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

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problematical, and which is also illustrative of the general problem of evaluating PM2.5 models because of uncertainties regarding measured data. PM 2.5 (µg/m³) 25 20 15 10 5 0 490000 510000 530000 Easting, metres PCM 2009 ADMS high resolution 2008 ADMS 1km resolution 2008 FDMS 2009 Partisol 2009 FDMS 2008 550000 570000 Figure 5.5: Annual mean PM2.5 concentrations predicted using the ADMS- Urban (2008) and PCM (2009) models together with observations from FDMS and Partisol instruments (mainly 2009) though Central London. The ADMS- Urban predictions are shown at 10 m x 10 m resolution (blue line) and at 1 km x 1 km resolution (red line). 5.4 Components of PM2.5 and source attribution Modelling PM2.5 and the future 25. Total PM2.5 includes contributions from primary sources, not all of which are represented in emission inventories, and from secondary particulates formed from precursor gases during atmospheric transport. The latter includes both secondary inorganic aerosol (SIA), in the form of nitrate, sulphate and ammonium compounds, and secondary organic aerosol (SOA). In addition, other contributions come from natural sources and water (see Chapter 2 for measurement perspective). 26. An important function of modelling is source attribution, i.e. differentiating components and estimating how different sources or groups of sources contribute to concentrations. Examples are given in Figures 5.6 and 5.10, and Tables 5.4 and 5.5. Figure 5.6 is derived from the PCM model (A2.8) and gives a breakdown of contributions to concentrations of PM2.5 for a transect across London and south-east England (coincident with but extending further than the transect shown in Figure 5.5), and Figure 5.10 gives a more detailed breakdown of components at background monitoring sites where totals can be compared with measurements. As an indicator of exposure, Tables 5.4 and 5.5 give a breakdown of the different contributions to population-weighted mean exposures from both the PCM and UKIAM models. 131
PM2.5 in the UK 132 PM component (µgm -3 ) 20 18 16 14 12 10 8 6 4 2 0 Annual mean PM2.5 transect across London for 2009 from PCM model 470500 473500 476500 479500 482500 485500 488500 491500 494500 497500 500500 503500 506500 509500 512500 515500 518500 521500 524500 527500 530500 533500 536500 539500 542500 545500 548500 551500 554500 557500 560500 563500 566500 569500 572500 575500 578500 581500 Easting (m) traffic area sources non-traffic area sources point sources urban dust rural dust regional primary secondary organic secondary inorganic residual sea salt Figure 5.6: Transect through the PM2.5 concentration distribution in London, showing a number of individual PM components from Henley-on-Thames in the west to Southend-on-Sea in the east (derived from PCM model). The transect is coincident with but extends further than that shown in Figure 5.5. 27. All of these examples show that the secondary inorganic aerosol accounts for a large proportion of total PM2.5 (~40% averaged over the UK), with data in Table 5.5 indicating a substantial contribution to this from sources outside the UK. The longer range nature of this transport accounts for the smooth spatial variation across the UK in Figure 5.7. Superimposed on this, the contribution from primary sources shows a much greater variability with sharp peaks in central London areas where emissions are concentrated. The remaining components of secondary organic aerosol, dust, sea salt and water content, are small individually. However, their combined contribution makes up a considerable fraction of the total. Representing each of these components and achieving mass closure (see Chapter 4) poses different problems as discussed below. 5.4.1 Modelled primary concentrations 28. Chapter 4 discusses the primary emissions of PM2.5 that can be quantified in emission inventories, and hence represented in modelling. The large uncertainties in these emissions and missing sources feed through to the models and the estimated concentrations. Although the contribution of primary PM2.5 emissions to overall concentrations in the UK is smaller than that of the secondary aerosol, the spatial pattern is correlated with the emissions and results in higher concentrations in London and other cities. This, together with additional urban dust, accounts for PM2.5 annual mean concentrations weighted by population density (‘population-weighted mean’) being around 3 to 4 µg m -3 higher in Inner London than in the Rest of England (see Table 5.3, derived from PCM).
