Contrasting mechanisms of photochemical oxidation at silica/air interfaces: 1-methoxynaphthalene and phenanthrene
- Oak Ridge National Lab., TN (United States)
Up to 90 {mu}g m{sup -3} of solid, water-insoluble, inorganic oxides such as SiO{sub 2}, Al{sub 2}O{sub 3} and CaCO{sub 3} are reported to be found in the earth`s troposphere. (1) Large polycyclic aromatic hydrocarbons (PAH) in the troposphere reside sorbed to particulate surfaces at ambient temperatures and above. (2) Photochemical transformation of PAH at the solid/air interface plays a role in controlling the fates of these anthropogneic pollutants. Laboratory studies of the photochemistry of small PAH sorbed onto SiO{sub 2} and Al{sub 2}O{sub 3} surfaces have been conducted. The use of small PAH facilitates the quantitative photoproduct identification necessary for mechanistic interpretation. The SiO{sub 2}/air interfacial photochemistry of 8 of EPA`s 13 priority pollutant PAH have been investigated, or are currently under investigation in our laboratory. Additional substituted naphthalenes and other small aromatic hydrocarbons that are not on the EPA list of priority pollutants have also been investigated. These studies involve performing product analysis and in situ spectroscopic studies along with conventional sensitization, quenching and reactive intermediate trapping experiments at the solid/air interface. Application of these methodologies has revealed two distinct photo-oxidative pathways which participate in the photolysis. One pathway is mediated by singlet molecular oxygen addition to the sorbed PAR The other oxidative pathway involves an electron transfer from the photo-excited PAH to surface active sites or atmospheric oxygen. The photochemical destruction of 1-methoxynaphthalene and phenanthrene represent examples of both oxidative pathways observed at silica/air interfaces.
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 437328
- Report Number(s):
- CONF-960807--
- Journal Information:
- National Meeting - American Chemical Society, Division of Environmental Chemistry, Journal Name: National Meeting - American Chemical Society, Division of Environmental Chemistry Journal Issue: 2 Vol. 36; ISSN 0270-3009; ISSN NMACDY
- Country of Publication:
- United States
- Language:
- English
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