Using molecular-scale approaches to understand soil chemical processes

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Chemical reactions in soils often control the mobility, toxicity, and availability of nutrients and contaminants in natural systems. Understanding precisely how soil chemical reactions proceed is therefore vital in assessing environmental fate. A recurring theme in the study of soil chemistry is that the most reactive soil surfaces are not the bulk crystalline minerals that make up 90-95% of soil, but instead are the highly reactive poorly-crystalline nano-minerals that form coatings on larger soil particles. The objective of this research is to better understand the factors that lead to the persistence and reactivity of two of these phases (ferrihydrite and dicalcium phosphates) that are important for both environmental and agronomic reasons. To accomplish this objective, we will use synchrotron-based X-ray Absorption Spectroscopy (XAS) at the Canadian Light Source. This method provides direct measurement of both the nano-mineral structure and details of how contaminants bond to those those minerals under hydrated conditions. This research in this program will improve the fundamental understanding of soil chemistry and the results will be important for agriculture in both temperate and tropical climates, environmental geochemistry and contaminant chemistry. This project also explores relationships between soil chemical processes with metal-organic frameworks; this could lead to major advances in our understanding of soil organic matter. Finally, the EEMS technique will be useful for a wide range of natural resource-related problems, including oil sands extractions, evaluating mining ores and tailings, and mineral exploration.