Approach adds explicit aquatic phase redox and pH to a decomposition cascade model.
Explicit aqueous phase redox, pH, and mineral interaction dynamics were coupled to the Converging Trophic Cascade (CTC) decomposition model, enabling prediction of carbon dioxide (CO2) and methane (CH4) production from Arctic polygonal tundra soils under laboratory incubations over a range of temperatures.
The extended model captures pH dynamics reasonably well in Arctic soil incubations. Temperature and pH sensitivity for microbial reactions is highlighted as an important area for further research.
Soil organic carbon turnover and CO2 and CH4 production are sensitive to redox potential and pH. However, land surface models typically do not explicitly simulate the redox or pH, particularly in the aqueous phase, introducing uncertainty in greenhouse gas predictions. To account for the impact of availability of electron acceptors other than oxygen (O2) on soil organic matter (SOM) decomposition and methanogenesis, researchers extended an existing decomposition cascade model (Converging Trophic Cascade model or CTC) to link complex polymers with simple substrates and add iron [Fe(III)] reduction and methanogenesis reactions. Because pH was observed to change substantially in the laboratory incubation tests and in the field and is a sensitive environmental variable for biogeochemical processes, the researchers used the Windermere Humic Aqueous Model (WHAM) to simulate pH buffering by SOM. To account for the speciation of CO2 among gas, aqueous, and solid (adsorbed) phases under varying pH, temperature, and pressure values, as well as the impact on typically measured headspace concentration, they used a geochemical model and an established reaction database to describe observations in anaerobic microcosms incubated at a range of temperatures (-2, +4, and +8 °C). The study’s results demonstrate the efficacy of using geochemical models to mechanistically represent the soil biogeochemical processes for Earth system models. The modeling approach demonstrated in this work will be evaluated against additional field and laboratory data and incorporated in new Earth system modeling development to improve prediction of greenhouse gas fluxes in Arctic tundra environments.
Contacts (BER PM)
Daniel Stover, Jared DeForest, and Dorothy Koch
Daniel.Stover@science.doe.gov (301-903-0289); Jared.DeForest@science.doe.gov (301-903-1678); and Dorothy.Koch@science.do.egov (301-903-0105)
Peter E. Thornton, Environmental Science Division and Climate Change Science Institute, Oak Ridge National Laboratory. email@example.com, 865-241-3742
This work was supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Oak Ridge National Laboratory Terrestrial Ecosystem Science Scientific Focus Area and Earth System Modeling (Accelerated Climate Model for Energy project).
Tang, G., J. Zheng, X. Xu, Z. Yang, D. E. Graham, B. Gu, S. Painter, and P. E. Thornton. 2016. “Biogeochemical Modeling of CO2 and CH4 Production in Anoxic Arctic Soil Microcosms,” Biogeosciences 13, 5021-41. DOI: 10.5194/bg-13-5021-2016. (Reference link)
SC-23.1 Climate and Environmental Sciences Division, BER
BER supports basic research and scientific user facilities to advance DOE missions in energy and environment. More about BER
May 10, 2019
Quantifying Decision Uncertainty in Water Management via a Coupled Agent-Based Model
Considering risk perception can improve the representation of human decision-making processes in age [more...]
May 09, 2019
Projecting Global Urban Area Growth Through 2100 Based on Historical Time Series Data and Future Scenarios
Study provides country-specific urban area growth models and the first dataset on country-level urba [more...]
May 05, 2019
Calibrating Building Energy Demand Models to Refine Long-Term Energy Planning
A new, flexible calibration approach improved model accuracy in capturing year-to-year changes in bu [more...]
May 03, 2019
Calibration and Uncertainty Analysis of Demeter for Better Downscaling of Global Land Use and Land Cover Projections
Researchers improved the Demeter model’s performance by calibrating key parameters and establi [more...]
Apr 22, 2019
Representation of U.S. Warm Temperature Extremes in Global Climate Model Ensembles
Representation of warm temperature events varies considerably among global climate models, which has [more...]
List all highlights (possible long download time)