Currently, there are two air quality objectives for hydrogen sulphide in Alberta. The one-hour average objective is based on odour perception. It is 10 parts per billion (ppb). The 24-hour average objective is based on health effects. It is 3 parts per billion.
The total number of hydrogen sulphide exceedances have increased since 1990 (partly in response to an increase in the number of stations monitoring for hydrogen sulphide). In 2007, exceedances occurred most frequently at the Mildred Lake, Mannix and Lower Camp stations in the oilsands region north of Fort McMurray. There were also several exceedances at Calgary East (17 1-hour exceedances) and Scotford (10 1-hour exceedances; not shown in figure above) in 2007. The major source of hydrogen sulphide at the Calgary East station is a nearby sewage treatment plant. However, high hydrogen sulphide levels at this location also occur during temperature inversions (when the air temperature increases with height), which are accompanied by stagnant wind conditions. The Scotford station is located in an industrial area, in proximity to oil and gas refineries. |
