Effects of dissolved organic matter surrogates on the partitioning of 17β-estradiol and p-nonylphenol between synthetic membrane vesicles and water

Partition coefficients of two estrogenic compounds, 17β-estradiol (E2) and p-nonylphenol (NP), between synthetic membrane vesicles (K‘lipw values) and water were determined using equilibrium dialysis to evaluate the potential biological uptake of these compounds with and without the presence of dissolved natural organic matter (DOM) surrogates, Suwannee River fulvic acid, dialyzed Aldrich humic acid, and polyphenolic tannic acid. Overall, K‘lipw values for E2 and NP reduced by 20−30% with the increase of DOM concentration from 0 to approximately 4 mg of C/L, a typical DOM concentration in the aquatic environment. This trend for E2 and NP is similar to that obtained by other researchers for moderately hydrophobic compounds including polycyclic aromatic hydrocarbons with three or four rings. A three-phase compartment model with three independent interactions, the sorption of E2 or NP by DOM surrogate (Koc), the sorption of DOM surrogates by membrane vesicles (KlipDOM), and the partition of E2 or NP by membr...