GAW Report No. 205 - IGAC Project

CHAPTER 6 - EUROPEFigure 11 - Wind direction at the SIRTA/IPSL site at Ecole Polytechnique, 20 km southwest of downtown Paris. Red bars:July 2005 – 2009, black bars: particular situation during the MEGAPOLI campaign in July 2009[Courtesy of M. Haeffelin, SIRTA / IPSL]6.3.4 General air pollution situationIn the Ile de France region, the Air Quality survey network AirParif(http://www.airparif.asso.fr/) has a dense routine measurement network with nearly 50 automatedsites located within the Paris agglomeration and neighbouring rural areas, giving hourlyconcentrations of target pollutants. Nearly 15 years of gathered data allow for a climatologicalanalysis of the evolution of urban and peri-urban pollution.Figure 12 illustrates that yearly averages of primary pollutants such as benzene and NO, orSO 2 (of dominant industrial origin) show a negative trend at urban background sites over the last tenyears. Ozone shows an upward trend, probably due to decreasing titration with fresh NO emissions.NO 2 and PM 10 do not show a significant trend. Both are due to primary emissions and secondarychemical transformation.Figure 12 - Trends of major atmospheric pollutants: SO2, (top left), of major industrial origin, NOX (top right), of major trafficorigin for urban background sites from the AirParif network; ozone monthly averages for year 2005(bottom, left) for anurban background site (dark purple) and an rural site (light purple), PM10 annual distribution for year 2009 showing largervalues in Paris downtown (inner circle)[AIRPARIF http://www.airparif.asso.fr/pages/polluants/evolution]203