Managing the Release of Emerging Agricultural Contaminants into the Environment

Recently there has been an increased interest regarding the environmental fate of veterinary medicines, however it is apparent that variability and knowledge gaps exist within the literature. The presented doctoral thesis employed novel, practical, and thorough experimental and analytical techniques to bridge these knowledge gaps but also to contribute towards a more robust and harmonised risk assessment.

Reported veterinary medicine half-lives in animal manures are highly variable, this indicates that current exposure assessments are inaccurate, consequently predicted soil concentrations maybe under or overestimated. Manure properties are highly heterogenic and the current guidance permits the use of just one manure per animal type. Therefore, an experiment was designed to investigate whether commonly reported pig slurry pH’s and anaerobic redox potentials are contributing towards variable degradation rates. The results demonstrate these parameters to have a significant and compound specific effect on degradation rates. Therefore, to conduct accurate and realistic environmental fate assessments manure degradation studies should encompass numerous manures with differing properties.

A semi-field experiment which evaluated the transfer of veterinary medicines under varying application techniques was conducted where eight veterinary medicines were identified to be transported to receiving waters. Incorporating slurries into soils and injection were identified to substantially reduce the transport of veterinary medicines over that of broadcast. A year-long field monitoring study was conducted to evaluate the fate of veterinary medicines at the farm scale and validate the modelling suite FOCUS_PEARL. Antibiotics recently utilized at the farm were detected in slurries, soils, and groundwaters. Antibiotics were observed to persist within groundwaters throughout the study, however, there was little compelling evidence to link this to their presence in slurries or soils. Moreover, the modelled predictions were observed to surpass that of the concentrations detected in groundwater.