Cha, Jongmun, authorCarlson, Kenneth H., advisor2024-03-132024-03-132007https://hdl.handle.net/10217/237632The occurrence and fate of antibiotics in the aquatic environment are an emerging area of interest due to the potential impact of these compounds on the environment. This study applied rapid, sensitive and reliable analytical methods for the determination of β-lactam and polyether ionophore antibiotics in surface water, wastewater, sediment, lagoon water, and animal manure. The method incorporated solid-phase extraction and liquid chromatography-ion trap tandem mass spectrometry (LC-MS-MS) with selected reaction monitoring. Specifically, the method was applied to evaluate the occurrence of these compounds in a small watershed in northern Colorado. The study also investigates the potential for on-farm removal of these compounds by measuring the biodegradation kinetics of oxytetracycline, sulfamethoxazole, tylosin, and monensin in bioreactors setup to simulate a dairy wastewater lagoon.Several product ions for LC-MS-MS detection of β-lactam and ionophore compounds have been identified and documented with their proposed fragmentation pathways. This study describes statistical analysis for determination of the method detection limit, accuracy and precision of the analytical method. Consequently, the average recovery of β-lactam and ionophore compounds from all the sample matrices was above 70% (excluding amoxicillin and ampicillin). Few of the β-lactams under investigation could be detected due to the poor stability of the β-lactam ring. These results indicate that the release of β-lactams, which are commonly used for human applications, from agricultural operations may not be an environmental concern since they rapidly hydrolyze or biodegrade. The concentration of ionophores ranged from 0.03 to 0.05 μg/L for surface water samples, and from 0.5 to 3.1 μg/kg for sediment samples. Monensin (94-1077 μg/L) was also measured in runoff ponds at beef feedlots.The research demonstrated biodegradation of oxytetracycline, sulfamethoxazole, tylosin, and monensin in dairy lagoon water at both 20 °C and 4 °C. However, the study found that within 175 days at 20 °C and 242 days at 4 °C, all antibiotics did not completely degrade under aerobic or anaerobic treatment. These results showed that degradation of antibiotics was faster under aerobic conditions, compared to anaerobic conditions and lower temperature (4 °C) reduced the biodegradation rate of antibiotics.born digitaldoctoral dissertationsengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.antibioticaquatic environmentbiodegradationmanurecivil engineeringsanitationenvironmental scienceenvironmental engineeringTextPer the terms of a contractual agreement, all use of this item is limited to the non-commercial use of Colorado State University and its authorized users.