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

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Concentrations and composition of PM2.5 36. Given this analysis, it is expected that the exposure reduction target will be the key driver for UK policy on exposure to PM2.5, while the PM10 objectives and limit values will supplement this control by driving policy on short-term (daily average) concentrations at hot spots. There may also be a role for the annual mean PM2.5 objective in Scotland to drive policy in Scotland. However, the PM10 objective is likely to be more stringent for these locations and is thus more likely to drive policy. 3.8.2 Relationship between PM2.5 and PM10 limit values and objectives 37. The 24-hour limit value and objective of no more than 35 days > 50 µg m -3 is taken to be equivalent to an annual mean PM10 concentration of 31.5 µg m -3 (Grice et al., 2010). Given the ratios of PM2.5:PM10 identified for different parts of the UK (see Figure 3.8), it is possible to equate this limit value/objective to annual mean PM2.5 concentrations (Table 3.1). The results in Table 3.1 show that the PM10 24-hour objective/limit value is more stringent than the annual mean PM2.5 limit value of 25 µg m -3 , especially in northern areas of the UK. Table 3.1: Indicative annual mean PM2.5 concentrations that equate to the 24hour PM10 limit value/objective in different parts of the UK. Region of UK PM2.5 (µg m -3 ) Scotland 17 a Northern Ireland 17 northern England 21 Wales 21 south-west and central England 22 south-east England and East Anglia 24 a In Scotland, this analysis only applies to the limit value, as a different objective applies. 38. In Scotland the PM10 annual mean objective of 18 µg m -3 is more stringent than the 24-hour mean PM10 objective of no more than seven days > 50 µg m -3 . Given the average PM2.5:PM10 ratio of around 0.55-0.6 identified for urban background sites in Scotland, the annual mean PM10 objective is equivalent to a PM2.5 concentration of 10-11 µg m -3 . On this basis, the PM10 objective will be more stringent than the PM2.5 objective of 12 µg m -3 . 67
PM2.5 in the UK 68 3.9 Composition 3.9.1 Overall composition of PM2.5 39. There have been few measurements of the overall composition of PM2.5 in the UK. Yin and Harrison (2008) collected 24-hour samples of PM2.5 from three sites in and around Birmingham between 2004 and 2006, sampling daily at a central urban background site (12 months), a roadside site (six months, mainly summer) and a rural site (six months, mainly winter). Samples were taken sequentially. A pragmatic mass closure model was used to assign compounds to the measured constituents. This mass closure model is a way of accounting for the measured mass concentration of airborne particles by summing scaled values of the concentrations of major chemical components in such a way as to allow for those components that are not directly measured (Harrison et al., 2003). The overall results for the central urban background site are shown in Figure 3.17a. Three components account for a large proportion of the total mass: nitrate, sulphate and organics. Iron-rich dusts are attributed to nonexhaust traffic emissions, calcium salts are attributed to construction/demolition dust and wind-blown soil, and sodium chloride to sea salt (although this should also include resuspended de-icing salt). Elemental carbon relates to primary combustion. Organic carbon (organics), both from combustion and natural sources, may be either primary or secondary. 40. Yin and Harrison (2008) also reported the PM2.5 composition on high pollution episode days (i.e. days with daily mean PM10 > 50 µg m -3 ). They reported a substantial increase in nitrate, which accounts for just under half the PM2.5 on episode days (Figure 3.17b). The authors note that this emphasises the importance of developing a better understanding of the sources of nitrate in airborne PM. Putaud et al. (2010) also report higher nitrate contributions at higher PM2.5 concentrations based on measurements carried out elsewhere in Europe. 41. Measurements of chemical composition are important for source apportionment and it is recommended that further measurements should be made of chemical composition in a variety of locations, principally rural, urban background and roadside, over different parts of the UK, to allow source apportionment to be conducted.
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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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Page 31 and 32: PM2.5 in the UK 20 5. The exact for
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Page 35 and 36: PM2.5 in the UK 24 2.3 Methods used
Page 37 and 38: PM2.5 in the UK 26 (e) During the
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Page 43 and 44: PM2.5 in the UK 32 43. Ratification
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Page 47 and 48: PM2.5 in the UK 36 57. Black carbon
Page 49 and 50: PM2.5 in the UK 38 2.4.4 PM2.5 elem
Page 51 and 52: PM2.5 in the UK 40 average of 93.6%
Page 53 and 54: PM2.5 in the UK Annex 1 - PM2.5 mon
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Page 57 and 58: PM2.5 in the UK 46 3.2.1 Diurnal va
Page 59 and 60: PM2.5 in the UK 48 PM2.5/µgm -3 20
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Page 67 and 68: PM2.5 in the UK 56 Correlation 0.8
Page 69 and 70: PM2.5 in the UK Figure 3.11: Polar
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Page 75 and 76: PM2.5 in the UK 64 secondary ammoni
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Page 83 and 84: PM2.5 in the UK 72 NO 3 6 4 2 2000
Page 85 and 86: PM2.5 in the UK 74 54. PM ammonium
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Page 89 and 90: PM2.5 in the UK 78 (k) Road traffic
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Page 95 and 96: PM2.5 in the UK Table 4.1: UK emiss
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Page 105 and 106: PM2.5 in the UK Emissions (ktonnes)
Page 107 and 108: PM2.5 in the UK 96 Figure 4.7: Spat
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PM2.5 in the UK 118 100% 90% 80% 70
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PM2.5 in the UK 120 105. Receptor m
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PM2.5 in the UK 122
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PM2.5 in the UK 124 5. At the regio
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PM2.5 in the UK 126 15. Some of the
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PM2.5 in the UK 128 Figure 5.2: Tot
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PM2.5 in the UK 130 µgm -3 160 140
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PM2.5 in the UK 132 PM component (
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PM2.5 in the UK 134 with larger dev
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PM2.5 in the UK 136 Figure 5.8: UKI
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PM2.5 in the UK Figure 5.9: Compari
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PM2.5 in the UK 140 PM2.5 concentra
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PM2.5 in the UK 142 the North Sea (
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PM2.5 in the UK 144 53. Modelling r
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PM2.5 in the UK Annex 2: PM modelli
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PM2.5 in the UK 148 2. Figure A2.1.
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PM2.5 in the UK 150 6. The non-line
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PM2.5 in the UK 152 Model 50 45 40
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PM2.5 in the UK 154 (a) (b) modPM 2
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PM2.5 in the UK 156 NO3 - concentra
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PM2.5 in the UK 158 26. This was in
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PM2.5 in the UK 160 SIA components
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PM2.5 in the UK 162 x 50 km grid fo
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PM2.5 in the UK 164 A2.6: Photochem
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PM2.5 in the UK 166 PM2.5 Emission
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PM2.5 in the UK 168 A2.8: PCM PM mo
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PM2.5 in the UK 170 illustrated by
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PM2.5 in the UK 172 trajectory mode
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PM2.5 in the UK 174
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PM2.5 in the UK 176 4. The delivery
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PM2.5 in the UK 178 12. With respec
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PM2.5 in the UK 180
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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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