Emission sources sensitivity study for ground-level ozone and PM₂.₅ due to oil sands development using air quality modeling system: Part I- model evaluation for current year base case simulation

The Community Multiscale Air Quality (CMAQ) and the Sparse Matrix Operator Kernel Emissions (SMOKE) modeling systems were used to simulate emissions and air quality in North Eastern Alberta where a rapid rise in oil sands development has caused air quality concerns over the last decade. The models were run on a 36/12/4 km domain for the four month period of May through August 2002. A model performance evaluation was conducted by comparing the CMAQ model estimates against ambient air quality measurements. In the Alberta oil sands region, the model tended to achieve or nearly achieve ozone model performance goals, albeit with an underestimation bias. The magnitudes of the observed PM₂.₅ concentrations were matched by the modeling system, except when the observed PM₂.₅ concentrations were influenced by emissions from forest fires in which case the model underestimated the observed PM₂.₅ concentrations. The CMAQ-estimated 4th highest daily maximum 8-hour ozone concentrations in the oil sands region were below the 65 ppb Canada Wide Standard (CWS) as well as the 58 ppb Alberta Management Plan Trigger Level. The highest estimated ozone concentrations occurred near the oil sands development area just north of Fort McMurray with values approaching, but below, the 58 ppb Management Plan Trigger Level; estimated ozone concentrations are much lower in the farther northern portions of the oil sands region. The acute (i.e., maximum 3-day value) SUM60 vegetative ozone exposure metric was mostly less than 100 ppb h, which is below the threshold of concern for crops. However, just north of Fort McMurray there were small areas where the acute SUM60 metric exceeded the 500–700 ppb h threshold of concern for crops with maximum values in plumes from sources in the oil sands mine area of ∼900 ppb h. The maximum chronic (three-month average) SUM60 ozone exposure metric was below the thresholds of concern. The CMAQ-estimated maximum 98th percentile 24-hour average PM₂.₅ concentration occurs in the mine area north of Fort McMurray and was below the CWS threshold (30 μg m⁻³), however it was above the Alberta Management Plan Trigger Level (20 μg m⁻³). The estimated 98th percentile 24- hour average PM₂.₅ concentrations were mostly in the 2–6 μg m⁻³ range with regions of higher PM₂.₅ concentrations predicted just north of Fort McMurray in the oil sands development region.