Sorption of tylosin onto swine manure

Sorption of tylosin was conducted on manure solids (<2 mm) and colloidal materials (<1.2 μm) collected from open (OL) and covered (CL) anaerobic swine manure lagoons. The aqueous concentration of tylosin in the sorption studies bracket the levels expected in lagoons, between 1 mg l−1 and 30 mg l−1. Sorption isotherms were found to be slightly non-linear for 2 mm solids, with Freundlich distribution coefficients (Kf) of 39.4 with n = 1.32 for CL slurry and 99.5 with n = 1.02 for OL. These values are comparable to those reported for loam soils, but higher than those reported for sandy or clay soils and lower than those reported for fresh manure. Normalization of Kd to the organic carbon content of the solids gave Koc values of 570 l kg−1 and 818 l kg−1, for CL and OL solids, respectively. The Kd and Kf values were not significantly different between colloids and 2 mm solids in OL slurry, but were significantly different in CL due to the non-linearity of the colloid isotherm. Based on the Kd values obtained and comparing the Kd values of other antibiotics, tylosin is strongly sorbed to manure, and would be more mobile than tetracyclines, but less mobile than sulfonamides, olaquindox, and chloramphenicol. However, tylosin mobility may be facilitated through transport with colloidal manure materials.