Figure 10
From: UK monitoring and deposition of tephra from the May 2011 eruption of Grímsvötn, Iceland
Total and non-primary concentrations of (a) PM 10 and (b) PM 2.5 in Leeds on 22–30 May 2011. The peak in total PM10 on 24 May has a corresponding peak in total PM2.5, but not in primary PM10 or PM2.5. This indicates a non-anthropogenic source with a range of grain sizes e.g. tephra. The peak in total PM10 on 28 May has no corresponding peak in PM2.5. (c) Map of sites where peak hourly non-primary PM10 and PM2.5 concentrations were higher than the annual 95th and 65th percentiles, respectively, during 24 May. Circle size is proportional to concentration and colour represents the time of day when peaks occurred. The timing of peak concentration increases southwards and also eastwards across England.