title: Sorption of tetracycline and chlortetracycline on K- and Ca-saturated soil clays, humic substances, and clay-humic complexes.
abstract: Tetracycline (TC) and chlortetracycline (CTC) are used extensively for growth promotion and therapeutic purposes in livestock production. The sorption of TC and CTC on clays, humic substances (HS), and clay-humic complexes (clay-HC) derived from two agricultural soils was quantified using dilute CaCl2 (Ca) and KCI (K) as background solutions. In all systems, the soil components sorbed > 96% of added tetracyclines. Strongest sorption was observed for clays, followed by HS, and then clay-HC. Greater sorption by the Ca systems than the K systems and decreased sorption with increasing pH suggests that cation bridging and cation exchange contribute to sorption. X-ray diffraction analysis showed that TC and CTC were sorbed in the interlayers of smectites and that the presence of HS reduced interlayer sorption of tetracyclines by smectites in clay-HC. The results indicate that tetracyclines are dominantly sorbed on soil clays and that HS in clay-HC either mask sorption sites on clay surfaces or inhibit interlayer diffusion of tetracyclines.
authors.affiliation: Agronomy Department, Iowa State University, 100 Osborne Drive, Ames, Iowa 50011, USA. jutta.pils@usa.dupont.com
authors.forename: Jutta R V
authors.initials: JR
authors.lastname: Pils
authors.forename: David A
authors.initials: DA
authors.lastname: Laird
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D002751:Chlortetracycline / Q000737:chemistry*; D002853:Chromatography, Liquid; D006812:Humic Substances / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D011188:Potassium / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry*; D013752:Tetracycline / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D000538:Aluminum Silicates; D006812:Humic Substances; D012989:Soil Pollutants; D013752:Tetracycline; D011188:Potassium; D002118:Calcium; D002751:Chlortetracycline