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

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18. The consequence of including this contribution without consideration of the measurement conditions would be misleading as a more realistic estimate of PBW would be ~10% (Harrison et al., 2004, and Green et al., 2009). The dry results (Figure A2.3.1b) show that the model underpredicts PM2.5 for 29 sites across the UK; the results are similar for PM10. Evaluation of CMAQ PM species 19. In the next step of the evaluation we compared the proportion of PM species in the model with the combined measurements at Harwell and London North Kensington. The PM components included nitrate (NO3 - ), sulphate (SO4 2- ), elemental carbon (EC), organic carbon (OC) and chloride (Cl - ), and are summarised in Figure A2.3.2. The results indicate that whilst the model underpredicts total PM10 concentrations, it replicates the proportion of each PM10 species reasonably well, slightly overpredicting observed NO3 - and SO4 2- fractions and underpredicting others such as Cl - , EC and OC. Observed PM component (of PM10) PM10Other 34% CI 11% EC 6% SO4 of PM10 13% OC 19% NO3 of PM10 17% Modelled PM component (of PM10) PM10Other 34% CI 7% EC 4% OC 13% SO4 of PM10 18% NO3 of PM10 24% Figure A2.3.2: Average observed and CMAQ PM10 components for 2008 at Harwell and London North Kensington. PM2.5 nitrate Annex 2: PM modelling in the UK 20. We then looked at the daily time series of each species, beginning with fine nitrate. Modelled daily PM2.5 NO3 - at London North Kensington (Figure A2.3.3) showed that the CMAQ model predicted the temporal trends and magnitudes of measurements reasonably well, although it was unable to predict some of the highest peaks. For the 12-month period the average modelled and measured fine nitrate concentrations were 1.3 and 2.4 µg m -3 respectively. Similar results were found at Harwell which gave model and measured concentrations of 1.4 and 2.6 µg m -3 respectively. 155
PM2.5 in the UK 156 NO3 – concentration (µg m -3 ) 25 20 15 10 5 0 Jan-08 Daily NO3 – of PM2.5 at N Kensington Feb-08 Mar-08 Apr-08 May-08 Jun-08 Jul-08 Aug-08 Sep-08 Oct-08 Nov-08 Dec-08 observed modelled Figure A2.3.3: Comparison between observed and modelled daily nitrate (NO3 - ) of PM2.5 at London North Kensington. 21. In contrast, CMAQ underestimated the coarse NO3 - fraction (2.5-10 µm) by a large margin. Model versus measured concentrations were 0.19 and 2.8 µg m -3 respectively. The main coarse mode NO3 - includes sodium nitrate (NaNO3) and calcium nitrate (Ca(NO3)2) from the reaction of nitric acid (HNO3) with sea salt and minerals (Hodzic et al., 2006) and the overnight reaction of sodium chloride (NaCl) with dinitrogen pentoxide (N2O5) (AQEG, 2005). 22. Elsewhere, Zhuang et al. (1999), Hien et al. (2005) and Kelly and Wexler (2005) reported that calcium and magnesium from mineral dust (especially, calcite (CaCO3) and dolomite (MgCa(CO3)2)) play an important role in coarse nitrate (Ca(NO3)2) formation. Sources of Ca 2+ and Mg 2+ cations include dust from soil erosion as well as emissions from urban and industrial sources (e.g. limestone quarrying, cement manufacture, concrete batching, industrial processes using limestone and dolomite, liming of soils, dust due to cultivation, construction, demolition and resuspension by traffic). Whilst these are estimated as part of the UK NAEI (AEA, 2006), it is important to further evaluate these emission sources and their role in coarse mode nitrate formation. PM10 chloride 23. CMAQ was unable to capture the magnitude of Cl - at both Harwell and London North Kensington. However, a comparison with the coastal predictions for three Norwegian monitoring sites (Birkenes, Kårvatn and Hurdal) (Figure A2.3.4) taken from the EBAS database (see http://ebas.nilu.no/) shows there to be good agreement for both Na + and Cl - at these locations. The annual average modelled and measured Cl - at the three Norwegian coastal sites was 0.25 and 0.32 µg m -3 respectively.
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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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PM2.5 in the UK 102 measurements an
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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 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
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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
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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
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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
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