Partitioning of Fluorotelomer Alcohols to Octanol and Different Sources of Dissolved Organic Carbon

Interest in the environmental fate of fluorotelomer alcohols (FTOHs) has spurred efforts to understand their equilibrium partitioning behavior. Experimentally determined partition coefficients for FTOHs between soil/water and air/water have been reported, but direct measurements of partition coefficients for dissolved organic carbon (DOC)/water (K_doc) and octanol/water (K_ow) have been lacking. Here we measured the partitioning of 8:2 and 6:2 FTOH between one or more types of DOC and water using enhanced solubility or dialysis bag techniques, and also quantified K_ow values for 4:2 to 8:2 FTOH using a batch equilibration method. The range in measured log K_doc values for 8:2 FTOH using the enhanced solubility technique with DOC derived from two soils, two biosolids, and three reference humic acids is 2.00−3.97 with the lowest values obtained for the biosolids and an average across all other DOC sources (biosolid DOC excluded) of 3.54 ± 0.29. For 6:2 FTOH and Aldrich humic acid, a log K_doc value of 1.96 ± 0.45 was measured using the dialysis technique. These average values are ∼1 to 2 log units lower than previously indirectly estimated K_doc values. Overall, the affinity for DOC tends to be slightly lower than that for particulate soil organic carbon. Measured log K_ow values for 4:2 (3.30 ± 0.04), 6:2 (4.54 ± 0.01), and 8:2 FTOH (5.58 ± 0.06) were in good agreement with previously reported estimates. Using relationships between experimentally measured partition coefficients and C-atom chain length, we estimated K_doc and K_ow values for shorter and longer chain FTOHs, respectively, that we were unable to measure experimentally.