MEASUREMENT AND DISPERSION BEHAVIOUR OF PARTICLES IN VARIOUS SIZE (5 nm>Dp<1000 nm) RANGES IN A CAMBRIDGE STREET CANYON

INTRODUCTION Current regulations for atmospheric particulate matter include PM10 and PM2.5 mass concentration. Fine particulates (those below 1000 nm) are not included in the regulatory limits. These particles contribute significantly to particle number concentration (PNC), but little to particle mass concentration. It is widely hypothesised that number concentrations of fine particles are better correlated with acute and chronic health effects and other environmental hazards than are particle mass concentrations (Donaldson et al., 1988; Pope III, 2000). Vehicles are a major source of fine particles in urban areas. High PNCs are common in urban street canyons, giving rise to health concerns for those exposed. It is important to understand the dispersion behaviour of fine particles in urban street canyons to enable better prediction of human exposure and design of regulatory mitigation strategies. The introduction of cleaner fuels, better emission control technologies and tighter legislations have decreased the total mass of particles emitted, but not significantly the number.