In this study, a combination of solid-state NMR techniques was employed to investigate the molecular assemblage of soil organic matter (OM) in its native state, yielding spatial arrangement data at the nanometer scale. An OM model assemblage based on this molecular-level information is discussed and tested in terms of (i) the role played by very small amounts of a completely miscible organic solvent in water in perturbing the association of OM and liberating organic matter from the geomatrix; these experiments can be viewed loosely as the whole soil analogs to those carried out on extracted humic materials, (ii) the role of hydration in the sorption of three pesticides of varying polarity by both time-course studies and batch sorption experiments, and (iii) the wettability of dehydrated OM in sediments and the role of shear. This work complements previous wetting experiments performed on soils by low-field NMR and, when combined, this set of studies gives consistent results that (i) both physical rearrangements as well as changes in the molecular interactions within the organic matrix take place during any sorption process and that (ii) hydration strongly influences these interactions. Finally, a series of engineered soil surrogates were synthesized to investigate the role of the different molecular moieties and OM hydration in pesticide binding.

Probing the role of organic matter arrangement and composition at the geosorbent-water interface

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.