Fairbanks, Alaska, faces a significant issue with fine particulate matter, known as PM2. 5. This tiny pollution is a big problem, especially in winter. The air quality standards set by the National Ambient Air Quality Standard (NAAQS) are often exceeded in Fairbanks. The standard for PM2. 5 is 35 micrograms per cubic meter over 24 hours, but Fairbanks has seen levels as high as 135 micrograms per cubic meter. Even the recent average from 2021 to 2023 was 56 micrograms per cubic meter, which is still way too high.

        The cold winters in Fairbanks trap pollutants near the ground due to strong temperature inversions. This leads to high concentrations of PM2. 5 and its precursor gases. The main contributors to PM2. 5 in Fairbanks are organic carbon and sulfate. To tackle this, control strategies have focused on reducing organic carbon through wood-stove measures and SO2 through fuel sulfur reductions.

        The Alaska Department of Environmental Conservation (ADEC) has been working on State Implementation Plans (SIPs) to meet the health-based standards. These plans are crucial for demonstrating the fastest path to cleaner air. Recently, ADEC upgraded to the CMAQ (Community Multi-Scale Air Quality) model version 5. 3. 3+ and updated Weather Research and Forecast (WRF) meteorology. This upgrade was part of a collaboration with the United States Environmental Protection Agency Office of Research and Development (EPA-ORD) and recent Alaska Layered Pollution and Chemical Analysis (ALPACA) studies. The emissions inventory for space heating and other pre-processing models have also been updated.

        These changes have improved model performance in representing stable boundary layers in meteorology and Model Performance Evaluation (MPE) of secondary sulfate. The new model predicts that 60% of the sulfate is primary, and 40% is secondary on average during winter. This is backed by studies showing similar results during the ALPACA field campaign.

        The goal is to bring Fairbanks into attainment for the 24-hour PM2. 5 standard by 2027. However, all control measures come at a cost to the community. Whether it's limiting wood stove use or mandating controls for SO2, the financial burden is felt by the residents. The modeling helps inform policy at the state and federal level to select the control strategies that will result in the fastest path to clean air while avoiding economic harm to the community.

        To focus the costs on wood stoves, a sensitivity model run was conducted with zero SO2 emissions from the point sources/electric utilities. The resulting secondary sulfate contribution to PM2. 5 was 0. 6 micrograms per cubic meter, with a concentration of 64 micrograms per cubic meter during the wintertime modeling period. The total PM2. 5 contribution from the electric utilities/point sources is estimated at 2. 2 micrograms per cubic meter from the modeling results. This contribution of point sources is in corroboration with the modeling work of Brett et al. 2024 on point-source contribution during the ALPACA campaign in Fairbanks.

        The key takeaway is that while Fairbanks faces significant challenges with air quality, especially during winter, there are strategies in place to improve it. The focus is on reducing wood smoke, which is a major contributor to PM2. 5. The community must balance the need for cleaner air with the economic impact of control measures.

AIR QUALITY MODELING

Fairbanks' Air Quality: A Winter Challenge

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