| Summary: | Ammonia (NH3) can harm ecosystems through deposition and react in the atmosphere to increase fine particulate (PM2.5) levels which impact climate and degrade air quality. Despite an abundance of field studies and modelling efforts there are still large uncertainties regarding the sources, sinks, and transport of NH3. These uncertainties are magnified in rural and remote regions where measurements are sparse. The Ambient Ion Monitor – Ion Chromatograph (AIM-IC) was deployed on three separate occasions to measure hourly averages of ambient NH3, SO2, and HNO3 as well as PM2.5 constituents (NH4+, SO42-, NO3-). AIM-IC measurements at a rural field in Ontario, in conjunction with soil measurements, revealed that a non-fertilized grassland exhibits bi-directional soil-atmosphere NH3 exchange. A “morning spike” of NH3 was occasionally observed around 7:00 to 9:00 local time and was investigated in a subsequent study at a remote park in Colorado. Simultaneous observations of dew composition, dew amount and NH3 suggested that the frequently observed, yet currently unexplained, morning spike is caused by NH3 released from evaporating dew. The AIM-IC was operated aboard a research icebreaker throughout the Canadian Arctic Archipelago. NH3 ranged between 30-650 ng m-3 and was usually sufficient to fully neutralize SO42-. Low values of NH4+ in the Arctic Ocean and melt ponds revealed they were always a net NH3 sink. Decomposing seabird guano and wildfires were identified as the primary NH3 sources through the use of a chemical transport model (GEOS-Chem) and particle dispersion model (FLEXPART-WRF). Lastly, AIM-IC measurements from a campaign in the Athabasca Oil Sands Region showed that air masses that had recently passed over bitumen upgrading facilities were enriched in NH3, SO2, HNO3, NH4+ SO42-, and NO3-. Comparison of observed NH3 to that predicted by the Extended – Aerosol Inorganics Model (E-AIM) implies that the aerosol system was in disequilibrium in polluted airmasses. Ph.D.
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