Sorption Characteristics of Veterinary Ionophore Antibiotics Monensin and Lasalocid and Soil Clay Constituents Kaolinite, Illite and Montmorillonite
Monensin and Lasalocid are veterinary ionophore antibiotics used for therapeutic and non-therapeutic treatment of livestock. Manure containing un-metabolized compounds is in turn used as beneficial amendment for agricultural crops, thus, these compounds may be available for transport through soils. These antibiotics have been detected in run-off, surface water, and groundwater and may be toxic to soil and aquatic biota. This research focuses on adsorption mechanisms of Monensin (MON) and Lasalocid (LAS) to clay constituents common in agricultural soils. Methods were developed to extract these compounds from water, soil, and sludge and for subsequent analysis using liquid chromatography tandem mass spectrometry. Batch equilibrium experiments indicated that Monensin and Lasalocid have unique adsorption mechanisms that are highly pH-dependent. Predicted order of adsorption strength and desorption capabilities were not observed. Illite (ILL) had optimal adsorption conditions for and showed strong affinity for both LAS and MON. Desorption was very high in the competitive study. Kaolinite (KAO) showed moderate adsorption and desorption was nearly twice as high when the compounds were paired. Montmorillonite (MTM) displayed low adsorption and desorption was higher in the non-competitive study. More retention of LAS by MTM was apparent in the competitive study. Manure (MAN) used in this study did not show a strong affinity for the MON and LAS complexes. Desorption from this manure was low, particularly for LAS in the competitive study. Ottawa sand (OTS) showed little adsorption as was expected. Desorption was generally moderate, except for MON which was high, particularly in the non-competitive study. Soil (GLRI) adsorption was generally high and there was a one order of magnitude difference between the non-competitive and competitive studies. Adsorption was rapid and partially irreversible unto all sorbents indicating that portions of these compounds may remain in soils, possibly toxic to biota until degradation occurs. Remaining adsorbed compound has limited availability for transport via runoff to surface waters, leaching to groundwater, transformation, and/or bioaccumulation. More research regarding the fate of Monensin and Lasalocid is necessary to fully understand their behavior in soil, particularly in Northwest Ohio which is a large agricultural region spatially proximate to the Great Lakes.
Agriculture, Animal Diseases, Environmental Geology, Environmental Management, Environmental Science, Geochemistry, Geology, Land Use Planning, Livestock, Soil Sciences, Veterinary Antibiotics, Monensin, Lasalocid, Clays, LC-MS/MS
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