Molecular signature and sources of biochemical recalcitrance of organic C in Amazonian Dark Earths

Details Molecular signature and sources of biochemical recalcitrance of organic C in Amazonian Dark Earths Molecular signature and sources of biochemical recalcitrance of organic C in Amazonian Dark Earths

May 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007gecoa..71.2285s&link_type=abstract

Geochimica et Cosmochimica Acta, Volume 71, Issue 9, p. 2285-2298.

Biology

Quantitative Biology

Biomolecules

Scientific paper

Amazonian Dark Earths (ADE) are a unique type of soils developed through intense anthropogenic activities that transformed the original soils into Anthrosols throughout the Brazilian Amazon Basin. We conducted a comparative molecular-level investigation of soil organic C (SOC) speciation in ADE (ages between 600 and 8700 years B.P.) and adjacent soils using ultraviolet photo-oxidation coupled with 13C cross polarization-magic angle spinning nuclear magnetic resonance (CP-MAS NMR), synchrotron-based Fourier transform infrared-attenuated total reflectance (Sr-FTIR-ATR) and C (1s) near edge X-ray absorption fine structure (NEXAFS) spectroscopy to obtain deeper insights into the structural chemistry and sources of refractory organic C compounds in ADE. Our results show that the functional group chemistry of SOC in ADE was considerably different from adjacent soils. The SOC in ADE was enriched with: (i) aromatic-C structures mostly from H- and C-substituted aryl-C, (ii) O-rich organic C forms from carboxylic-C, aldehyde-C, ketonic-C and quinine-C, and (iii) diverse group of refractory aliphatic-C moieties. The SOC in adjacent soils was predominantly composed of O-alkyl-C and methoxyl-C/N-alkyl-C structures and elements of labile aliphatic-C functionalities. Our study suggests that the inherent molecular structures of organic C due to selective accumulation of highly refractory aryl-C structures seems to be the key factor for the biochemical recalcitrance and stability of SOC in ADE. Anthropogenic enrichment with charred carbonaceous residues from biomass-derived black C (BC) is presumed to be the precursor of these recalcitrant polyaromatic structures. Our results also highlight the complementary role that might be played by organic C compounds composed of O-containing organic C moieties and aliphatic-C structures that persisted for millennia in these anthropic soils as additional or secondary sources of chemical recalcitrance of SOC in ADE. These organic C compounds could be the products of: (i) primary recalcitrant biomolecules from non-BC sources or (ii) secondary processes involving microbial mediated oxidative or extracellular neoformation reactions of SOC from BC and non-BC sources; and stabilized through physical inaccessibility to decomposers due to sorption onto the surface or into porous structures of BC particles, selective preservation or through intermolecular interactions involving clay and BC particles.

Affiliated with

Also associated with

No associations

Rating

Molecular signature and sources of biochemical recalcitrance of organic C in Amazonian Dark Earths does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Molecular signature and sources of biochemical recalcitrance of organic C in Amazonian Dark Earths, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Molecular signature and sources of biochemical recalcitrance of organic C in Amazonian Dark Earths will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-767122