Biogeochemical modeling of CO 2 and CH 4 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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Published in:Biogeosciences
Main Authors: G. Tang, J. Zheng, X. Xu, Z. Yang, D. E. Graham, B. Gu, S. L. Painter, P. E. Thornton
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2016
Subjects:
Online Access:https://doi.org/10.5194/bg-13-5021-2016
https://doaj.org/article/706ec24b83b8461999d291b01ec2e1a3
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spelling ftdoajarticles:oai:doaj.org/article:706ec24b83b8461999d291b01ec2e1a3 2023-05-15T14:59:56+02:00 Biogeochemical modeling of CO 2 and CH 4 production in anoxic Arctic soil microcosms G. Tang J. Zheng X. Xu Z. Yang D. E. Graham B. Gu S. L. Painter P. E. Thornton 2016-09-01T00:00:00Z https://doi.org/10.5194/bg-13-5021-2016 https://doaj.org/article/706ec24b83b8461999d291b01ec2e1a3 EN eng Copernicus Publications http://www.biogeosciences.net/13/5021/2016/bg-13-5021-2016.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 1726-4170 1726-4189 doi:10.5194/bg-13-5021-2016 https://doaj.org/article/706ec24b83b8461999d291b01ec2e1a3 Biogeosciences, Vol 13, Iss 17, Pp 5021-5041 (2016) Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 article 2016 ftdoajarticles https://doi.org/10.5194/bg-13-5021-2016 2022-12-31T02:46:03Z 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. Article in Journal/Newspaper Arctic Directory of Open Access Journals: DOAJ Articles Arctic Biogeosciences 13 17 5021 5041
institution Open Polar
collection Directory of Open Access Journals: DOAJ Articles
op_collection_id ftdoajarticles
language English
topic Ecology
QH540-549.5
Life
QH501-531
Geology
QE1-996.5
spellingShingle Ecology
QH540-549.5
Life
QH501-531
Geology
QE1-996.5
G. Tang
J. Zheng
X. Xu
Z. Yang
D. E. Graham
B. Gu
S. L. Painter
P. E. Thornton
Biogeochemical modeling of CO 2 and CH 4 production in anoxic Arctic soil microcosms
topic_facet Ecology
QH540-549.5
Life
QH501-531
Geology
QE1-996.5
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 Article in Journal/Newspaper
author G. Tang
J. Zheng
X. Xu
Z. Yang
D. E. Graham
B. Gu
S. L. Painter
P. E. Thornton
author_facet G. Tang
J. Zheng
X. Xu
Z. Yang
D. E. Graham
B. Gu
S. L. Painter
P. E. Thornton
author_sort G. Tang
title Biogeochemical modeling of CO 2 and CH 4 production in anoxic Arctic soil microcosms
title_short Biogeochemical modeling of CO 2 and CH 4 production in anoxic Arctic soil microcosms
title_full Biogeochemical modeling of CO 2 and CH 4 production in anoxic Arctic soil microcosms
title_fullStr Biogeochemical modeling of CO 2 and CH 4 production in anoxic Arctic soil microcosms
title_full_unstemmed Biogeochemical modeling of CO 2 and CH 4 production in anoxic Arctic soil microcosms
title_sort biogeochemical modeling of co 2 and ch 4 production in anoxic arctic soil microcosms
publisher Copernicus Publications
publishDate 2016
url https://doi.org/10.5194/bg-13-5021-2016
https://doaj.org/article/706ec24b83b8461999d291b01ec2e1a3
geographic Arctic
geographic_facet Arctic
genre Arctic
genre_facet Arctic
op_source Biogeosciences, Vol 13, Iss 17, Pp 5021-5041 (2016)
op_relation http://www.biogeosciences.net/13/5021/2016/bg-13-5021-2016.pdf
https://doaj.org/toc/1726-4170
https://doaj.org/toc/1726-4189
1726-4170
1726-4189
doi:10.5194/bg-13-5021-2016
https://doaj.org/article/706ec24b83b8461999d291b01ec2e1a3
op_doi https://doi.org/10.5194/bg-13-5021-2016
container_title Biogeosciences
container_volume 13
container_issue 17
container_start_page 5021
op_container_end_page 5041
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