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Title: Influence of hydrological, biogeochemical and temperature transients on subsurface carbon fluxes in a flood plain environment

Abstract

Flood plains play a potentially important role in the global carbon cycle. The accumulation of organic matter in flood plains often induces the formation of chemically reduced groundwater and sediments along riverbanks. In this study, our objective is to evaluate the cumulative impact of such reduced zones, water table fluctuations, and temperature gradients on subsurface carbon fluxes in a flood plain at Rifle, Colorado located along the Colorado River. 2-D coupled variably-saturated, non-isothermal flow and biogeochemical reactive transport modeling was applied to improve our understanding of the abiotic and microbially mediated reactions controlling carbon dynamics at the Rifle site. Model simulations considering only abiotic reactions (thus ignoring microbial reactions) underestimated CO 2 partial pressures observed in the unsaturated zone and severely underestimated inorganic (and overestimated organic) carbon fluxes to the river compared to simulations with biotic pathways. Both model simulations and field observations highlighted the need to include microbial contributions from chemolithoautotrophic processes (e.g., Fe +2 and S -2 oxidation) to match locally-observed high CO 2 concentrations above reduced zones. Observed seasonal variations in CO 2 concentrations in the unsaturated zone could not be reproduced without incorporating temperature gradients in the simulations. Incorporating temperature fluctuations resulted in an increase inmore » the annual groundwater carbon fluxes to the river by 170 % to 3.3 g m -2 d -1, while including water table variations resulted in an overall decrease in the simulated fluxes. We thus conclude that spatial microbial and redox zonation as well as temporal fluctuations of temperature and water table depth contribute significantly to subsurface carbon fluxes in flood plains and need to be represented appropriately in model simulations.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [2]
  1. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). Energy Geosciences Division
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1439194
Report Number(s):
PNNL-SA-119410
Journal ID: ISSN 0168-2563; ark:/13030/qt8kb037c2
Grant/Contract Number:  
AC02-05CH11231; AC05-76RL01830
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Biogeochemistry
Additional Journal Information:
Journal Volume: 127; Journal Issue: 2-3; Related Information: © 2016, US Government.; Journal ID: ISSN 0168-2563
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Flood plain; Reduced zones; Subsurface carbon dynamics; Temporal variability; Biogeochemical processes

Citation Formats

Arora, Bhavna, Spycher, Nicolas F., Steefel, Carl I., Molins, Sergi, Bill, Markus, Conrad, Mark E., Dong, Wenming, Faybishenko, Boris, Tokunaga, Tetsu K., Wan, Jiamin, Williams, Kenneth H., and Yabusaki, Steven B. Influence of hydrological, biogeochemical and temperature transients on subsurface carbon fluxes in a flood plain environment. United States: N. p., 2016. Web. doi:10.1007/s10533-016-0186-8.
Arora, Bhavna, Spycher, Nicolas F., Steefel, Carl I., Molins, Sergi, Bill, Markus, Conrad, Mark E., Dong, Wenming, Faybishenko, Boris, Tokunaga, Tetsu K., Wan, Jiamin, Williams, Kenneth H., & Yabusaki, Steven B. Influence of hydrological, biogeochemical and temperature transients on subsurface carbon fluxes in a flood plain environment. United States. doi:10.1007/s10533-016-0186-8.
Arora, Bhavna, Spycher, Nicolas F., Steefel, Carl I., Molins, Sergi, Bill, Markus, Conrad, Mark E., Dong, Wenming, Faybishenko, Boris, Tokunaga, Tetsu K., Wan, Jiamin, Williams, Kenneth H., and Yabusaki, Steven B. Fri . "Influence of hydrological, biogeochemical and temperature transients on subsurface carbon fluxes in a flood plain environment". United States. doi:10.1007/s10533-016-0186-8. https://www.osti.gov/servlets/purl/1439194.
@article{osti_1439194,
title = {Influence of hydrological, biogeochemical and temperature transients on subsurface carbon fluxes in a flood plain environment},
author = {Arora, Bhavna and Spycher, Nicolas F. and Steefel, Carl I. and Molins, Sergi and Bill, Markus and Conrad, Mark E. and Dong, Wenming and Faybishenko, Boris and Tokunaga, Tetsu K. and Wan, Jiamin and Williams, Kenneth H. and Yabusaki, Steven B.},
abstractNote = {Flood plains play a potentially important role in the global carbon cycle. The accumulation of organic matter in flood plains often induces the formation of chemically reduced groundwater and sediments along riverbanks. In this study, our objective is to evaluate the cumulative impact of such reduced zones, water table fluctuations, and temperature gradients on subsurface carbon fluxes in a flood plain at Rifle, Colorado located along the Colorado River. 2-D coupled variably-saturated, non-isothermal flow and biogeochemical reactive transport modeling was applied to improve our understanding of the abiotic and microbially mediated reactions controlling carbon dynamics at the Rifle site. Model simulations considering only abiotic reactions (thus ignoring microbial reactions) underestimated CO2 partial pressures observed in the unsaturated zone and severely underestimated inorganic (and overestimated organic) carbon fluxes to the river compared to simulations with biotic pathways. Both model simulations and field observations highlighted the need to include microbial contributions from chemolithoautotrophic processes (e.g., Fe+2 and S-2 oxidation) to match locally-observed high CO2 concentrations above reduced zones. Observed seasonal variations in CO2 concentrations in the unsaturated zone could not be reproduced without incorporating temperature gradients in the simulations. Incorporating temperature fluctuations resulted in an increase in the annual groundwater carbon fluxes to the river by 170 % to 3.3 g m-2 d-1, while including water table variations resulted in an overall decrease in the simulated fluxes. We thus conclude that spatial microbial and redox zonation as well as temporal fluctuations of temperature and water table depth contribute significantly to subsurface carbon fluxes in flood plains and need to be represented appropriately in model simulations.},
doi = {10.1007/s10533-016-0186-8},
journal = {Biogeochemistry},
number = 2-3,
volume = 127,
place = {United States},
year = {Fri Feb 12 00:00:00 EST 2016},
month = {Fri Feb 12 00:00:00 EST 2016}
}

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Works referenced in this record:

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