Reactive water
Subtitle: the role of photooxidants in limiting the persistence of organic pollutants in the aquatic environment.
Contributors: University of Toronto.  Dept. of Chemistry.
Published: 2005
Language: eng
Number of pages: 202
Description: The photochemical transformation reactions and kinetics of the anti-depressant, fluoxetine, in surface water were studied. Direct and indirect photolysis reactions resulted in the formation of an O-dealkylation product, which was identified using an authentic standard. Experiments involving O2 depletion and O-18 labeled water were used to elucidate and confirm the proposed mechanisms of aryl ether cleavage.Phototransformation reactions provide an important elimination process for aqueous organic compounds that may not be efficiently removed by other pathways in surface waters exposed to sunlight. The hydroxyl and carbonate radical, singlet oxygen, and transient intermediates derived from dissolved organic matter are major reactive oxygen species generated from photoreactive natural water constituents that will react with and degrade pollutants in the aquatic environment. The role of these photooxidants in limiting the persistence of pharmaceutical agents, which are considered a new and emerging group of aquatic contaminants, provides the premise for this research.The field persistence of eight pharmaceuticals from different therapeutic classes was investigated using HPLC-UV and LC-MS-MS in an outdoor microcosm study. Phototransformation reactions were demonstrated to be important in the degradation of these compounds. The anti-epileptic, carbamazepine, was observed to have the longest half-life of 82 +/- 11 days, while acetominophen exhibited the shortest half-life of 0.9 +/- 0.2 days.The concentrations of the photooxidants in the PhotoFate test system were measured and a comparison of the experimental values with predicted and actual concentrations illustrated this system is a suitable representation of environmental concentrations and variability. A general positive correlation between the steady-state concentration of hydroxyl radical and observed degradation rate constants of several aquatic pollutants was observed, suggesting this highly reactive and non-selective photooxidant is important in contributing to the elimination of aqueous organic contaminants despite its low concentrations.Photooxidants were more important in the degradation of carbamazepine and atorvastatin compared to sulfamethoxazole and levofloxacin. Degradation products resulting from direct and indirect photochemical reactions were proposed based on new and previously published mass spectral data. Although the photoproducts were less susceptible than the parent molecule to direct photolysis,  &bull;OH-mediated transformation reactions proceeded faster for the photoproducts of the select pharmaceuticals.
Notes: Source: Dissertation Abstracts International, Volume: 66-10, Section: B, page: 5369.

Advisor: Scott Mabury

Thesis (Ph.D.)--University of Toronto, 2005.

Electronic version licensed for access by U. of T. users.