Measurements of particulate matter at intersection in Hong Kong

An experimental study of particulate matter from vehicle emission was carried out at a typical traffic intersection in Hong Kong downtown area and aimed to explore the varing trends of particulate matter on roadsides. Seven particle number concentrations with different size groups (0.02-0.3mm,0.3-0.49mm, 0.5-0.99mm, 1-1.99mm, 2-4.99mm, 5-9.99mm, and >10mm) were collected and analyzed. It was found that the particulate levels, in general, present periodic variations with the traffic signal intervals. The concentrations of the particulate matter increase and accumulate to the corresponding peak points during the green time and then diffuse to a relatively stable level during the red one. In addition, the principal component analysis (PCA) was utilized to reveal the correlation between the measured particulate matters. The results show that particles between size range of 0.02-0.3mm and 0.5-4.99mm have similar characteristics and can be combined as the first principal components, followed by particles larger than 5mm and within the range of 0.3-0.49mm. It can be deduced that the particle size in 0.02-0.3mm and 0.5-4.99mm are mostly originated from traffic emission.