Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2006
Publication Date: 10/27/2006
Citation: Wang, Q., Bradford, S.A., Zheng, W., Yates, S.R. 2006. Sulfadimethoxine degradation kinetics in manure as affected by initial concentration, moisture, and temperature. Journal of Environmental Quality. Vol 35:2162-2169 Interpretive Summary: Sulfadimethoxine is an antibiotic widely used for therapeutic treatment and for 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 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. 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 manure 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 moisture, and temperature on degradation were investigated.
Technical Abstract: The degradation kinetics of sulfadimethoxine, a widely used sulfonamide veterinary antibiotic, in manure under aerobic condition was investigated. Based on the first-order kinetics and the assumption of sulfadimethoxine availability for degradation in manure, a new kinetic model was developed and was found to fit the degradation kinetics well. The degradation rate in sterilized manure showed to be much lower than in non-sterilized manure, indicating that microorganisms were responsible for a significant portion of degradation of this antibiotic in manure. In non-sterilized manure, the degradation rate constant decreased with increasing initial concentration of sulfadimethoxine, implying that the bioactivity of degrading microorganisms was gradually inhibited. Increasing moisture or temperature was found to effectively enhanced sulfadimethoxine degradation in manure. Mixing highly contaminated manure with less/non- contaminated to lower the initial concentration, while keeping manure humid and storing in a moderately warm place under aerobic conditions, may greatly diminish sulfadimethoxine contamination in manure and thus significantly reduce sulfadimethoxine input into the agricultural environment.