An examimation of air pollution behaviour in relation to monitoring station's surroundings

This study explores the appropriateness of the locality of air monitoring stations which are meant to indicate air quality in the area. Daily variations in NO2 and PM10 concentrations at fourteen monitoring stations in Hong Kong are examined. The daily variations in NO2 at a number of background monitoring stations exhibit patterns similar to variations in traffic volume while variations in PM10 concentration exhibit less discernible pattern. Principal Component Analysis (PCA) and Cluster Analysis (CA) are applied to analyse NO2 and PM10 measurements between January 2001 and December 2005. The results show that NO2 concentrations at background stations within the urban area are highly influenced by vehicle emissions. The effect vehicle emission has on NO2 at stations within new towns is smaller. CA results also show that variations in PM10 concentrations are distinguished by the area the station is located in. The strong influence of roadside emissions towards concentrations of NO2 and PM10 at a number of urban background stations may be due to their close proximity to busy roadways and the high density of surrounding tall buildings, which creates an enclosure that hinders dispersion of roadside emissions and results in air pollution behaviour that reflects variation in traffic.