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Iron-Bound Organic Carbon in Forest Soils: Quantification and Characterization
Author
Zhao, Q.Poulson, Simon R.
Obrist, Daniel
Sumaila, S.
Dynes, James J.
McBeth, Joyce M.
Yang, Y.
Date
8/24/2016Type
ArticleAbstract
Iron oxide minerals play an important role in stabilizing organic carbon (OC) and regulating the biogeochemical cycles of OC on the earth surface. To predict the fate
of OC, it is essential to understand the amount, spatial variability, and characteristics of Fe-bound OC in natural soils.
In this study, we investigated the concentrations and characteristics of Fe-bound OC in soils collected from 14 forests
in the United States and determined the impact of ecogeographical variables and soil physicochemical properties on
the association of OC and Fe minerals. On average, Fe-bound
OC contributed 37.8 % of total OC (TOC) in forest soils.
Atomic ratios of OC : Fe ranged from 0.56 to 17.7, with values of 1–10 for most samples, and the ratios indicate the
importance of both sorptive and incorporative interactions.
The fraction of Fe-bound OC in TOC (fFe-OC) was not related to the concentration of reactive Fe, which suggests that
the importance of association with Fe in OC accumulation
was not governed by the concentration of reactive Fe. Concentrations of Fe-bound OC and fFe-OC increased with latitude and reached peak values at a site with a mean annual
temperature of 6.6 ◦C. Attenuated total reflectance–Fourier
transform infrared spectroscopy (ATR-FTIR) and near-edge
X-ray absorption fine structure (NEXAFS) analyses revealed
that Fe-bound OC was less aliphatic than non-Fe-bound OC.
Fe-bound OC also was more enriched in 13C compared to
the non-Fe-bound OC, but C/ N ratios did not differ substantially. In summary, 13C-enriched OC with less aliphatic
carbon and more carboxylic carbon was associated with Fe
minerals in the soils, with values of fFe-OC being controlled
by both sorptive and incorporative associations between Fe
and OC. Overall, this study demonstrates that Fe oxides play
an important role in regulating the biogeochemical cycles of
C in forest soils and uncovers the governing factors for the
spatial variability and characteristics of Fe-bound OC.
Permanent link
http://hdl.handle.net/11714/943Additional Information
Rights | Creative Commons Attribution 4.0 United States |
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Rights Holder | Author(s) |