The impacts of colloidal material on the fate and transport of 17 B-estradiol in three Iowa soils

Estrogenic compounds occur in land-applied animal manure and pose a biological risk if they enter aquatic ecosystems through agricultural drainage or shallow groundwater. Therefore, it is important to understand the fate of estrogens in soil systems. Estrogens are nonpolar and strongly adsorbed by soil organic matter, limiting their miscible transport, but presenting another possible transport vector. The movement of colloids that are rich in organic matter may facilitate the transport of estrogens through soil and ultimately to surface water. As a first step in considering colloid mediated transport mechanisms, the objective of this study was to determine the intensity of adsorption of 17β-estradiol (E2) and estrone (E1) to three Iowa soils, to colloidal components of those soils, and colloidal components of swine manure. By using batch incubations, adsorption isotherms were measured for E2 and E1 binding to Clarion, Hanlon, and Zook soil materials, to the derived water-dispersible soil colloids, and to colloidal material fractionated from swine manure. Following incubation (24 h), solution concentrations of E2 and E1 were measured by using solid phase extraction to clean and concentrate the sample before final analysis by high pressure liquid chromatography. The soils selected ranged from 70 to 400 g kg -1 in clay content, 7 to 30 g kg -1 organic carbon, 12 to 60 cmol kg -1 CEC, and 7 to 11 in C/N ratio. Colloidal materials