Source Apportionment of PM_2.5 in a Subarctic Airshed - Fairbanks, Alaska

Fairbanks, Alaska has some of the highest measured ambient PM_2.5 concentrations in the United States, with wintertime levels often exceeding the 24-hour PM_2.5 National Ambient Air Quality Standard (NAAQS) of 35 μg/m³. In an effort to understand the sources of PM_2.5 in the Fairbanks airshed, source apportionment using Chemical Mass Balance (CMB) modeling was conducted at four locations in Fairbanks over a three-winter period (2008/2009, 2009/2010, and 2010/2011). At each of the four sites, PM_2.5 concentrations averaged between 22.5 ± 12.0 μg/m³ and 26.5 ± 18.9 μg/m³, with frequent exceedances of the 24-hour NAAQS on the scheduled sample days. The results of the CMB modeling revealed that wood smoke (likely residential wood combustion) was the major source of PM_2.5 throughout the winter months in Fairbanks, contributing between 60% and nearly 80% of the measured PM_2.5 at the four sites. The other sources of PM_2.5 identified by the CMB model were secondary sulfate (8-20%), ammonium nitrate (3-11%), diesel exhaust (not detected-10%), and automobiles (not detected-7%). Approximately 1% of the PM_2.5 was unexplained by the CMB model. Additional research is needed to confirm the woodsmoke results of the CMB model, as well as determine which sources (fuel oil residential heating, coal combustion, etc.) contribute to the measured secondary sulfate.