Congener specific organic carbon normalized soil and sediment-water partitioning coefficients for the C1 through C8 perfluorinated alkylsulfonic and alkylcarboxylic acids

摘要

Organic carbon normalized soil and sediment-water partitioning (Koc) coefficients were estimated for all C1 through C8 perfluorinated alkylsulfonic acid (PFSA) and alkylcarboxylic acids (PFCA) congeners. The limited experimental Koc dataset for the straight chain C7 through C10 PFCAs and C8 and C10 PFSAs was correlated to SPARC and ALOGPS computationally estimated octanol-water partitioning constants and used to predict Koc values for both branched and linear C1 through C8 isomers. All branched and linear congeners in this homologue range are expected to have Koc values>1, leading to their accumulation in organic matter on sediments and soils, retardation during ground and pore water flow, and the preferential association with dissolved organic matter in aquatic systems. Both increasing perfluoroalkyl chain length and linearity increase Koc values with substantial intra- and inter-homologue variation and interhomologue mixing. Variability in Koc values among the PFCA and PFSA congeners will likely lead to an enrichment of more linear and longer chain isomers in organic matter fractions, resulting in aqueous phases fractionated towards shorter chain branched congeners. The expected magnitude of fractionation will require inclusion in source apportionment models and risk assessments. A comparison of representative established quantitative structure property relationships for estimated Koc values from octanol-water partitioning constants suggests that equilibrium partitioning frameworks may be applicable towards modeling PFCA and PFSA environmental fate processes and warrants further study using other partitioning coefficients for which suitable experimental data is available.