Kinetics of the reactions of soot surface-bound polycyclic aromatic hydrocarbons with O3.

The kinetics of the heterogeneous reactions of O(3) with 17 polycyclic aromatic hydrocarbons (PAHs) present on laboratory generated kerosene soot surface was studied at T=255-330 K in a low pressure flow reactor combined with an electron-impact mass spectrometer. The kinetics of soot-bound PAHs consumption in reaction with O(3) was monitored using off-line HPLC measurements of their concentrations in soot samples as a function of time of exposure to O(3). Concentration of ozone in the gas phase was analyzed by mass spectrometry. The first-order rate constants measured for individual PAHs ranged from 0.004 to 0.008 s(-1) and were found to be independent of the ozone concentration ([O(3)]=(0.5-92) x 10(12) mol cm (-3)) and temperature (255-330 K). Results show that reaction with ozone can be an important degradation pathway of the particulate PAHs in the atmosphere.