Characteristics Of Fluorescence Spectra Of Dissolved Organic Matters And Mechanism Of Its Photosensitized Transformation Of Monophenol

With convenience in operation and high sensitivity,spectroscopy has been used in revealing sources,compositions and chemical structures of dissolved organic matter?DOM?.DOM can absorb sunlight and thus induce kinds of reactive species in water,which have high reactivity with organic pollutants.Fluorescence spectra,especially time-resolved fluorescence,of seven DOMs with different sources were investigated to characterize the structural basis.Acetaminophen?APAP?,2,4,6-trimethylphenol?TMP?and tyrosine?Tyr?were chosen as representatives of monophenol.Intermediates and individual contribution of reactive species were investigated to reveal the mechanism of phenols'photosensitized transformation induced by DOM.Main conclusions are listed below:?1?Steady-state and time-resolved fluorescence of DOM were Ex/Em-dependent and fluorophores of DOM were complex,most of which were short-lived.NaBH₄reduction influenced differently on time-resolved fluorescence,indicating that intramolecular fluorescence quenching existed in DOM.Intramolecular fluorescence quenching resulted from charge transfer?CT?between electron donor and electron acceptor,but contribution of CT complex to fluorescence was quite limited.?2?Main intermediates produced in APAP's photosensitized transformation were APAP-oxidation and APAP-dimer.Reaction of phenoxyl radical?PhO·?with superoxide radical(O₂^·-)and reaction of phenol?phenolate ions?with singlet oxygen?¹O₂?can both lead to the generation of APAP-oxidation.APAP-dimer was formed through PhO·polymerization.On conditions set in this thesis,autochthonous DOM contributed little to fluorescence and photosensitization property of mixed DOM.?3?Besides addition reaction,reaction between PhO·and O₂^·-can also cause the regeneration of the parent phenol.Contribution of O₂^·-was first introduced in the kinetic model of DOM photosensitization,and the calculated quantum yields of triplet of Aladdin-HA and SRHA were 0.8%and 1.1%,respectively.During photosensitization reaction,especially after long-time and intense radiation,DOM's structure also changed and the change was related to pH and presence of phenols.