Investigating the Effect of Soil pH on Sorption of Salinomycin in Clay and Sandy Soils

Abstract

Salinomycin is a polyether ionophore that is often used to prevent coccidial infections and promote growth in poultry. A considerable portion of the antibiotic is excreted as the parent chemical, which eventually ends up in agricultural soils. This necessitates researchers conducting sorption-desorption studies to better understand the compound's behaviour in the soil environment.  Salinomycin sorption was studied in four agricultural soils, including a clay soil with low organic matter content (LOM), a clay soil with high organic matter content (HOM), a sandy soil with HOM, and a loamy sandy (LOM) soil, at three pH levels: 4, 7, and 9. The batch equilibration approach was used to conduct the desorption investigations. All soils were shown to be severely sorbed by more than 98 percent salinomycin, regardless of soil organic matter level or pH. Salinomycin sorption to the sandy soil increased marginally as the pH decreased, while sorption to the two clay soils increased marginally as the pH increased. Salinomycin desorption in methanol was less than 0.2 percent of the amount administered after 72 hours; whereas, it was greater than 70% with phosphate buffer (pH 7). Salinomycin could offer major threats to both shallow ground water and surface water bodies, because the phosphate buffer would imitate, to some extent, the quality of water flowing through field soils containing various salts.