Analysis of Natural Aquifer Sediments to Characterize Potential Intercalation of TCE by Constituent Clay Minerals: A Rapid-Access Research Proposal Submitted to The Pacific Northwest National Laboratory
EMSL Project ID
43792
Abstract
Pump-and-treat systems are widely used to remediate hazardous waste sites wherein groundwater is contaminated by compounds such as TCE (trichloroethene). It is well known that removal of contaminant mass by pump and treat becomes less effective over time, with a persistent mass discharge causing greatly extended operational periods. One mechanism potentially responsible for this persistent mass discharge is “back diffusion�, wherein dissolved contaminant stored in lower-permeability layers diffuses into the higher-permeability zones that are more readily swept via pump and treat. Because the lower-permeability layers typically contain high fractions of clay minerals, a question of great interest is whether contaminant-clay interactions may influence the back-diffusion process. For example, intercalation of TCE into the interlayer spaces of clay minerals could possibly increase the time that it takes for TCE in the interlayer spaces to diffuse into the pore spaces within the lower-permeability region, thereby further constraining the mass-transfer process. The primary objective of this research is to determine if TCE molecules are present in interlayer spaces of clay minerals associated with aquifer sediment samples collected from a TCE-contaminated site in AZ. The minerals that we will analyze include smectite, mica, kaolinite, and illite. Samples with and without exposure to TCE will be characterized via X-ray diffraction (XRD) to evaluate potential differences in d-spacing.
This project relates to the EMSL Science Themes of the Science of Interfacial Phenomena and the Geochemistry/Biogeochemistry and Subsurface Science Theme. This research could help to advance our understanding of the role that interactions between organic molecules and internal surfaces of clays have in mediating transport of groundwater contaminants through porous media. The experiments that we are proposing help improve the linkage of fundamental studies of molecular geochemistry and environmental chemistry to field-scale contaminant transport processes, thereby enhancing our understanding of the transport and remediation of organic contaminants in subsurface environments.
Project Details
Project type
Limited Scope
Start Date
2011-06-27
End Date
2011-08-27
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Matthieu DE, III, M Brusseau, GR Johnson, ME Bowden and JL Artiola. 2012. "Intercalation of TCE by Sediment-Associated Clay Minerals & Implications for Low-Concentration Elution Tailing & Back Diffusion." Chemosphere.