Enhanced photolysis in natural waters: Naturally occurring sensitizers, substrates, and applications to the fate of aquatic pollutants.

摘要

Investigations into the enhanced photochemical reactions occurring in natural water systems were accomplished through several avenues. First, the study of the photochemical properties of dissolved organic matter (DOM), the principal sensitizing moiety in natural waters is presented. This is followed by the application of the fundamental photochemistry of natural waters to a study of how these reactions affect the environmental longevity of a class of pollutants.; Specifically, the photosensitizing and photostability properties of a class of recently discovered components of chromophoric dissolved organic matter (CDOM), chlorinated aromatic compounds, were explored.; Chapter three also investigates the photochemical behavior of a subset of DOM, dissolved free amino acids. In this study, the role of photochemically generated singlet oxygen (1O2) in the DOM sensitized degradation of eighteen dissolved free amino acids is investigated. Only four free amino acid residues were found to be photolabile under environmentally relevant conditions, and include histidine, methionine, tyrosine, and tryptophan. The fraction of the sensitized degradation due to reaction with 1O 2 ranges from an upper value of 80--110% for histidine to 7.6--26% for tryptophan, with 28% for methionine and 30% for tyrosine. Additionally, the remaining fraction of amino acid degradation is unique for each compound. Due to the variant nature of the additional degradation pathways, these four amino acids are suggested as a series of probes to evaluate DOM reactivity.; The remaining chapters assess the application of natural water photochemistry to the fate of the newly identified class of aquatic pollutants, pharmaceuticals and personal care products (PPCPs). Chapter four is a review of current literature on the topic of photochemistry of PPCPs, with the bulk of the literature coming from phototoxicity studies. The goal of the review is to highlight the use of this data applied to environmental systems. Chapters five and six investigate the photochemical fate of a specific class of pharmaceuticals, the sulfa drugs. (Abstract shortened by UMI.)