Abstract: | Nitration by NO2 of pyrene or benzoa]pyrene adsorbed from the vapor phase onto six coal ashes, alumina, and silica substrates is not observed if the NO2 is thoroughly purged of nitric acid. Also, the photochemical transformation of pyrene or benzoa]pyrene adsorbed on these substrates is not detectably influenced by the presence of nitric acid-free NO2. Photochemical production of nitro derivatives of adsorbed polycyclic aromatic hydrocarbons in the presence of NO2 does not appear to be a significant process unless appreciable concentrations of nitric acid, or perhaps strong oxidants such as ozone, also are present. |