The Wood Buffalo Environmental Association (WBEA), Fort McMurray, Alberta requested that an analysis of air quality monitoring data be undertaken for the Regional Municipality of Wood Buffalo to assist stakeholders and interested parties in understanding the state of and trends in regional air quality. This report presents results of an investigation of short-term behaviors and long-term trends in continuously-measured ambient air quality data for the WBEA.
Daily and monthly (seasonal) behaviors and long-term trends in historical data for a number of air pollutants were investigated over the period 1998 to 2007. This period of time represented the most complete set of air quality data that was available in which to perform the investigation. Air pollutants included oxides of nitrogen, sulphur dioxide, particulate matter with aerodynamic diameter less than or equal to 2.5 μm (PM2.5), ground level ozone, total hydrocarbon, total reduced sulphur or hydrogen sulphide, and carbon monoxide. An objective of the study was to establish whether, and the extent to which, concentrations of air pollutants have changed over this time period in relation to industrial and community development.
Percentiles values taken from a cumulative frequency distribution of data can be more representative than general average values. Values representing 50th, 65th, 80th, 90th, 95th, and 98th percentile concentrations were identified from frequency distributions for each year and used for trend analysis. One definition of a percentile for a distribution of values is that it is the percentage of values that are smaller than the value at that percentile.
For example, if the 50th percentile 1-hour concentration for ozone is 20 ppb during
a year, 50% of the 1-hour concentrations are smaller than 20 ppb and 50% are larger. For a
98th percentile 1-hour concentration of 40 ppb during the year, 98% of the 1-hour concentrations are smaller than 40 ppb and only 2% are larger. A 50th percentile concentration is a typical concentration experienced on any given day. A 98th percentile concentration is a high-end value, or something that – on average – occurs much less frequently or not at all on any given day.
Table ES-1 summarizes trends for hourly average concentrations of air pollutants at WBEA monitoring stations. The record for three monitoring stations (AMS 3 – Lower Camp; AMS 14 – Anzac; and AMS 15 – CNRL Horizon) was less than four years. This period is considered too short to offer a meaningful understanding about concentration trends. Therefore results for these stations are not shown in Table ES-1.
Results indicated statistically significant increasing hourly concentrations for oxides of nitrogen (including nitric oxide and nitrogen dioxide) at the Fort McMurray Patricia McInnes station and the Fort McKay station.