Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in surface waters, sediments, soils and wastewater - A review on concentrations and distribution coefficients.

The sorption of perfluorinated compounds (PFCs) to soils and sediments determines their fate and distribution in the environment, but there is little consensus regarding distribution coefficients that should be used for assessing the environmental fate of these compounds. Here we reviewed sorption coefficients for PFCs derived from laboratory experiments and compared these values with the gross distribution between the concentrations of PFCs in surface waters and sediments or between wastewater and sewage sludge. Sorption experiments with perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) suggest that their sorption can be described reasonably well as a partitioning-like process with an average log K(oc) of approximately 2.8 for PFOA and 3.0 for PFOS. However, median concentrations in sediments (PFOA, 0.27 ng g(-1); PFOS, 0.54 ng g(-1)) or sewage sludge (PFOA, 37 ng g(-1); PFOS, 69 ng g(-1)) in relation to median concentrations in surface water (PFOA, 3ngl(-1); PFOS, 3ngl(-1)) or wastewater treatment effluent (PFOA, 24 ng l(-1); PFOS, 11 ng l(-1)), suggest that effective log K(oc) distribution coefficients for the field situation may be close to 3.7 for PFOA and 4.2 for PFOS. Applying lab-based log K(oc) distribution coefficients can therefore result in a serious overestimation of PFC concentrations in water and in turn to an underestimation of the residence time of PFOA and PFOS in contaminated soils. Irrespective of the dissipation kinetics, the majority of PFOA and PFOS from contaminated soils will be transported to groundwater and surface water bodies.