Characterization of S(IV) Species and Sulfate in PM2.5 in Fairbanks, Alaska using Ion Chromatography

KAYANE DINGILIAN, Michael Battaglia, James Campbell, Jingqiu Mao, Rodney J. Weber, Georgia Institute of Technology

     Abstract Number: 175
     Working Group: Aerosol Chemistry

Abstract
Fairbanks, Alaska is an arctic city that is severely polluted during the winter with notably high concentrations of atmospheric particulate matter (PM_2.5). Sulfate (SO₄^2-) and S(IV) species have been identified as a significant component of PM_2.5 (about 20%), but their chemistry is still not well-understood under typical local conditions of extreme cold and low concentrations of oxidants such as O₃. Hydroxymethanesulfonate (HMS) is an adduct of formaldehyde (HCHO) and the precursors sulfite (SO₃^2-) and bisulfite (HSO₃^-), and it was recently identified in heavy pollution events elsewhere. As part of the Alaska Pollution and Chemical Analysis (ALPACA) Campaign that took place in January-February of 2022, we deployed several instruments to Fairbanks to obtain both online and offline measurements of sulfur-containing species. The Particle-Into-Liquid-Sampler (PILS) system coupled to ion chromatography was used to obtain 20-minute continuous measurements of sulfate and total S(IV). PM_2.5 filters were collected daily, and these were extracted and analyzed offline with ion chromatography. These data show that total S(IV) levels are enhanced at high levels of sulfate and low temperatures, and the fraction increases with increasing levels of sulfate during pollution events. Additional experiments were performed on filter extractions to determine the partitioning of HMS, bisulfite, and sulfite. Preliminary data suggests that about 68% of the PM_2.5 S(IV) measured in Fairbanks during this time is HMS, and that HMS scales linearly with total S(IV). This work is one part of a greater collaborative effort to better characterize low-temperature atmospheric sulfur chemistry and the chemistry within supercooled aerosol droplets, as well as improve current models to reflect an updated understanding of reaction mechanisms and aerosol phenomena.