In this project we propose to evaluate three common farm-animal antibiotics, chlortetracycline (Aureomycin), oxytetracycline (Terramycin) and erythromycin (a macrolide) with respect to their fate in Iowa’s soil/water environment. The expected results of this study will involve three aspects concerning fate of antibiotics. One aspect will involve elucidation of surface sorption of the selected antibiotics by organic and inorganic soil components. A second aspect will involve elucidation of the role of sorption on antibiotic mobility in soil, and a third aspect will involve half-life quantification of the selected antibiotics and cooperative or anti-cooperative contributions of the organic and inorganic surface-antibiotic interactions to the abiotic/biotic degradation process. The results from this project will allow us to elucidate and predict the potential long-term consequences of antibiotics with respect to their potential distribution and persistence in Iowa’s soil/water system. This type of information is of paramount importance in understanding the fate of antibiotics in the soil/water environment and proposing potential solutions to the problem.