Applications of Fluorescence Spectroscopy to Environmental Chemistry

摘要

This thesis consists of three sections. In chapter two, fluorescence quantumyields and lifetimes were measured for a series of nitroxide-fluorophore adducts, and quenching rates were shown to be high (kq=108-1010s-1), even at distances of -12A. An excellent correlation was observed between kq and the non-radiative relaxation rate. In the third chapter, diffusional quenching by charged and neutral nitroxides was employed to investigate the electrostatic properties of fulvic and humic acids. Cationic nitroxides were found to be up to 16 times more effective than neutral analogues in quenching the fluorescence of humic materials. This result is attributed to the enhanced coulombic attraction of cations to anionic surfaces. Chapters four, five and six explore the optical properties of colored marine DOM. Absorption spectra were characterized by their log-linearized slopes (S). S is found to be much greater for blue-water samples than for riverine and coastal samples. Fluorescence quantum yields were similar for a wide range of samples. Complete excitation/emission fluorescence spectra were collected and normalized to their respective absorbance spectra. DOM isolated on C-18 columns had somewhat different optical characteristics than whole water samples. Fluorescence, Marine optics, Dissolved organic matter.