Aspects of the atmospheric chemistry of alkylnaphthalenes, phenanthrene and their atmospheric reaction products
Abstract
Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrated derivatives, observed in ambient atmospheres, are confirmed or suspected mutagens and animal carcinogens. They can undergo atmospheric chemical transformation processes, including photolysis and reactions with hydroxyl (OH) radicals, nitrate (NO3) radicals, Cl atoms and ozone (O3). In this work, atmospheric reactions were simulated in environmental chambers to study the atmospheric chemistry of naphthalene, alkylnaphthalenes, phenanthrene and their atmospheric reaction products, using chromatographic and spectroscopic techniques. Ambient measurements were conducted to assess the presence of atmospheric reaction products that were identified under laboratory conditions. Rate constants for the gas phase reactions of Cl atoms with naphthalene and alkylnaphthalenes were measured. The measured deuterium isotope effects and product yields indicate the reactions proceed by initial H- (or D-) atom abstraction. The products of the gas-phase reactions of OH radicals with naphthalene and alkylnaphthalenes were investigated. The major reaction products are ring-opened dicarbonyls that are 32 mass units higher in molecular weight than the parent compound, one or more ring-opened dicarbonyls of lower molecular weight resulting from loss of two beta-carbons and associated alkyl groups, and ring-containing compounds that may be epoxides. Phthalic anhydride and alkyl-substituted phthalic anhydrides were observed as second-generation products. A subsequent study investigated the photolysis and OH radical reactions of products formed from the OH radical-initiated reactions of naphthalene and alkylnaphthalenes, including phthaldialdehyde, 2-acetylbenzaldehyde and 1,2-diacetylbenzene. Environmental chamber studies have also been carried out to study the oxygenated and nitrated products from the gas-phase reactions of naphthalene and alkylnaphthalenes with NO3 radicals. Observed profiles of dimethyl-/ethyl-nitronaphthalenes (DNINNs/ENNs) from chamber reactions were compared to those obtained from ambient measurements. Photolysis of selected alkylnitronaphthalenes was performed to investigate the formation of alkylnaphthoquinones. In addition, studies of the products formed from the gas-phase reactions of phenanthrene with OH radicals. NO3 radicals and ozone were conducted. Daytime OH radical-initiated and nighttime NO3 radical-initiated reactions of gas-phase phenanthrene are suggested to be significant sources of 9,10-phenanthrenequinone in ambient atmospheres.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 2006
- Bibcode:
- 2006PhDT.......171W