Assessing the Oxidative Potential of Outdoor PM 2.5 in Wintertime Fairbanks, Alaska.

The oxidative potential (OP) of outdoor PM 2.5 in wintertime Fairbanks, Alaska, is investigated and compared to those in wintertime Atlanta and Los Angeles. Approximately 40 filter samples collected in January-February 2022 at a Fairbanks residential site were analyzed for OP utilizing dithiothreitol-depletion (OP DTT ) and hydroxyl-generation (OP OH ) assays. The study-average PM 2.5 mass concentration was 12.8 μg/m 3 , with a 1 h average maximum of 89.0 μg/m 3 . Regression analysis, correlations with source tracers, and contrast between cold and warmer events indicated that OP DTT was mainly sensitive to copper, elemental carbon, and organic aerosol from residential wood burning, and OP OH to iron and organic aerosol from vehicles. Despite low photochemically-driven oxidation rates, the water-soluble fraction of OP DTT was unusually high at 77%, mainly from wood burning emissions. In contrast to other locations, the Fairbanks average PM 2.5 mass concentration was higher than Atlanta and Los Angeles, whereas OP DTT in Fairbanks and Atlanta were similar, and Los Angeles had the highest OP DTT and OP OH . Site differences were observed in OP when normalized by both the volume of air sampled and the particle mass concentration, corresponding to exposure and the intrinsic health-related properties of PM 2.5 , respectively. The sensitivity of OP assays to specific aerosol components and sources can provide insights beyond the PM 2.5 mass concentration when assessing air quality.