DISPERSION MODELING OF OXIDES OF NITROGEN, SULFUR DIOXIDE AND PM2.5 IN THE PROVINCE OF NOVA SCOTIA, CANADA

Abstract

This study focuses on NOx, PM2.5 and SO2 dispersion modeling in seven domains across the province of Nova Scotia. The emission sources of the above pollutants include major industrial sources and highways across the province. US EPA steady state Gaussian Plume model AERMOD is used to conduct the dispersion simulation study. Due to the limitation of AERMOD to compute the short range (<50km) dispersion, the domains are of size equal to or less than 50 km. Pollutant emission data, vehicle count and the emission source’s characteristics were taken from the NPRI database. Although this study was aimed to conduct the dispersion modeling for a span of four year from 2004 to 2007, due to missing records in the database, simulations were carried out in different years in each domain depending upon maximum available data for model input. Meteorological data is obtained from Halifax International Airport, Sydney and Yarmouth MET stations. Elevations of the surface are obtained using Geotiff files from ArcGIS v9.3. Nova Scotia’s Comprehensive Air Pollutant Emission Source Inventory is used to obtain emission source characteristics and total emissions per year. Modeling results demonstrate that dispersion of the pollutants is governed by the wind direction, ambient temperature and emission rate of the NOx, PM2.5 and SO2. Modeling results of NOx, PM2.5 and SO2 are compared with Environment Canada’s monitored NAPS data during 2004. The comparison results show better agreement between monitored and modeled data in Sydney and Prohawksbury areas compared to Halifax. This phenomenon is caused by the exclusion of ship emission at Halifax harbor and automobile emission in downtown Halifax area. Overall the model showed reasonable agreement with the monitored values. Model performance can be improved by including more number of available emission sources and hourly emission rates.