Geothermal, Oceanic, Wildfire, Meteorological and Anthropogenic Impacts on PM<sub>2.5</sub> Concentrations in the Fairbanks Metropolitan Area

The impacts of low and high-frequency variability from teleconnections between large scale atmospheric processes and local weather as well as emissions changes on concentrations of particulate matter of 2.5 m or less in diameter ([PM 2.5 ]) were examined for the Fairbanks Metropolitan Area (FMA). October to March and May to August mean [PM 2.5 ] were 1.8 and 3.1 gm -3 higher for positive than negative annual mean Pacific Decadal Oscillation. Annual mean [PM 2.5 ] were 3.8 gm -3 lower for positive than negative Southern Oscillation Index. On 1999-2018 average, [PM 2.5 ] decreased 2.9 gm -3 decade -1 . On average over October to March, decadal and inter-annual variability caused higher or similar differences in mean observed [PM 2.5 ] and its species than emission-control measures. The 2006 implementation of Tier 2 for new vehicles decreased observed sulfate concentrations the strongest (~4.95 gm -3 decade -1 ) of all occurred emissions changes. On average, observed [PM 2.5 ] showed elevated values at all sites when wind blew from directions of hot springs. The same was found for the sulfate, ammonium and non-metal components of PM 2.5 . Observations showed that these geothermal waters contain sulfate, ammonia, boric acid and non-metals. Hot springs of such composition are known to emit hydrogen sulfide and ammonia that can serve as precursors for ammonium and sulfate aerosols.