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Title: ADSORPTION OF TETRACYCLINE AND CHLOROTETRACYCLINE ON K- AND CA-SATURATED SOIL CLAYS AND HUMIC SUBSTANCES

Author
item PILS, JUTTA - IOWA STATE UNIVERSITY
item Laird, David

Submitted to: Clay Minerals Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/24/2004
Publication Date: 6/24/2004
Citation: Pils, J.R., Laird, D.A. 2004. Adsorption of tetracycline and chlorotetracycline on k- and ca-saturated soil clays and humic substances [abstract]. Program and Abstracts of the 41st Annual Meeting of the Clay Minerals Society. p.57

Interpretive Summary:

Technical Abstract: Chlorotetracycline (CTC) and Tetracycline (TC) 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 potassium- (K-) and calcium- (Ca-) saturated soil clays and clay-humic complexes. Sorption isotherms 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. 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. Furthermore, both, TC and CTC are strongly sorbed on both soil clays and soil humic substances. However, TC and CTC are much more strongly sorbed on clays than on humic substances. Interactions between clays and humic substances significantly diminish sorption of TC and CTC on soil clay-humic complexes. The effect may be caused by competition between tetracyclines and humic substances for sorption sites, or by the structural organization of clay-humic complexes. Desorption studies show that little CTC is desorbed from soil components, but small amounts of TC may be desorbed from clay-humic complexes back to the soil solution.