Model Assessment of Biogeochemical Controls on Dissolved Organic Carbon Partitioning in an Acid Organic Soil

A chemical model (constructed in the ORCHESTRA modeling framework) of an organic soil horizon was used to describe soil solution data (10 cm depth) and assess if seasonal variations in soil solution dissolved organic carbon (DOC) could be explained by purely abiotic (geochemical controls) mechanisms...

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Bibliographic Details
Published in:Environmental science & technology 2005-10, Vol.39 (20), p.8057-8063
Main Authors: Lumsdon, David G, Stutter, Marc I, Cooper, Richard J, Manson, John R
Format: Article
Language:English
Subjects:
Acids
Biogeochemistry
Biological activity
Carbon
Carbon - analysis
Cations
Dissolved organic carbon
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
Exact sciences and technology
Geochemistry
Humic acids
Humic Substances - analysis
Hydrogen-Ion Concentration
Models, Chemical
Organic chemistry
Organic matter
organic soils
Pollution, environment geology
Q1
Scotland
Seasonal variations
Seasons
Soil - analysis
Soil and rock geochemistry
Soil Microbiology
soil temperature
Soils
Surficial geology
Temperature
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Summary:A chemical model (constructed in the ORCHESTRA modeling framework) of an organic soil horizon was used to describe soil solution data (10 cm depth) and assess if seasonal variations in soil solution dissolved organic carbon (DOC) could be explained by purely abiotic (geochemical controls) mechanisms or whether factors related to biological activity are needed. The NICA-Donnan equation is used to describe the competitive binding of protons and cations and the charge on soil organic matter. Controls on organic matter solubility are surface charge and a parameter, γ, that accounts for the distribution of humic molecules between hydrophobic and hydrophilic fractions. Calculations show that the variations in solute chemistry alone are not sufficient to account for the observed variations of DOC, but factors that alter γ, such as biological activity, are. Assuming that DOC in organic soils is derived from soluble humic material and that γ is modified seasonally due to biological activity (with monthly soil temperature used as a surrogate for biological activity) we are able to model the observed seasonality of soil solution DOC over a 10-year period. Furthermore, with modeled DOC coupled to other geochemical processes we also model soil solution pH and Al concentrations.
ISSN:0013-936X
1520-5851
DOI:10.1021/es050266b