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

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were for daily PM2.5 nitrate and for daily PM10 sea salt and sulphate, and some were for daily PM10 EC/OC (for the last five months of 2008). 13. In general, the model underpredicts hourly PM2.5 measurements when using estimates of modelled PM2.5 mass without particle bound water (Figure A2.3.1). A similar conclusion can be drawn for total PM10 concentrations. Despite the underprediction of PM10, the model replicates the proportion of each species reasonably well, slightly overpredicting observed NO3 - and SO4 2- fractions and underpredicting others such as Cl - , EC, SOA and OC (Figure A2.3.2). The model results for fine mode PM nitrate (Figure A2.3.3) and POC (Figure A2.3.7) are in reasonable agreement with measurements, although some of the peak concentrations were not well predicted. Some of the coarse mode particles were underpredicted and require further evaluation, especially in the case of nitrate and sea salt. EC, SO4 2- (Figure A2.3.5) and SOA were also underpredicted. 14. Improving the predictive capability of the model for some components (EC) can be achieved in a straightforward way by improving emissions estimates. Improving the predictive capability for others (Cl - and coarse mode nitrate) may prove to be more difficult because there is a combination of possible reasons for the model underprediction. 15. An examination of the chemical composition of the PM2.5 mass in 2008 revealed that 58% was estimated to be particle bound water (PBW) (Figure A2.3.1). This is a model estimate of ambient PBW and contrasts with measurements, where PBW is mostly removed by conditioning in the field or in the laboratory and water content is typically reduced to around 10% (Harrison et al., 2004, and Green et al., 2009). As a consequence, including modelled PBW without correcting for the measurement conditions can undermine attempts to evaluate the model for total PM2.5 or PM10 as well as for hygroscopic particles such as SO4 2- and possibly NO3 - and SOA. These results demonstrate the importance of PBW when quoting PM concentrations and it would be worth considering quoting the assumptions made alongside the concentrations from measurements and models. Hourly predictions of PM2.5 Annex 2: PM modelling in the UK 16. Speciated PM analysis was conducted against measurements from the AURN and London Air Quality Network (LAQN) during 2008, using CMAQ (v4.7) and the WRF meteorological driver. The WRF-CMAQ model was operated with 23 vertical layers (up to approximately 15 km above ground) and two nesting levels, downscaling from 81 km grid resolution over Europe to 9 km grid resolution over the UK. The emissions from EMEP, NAEI and the European Pollutant Emission Register (EPER) were processed into hourly 3-D gridded chemical species and used the CB05 chemical scheme which included the aqueous and aerosol (AERO5) extension. 17. In 2008 CMAQ PM10 and PM2.5 predictions were assessed against measurements from AURN and LAQN, including 70 PM10 sites (three rural, 12 suburban and 55 urban background) and 29 PM2.5 sites (two rural, six suburban and 21 urban background). In comparing the hourly average concentrations we have removed the model’s predictions for water. The reason for doing this is that CMAQ water estimates can be high (58%), as demonstrated by the modelled estimate of particle bound water (PBW) at ambient conditions in Figure A2.3.1a. 153
PM2.5 in the UK 154 (a) (b) modPM 2.5 SO4 NO3 NH4 OC EC Cl Na Other (minerals) Water 100 80 60 40 20 20 40 60 80 Modelled Water 9.0 58% 100 100 80 60 40 20 obsPM 2.5 Modelled Other (minerals) 0.6 4% Modelled SO4 1.5 10% Modelled Cl 0.1 0% Modelled Na 0.0 0% 20 40 60 80 100 rural suburban urban background Modelled NO3 1.5 10% Modelled NH4 1.0 6% Modelled OC 1.4 9% Modelled EC 0.5 3% Counts 5828 3390 1972 1147 667 388 226 131 76 44 26 15 9 5 3 2 1 Figure A2.3.1: (a) London North Kensington PM2.5 components in 2008, including particle bound water without correction for measurement conditions; and (b) scatter plot of modelled and observed 2008 PM2.5 at two rural, six suburban and 21 urban background sites without particle bound water.
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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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PM2.5 in the UK 80 provided by spec
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PM2.5 in the UK 82 14. The London L
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PM2.5 in the UK Table 4.1: UK emiss
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PM2.5 in the UK 86 24. National inv
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PM2.5 in the UK 88 Figure 4.5: Spat
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PM2.5 in the UK 90 either nanoparti
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PM2.5 in the UK 92 37. Further cons
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PM2.5 in the UK Emissions (ktonnes)
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PM2.5 in the UK 96 Figure 4.7: Spat
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PM2.5 in the UK 98 4.4 A critical a
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PM2.5 in the UK 100 60. At a local
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Page 119 and 120: PM2.5 in the UK 108 4.6.1 Receptor
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Page 125 and 126: PM2.5 in the UK 114 inorganic parti
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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
Page 141 and 142: PM2.5 in the UK 130 µgm -3 160 140
Page 143 and 144: PM2.5 in the UK 132 PM component (
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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.
Page 161 and 162: PM2.5 in the UK 150 6. The non-line
Page 163: PM2.5 in the UK 152 Model 50 45 40
Page 167 and 168: PM2.5 in the UK 156 NO3 - concentra
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Page 171 and 172: PM2.5 in the UK 160 SIA components
Page 173 and 174: PM2.5 in the UK 162 x 50 km grid fo
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
Page 181 and 182: PM2.5 in the UK 170 illustrated by
Page 183 and 184: PM2.5 in the UK 172 trajectory mode
Page 187 and 188: PM2.5 in the UK 176 4. The delivery
Page 189 and 190: PM2.5 in the UK 178 12. With respec
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Page 199 and 200: PM2.5 in the UK Chapter 5 Modelling
Page 201 and 202: PM2.5 in the UK Jones A.M., Harriso
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