Interpretation Of Air Quality In Relation To Monitoring Station's Surroundings

摘要

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 NO_2 and PM_(10) concentrations at 14 monitoring stations in Hong Kong are examined. The daily variations in NO_2 at a number of background monitoring stations exhibit patterns similar to variations in traffic volume while variations in PM_(10) concentration exhibit less discernible pattern. Principal component analysis (PCA) and cluster analysis (CA) are applied to analyse NO_2 and PM_(10) measurements between January 2001 and December 2005. The results show that NO_2 concentrations at background stations within the urban area are highly influenced by vehicle emissions. The effect vehicle emission has on NO_2 at stations within new towns is smaller. CA results also show that variations in PM_(10) concentrations are distinguished by the area the station is located in. PCA results show that there are two principal components (PC's) associated with variations in roadside concentration of PM_(10). The strong influence of roadside emissions towards concentrations of NO_2 and PM_(10) 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.