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Environmental Geochemistry

PhD student Dana Thomas and Kate Maher in Iceland. Dana is studying natural CO2-rich springs as analogues for CO2 injection into basaltic rocks. In addition to assessing carbonate mineral formation, Dana is evaluating the potential release of arsenic (As) and nickel (Ni) to groundwater.
California Columbine, Cedars Preserve.
PhD student Natalie Johnson and M.S. student Valerie Rosen collect waters from a pH 11 spring in serpentine rocks, Cedars Preserve, CA.
M.S. student Valerie Rosen and PhD student Pablo Garcia del Real collect water samples and carbonate minerals from a high pH spring in the Cedars Preserve, CA.
PhD student Cynthia McClain scopes out a potential sampling site to examine Cr weathering from ultramafic rocks at the McLaughlin Preserve, CA.
PhD student Cynthia McClain discovers an old monitoring well at the McLaughlin Preserve, CA.
Human activities, such as agriculture, may be promoting groundwater contamination.
Groundwater contamination by human activities still remains an outstanding challenge.

Environmental Geochemistry

>> See our research in the news: "Opal offers fast, lasting remedy for uranium contamination", Stanford News

>> Learn about geochemistry in small spaces: "Poresize dependent geochemistry", a video about enhanced metal sorption in tiny pores, by GCEP Distinguished Student Lecturer and EIG PhD student Joey Nelson.

Research Overview: 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).