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AIR QUALITY EXPERT GROUP Fine Parti
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This is a report from the Air Quali
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II Membership Chair Professor Paul
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IV Acknowledgements The Air Quality
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VI 2.5 Summary 39 2.5.1 What does t
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VIII 5.4 Components of PM2.5 and so
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PM2.5 in the UK 2 Air Quality Direc
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PM2.5 in the UK 4 I.2.1 Concentrati
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PM2.5 in the UK 6 • PM2.5 emissio
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PM2.5 in the UK 8 I.4.1 Modelling r
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PM2.5 in the UK 10 4. In broad term
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PM2.5 in the UK Table 1.2: National
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PM2.5 in the UK 14 17. Dry depositi
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PM2.5 in the UK 16 in ozone in the
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PM2.5 in the UK 18
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PM2.5 in the UK 20 5. The exact for
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PM2.5 in the UK 22 12. These diffic
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PM2.5 in the UK 24 2.3 Methods used
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PM2.5 in the UK 26 (e) During the
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PM2.5 in the UK 28 2.3.3 The Partis
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PM2.5 in the UK 30 35. For non-auto
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PM2.5 in the UK 32 43. Ratification
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PM2.5 in the UK 34 49. Many of the
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PM2.5 in the UK 36 57. Black carbon
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PM2.5 in the UK 38 2.4.4 PM2.5 elem
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PM2.5 in the UK 40 average of 93.6%
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PM2.5 in the UK Annex 1 - PM2.5 mon
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PM2.5 in the UK 44
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PM2.5 in the UK 46 3.2.1 Diurnal va
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PM2.5 in the UK 48 PM2.5/µgm -3 20
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PM2.5 in the UK 50 3.2.4 Seasonal v
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PM2.5 in the UK 52 12. Results are
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PM2.5 in the UK 54 3.4.2 Relationsh
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PM2.5 in the UK 56 Correlation 0.8
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PM2.5 in the UK Figure 3.11: Polar
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PM2.5 in the UK 60 south. Further a
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PM2.5 in the UK 62 3.7 PM2.5 episod
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PM2.5 in the UK 64 secondary ammoni
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PM2.5 in the UK 66 3.8 PM2.5 concen
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PM2.5 in the UK 68 3.9 Composition
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PM2.5 in the UK 70 43. The UK has i
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PM2.5 in the UK 72 NO 3 6 4 2 2000
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PM2.5 in the UK 74 54. PM ammonium
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PM2.5 in the UK 76 58. Data from th
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PM2.5 in the UK 78 (k) Road traffic
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Page 119 and 120: PM2.5 in the UK 108 4.6.1 Receptor
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Page 129 and 130: PM2.5 in the UK 118 100% 90% 80% 70
Page 131 and 132: PM2.5 in the UK 120 105. Receptor m
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Page 139 and 140: PM2.5 in the UK 128 Figure 5.2: Tot
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Page 147 and 148: PM2.5 in the UK 136 Figure 5.8: UKI
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Page 153 and 154: PM2.5 in the UK 142 the North Sea (
Page 155 and 156: PM2.5 in the UK 144 53. Modelling r
Page 157 and 158: PM2.5 in the UK Annex 2: PM modelli
Page 159 and 160: PM2.5 in the UK 148 2. Figure A2.1.
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Page 163 and 164: PM2.5 in the UK 152 Model 50 45 40
Page 165 and 166: PM2.5 in the UK 154 (a) (b) modPM 2
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Page 171 and 172: PM2.5 in the UK 160 SIA components
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Page 175 and 176: PM2.5 in the UK 164 A2.6: Photochem
Page 177 and 178: PM2.5 in the UK 166 PM2.5 Emission
Page 179 and 180: PM2.5 in the UK 168 A2.8: PCM PM mo
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PM2.5 in the UK Chapter 2: Measurin
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PM2.5 in the UK RoTAP (2012). Revie
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PM2.5 in the UK Harrison R.M. and Y
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PM2.5 in the UK Chapter 5 Modelling
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PM2.5 in the UK Jones A.M., Harriso
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PB13837 Nobel House 17 Smith Square
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