GAW Report No. 205 - IGAC Project

CHAPTER 6 - EUROPEFigure 4 - [Carslaw, 2005] Trends in monthly mean concentrations of NOX and NO2 averaged across 36 air pollutionmonitoring sites in London (1997-2003). A 12-month moving average trend has been fitted to both data setsFigure 5 - Running annual mean PM10 in London from 1994 to 2004 showing outer London background concentrations(mean of 3 sites), inner London background concentrations (mean of 3 sites), and central London roadside concentrations(1 site). Measurements made during 2004 are provisional [Fuller and Green, 2006]Although there are no extensive ambient VOC monitoring sites across Europe, there havebeen a number of studies done in the UK, with monitoring sites in London [Dollard et al., 2007; Fieldet al., 1994]. Data from Field et al., [1994] showed that generally, VOC concentrations declined from1986 to 1992, especially those associated with motor vehicle exhaust. Later monitoring by Dollardet al. [2007] throughout the UK from 1993 to 2004 also found decreasing VOC concentrations. Theconcentrations were observed to be highest at curbside monitoring stations and lowest in rurallocations; decreases were attributed to the implementation of exhaust gas catalyst and evaporativecanister control technologies on gasoline motor vehicles [Dollard et al., 2007]. Annual meanconcentrations in 2000 ranged from 1.3 to 28.8 µg m -3 for toluene, 0.6 to 14.6 µg m -3 for ethylene,and 0.4 to 7.2 µg m -3 for propylene at rural and curbside locations, respectively [Dollard et al., 2007].Over the past decade, reductions of carbon monoxide and sulphur dioxide concentrations inLondon have been successful. For both, significant decreases in concentration have been observedsince the late 1990s. Carbon monoxide was decreased by 56% from 1997 to 2007, and has been inattainment of the EU limit of 10 mg m -3 (max daily 8h mean) since 2000 [Fuller et al., 2007]. Thehighest concentrations of CO are found near roadways, reflecting the fact that motor vehicles arethe main source. Sulphur dioxide concentrations in London decreased by 78% from 1997 to 2007198