Air quality expert group - Fine particulate matter (PM2.5) in ... - Defra

PM2.5 in the UK
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58. Data from the aethalometer instruments are reported hourly, so that variations
through the day can be observed. Diurnal variations averaged over 2010 are
shown for four sites chosen to illustrate the different temporal patterns that
arise from different sources (Figure 3.23). The shaded area represents the
uncertainty in the mean value for each hour at the 95% confidence level.
It does not represent the overall measurement uncertainty. As noted above,
the London Marylebone Road kerbside concentrations are much higher and
persist during the day; there are no morning and evening rush hour peaks.
The influence of domestic heating on black carbon at the Strabane site is very
evident, with an evening peak of a few µg m -3 . There is thus evidence that
the use of solid and/or liquid fuel for domestic heating can contribute
to higher black carbon concentrations, with this being most significant
during the evening.
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10
8
6
4
2
0
MAN MY1 STR HAR
6 12
hour
18 23
Figure 3.23: Black carbon diurnal variation in 2010 (µg m -3 ) at London
Marylebone Road (MY1), Manchester Piccadilly (MAN), Harwell (HAR) and
Strabane 2 (STR) (Northern Ireland). The shading represents the 95% confidence
interval of the mean.