| Antibiotics are a class of pharmaceuticals specifically engineered to kill pathogenic bacteria. In addition to medicinal applications for treating people, antibiotics are also used in a number of agricultural industries to prevent the spread of harmful and costly diseases. However, the increased prevalence of resistant strains of bacteria has raised concern about the environmental fate of such compounds, particularly once in the natural environment. For many antibiotics, little information is known about their breakdown or fate in natural waters.;This work investigated the photochemical transformation of two antibiotics commonly used in aquaculture (catfish), sulfadimethoxine and ormetoprim and the role that dissolved organic matter (DOM) composition plays on the fate of these compounds. Sulfadimethoxine degradation was found to be dependent on DOM source composition, and degraded via triplet excited state pathways. Ormetoprim was found to degrade through indirect pathways that included transformation via two reactive oxygen species (ROS) promoted by DOM - the hydroxyl radical and singlet oxygen.;The effects of source on dissolved organic matter composition were studied, and an intensive investigation was performed to characterize the photoreactivity of a fulvic acid isolated from Pony Lake on Cape Royds, Ross Island, Antarctica, a completely microbially-derived DOM end-member. |
