NWT Air Quality Report (2011) - Environment and Natural ...

The graph in Figure 5 presents the PM 10data for 2011 and clearly shows the annual ‘dust’event, which is typical mainly for the month of April. This is due to residual gravel on theroads following the spring snow thaw. There were thirteen exceedances of the adoptedstandard of 50µg/m 3 in 2011. The majority of these occurred in April and correlate well withthe springtime “dust event”. The other exceedances occurred during the months of Juneand July and were attributed to the previously mentioned smoke from forest fires.Figure 5: 2011 Yellowknife BAM PM 1060.0(μg/m 3 )140.0Monthly Average50.040.030.020.010.0120.0100.080.060.040.020.0Maximum Daily Average0.0J F M A M J J A S O N D0.0Monthly AverageMaximum Daily AverageFigure 5 shows the BAM PM 10monthly averages and maximum daily averages per monthmeasured at the Yellowknife station in 2011. The highest maximum daily concentration was127.9μg/m 3 , occurring in April.Sulphur Dioxide (SO 2)Continuous monitoring for SO 2has been conducted in Yellowknife at several locations since1992, primarily to monitor the effects from the former gold mine operations. The current SO 2monitoring location at the Sir John Franklin station has been in place since 2004.There were no exceedances of the NWT hourly (450μg/m 3 ) or 24-hour (150μg/m 3 ) standardsin 2011 in Yellowknife. The annual average was less than 2μg/m 3 , a level that is well belowthe NWT (30μg/m 3 ) standard.14 NWT Air Quality Report 2011