Our research group is interested in the chemistry that occurs at the interface between minerals and water. With a combination of microscopic and spectroscopic techniques in the laboratory, we use the tools of analytical chemistry to probe geochemical systems in several different environmental contexts.
One of our areas of interest is the geochemistry of clay minerals - silicate minerals with sheet-like structures - which are major components of soils and sediments. One of the unique properties of these minerals is their ability to swell by incorporating varying amounts of water and exchangeable cations between the layers. The swelling of clay minerals plays a major role in the transport of nutrients and pollutants in the environment, waste containment technologies, and borehole stability. To date, commonly used techniques for studying swelling in the laboratory have only been able to measure the average change in layer separation of many clay layers and consequently are limited in the information they can provide. Our research group has developed a new method to study this process using atomic force microscopy (AFM) to investigate clay swelling in situ in an aqueous environment. AFM is used to produce three dimensional images of the surface of a material, and unlike a conventional optical microscope, it can "see" features up to a million times smaller than the width of a human hair. With our technique, changes in swelling within individual isolated stacks of clay layers can be directly measured in solutions that mimic environmental conditions.
Another of our projects focuses on colloids in natural waters. Colloids are the small, solid particulates that remain suspended in water. Because colloidal particles are charged and have a very large surface area relative to their volume, they often act as a carrier for contaminants in natural waters. In many situations, colloids are also reactive intermediates between dissolved metal species and larger precipitates that eventually settle to the streambed. Consequently, the stability of the colloidal phase will play a major role in the mobility of metal species and other contaminants. In collaboration with Ellen Herman in the Department of Geology, we are using a combination of field sampling, chemical and mineralogical characterization in the laboratory, and mixing studies in a flume to investigate the range of both chemical and hydrological variables that affect colloid formation and stability.
Associate Professor of Chemistry; Director, Environmental Studies Program
211 Rooke Chemistry Bldg
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