
Biogeochemical modeling of CO2 and CH4 production in anoxic Arctic soil microcosms |
title_full |
Biogeochemical modeling of CO2 and CH4 production in anoxic Arctic soil microcosms |
title_fullStr |
Biogeochemical modeling of CO2 and CH4 production in anoxic Arctic soil microcosms |
title_full_unstemmed |
Biogeochemical modeling of CO2 and CH4 production in anoxic Arctic soil microcosms |
title_sort |
biogeochemical modeling of co2 and ch4 production in anoxic arctic soil microcosms |
publishDate |
2018 |
url |
https://doi.org/10.5194/bg-13-5021-2016 https://www.biogeosciences.net/13/5021/2016/ |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic |
genre_facet |
Arctic |
op_source |
eISSN: 1726-4189 |
op_relation |
doi:10.5194/bg-13-5021-2016 https://www.biogeosciences.net/13/5021/2016/ |
op_doi |
https://doi.org/10.5194/bg-13-5021-2016 |
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Biogeosciences |
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13 |
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17 |
container_start_page |
5021 |
op_container_end_page |
5041 |
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1766331980044042240 |