The Chemistry and Photochemistry of the Insecticide Carbaryl in Aquatic Environments
Large quantities of pesticides have been used for many years in New Zealand to control agricultural and horticultural pests. The fate of a pesticide after application as a powder or solution to the target organism depends on its chemical structure and mode of application. Once in the environment, it may degrade by any number of physical, chemical or biological mechanisms. The time scale for this degradation can span from hours to years and the degradation products may be as toxic, if not more, than the parent molecule. Thus pesticides may become ‘xenbiotic’ pollutants and eventually have adverse effects not only in the environment but they may also bioaccumulate in the food chain and even ultimately affect humans. One of the common degradation pathways of many chemical species ion the environment is via sunlight-induced photochemistry either in the solid state or in solution. The aim of this project was to examine this degradation pathway for solutions of a pesticide in common usage in New Zealand. It was hoped that the results from this study would provide some indication of the relative importance of sunlight as a method of pesticide degradation. In the New Zealand environment, a significant fraction of all pesticides are ultimately washed off the target plants and organisms to form solutions in natural aquatic environments, such as streams, rivers, lakes and coastal estuaries. […] In this study, detection methods were first developed for carbaryl , 1-naphthol and 1-naphtholate based on the fluorescence of these species. The hydrolysis of carbaryl and the degradation of 1-naphthol plus 1-naphtholate were then investigated under typical water pH conditions (8.2) in the absence of light and microorganisms. Photolysis equipment was developed to study the photochemical degradation of carbaryl and 1-naphthol in aqueous solution under various conditions and a comparison made with the results for degradation in the absense of light. [Extract from Introduction]
Advisor: Peake, Barrie M.
Degree Name: Bachelor of Science with Honours
Degree Discipline: Chemistry
Publisher: University of Otago
Research Type: Dissertation