Research Project Full Title: Biogeochemical Processes that Control Natural Attenuation of Trichloroethylene in Low Permeability Zones
Researchers: University of Illinois- Urbana Champaign; Colorado School of Mines, Hemholtz Munich University; CDM Federal Program Corporation.
Sponsor(s): DoD Strategic Environmental Research and Development Program (SERDP)
Full Abstract: It is widely recognized that the most challenging hazardous waste sites for groundwater remediation are those with DNAPL sources in highly heterogeneous aquifers. At DoD sites with a history of contamination, DNAPL has slowly dissolved from trapped ganglia or pools resulting in groundwater plumes with high levels of contamination. Dissolved contaminants in high permeability zones (HPZs) within these plumes can diffuse over long time periods into low permeability zones (LPZs) such as rock matrices, clay aquitards and lenses, i.e., “matrix diffusion.” When contaminant mass in the HPZ is depleted through natural attenuation or active remediation, back-diffusion of contaminants from LPZs into groundwater flowing through HPZs can occur for decades. The overall objectives of our SERDP proposal are to quantify the biotic and abiotic attenuation mechanisms that impact the fate of trichloroethylene (TCE) within and at the boundaries of LPZs comprised of clays and silts, and to incorporate these processes into a computationally efficient model that can be used to directly address key questions regarding natural attenuation time scales and cleanup at TCE-impacted sites. We hypothesize that a suite of naturally occurring biotic and abiotic mechanisms may serve to significantly attenuate diffusive flux of TCE and TCE degradation products from LPZs over long time periods, resulting in decreased impacts (both magnitude and timeframe) of back-diffusion on groundwater quality. These mechanisms may occur within the LPZ itself, or at the LPZ-HPZ interface. Furthermore, we hypothesize that biogeochemical conditions (e.g., reducing, aerobic, Fe minerals, organic carbon) will impact these naturally occurring mechanisms.
Additional Links: Strategic Environmental Research and Development Program (SERDP): https://www.serdp-estcp.org