Volatile organic compound levels at one site in Rome urban air

Volatile organic compound (VOC), nitrogen dioxide (NO2) and ozone (O3) concentrations were measured at one site in Rome urban air during 2011. The seasonal mean concentrations of VOCs varied from 78 μg m−3 in winter to 37 μg m−3 in summer. Total aromatic concentration was reduced by 59% during summertime, alkanes of 39% and alkenes of 71%. VOC diurnal pattern exhibited a primary peak during the morning and a secondary peak in the evening hours coinciding with rush–hour traffic. The high correlation between benzene and toluene evidenced their common origin probably due to vehicular traffic. In summer isoprene diurnal profile showed both biogenic and anthropogenic origin. NO2 and O3 daily trends during summertime evidenced both photostationary state typical conditions and photochemical smog episodes. VOC and O3 trends also evidenced a reduction in VOC levels during O3 formation. Based on the Maximum Incremental Reactivity scale, the highest contributors to ozone production in Rome were propene, ethene and toluene. Comparing data found in Rome at the same site in 1992, 2007 and 2011, a decreasing trend in VOC levels was observed, suggesting the effectiveness of European Directives on air quality. In addition, our results were confirmed by similar data found in other urban areas around the world.