Controls of bioorganic constituents of soils in the confined regions between mineral surfaces on nucleation and aggregation
EMSL Project ID
50824
Abstract
The aims of the proposed research are to: 1) Determine the structure of the near surface water layer in the confined region between approaching mineral surfaces and determine the impact of electrolytes and bioorganic ligands on that structure, and 2) Measure the effect of oxalate on hydration structure at the hematite (001) and (012) surfaces, calculate the face-specific oxalate binding energies and chemical potentials of the relevant species, and directly image hematite growth of in the presence of oxalate. To accomplish these aims, we will apply a combination of SFG, TEM, AFM and classical DFT to define the structure of water at the mineral interface, determine the near-surface distribution of ionic species, and track mineral nucleation and aggregation in situ. We will perform these measurements and simulations for the common soil minerals hematite and mica and the carboxylated bioorganic ligands oxalate and citrate. The interaction between mineral surfaces and organic moieties common in soils has widespread impacts on environmental processes, including nucleation of new soil minerals, the aggregation of mineral nanoparticles and the persistence of soil organic matter (SOM). For example, organic films can drive mineral nucleation events, interactions of soluble bioorganic molecules with growing mineral surfaces can lead to growth inhibition or acceleration, and interactions with solution species can direct nucleation pathways via precursor phases. Conversely, long residence times of SOM are commonly attributed to sorption of organic species to mineral surfaces, which provide reactive sites for physical and chemical stabilization that prevent SOM degradation by enzymes and microbes. Our recent work using EMSL facilities revealed: 1) the important role of bioorganic molecules in dramatically altering growth of hematite to occur by "oriented attachment" of new hematite nanoparticles, and 2) interfacial water is highly structured with distinct molecular orientations on muscovite mica, but the order depends on electrolyte type/concentration. However, major gaps exist in our understanding of both phenomena. How the hematite-oxalate interface drives both the formation of new particles and their assembly into high surface area, highly reactive structures is unclear; and unexplored is the impact that both soil organic molecules and confinement of water between mineral surfaces separated by nm-scale distances has on water structure and, in turn, on organic adsorption and stability. By filling those gaps our proposed research will provide new insights into the molecular mechanisms of SOM-mineral interactions and their outcomes.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2019-10-01
End Date
2021-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Kerisit S.N., and J.J. De Yoreo. 2020. "Effect of Hydrophilicity and Interfacial Water Structure on Particle Attachment." Journal of Physical Chemistry C 124, no. 9:5480-5488. PNNL-SA-149628. doi:10.1021/acs.jpcc.9b12053