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

VI
2.5 Summary 39
2.5.1 What does the PM2.5 metric measure? 39
2.5.2 How do PM10 and PM2.5 measurement issues compare? 39
2.5.3 Do we have robust measurements of PM2.5? 39
2.5.4 What about measurements of chemical components of PM2.5? 41
2.6 Recommendations 41
Annex 1 PM2.5 measurement sites in the UK 42
Chapter 3: Concentrations and composition of PM2.5 45
3.1 Introduction 45
3.2 PM2.5 concentrations across the UK: Temporal variations and trends 45
3.2.1 Diurnal variations of PM2.5 at urban background sites 46
3.2.2 Diurnal variations of PM2.5 at roadside and industrial sites 48
3.2.3 Diurnal variations at a site in Lisburn, Northern Ireland 49
3.2.4 Seasonal variations in PM2.5 at urban background sites 50
3.3 Trends in PM2.5 concentrations 51
3.4 Relationship of PM2.5 with other pollutants 52
3.4.1 Relationship of PM2.5 with PM10 52
3.4.2 Relationship of PM2.5 with PM10, NOx and NO2 54
3.5 Spatial patterns 55
3.5.1 Spatial homogeneity of PM2.5 hourly mean concentrations 55
3.5.2 Differences in annual mean PM2.5 concentrations by site type 56
3.6 Relationship with wind direction and air mass trajectory 57
3.6.1 Relationship of hourly mean PM2.5 concentrations
with wind direction 57
3.6.2 Relationship of hourly mean PM2.5 concentrations with
air mass trajectory 59
3.7 PM2.5 episodes 62
3.7.1 Winter episodes 62
3.7.2 Transport from continental Europe 63
3.7.3 Bonfires and fireworks 65
3.8 PM2.5 concentrations in relation to standards 66
3.8.1 EU and UK requirements for PM2.5 66
3.8.2 Relationship between PM2.5 and PM10 limit values and
objectives 67