Ambient Gases and Particles
Polycyclic Aromatic Hydrocarbons and Polycyclic Aromatic Compounds
Environment Canada has been monitoring ambient air for polycyclic aromatic hydrocarbons (PAHs), polycyclic aromatic compounds (PACs) and selected trace metals/elements since November/December 2010 under an enhanced deposition study.
The presence of PACs in air is reported for 17 sites across the oil sands region for the first year of sampling. The results show that concentrations of PACs vary considerably across the region. Higher concentrations of PACs (including benzo(a)pyrene) are measured at sites that are closer to oil sands mining and upgrading facilities compared to sites that are further away. On average, the PACs concentrations in air at the closer sites are twice as high as the concentrations at further sites.
Passive samplers were used to collect data because there is no access to electrical power in remote locations of the oil sands region. This type of sampler is a simple device that passively collects air samples over a long period of time without the use of pumps to draw air through the sampler.
Passive sampling has key differences in the way samples are collected and so the results cannot at this time be related to the results obtained from more typical active sampling. In future, the data will be converted to a unit that is more commonly used (i.e. concentration of chemicals per volume of air or ng/m3), which will allow air concentrations in the oil sands region to be compared to levels in other parts of Canada, as well as to air quality objectives for benzo(a)pyrene.
In Canada, PAHs and PACs are emitted from both natural and human-made sources. According to the 2010 National Pollutant Emissions Inventory1 (NPRI), forest fires are the single most important natural source of PAHs in Canada (29%). Human-made sources are numerous and result in emissions of PAHs into many regions or municipalities across Canada.
According to the NPRI, the greatest anthropogenic sources of PAHs released to the atmosphere are residential wood heating (49%) and aluminum smelters (19%), with mobile sources contributing 1%. PAHs have drawn significant attention over the last 30 years because some species of PAHs are known carcinogens. For this reason, a number of PAHs can be found on the Canadian Environmental Protection Act priority substance list, and are either designated as constituting a danger to human life or health or as having a harmful effect on the environment.
In contrast, the presence of PACs in air is primarily associated with the incomplete combustion of petroleum products. In the oil sands region, sources of PACs can include bitumen mining and upgrading activities2. Compared to PAHs, PACs are often more persistent in the environment and more toxic3,4.
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Enhanced Monitoring of Total Gaseous Mercury
Environment Canada began monitoring of total gaseous mercury (TGM) at the Patricia McInnes air quality monitoring site in Fort McMurray in October 2010. The monitoring follows the established CAPMoN (Canadian Air and Precipitation Monitoring Network) standard operating procedures for its operation of the TGM analyzers. Information from these additional measurements will help to provide further information on the impacts to local and regional air quality and potential cumulative environmental impacts.
A preliminary analysis of quality-controlled data collected at the Patricia McInnes monitoring station from October 21, 2010, to May 31, 2011, shows that average ambient TGM concentrations averaged 1.40±0.15 ng m-3. This average is similar to average TGM concentrations measured elsewhere in Canada5,6. There is no current Environment Canada or Canadian Council of Ministers of the Environment air quality guideline for TGM. This dataset excludes data collected during the forest fire period in May 2011, in order to avoid including this natural source of mercury emissions. This information was published in Alberta Oil Sands: Energy, Industry and the Environment. Development in Environmental Science 11.
The next steps for this TGM data set will be to quality control the data up to December 2012 and conduct a full analysis, including summary statistics and seasonal/diurnal averages.
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The Canadian Air and Precipitation Monitoring Network (CAPMoN) is designed to study and monitor regional patterns and trends of atmospheric pollutants in both air and precipitation. There are no CAPMoN sites in the oil sands region. The CAPMoN data are included here for possible use as a reference or comparator.
CAPMoN monitors a wide suite of pollutants, including ground-level ozone, total gaseous mercury, reactive nitrogen, precipitation chemistry, ambient particles and gases and various sizes of particulate matter.
The network operates 33 monitoring sites (as of 2010) across Canada, predominantly in central and eastern Canada, but new sites are being developed in the west. Among these new sites to be developed, two sites (one in Alberta upwind of the oil sands region and one in Wood Buffalo National Park) will measure baseline levels and four sites downwind in Saskatchewan will monitor emissions from the oil sands region.
