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Organo-organic and organo-mineral interfaces in soil at the nanometer scale.

Angela R PossingerMichael J ZachmanAkio EndersBarnaby D A LevinDavid A MullerLena F KourkoutisJohannes Lehmann
Published in: Nature communications (2020)
The capacity of soil as a carbon (C) sink is mediated by interactions between organic matter and mineral phases. However, previously proposed layered accumulation of organic matter within aggregate organo-mineral microstructures has not yet been confirmed by direct visualization at the necessary nanometer-scale spatial resolution. Here, we identify disordered micrometer-size organic phases rather than previously reported ordered gradients in C functional groups. Using cryo-electron microscopy with electron energy loss spectroscopy (EELS), we show organo-organic interfaces in contrast to exclusively organo-mineral interfaces. Single-digit nanometer-size layers of C forms were detected at the organo-organic interface, showing alkyl C and nitrogen (N) enrichment (by 4 and 7%, respectively). At the organo-mineral interface, 88% (72-92%) and 33% (16-53%) enrichment of N and oxidized C, respectively, indicate different stabilization processes than at organo-organic interfaces. However, N enrichment at both interface types points towards the importance of N-rich residues for greater C sequestration.
Keyphrases
  • organic matter
  • electron microscopy
  • water soluble
  • high resolution
  • magnetic resonance
  • single molecule
  • mass spectrometry
  • ionic liquid
  • solar cells
  • contrast enhanced
  • visible light