Photochemical degradation of polycyclic aromatic and nitroaromatic hydrocarbons in the urban atmosphere

Possible mechanisms of the photochemical conversion of polycyclic aromatic and nitroaromatic hydrocarbons in the urban atmosphere under the action of sunlight were analyzed. A kinetic model of the process was proposed, which takes into account the emission of harmful substances and the deposition of these substances onto the Earth's surface. It was found that emission is a predominant process within the bounds of a city. Beyond the precincts of a city, the concentrations of these hydrocarbons decrease because of photochemical degradation. In this case, the rate of this process for compounds adsorbed by soot particles is much higher than the corresponding value for compounds that occur in the gas phase. The results of calculations were compared with measurement data.