Satellite study finds NO2 and SO2 pollution over Canadian oil sands region comparable to that of a large power plant
|North American, annual-mean OMI (Ozone Monitoring Instrument) tropospheric NO2 VCDs (vertical column density) (2005–2010) averaged onto a 0.25° x 0.25° grid. The oil sands region within Alberta is indicated. McLinden et al. Click to enlarge.|
Atmospheric nitrogen dioxide and sulfur dioxide pollution over Canada’s oil sands region is comparable to that seen over a large power plant, according to satellite remote sensing observations of the two pollutants reported in a paper in Geophysical Research Letters, a publication of the American Geophysical Union.
The international team of researchers created high-resolution maps that revealed distinct enhancements in both pollutant species over an area (roughly 30 km x 50 km, or 19 miles x 31 miles) of intensive oil sands surface mining at scales of a few kilometers. The magnitude of these enhancements, quantified in terms of total mass, are comparable to the largest seen in Canada from individual sources, the team said.
For both gasses, the levels are comparable to what satellites see over a large power plant—or for nitrogen dioxide, comparable to what they see over some medium-sized cities. It stands out above what’s around it, out in the wilderness, but one thing we wanted to try to do was put it in context.—Chris McLinden, a research scientist with Environment Canada
The scientists found that sulfur dioxide amounts peaked over two of the largest mining operations in the Alberta oil sands, with a peak of 1.2x1016 molecules per square centimeter. Nitrogen dioxide concentrations reached about 2.5x1015 molecules per square centimeter. When researchers looked at the concentrations over the years using older satellite information, they found that the amount of nitrogen dioxide increased at 10.4 ± 3.5% each year between 2005 and 2010, keeping pace with the growth of the oil sands industry. An increase in SO2 was also found, but given larger uncertainties, was not deemed statistically significant.
It is important to provide some context for these results. The OMI SO2 enhancement over the oil sands is as large as that from any other individual emissions source in Canada, including the large base-metal smelting operations in Manitoba and Ontario. These results may also be compared with OMI SO2 enhancements seen near US coal-burning power plants...Values over the oil sands are similar as those of moderate to large power plants with annual emission rates of 100 kt[SO2]. The situation with NO2 is somewhat different: while the OMI NO2 signal is significant and comparable to that measured over large, individual sources such as coal-burning power plants, it is smaller than what is observed over large metropolitan areas....The city of Edmonton, with a population of approximately one million and large power plants and oil refineries nearby, has NO2 VCDs that are a factor of 2–3 larger and cover a much larger area.—McLinden et al.
The independent report on the levels of these airborne pollutants, which can lead to acid rain if they are in high enough concentrations, is a part of Environment Canada’s efforts to monitor the environmental impact of the oil sands’ surface mines. While some land-based measurements have been taken at particular points by other researchers, and a NASA airplane made another set of localized measurements, no one had calculated the overall extent of the oil sands’ air quality impacts including the giant dump trucks, huge refining facilities where the bitumen is processed, and more.
To do that, McLinden and his colleagues turned to satellite data. Several satellites orbiting Earth detect sunlight that passes through the atmosphere and is reflected back up to the space. Based on the patterns of reflected wavelengths, scientists can calculate the concentration of certain gasses—in particular nitrogen dioxide and sulfur dioxide. It’s a relatively new way to study pollution over small areas, McLinden said.
It’s important to examine the overall impact of the excavation and processing from the oil sands, said Isobel Simpson, an atmospheric chemist with the University of California at Irvine. She was not involved in this study, but previously participated in the airplane-based research of air quality over the oil sands.
Simpson called for broader, future studies that would measure additional pollutants and map their extents. With the oil sands industry expanding, she said, the area needs more monitoring.
McLinden, C. A., V. Fioletov, K. F. Boersma, N. Krotkov, C. E. Sioris, J. P. Veefkind, and K. Yang (2012), Air quality over the Canadian oil sands: A first assessment using satellite observations, Geophys. Res. Lett., 39, L04804, doi: 10.1029/2011GL050273