| Long term trend and pollution roses for selected pollutant were examined across major cities of Canada, include carbon monoxide (CO), sulphur dioxide (SO2), nitrogen dioxide (NO2), nitric oxide (NO), nitrogen oxide (NO), ozone (O3), and particulate matter (PM). Linear regression was used to obtain the annual mean trend from 1998--2007. There was a statistically significant downward trend for all pollutants studied except O3 in most cities indicating effective regulatory provision and reduced emissions during the past decade. O3 showed an upward trend and large year-to-year variation indicating strong influence of meteorological conditions and photochemical reactions. Wind rose and percentile pollution rose plots suggest that the higher concentration of SO2 was associated with specific sources, while CO, PM, NOx were associated with local production. O3 was found to be regional with high concentrations mostly occurring in the direction of industrial cities of United States. Overall, the finding of the study indicates CO, SO2, NOX and PM as improved local pollutants. Future studies should take into consideration the effect of volatile organic compound levels on the long term trend of O 3. |
