Characterization of the temporal and spatial variabilities of pollution in Ile-de-France: From personal exposure measurements to sources definition

Air pollution results from a complex mixture of compounds, gases and particulate matter, whose effects have proven to be harmful. Volatile organic compounds (VOCs) play a major role in atmospheric chemistry and are precursors of ozone and secondary organic aerosols (SOAs). In Ile-de-France, exposure to pollution is a concern; however, significant uncertainties are still associated with the pollutants' sources, as well as their intensity and variability at different time scales, and very few investigations have focused on quantifying personal exposure. In this context, this research sought to better characterize the temporal and spatial variabilities of pollution in Ile-de-France. The questionable reliability of portable sensors has been addressed by the design of a selection and qualification protocol including various tests in static measurements, controlled chamber and mobility. This new methodology, based in particular on the use of a tool combining different statistical indicators, was applied to choose the AE51, Cairclip and Canarin, measuring black carbon (BC), nitrogen dioxide (NO₂) and particulate matter (PM) respectively. These three sensors were deployed during measurement campaigns involving about thirty volunteers. The personal exposure thus quantified is higher in fall than in spring and varies substantially according to the different environments frequented. Proximity to road traffic (for BC and NO₂) as well as cooking activities and tobacco smoke (for PM) make significant contributions to total exposure (up to 34 %, 26 % and 44 % respectively), even though the time spent in these environments is short. In addition to road traffic, BC is traditionally attributed to wood burning. A winter measurement campaign (3.5 months) attributed respectively 22 % and 47 % of the measured VOCs to these two sources. Compounds including benzenediol and methyl-butenone were measured and associated with wood burning for the first time in ambient air. A comparison with the regional emissions inventory identified similarities as well as differences and suggested improvements. (author)