The photochemistry of polycyclic aromatic hydrocarbons adsorbed on the surface of coal fly ash

Author

Robert Alonzo Yokley

Date of Award

3-1985

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Gleb Manatov, Earl L. Wehry

Abstract

The fate of airborne particulate-associated polycyclic aromatic hydrocarbons is a problem of substantial concern, especially since recent observations indicate that the mutagenicity of organic extracts from sampled airborne particulate matter cannot be related solely to the presence of polycyclic aromatic hydrocarbons (PAHs). Reactions between particulate-associated PAHs and gaseous species, such as O₂, O₃, SO₂, and NO₂, either photochemically or non-photochemically, may be responsible for this excess mutagenicity.

The chemical reactivity of the PAHs pyrene and benzo(a)pyrene, adsorbed on coal fly ash surfaces, has been examined. Eight fly ashes, of varying origin and composition, were used as substrates for the adsorbed PAHs. Samples were subjected to micro-soxhlet extraction, before and after illumination by a solar spectrum-simulating lamp, and then quantified by ultraviolet absorption and fluorescence spectroscopy. Some of the samples were stored in the dark and then reextracted while other samples were exposed to NO₂ and HNO₃, as well as illumination. Many of these samples were subjected to direct-probe mass spectrometry.

Coal fly ash tends to stabilize pyrene and benzo(a)pyrene against photochemical transformations as compared with the same compounds adsorbed on silica gel, alumina, or glass. Non-photochemical trans formations are so slow that their environmental significance is negligible. It appears that HNO₃ is required, either as a reactant or as a catalyst, for nitration of coal fly ash-associated PAHs, photochemically or non-photochemically, when the adsorbed PAHs are exposed to NO₂•

It appears that carbon content and absorbance (or color) of coal fly ash are significant factors affecting the photochemical behavior of adsorbed PAHs. Furthermore, it appears that ambient atmospheric HNO₃ concentrations may be sufficient for nitration of particulate-associated PAHs; many of the nitro-PAHs are extremely mutagenic compounds.

Recommended Citation

Yokley, Robert Alonzo, "The photochemistry of polycyclic aromatic hydrocarbons adsorbed on the surface of coal fly ash. " PhD diss., University of Tennessee, 1985.
https://trace.tennessee.edu/utk_graddiss/12808