Environmental Geochemistry

Our research in this area determines how chemical reactions between fluids and solids may attenuate, or exacerbate, groundwater contamination. We are currently focusing on several different types of contaminants, including metals and actinides/radionuclides. To conduct these studies we use geochemical measurements, isotopic tracers and reactive transport models.Currently, groundwater contamination due to chemicals introduced directly by agricultural and industrial activity is a well-recognized problem throughout the world. In contrast, natural or geologic groundwater contamination, including trace metals and radionuclides, is emerging as an environmental and human health problem of unsurpassed magnitude. Our research thus focuses on both groundwater contamination directly associated with human activity, and natural or geologic contaminants that may be enhanced by land or water use practices.  Some examples of our current research are described below.

1. Uranium fate and transport in the environment: We are currently examining the incorporation of uranium into amorphous silica as an approach for remediating uranium contaminated aquifers. To understand how uranium is incorporated into amorphous silica (e.g., opal) we are conducting experimental studies and using spectroscopic approaches to determine the molecular configuration of uranium after incorporation.  In addition, we are developing uranium isotopes as an approach for tracking the fate of uranium in subsurface. 
2. The effect of pore size on metal retention: Tiny nanometer-size pores called "mesopores" are common in natural porous media and often dominate the interfaces between solids and fluids. As such, these tiny pores can determine the reactivity of metals and contaminants. We are investigating the reactivity of metals in these pores to determine how they influence the aquifer scale behavior of metal and radionuclide contaminants.
3. Chromium (VI) generation from weathering of Cr-bearing rocks, and potential impacts from human activities: Chromium (Cr) is an example of an emerging geological contaminant—in many parts of the world natural Cr contamination jeopardizes surface and groundwater quality, and release of this contaminant may be further enhanced by human activities. In this project, we are combining field studies, reactive transport modeling and an analysis of farming practices to assess the future of chromium contamination in California groundwater, an approach that may be appropriate for other emerging geologic contaminants (e.g., As, Se and U).