Understanding Alaskan Wintertime Air Pollution: Outdoor-Indoor Transport and Phase Partitioning of Chemically Resolved Semi-Volatile Organic Compounds during the ALPACA 2022 Campaign

KAROLINA CYSNEIROS DE CARVALHO, Ellis Robinson, Andrew Holen, Judy Wu, Vanessa Selimovic, Damien Ketcherside, William Simpson, Lu Hu, Kerri Pratt, Peter F. DeCarlo, Robert J. Yokelson, Brent Williams, Washington University in St. Louis

     Abstract Number: 456
     Working Group: Biomass Combustion: Outdoor/Indoor Transport and Indoor Air Quality

Abstract
Alaska is often thought of as a place to escape from urban air pollution, with its vast and pristine wilderness. However, with limited sunlight and temperatures reaching below -40^oC, Arctic and Subarctic cities are challenging places to live during the winter. These extreme conditions lead to an increase in local particulate matter emissions due to more intense domestic heating and power generation. The cold temperatures, in conjunction with reduced solar radiation, are responsible for stronger temperature inversions that trap these pollutants in the lower atmosphere, resulting in very poor outdoor air quality.

While spending most of their time indoors during the winter, Alaskan residents experience higher exposure to air pollution during this season due to outdoor-indoor air infiltration, indoor pollution sources, and chemical transformations. However, the understanding of atmospheric chemical reactions of these pollutants is poor and so is the extent of human exposure risks in this unique environment. The Alaskan Layered Pollution And Chemical Analysis (ALPACA) field project occurred during the 2022 winter in Fairbanks, Alaska to improve our understanding of how pollutants behave under these cold and dark conditions.

A Semi-Volatile Thermal desorption Aerosol Gas chromatograph (SV-TAG), capable of identifying and quantifying speciated organic compounds in both gas and particle phases, was deployed inside the garage of a residential home, along with complementary gas-phase (PTR-ToF-MS - Proton Transfer Reaction Time-of-Flight Mass Spectrometer) and particle-phase mass spectrometers (ATOFMS - Aerosol Time-of-Flight Mass Spectrometer and AMS - Aerosol Mass Spectrometer). The TAG system is composed of two collection cells that provide direct measurement of phase partitioning. This presentation discusses indoor and outdoor organic aerosols sampled during the seven-week study. Results include understanding the extent of particle-to-gas phase partitioning of semi-volatile organic compounds upon warming due to transport indoors, the major sources that contributes to indoor and outdoor air pollution, as well as the relationship between indoor and outdoor aerosol composition.