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In addition to ground-level monitoring of air quality in Canada, Environment Canada and its partners have been conducting measurements to quantify the levels of ozone and other selected gases and particles in the upper air. These measurements are important for understanding how air quality in Canada is affected both by local sources, such as forest fires and industry, and by sources as far away as Asia.
In the oil sands air monitoring component, both historical and new data from two upper air measurement programs, ozonesondes and AeroCAN, will be used to establish a baseline and to assess contributions from natural and human-made sources in the region to the ozone and aerosol concentrations, and compare these to other areas in Canada.
Ozone concentration measurements are done using ozonesondes, which are small, disposable instruments that are carried on weather balloons. The data from ozonesonde measurements quantify the concentration of ozone at various altitudes in the atmosphere from near the surface up to a height of 35 kilometers. The data from the stations operated by Environment Canada7 near and downwind of the oil sands region can support future analysis of oil sands developments effect on ozone levels in the upper air. The data are included here for possible use as a reference or comparator.
Measurements of the concentration and size of aerosol particles are made using the sun photometer instruments of the AeroCAN network, which is a joint collaboration between Environment Canada and the Université de Sherbrooke.
For more than a decade, the AeroCAN network has characterized the concentration and size of aerosols in the atmosphere on a regional and national scale. The network conducts measurements from over a dozen sites across Canada, and one of the instruments is located in Fort McMurray. The AeroCAN measurements are complemented by similar aerosol measurement performed by satellite. The data are included here for possible use as a reference or comparator.
Using the AeroCAN network, measurement of aerosol concentration and size made in the oil sands region will be able to be compared with those in other Canadian locations. The data will also assist scientists in determining the source of the aerosols measured, which can be from forest fires, transportation and industrial activity.
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In the oil sands air monitoring component, nitrogen dioxide (NO2) and sulphur dioxide (SO2) levels are monitored by ground-based instruments, satellites and other measurements. Monitoring of air pollutants from satellites is becoming an alternative to surface and aircraft measurements, and allows for better understanding of the global distribution, sources and trends of pollutants.
Using satellite data for the oil sands region, high-resolution air pollutant maps show distinct concentrations of NO2 (Figure 1a) and SO2 (Figure 1b) over an area (roughly 30 km x 50 km, or 19 miles x 31 miles) of intensive oil sands surface mining8. The map shows that NO2 concentrations are significant and are comparable to measurements made by large, individual sources such as coal-burning power plants. NO2 concentrations in the oil sand region are smaller than the signal observed over large metropolitan areas in Canada and significantly smaller that the signal observed elsewhere in North America (Figures 1c and 1d). The SO2 concentrations are also significant and are comparable to those from individual industrial emissions sources, including large base-smelting operations in Manitoba and Ontario. While the Canadian Council of Ministers of the Environment has begun work to develop Canadian Ambient Air Quality Standards for NO2 and SO2, these may not be directly comparable to the satellite-derived results that are presented here. Nevertheless, the satellite data will be helpful for understanding the impact of the response to any future standards.
Figure 1: This image shows long-term averages of NO2 and SO2 from the satellite-based Ozone Monitoring Instrument. Panels (a) and (b) show NO2 and SO2, respectively,
over the oil sands surface mining area. For comparison, NO2 is shown over a larger area in panel (c), which includes the city of Edmonton and coal-fired power plants to the west, and in panel (d), which shows the North American continent and includes many large population centres and coal-fired power plants [the boxed area in both panels corresponds to the oil sands area shown in panel (a)].
For the purpose of comparison to another region with large point-source emissions, panel (e) shows SO2 over the city of Thompson, Manitoba and a nearby nickel smelter. The data used here span the period of 2005 to 2010. Note that the intensity is slightly smaller over Thompson although emissions are greater than those in the oil sands. This reflects the impacts of winds that disperse the SO2 more quickly over the city of Thompson.
When compared to data collected in the last seven years, the amount of NO2 in the air over the surface mining region increased at 10.4 ± 3.5% each year between 2005 and 2010 (Figure 2).
Figure 2: Time series of OMI data for total mass of NO2 enhancement (in tonnes) over the period of 2005 to 2010. These data have been averaged seasonally. The seasonal cycle (maximum in winter, minimum in summer) is due primarily to a change in the NO2 lifetime.
The next steps will be the analysis of the satellite data sets to extend the time series for NO2 and SO2, as well as to determine other contaminants of interest in the oil sands region that can be measured by satellite.
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