2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 6
Presentation Time: 8:00 AM-6:00 PM

Factors Influencing Tetracycline Sorption by Smectite Clays from Water

DING, Jason Y., TEPPEN, Brian J., BOYD, Stephen A. and LI, Hui, Department of Crop and Soil Sciences, Michigan State University, East Lansing, MI 48824, dingyunj@msu.edu

Tetracyclines are a class of antimicrobials that have been extensively used to improve human and veterinary health. A large portion of tetracyclines used by humans and animals can be released into the environment, raising concerns regarding the potential risks to ecosystems and environmental quality. Sorption by soils is a determinant controlling transport, fate and hence exposure in the environment. Soil mineral fractions are the dominant sorptive domains for retaining these compounds. In this study, sorption of tetracycline by K+- and Ca2+-saturated smectite clays was measured using a batch equilibration method. Sorption manifested nonlinear isotherms, and was strongly suppressed by the presence of high levels of inorganic cations (e.g., K+ and Ca2+) in solution. Sorption of tetracycline by K-, and Ca-smectite was concomitant with the release of K+ and Ca2+ from the clays, suggesting that cation exchange process is responsible for the sorption of tetracycline. X-ray diffraction patterns showed that the interlayer distances of smectite clays increased as tetracycline sorption increased, and gradually approached a constant basal spacing of 17.5 to 18 Å. These results indicate that the clay-sorbed tetracyclines are intercalated in interlayer regions.