Utilizing column experiments to determine the mobility of dissolved low concentration perchloroethylene in a remediated aquifer material
Stelmack, William Joseph
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Oxidation of dense non-aqueous phase liquids (DNAPLs) by the introduction of dissolved potassium permanganate solutions into the subsurface has emerged as a viable technology for the remediation of contaminated sites. Previous studies examining the extent of sorption of hydrophobic organic contaminants to aquifer materials have determined that the oxidation of soil organic matter can have a measurable effect on the extent of sorption of these chemicals. The hypothesis tested in this work was that a permanganate treatment would result in a measurable increase in the retardation of low concentration perchloroethylene (PCE) due to increases in the accessibility of "hard" carbon adsorption sites. To test the hypothesis, a series of laboratory column experiments were conducted to probe the migration of dissolved, low concentration perchloroethylene (25.0 μg L -1 or 0.01% of solubility) through bulk aquifer material collected from Canadian Forces Base Borden, Ontario, Canada. Column experiments were conducted with unaltered and oxidant treated bulk aquifer material using identical experiment methodology. The untreated aquifer material displayed a perchloroethylene retardation factor of 1.7. The retardation factor observed in the oxidant treated material was 1.5 with a concomitant decrease in the fraction organic carbon content (43% reduction) attributable to oxidation by the potassium permanganate treatment. The organic carbon normalized sorption distribution coefficient (Koc) determined from the above data are 630 ± 10 ml/g and 810 ± 320 ml/g for the untreated and oxidant treated material. Hence, the results do not support the hypothesis. Because the differences are small and the apparatus background retardation is significant in these experiments, the result may be considered equivocal.