Assessing the Oxidative Potential of Outdoor PM_2.5 in Wintertime Fairbanks, Alaska

Abstract

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/m³, with a 1 h average maximum of 89.0 μg/m³. 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.