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Extent of Sorption and Biodegradation of Perfluorooctanoic Acid (PFOA) and Perfluorooctanesulfonic Acid (PFOS) in Aquifer Sediment
Citation:
Ferrey, M. AND J. T. WILSON. Extent of Sorption and Biodegradation of Perfluorooctanoic Acid (PFOA) and Perfluorooctanesulfonic Acid (PFOS) in Aquifer Sediment. Presented at The Tenth International In Situ and On-Site Bioremediation Symposium, Baltimore, MD, May 05 - 08, 2009.
Impact/Purpose:
To share information.
Description:
Fluoropolymers such as Perfluorooctanoic Acid (PFOA) and Perfluorooctanesulfonic acid (PFOS) were used provide non-stick surfaces on cookware and waterproof, breathable clothing. PFOA is very persistent in the environment and is found at low concentrations in the environment and in the blood of the general U.S. population. Studies indicated that PFOA can cause developmental and other adverse effects in laboratory animals. PFOA appears to persist in the human body for many years. During its years of operation, the Washington County Sanitary Landfill near St. Paul, Minnesota accepted both municipal and industrial solid waste. Several years of ground water monitoring performed by the MPCA indicates that some of the waste disposed of at this landfill contained PFOA. The PFOA has leached into the ground water and moved with the ground-water flow. It has also moved deeper, affecting the bedrock aquifer where it was found at low levels. As part of a risk evaluation, a microcosm study was performed to predict transport and fate of PFOA and PFOS in leachate from the landfill. Realistic concentrations of PFOA and PFOS were added to microcosms constructed with sediment that was collected from beneath the water table at the Washington County Landfill. Microcosms were then sealed and incubated in the laboratory. Three microcosms of each treatment were sacrificed at quarterly intervals for analysis. Aqueous concentrations of PFOA and PFOS increased in the microcosms over the incubation period. Shortly after the addition of PFOS and PFOA, the adsorption constant, Kd, averaged 0.9748 L Kg-1 for PFOA and 1.1503 L Kg-1 for PFOS. At 574 days, the Kd averaged 0.0690 L Kg-1 and 0.1973 L Kg-1 for PFOA and PFOS, respectively. Corresponding retardation constants were 2.3 and 10.2 for PFOA and PFOS at the beginning of the study, which decreased to 1.55 and 2.58, respectively, after 574 days. The fraction organic carbon in the sediments was 0.034%. The Koc after 574 days of incubation was 203 L Kg-1 and 580 L Kg-1 for PFOA and PFOS, respectively. Higgins and Luthy (ES&T 40: 7251-7256, 2006) determined values of Koc for PFOA and PFOS for freshwater sediments of 130 L Kg-1 and 480 L Kg-1 for PFOA and PFOS, respectively. After 574 days of incubation, there was good agreement between Koc for sediment and Koc for aquifer material. At the concentrations of organic material found in water supply aquifers, both PFOA and PFOS should be highly mobile. No evidence of degradation of PFOA or PFOS was observed. This is an abstract of a proposed presentation and does not necessarily reflect MPCA or EPA policy.
