Distribution and desorption of perfluorinated compounds in fractionated sediments.

This study provides particle-scale understanding of perfluorinated compounds (PFCs) distribution in sediments collected from two locations in Tianjin, China. The sediments were fractionated according to particle size and density. Even though lower density carbonaceous fractions contributed only 17.8-22.3% of the total sediment mass, they displayed stronger affinity to PFCs with much higher PFC concentrations than in the heavy fractions. Hydrophobic interaction predominated the partition of longer chain PFCs while electrostatic interaction could affect the sorption of short chain PFCs in sediment fractions. The individual PFC concentrations increased with increasing perfluorocarbon chain length, and the concentrations of perfluoroalkanesulfonates (PFSAs) in the same sediment fraction were higher than perfluorocarboxylates (PFCAs) with the same chain length. Log K(oc) was in the range of 1.70-3.80 for C5-C12 PFCAs and 1.75-2.97 for C4-C8 PFSAs. Desorption experiments indicated desorption became difficult as the chain length increased, and PFSAs were harder to be desorbed than the corresponding PFCAs.