Temporal trend and ozone formation potential of aromatic hydrocarbons in urban air of Rome

This work reports concentration data of aromatic hydrocarbons measured in the urban air of Rome in 2007 during hot and cold period. The correlation between benzene and toluene evidences the common origin of the two pollutants due to the auto vehicular traffic. The daily trend of aromatic hydrocarbons confirms that motor exhaust emissions are their dominant source. The comparison between our data and the relative data reported in literature for the years 1992 and 1998 shows the decrease of benzene from 11.1 ppbV in 1992 to 1.5 ppbV in 2007. Such reduction is due to both lower benzene content in fuel and the adoption of catalytic converters. Moreover, the contribution of aromatic hydrocarbons to local ozone production was evaluated in terms of Maximum Incremental Reactivity (MIR). Based on the MIR scale, the largest contributors to ozone production in Rome are m-xylene and toluene and both are characteristic emissions from vehicular exhaust. The largest influence of a volatile aromatic compound over another on the formation of ozone can help to define future emission reduction strategies.