| This research presents an evaluation of ambient air trends from Tomahawk and Carrot Creek, in rural western Alberta. Pollutants---O3, NO 2, SO2, and PM2.5---were examined to assess trends over time using, (a) various percentiles of hourly concentration distributions from each year, and (b) frequencies in which various benchmark concentrations were exceeded each year. Hypothesis tests were conducted (at alpha = 0.05) to identify statistically significant deviations. Results from the two methods were found to be consistent with each other. At Tomahawk, no statistically significant change was detected in air quality with respect to O3 and PM2.5, while SO2 and NO2 showed decreasing trends. At Carrot Creek, SO2 exhibited statistically significant decreasing trends, while O3 and NO2 showed no change. The decreasing trends observed with SO2 appeared consistent with reduced natural gas flaring and venting data over the same time period. Only O3 showed considerable diurnal and seasonal variations at both stations. |
