FT-IR Kinetic Study on the Gas-Phase Reactions of the OH Radical with a Series of Nitroaromatic Compounds

Large quantities of harmful VOCs are emitted into the troposphere from anthropogenic sources (Calvert et al., 2002). Aromatic hydrocarbons are an important class of VOCs present in the atmosphere, which contribute significantly to the chemistry of urban air (Atkinson, 2000; Atkinson and Arey, 2003). Estimations of the global emissions of aromatic hydrocarbon suggest that they comprise between 17-25% of the total anthropogenic NMVOC emissions (Calvert et al., 2002). The degradation of aromatic hydrocarbons is mainly initiated during the day by reaction with the hydroxyl radical (OH). Based on the presently accepted but inadequate mechanism for the atmospheric degradation of aromatic hydrocarbons, it has been calculated that this class of VOC could account for up to 30% of the photooxidant formation in urban areas (Derwent et al., 1996, 1998). Besides the photooxidant formation, this class of hydrocarbon is also assumed to make a significant contribution to secondary organic aerosol (SOA) formation in urban areas (Odum et al., 1996; Forstner et al., 1997; Hurley et al., 2001). This ranks aromatic hydrocarbon as one of the most important classes of hydrocarbons emitted into the urban atmosphere. Formulation of a realistic photo-oxidation mechanism for aromatic hydrocarbons represents one of the most important and challenging problems remaining to be solved in chemical models of tropospheric photooxidant formation.