178-estradiol (E2) is a potent endocrine disrupting compound that is found in swine manure. Liquid swine manure or otherwise knov.n as swine slurry is commonly used as a form of fertilizer in agricultural practices. Laboratory studies have demonstrated that E2 binds readily and strongly to soil and degrades within hours. However, field studies detect E2 in the environment at frequencies that suggest its moderate mobility and persistence. The objective of this study was to determine if colloidal organic carbon (COC; < I kDa) and dissolved organic carbon (DOC;> I kDa to< 0.45μm) from swine slurry affect the sorption and persistence of E2 in soil. Batch experiments were used to determine the sorption of 14C labeled E2 in soil with slurry solution compared to the sorption of E2 in soil with only a 0.0IM CaCh solution. Samples were quantified for total radioactivity using liquid scintillation counting (LSC), and thin layer chromatography (TLC) was used to identify the formation of any E2 metabolites. Oxidation analysis was also used to determine the quantitative amounts of extractable and non-extractable E2 and metabolites at each time point in the aqueous and soil-bound phases. To determine ifE2 preferentially associated with a manure organic carbon fraction (DOC or COC), ultrafiltration was performed. Although E2 was present in both the slurry and CaCh solution phase after 14 d, the fractional recovery for E2 in the slurry solution was 12% and only 8% for the CaCh solution. 17~-estradiol persisted in the parent form and did not convert to its metabolite, estrone (El) in the slurry solution. In the CaCh solution, conversion ofE2 to El was complete after 3 d. Ultrafiltraion results indicated that E2 preferentially associated with the COC fraction of the slurry. Results suggest that the suspended COC fraction facilitates the persistence and potential mobility of E2 in the soil environment.