Behavior and Fate of PFOA and PFOS in Sandy Aquifer Sediment

Abstract

Microcosms were constructed with sediment from beneath a landfill that received waste containing PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate). The microcosms were amended with PFOA and PFOS, and sampled after 91, 210, 343, 463, 574, and 740 d of incubation. After 740 d, selected microcosms were extracted to determine the mass of PFOA and PFOS remaining. There was no evidence for degradation of PFOA or PFOS. Over time, the aqueous concentrations of PFOA and PFOS increased in the microcosms, indicating that PFOA and PFOS that had originally sorbed to the sediment was desorbing. At the beginning of the experiment, the adsorption coefficient, Kd, averaged 0.27 L/kg for PFOA and 1.2 L/kg for PFOS. After 740 d of incubation, sorption of PFOA was not detectable and the Kd of PFOS was undetectable in two microcosms and was 0.08 L/kg in a third microcosm. During incubation, the pH of the pore water in the microcosms increased from pH 7.2 to pH ranging from 8.1 to 8.8. The zeta potential of the sediment decreased with increasing pH. These observations suggest that the sorption of PFOA and PFOS at near neutral pH was controlled by the electrostatic sorption on ferric oxide minerals, and not by the sorption to organic carbon. Accurate predictions of PFOA and PFOS mobility in ground water should be based on empirical estimates of sorption using affected aquifer sediment.

North Atlantic Deep Water formation inhibits high Arctic contamination by continental perfluorooctane sulfonate discharges

“…We consider uncertainty in the empirically measured partition coefficient for PFOS using sensitivity analysis on the upper and lower bounds reported in the literature (log K oc = 2.4 to 3.8) [Ahrens et al, 2011;Ferrey et al, 2012]. Results of our simulation suggest that the mass of vertically transported PFOS in the ocean associated with settling particles is negligible compared to that from lateral and vertical ocean circulation ( Figure S8).…”

Perfluoroalkyl and polyfluoroalkyl substances thermal desorption evaluation

“…After homogenizing the soil in a stainless steel mixing bowl, the soil was separated into 250‐gram (g) samples for testing. To perform this testing, the soil was heated using a temperature‐controlled oven (Programmable RapidFire Pro; TableTop Furnace Company, Tacoma, Washington) that heated and maintained the soil temperature in a controlled environment Ferrey et al (). PFAS‐impacted soils were heated in separate test groups at 220°C, 300°C, 350°C, and 400°C for 10–14 days within sealed, 1‐quart galvanized steel containers (unlined; Cornucopia Brands, Corbin, Kentucky) with brass compression fittings and 1/8‐inch copper tubing for vacuum and flow lines extending from the temperature‐controlled oven.…”

Making Strides in the Management of “Emerging Contaminants”

“…PFAAs have been found to be resistant to biodegradation and are dead end daughter products to the thousands of other PFAS, which bio‐transform in the environment to yield PFAAs that may remain unaltered in soil and groundwater indefinitely. Biodegradation of PFOS and PFOA has been evaluated under conventional waste water treatment conditions (Dasu et al ) and natural aquifer conditions (Ferrey et al ); however, evidence to support the occurrence of biological degradation of these compounds is lacking, with a similar recalcitrance evident for other PFAAs.…”