BACs to dissolved organic components in the test medium is considered negligible and the measured Cw is regarded as Cfree in this study. Desorption equilibrium was reached within the 24 h pre-equilibration time for C14-and C16-BACs and 48 h for C18-BAC (Figure ). Sorption to the glass beaker ranged from 0.1 to 6 % of the total measured mass (i.e., the sum of masses from water, PES membrane, and glass beaker) and increased with alkyl chain length (Figure ). The PES membrane retained >91% of the loaded BACs, indicating that the PES membrane served as a partitioning source. The calculated mean log KPESw for C14-, C16-, and C18-BACs within the tested concentration range were 4.61-4.80, 4.45-5.41 and 4.14-5.33, respectively (Table ). Sorption isotherms of C14-C18-BACs on PES membrane (Figure ) indicate that BACs with longer alkyl chain lengths have higher Freundlich coefficients and lower Freundlich exponents,