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item Yates, Scott

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2005
Publication Date: 1/11/2006
Citation: Wang, Q., Yates, S.R. 2006. Degradation kinetics of manure-derived sulfadimethoxine in amended soil. Journal of Agricultural and Food Chemistry.54(1):157-163.

Interpretive Summary: Sulfadimethoxine is an antibiotic used for therapeutic treatment and growth promotion in animal production. It has been estimated that more than 22 million pounds of antibiotics were used to treat farm animals and pets in the US during 2002. Antibiotics given to animals for treatment will eventually enter the environment. A major pathway through which veterinary antibiotics enter the environment is the excretion of feces and urine from medicated animals in livestock and poultry farming, and the subsequent application of contaminated manure as fertilizer on agricultural land. This has led to frequent reports of soil and water contamination from manure fertilization and at concentrated animal operations. The widespread contamination of antibiotics in the environment may put human health and ecosystems at risk. Antibiotics may cause the formation of resistance, even cross- and multiple-resistance, in organisms in the environment and eventually threaten human and animal heath by diminishing the success of antibiotic treatment. Therefore, there is a need to understand the environmental fate of antibiotics in the environment and to develop method to eliminate this potential source of contamination. In this study, the degradation of sulfadimethoxine in soil was studied and a model was developed based on the first-order kinetics to describe the degradation process. The effects of the initial concentration, manure amendment ratio, moisture, and aging on degradation were investigated.

Technical Abstract: Spreading of contaminated manure into agricultural lands, as fertilizer is the major route through which veterinary antibiotics enter the environment. In this study, the degradation of manure-derived sulfadimethoxine, a widely used sulfonamide antibiotic, in manure-amended soil was investigated. A kinetic model called the availability-adjust first-order model was developed based upon the first-order kinetics and the assumption of the availability of target compound during the degradation process and was found to fit degradation of manure-derived sulfadimethoxine well. The effect of initial sulfadimethoxine concentration showed that the degradation rate constant increased with the decreasing initial concentration, indicating that the bioactivity of the degrading microorganisms in manure-amended soil was sensitive to sulfadimethoxine concentration. Application of heavily contaminated manure may significantly lengthen the persistence of sulfadimethoxine in amended soil and thus should be avoided. Sulfadimethoxine degradation was accelerated with the increasing manure content in amended soil. Degradation in non-amendment soil was much slower than in manure-amended soil, indicating that sulfadimethoxine may become more persistent once it reaches soil from manure and storage of manure for a certain period is needed for diminishing sulfadimethoxine. Sulfadimethoxine degradation was effectively enhanced with the increasing moisture of amended soil. No adverse effect was observed with manure storage on the degradation of manure-derived sulfadimethoxine after application into soil.