Factors which influence polycyclic aromatic hydrocarbon decomposition on wood smoke particles

The rates of decomposition of selected polycyclic aromatic hydrocarbons (PAH) on airborne wood soot in the presence of sunlight, O 3, or NO 2 (in the dark), were estimated. Experiments were conducted in 25-m 3 outdoor Teflon film chambers. PAH with molecular masses of 228 (benzo[a]anthracene) or greater exhibited small sampling losses and were found primarily in filter as opposed to XAD-2 extracts. Preliminary experiments indicated that major PAH losses due to O 3 reaction during filter sampling did not occur. PAH were found to be stable on airborne wood soot particles in the dark. In sunlight, however, a rapid decay resulted. Pseudo-first-order decay rates were calculated for selected PAH. These ranged from 0.01 to 0.02 min −1 for outdoor solar intensities of 1.1–1.3 cal cm −2 min −1 (4.6–5.4 Joule cm −2 min −1). At concentrations of 0.1–0.2 μL/L of O 3 or NO 2, estimated PAH decay in the dark was much slower than that which was observed under midday sun.