Volatile organic compounds sources in Paris in spring 2007. Part I: qualitative analysis

Abstract

Environmental context Megacities are huge hotspots of pollutants that have an impact on atmospheric composition on local to larger scales. This study presents for the first time detailed results of measurements of volatile organic compounds in Paris and shows that, whereas non-methane hydrocarbons are mainly of local and regional origin associated with traffic emissions, a significant part of oxygenated volatile organic compounds originates from continental import. This highlights the importance of measuring volatile organic compounds instead of non-methane hydrocarbons alone in source classification studies. Abstract High-time-resolution measurements of volatile organic compounds (VOCs) were performed in the Paris city centre in spring 2007. The studied region was influenced mainly by air masses of two origins: (1) from the Atlantic Ocean, and (2) from north-eastern Europe. Although the baseline levels (i.e. those not influenced by local emissions) of non-methane hydrocarbons (NMHC) and CO were only slightly impacted by changes in the air-mass origin, oxygenated compounds such as acetone and methanol showed much higher baseline levels in continentally influenced air masses. This suggests that NMHC and CO mixing ratios were mainly influenced by local-to-regional-scale sources whereas oxygenated compounds had a more significant continental-scale contribution. This highlights the importance of measuring VOCs instead of NMHC alone in source classification studies. The period of Atlantic air influence was used to characterise local pollution, which was dominated by traffic-related emissions, although traffic represents the source of only one third of total VOCs emissions in the local inventory. In addition to traffic-related sources, additional sources were identified; in particular, emissions from dry-cleaning activities were identified by the use of a specific tracer (i.e. tetrachloroethylene).