Water Trapping Dynamics in Carbohydrate-Populated Clay Nanoaggregates

Abstract:

A fundamental understanding of the long-term residence of soil moisture requires nanoscale to molecular-scale investigations of water dynamics in organo-mineral nanoaggregates. Of particular interest are smectite-type expandable clay minerals, which are known to play a critical role in the trapping of fluids and carbons. In my group, we seek to gain new insights on water trapping dynamics within montmorillonite interlayer nanopores populated with carbohydrate compounds of different structures. Carbohydrates, which include small compounds (sugars) and complex biopolymers (cellulose, starch), are intimately involved in the cycling of water and carbon. Notably, biological secretions of carbohydrates are implicated in the retention of hydrated soil pores near plant roots and microbial cells, despite severe dryness in the bulk soil. To study the dynamics of water trapping in carbohydrate-montmorillonite nanoaggregates, we have applied a combination of in situ moisture dependent X-ray diffraction, infrared, nuclear magnetic resonance, and mass spectrometry to capture changes in interlayer nanopore sizes, exchangeable water populations, mechanisms of carbohydrate-mineral interactions, and quantitative analysis of water retention, respectively. This talk will present new insights from our nanoscale and molecular-scale data with respect to the influence of carbohydrates in restructuring smectite interlayer nanopores and water trapping dynamics, with important implications for predicting moisture retention in engineered or natural clay environments.