Effects of physical-chemical characteristics on the sorption of selected endocrine disrnptors by dissolved organic matter surrogates

Sorption coefficients (K-oc values) of selected endocrine disruptors for a wide variety of dissolved organic matter (DOM) were measured using fluorescence quenching and solubility enhancement. 17beta-Estradiol, estriol, 17alpha-ethynylestradiol, p-nonylphenol, p-tert-octylphenol, and dibutylphthalate were selected as endocrine disruptors. Aldrich humic acid, Suwannee River humic and fulvic acids, Nordic fulvic acid, alginic acid, dextran, and tannic acid were selected as DOM surrogates. The resulting sorption coefficients (log K-oc) were independent of octanolwater partitioning coefficients (log K-oc) of the selected endocrine disruptors, indicating the hydrophobic interaction is not the predominant sorption mechanism. Moreover, the K-oc values for the selected endocrine disruptors, especially the steroid estrogens, correlated much better with UV absorptivity at 272 nm (A(272)) and phenolic group concentration of the DOM than with either the H/O or the (O+N)/C atomic ratio of the DOM. This suggests that the sorption mechanism is closely related to the interaction between pi-electrons and the hydrogen bonds, i.e.,the affinity between phenolic groups of the steroid estrogens and DOM is suggested to provide a relatively large contribution to the overall sorption and yield the K-oc values of the steroid estrogens as high as those of the alkylphenols and dibutylphthalate, which are suggested to be dominated by nonspecific hydrophobic interaction.