Using molecular-scale approaches to understand soil chemical processes

土壤中的化学反应通常控制着自然系统中营养物质和污染物的流动性、毒性和可用性。因此，准确了解土壤化学反应是如何进行的，对于评估环境命运至关重要。土壤化学研究中一个反复出现的主题是，最具反应性的土壤表面不是占土壤90-95%的大块晶体矿物质，而是在较大土壤颗粒上形成涂层的高反应性低结晶纳米矿物质。 本研究的目的是更好地了解这些阶段（水铁矿和磷酸二钙），这是重要的环境和农艺原因的持久性和反应性的因素。为了实现这一目标，我们将在加拿大光源使用基于同步加速器的X射线吸收光谱（XAS）。这种方法提供了直接测量纳米矿物结构和污染物如何在水合条件下与这些矿物结合的细节。 该计划的这项研究将提高对土壤化学的基本认识，其结果对温带和热带气候的农业，环境地球化学和污染物化学都很重要。该项目还探讨了土壤化学过程与金属有机框架之间的关系;这可能会导致我们对土壤有机质的理解取得重大进展。最后，EEMS技术将用于广泛的自然资源相关问题，包括油砂提取，评估采矿矿石和尾矿，以及矿产勘探。

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.