Spatial Distribution of Nitrogen Oxides and Particulate Matter Concentrations in Taipei

Abstract

PP-30-013 Background/Aims: Spatial patterns of nitrogen oxides (NOx) and particulate matter (PM), 2 major traffic-related air pollutants in urban environments, have not been characterized in most cities. The purpose of this study is to characterize horizontal and vertical distributions of NOx, PM concentration distribution, and investigate factors affecting their distributions in Taipei. Methods: We used a population density based sampling strategy to select 40 locations as our sampling sites in Taipei, including 20 urban background sites at small alleys with limited traffics and 20 traffic background sites neighboring roads with 4–6 lanes. Among these monitoring sites, 11 sites were used to characterize vertical profiles of NOx in Taipei. We used Ogawa passive samplers to measure NOx and NO2, and Harvard impactors to measure PM10, PM2.5 simultaneously for 2 weeks per season for 2 seasons during 2009–2010. Results: NOx concentrations at traffic sites (46.6 ppb) were significantly higher than the urban background sites (31.1 ppb). And PM2.5 concentration at traffic sites is 2.72 μg/m3 higher than at urban sites. PM10 concentration at traffic sites is 9.05 μg/m3 higher than at urban sites. Seasonal difference was significant for both NOx and PM concentrations. On the aspect of the vertical profile of NOx, the NOx and NO2 concentrations at 4th–6th floors were 0.79 times and 0.75 times lower than the concentrations at first—third floors, the NOx and NO2 concentrations at seventh—eighth floors were 0.64 times and 0.67 times lower than the concentrations which at first—third floors, respectively. There is a significant difference between our sampling results and the monitoring data from fixed-site stations nearby. Conclusion: Our study indicates that traffic pattern is an important factor for influencing the spatial distributions of both NOx and PM in urban environments.