Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/6/2003
Publication Date: 11/6/2003
Citation: PILS, J.R., LAIRD, D.A. ADSORPTION OF TETRACYCLINE AND CHLOROTETRACYCLINE ON K- AND CA-SATURATED SOIL CLAYS AND HUMIC SUBSTANCES. ASA-CSSA-SSSA ANNUAL MEETING ABSTRACTS. 2003. CD-ROM. MADISON, WI.
Technical Abstract: Tetracycline (TC) and Chlorotetracycline (CTC) are used extensively for growth promoting and therapeutic purposes in livestock production. In order to elucidate the environmental fate of these drugs, batch equilibrium studies were conducted for K- and Ca-saturated soil clays and clay-humic complexes. Both TC and CTC were very strongly adsorbed on soil clay-humic complexes. Freundlich constants (KF) for sorption on Ca-saturated clay-humic complexes (pH 5.4) were 73793 and 28158 for CTC and TC, respectively. By contrast, the KF values for sorption on K-Saturated clay-humic complexes (pH 6.6) were 12187 and 9550 for CTC and TC, respectively. The results indicate that Ca promotes sorption relative to K and that CTC is more strongly adsorbed than TC. Raising the pH of the Ca-clay-humic complexes from 5.4 to 7.0 decreased sorption of CTC and TC by a factor of 4.1 and 1.7, respectively. Between pH 3.3 and 7.4 both CTC and TC are zwitterions. The greater sorption in the Ca-systems and the decreased sorption with increasing pH suggest that both charge neutralization and cation bridging contribute to sorption. Negligible CTC and TC were desorbed by one-step extractions with the same background electrolyte solutions.