Sorptive fractionation of organic matter and formation of organo-hydroxy-aluminum complexes during litter biodegradation in the presence of gibbsite

K. Heckman, A. S. Grandy, X. Gao, M. Keiluweit, K. Wickings, K. Carpenter, Jon Chorover, Craig Rasmussen

Research output: Contribution to journalArticle

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Abstract

Solid and aqueous phase Al species are recognized to affect organic matter (OM) stabilization in forest soils. However, little is known about the dynamics of formation, composition and dissolution of organo-Al hydroxide complexes in microbially-active soil systems, where plant litter is subject to microbial decomposition in close proximity to mineral weathering reactions. We incubated gibbsite-quartz mineral mixtures in the presence of forest floor material inoculated with a native microbial consortium for periods of 5, 60 and 154days. At each time step, samples were density separated into light (<1.6gcm-3), intermediate (1.6-2.0gcm-3), and heavy (>2.0gcm-3) fractions. The light fraction was mainly comprised of particulate organic matter, while the intermediate and heavy density fractions contained moderate and large amounts of Al-minerals, respectively. Multi-method interrogation of the fractions indicated the intermediate and heavy fractions differed both in mineral structure and organic compound composition. X-ray diffraction analysis and SEM/EDS of the mineral component of the intermediate fractions indicated some alteration of the original gibbsite structure into less crystalline Al hydroxide and possibly proto-imogolite species, whereas alteration of the gibbsite structure was not evident in the heavy fraction. DRIFT, Py-GC/MS and STXM/NEXAFS results all showed that intermediate fractions were composed mostly of lignin-derived compounds, phenolics, and polysaccharides. Heavy fraction organics were dominated by polysaccharides, and were enriched in proteins, N-bearing compounds, and lipids. The source of organics appeared to differ between the intermediate and heavy fractions. Heavy fractions were enriched in 13C with lower C/N ratios relative to intermediate fractions, suggesting a microbial origin. The observed differential fractionation of organics among hydroxy-Al mineral types suggests that microbial activity superimposed with abiotic mineral-surface-mediated fractionation leads to strong density differentiation of organo-mineral complex composition even over the short time scales probed in these incubation experiments. The data highlight the strong interdependency of mineral transformation, microbial community activity, and organic matter stabilization during biodegradation.

Original languageEnglish (US)
Pages (from-to)667-683
Number of pages17
JournalGeochimica et Cosmochimica Acta
Volume121
DOIs
StatePublished - Nov 15 2013

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gibbsite
Fractionation
Biodegradation
Aluminum
Biological materials
Minerals
biodegradation
litter
fractionation
aluminum
organic matter
mineral
polysaccharide
hydroxide
Polysaccharides
stabilization
Bearings (structural)
Stabilization
Chemical analysis
imogolite

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Sorptive fractionation of organic matter and formation of organo-hydroxy-aluminum complexes during litter biodegradation in the presence of gibbsite. / Heckman, K.; Grandy, A. S.; Gao, X.; Keiluweit, M.; Wickings, K.; Carpenter, K.; Chorover, Jon; Rasmussen, Craig.

In: Geochimica et Cosmochimica Acta, Vol. 121, 15.11.2013, p. 667-683.

Research output: Contribution to journalArticle

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AU - Grandy, A. S.

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AU - Keiluweit, M.

AU - Wickings, K.

AU - Carpenter, K.

AU - Chorover, Jon

AU - Rasmussen, Craig

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