Abstract
Particle concentrations and size distributions were measured simultaneously at a busy roadside and at nearby urban background sites in Birmingham, UK. The evolution of the particle size distribution during dispersion was measured by operating two scanning mobility particle sizers simultaneously. The morphology of the particles was examined using transmission electron microscopy, and results from a simple coagulation box model, which is outlined, were compared with the measurements. An electrical low-pressure impactor was utilized to measure real-time particle concentration and size distribution. Results showed that the data generated by the various instruments was comparable. At the roadside, the total number concentration ranged 1.6 1.9 10 super(5)/cm super(3), and more than 50% of the particles were smaller than 30 nm. At the background locations, the 24-h average number concentration was 2.68 10 super(4)/cm super(3). The number concentration decreased faster than the mass concentration downwind of the traffic.