Doug Mateas (Illinois) co-authored an article entitled "In situ stabilization of NAPL contaminant source-zones as a remediation technique to reduce mass discharge and flux to groundwater," published in the Journal of Contaminant Hydrology on July 25, 2017.

Doug's co-authors were Geoffrey R. Tick and Kenneth C. Carroll.

The Journal of Contaminant Hydrology is an international journal publishing scientific articles pertaining to the contamination of groundwater. Emphasis is placed on investigations of the physical, chemical, and biological processes influencing the behavior of organic and inorganic contaminants in both the unsaturated (vadose) and saturated zones. Articles on contamination of surface water are not included unless they specifically deal with the link between surface water and groundwater.

The journal's scope embraces a wide range of topics including: experimental investigations of contaminant sorption, diffusion, transformation, volatilization and transport in the unsaturated and saturated zones; characterization of soil and aquifer properties only as they influence contaminant behavior; development and testing of mathematical models of contaminant behavior; innovative techniques for restoration of contaminated sites; and development of new tools or techniques for monitoring the extent of soil and groundwater contamination.

Abstract

Widely used flushing and in situ destruction based remediation techniques (i.e. pump-and treat, enhanced-solubilization, and chemical oxidation/reduction) for sites contaminated by nonaqueous phase liquid (NAPL) contaminant sources have been shown to be ineffective at complete mass removal and reducing aqueous-phase contaminant of concern (COC) concentrations to levels suitable for site closure. A remediation method was developed to reduce the aqueous solubility and mass-flux of COCs within NAPL through the in situ creation of a NAPL mixture source-zone. In contrast to remediation techniques that rely on the rapid removal of contaminant mass, this technique relies on the stabilization of difficult-to-access NAPL sources to reduce COC mass flux to groundwater. A specific amount (volume) of relatively insoluble n-hexadecane (HEXDEC) or vegetable oil (VO) was injected into a trichloroethene (TCE) contaminant source-zone through a bench-scale flow cell port (i.e. well) to form a NAPL mixture of targeted mole fraction (TCE:HEXDEC or TCE:VO). NAPL-aqueous phase batch tests were conducted prior to the flow-cell experiments to evaluate the effects of various NAPL mixture ratios on equilibrium aqueous-phase concentrations of TCE to design optimal NAPL (HEXDEC or VO) injection volumes for the flow-cell experiments. The NAPL-stabilization flow-cell experiments initiated and sustained significant reductions in COC concentration and mass flux due to a combination of both reduced relative permeability (increased NAPL-saturation) and via modification of NAPL composition (decreased TCE mole fraction). Variations in remediation performance (i.e. impacts on TCE concentration and mass flux reduction) between the different HEXDEC injection volumes were relatively minor, and therefore inconsistent with Raoult's Law predictions. This phenomenon likely resulted from non-uniform mixing of the injected HEXDEC with TCE in the source-zone. VO injection caused TCE concentrations and mass-flux to decrease more rapidly than with HEXDEC injections. This phenomenon occurred because the injected VO was observed to mix more uniformly with TCE in the source-zone due to a lower mobilization potential. The relative lower density differences (buoyancy effects) between VO and the flushing solution (water) was the primary factor contributing to the lower mobilization potential for VO. Overall, this study indicated that the delivery of HEXDEC or VO into the toxic TCE source-zone was effective in significantly reducing contaminant aqueous-phase concentration and mass-flux. However, the effectiveness of this in situ NAPL stabilization technique depends on source delivery, uniform mixing of amendment, and that the amendment remains immobilized within and around the NAPL contaminant source.

More Information

Read the article: http://www.sciencedirect.com/science/article/pii/S0169772216302911
Read the Journal: Journal of Contaminant Hydrology.
For consultation regarding in situ stabilization of NAPL contaminant source-zones, contact Doug Mateas at This email address is being protected from spambots. You need JavaScript enabled to view it..
Learn more about Doug at: https://www.linkedin.com/in/dougmateas/