Partitioning Behavior of Bisphenol Alternatives BPS and BPAF Compared to BPA

With the pressure to ban or limit the use of bisphenol A (BPA), production of alternatives such as bisphenol AF (BPAF) and bisphenol S (BPS) are increasing, but little is known on their partitioning behavior for use in assessing distribution in the ecosystem. Octanol-water (D_ow^pH) and soil-water partitioning were measured at several pH values for BPA, BPAF, and BPS. Sorption isotherms were constructed from measured aqueous and soil phase concentrations and were fit sufficiently well with a linear sorption model. pH-dependent distribution was observed in both octanol-water and soil-water systems particularly for BPS and BPAF, which have lower estimated pK_a values than those for BPA. Accounting for soil organic carbon (OC) content and pH was sufficient to describe sorption reasonable well across the four soils (%OC 0.1-2.5, pH 3.8-8.6); no other soil properties correlated well with bisphenol sorption. However, for a given soil especially for the two high clay low OC soils, BPS sorbed much more than expected relative to observed trends in D_ow^pH and magnitude appeared correlated to % kaolinite; therefore, Ca²⁺-bridging of BPS to clay edge sites was assessed by comparing sorption from 0.01 N KCl and 0.01 N CaCl₂; however, no significant differences were observed.