Sorption of Estrogens onto Different Fractions of Sediment and Its Effect on Vitellogenin Expression in Male Japanese Medaka

This study investigated the sorption capacity of estrogenic compounds-such as estrone (E1), 17 beta-estradiol (E2), and 17 alpha-ethynylestradiol (EE2)-of different sediment particle fractions. Two-sized fractions of sediment were used in the experiments, with a particle size < 1 mu m (mostly from 450 to 800 nm) and > 1 mu m up to 50 mu m. Sorption kinetics were followed using a two-step reaction in which the major amount of chemicals was sorbed rapidly within minutes and then gradually increased until equilibrium was reached after 48 h. The sorption capacity of the fine particle fraction (particle size < 1 mu m) was shown to be significantly higher than that of the large fraction (1 mu m < particle size < 50 mu m). The sorption kinetics and isotherm were adequately predicted by using a pseudo second-order model and the Freundlich equation, respectively. Total organic carbon (TOC) content and surface area of particle fractions were also measured. Although the effects of TOC on the sorption of estrogens could not be verified, a higher surface area of fine particle fractions may significantly increase sorption capacity to target compounds. Sorption of estrogens onto sediment particles could be used to explain the differences of estrogenic activity of E2 spiked into different size fractions of particle suspensions.