Abstract
Imposed redox frequency and amplitude flux in the study of iron biogeochemical dynamics
Mineralogical magazine, Vol.76(6), p.2549
Goldschmidt 2012
2012
Abstract
The chemical stability and microbial bioavailability of iron (Fe) oxides in soils, and the coupling between carbon (C), Fe and phosphorous (P) cycles, depends on biogeochemical conditions and their temporal variability. To assess the impact of periodic redox fluctuations commonly found in variably saturated soils, a custom bioreactor system was developed in which redox fluctuations (i.e. Eh frequency and amplitude) were imposed via N (sub 2) and O (sub 2) gas exchange with Bisley, Puerto Rico, (CZO) soil suspensions while allowing for sub-sampling of Fe, P, CO (sub 2) and microbial DNA. Characterization of Bisley site soils included variable temperature (super 57) Fe-Mossbauer spectroscopy (at 298, 140, 70, and 15K), X-ray diffraction (XRD) and chemical extractions of operationally defined Fe pools to evaluate Fe phase heterogeneity. Extraction data show that 20% of the total Fe oxide pool is associated with the dithionite-citrate-bicarbonate (DCB) fraction, of which half is associated with the citrate-ascorbic acid (CA) fraction. Mossbauer spectra show quadrapole distribution sites for Fe (super II) /Fe (super III) in clay and a hyperfine distribution site (sextet) that closely resembles that of nano-goethite. The difference between averaged sextet spectral areas at 70 and 15K (11.7% relative abundance) may correlate with the % abundance of CA extracted Fe. Currently, microbial fingerprinting techniques (i.e. denaturing gradient gel electrophoresis (DGGE) and ribosomal intergenic transcribed spacer analysis (RISA)) are being used to characterize changes in bacterial community composition in response to bioreactor redox oscillations. Finally, process-based kinetic model simulations have been used to describe and test mechanisms of Fe reduction, abiotic transformations, phase partitioning, and microbial population growth in the Bisley (CZO) soils. Preliminary simulations show that Fe concentrations can be reproduced closely by adjusting the time period in oxic and anoxic cycles in accord with experimental conditions.
Details
- Title: Subtitle
- Imposed redox frequency and amplitude flux in the study of iron biogeochemical dynamics
- Creators
- Jared Wilmoth - University of Georgia, Department of Crop and Soil Sciences Athens, GA USA United StatesChristof MeileBrian GinnTim PasakarnisSteven HallMichelle M SchererAaron Thompson
- Resource Type
- Abstract
- Publication Details
- Mineralogical magazine, Vol.76(6), p.2549
- Conference
- Goldschmidt 2012
- Publisher
- Mineralogical Society
- ISSN
- 0026-461X
- eISSN
- 1471-8022
- Alternative title
- Goldschmidt 2012 abstract volume
- Language
- English
- Date published
- 2012
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9984202132702771
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