Heterogeneous ozonation kinetics of polycyclic aromatic hydrocarbons on organic films

The room temperature heterogeneous reaction rates of gas-phase ozone with naphthalene, anthracene, fluoranthene, phenanthrene, pyrene, and benzo[a]pyrene were measured over a range of ozone concentrations from 3.5×1014 to 2.3×1016 molec. cm−3. The polycyclic aromatic hydrocarbons (PAHs) were dissolved in organic mixtures composed of octanol or decanol along with proxies for compounds known to be present in “urban grime” films. In all cases, the reaction kinetics were well-described by the Langmuir–Hinshelwood mechanism, which suggests a surface reaction. The adsorption of PAHs to the air–organic interface was confirmed by an adsorption isotherm of anthracene. The presence of the additional organic compounds generally did not affect the reaction rates; however, unsaturated species such as oleic acid and squalene reduced the observed rates significantly.