AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Impact of Wildfire Emissions on Chloride and Bromide Depletion in Marine Aerosol Particles
RACHEL BRAUN, Hossein Dadashazar, Alex MacDonald, Aldhaif Abdulamonam, Lindsay Maudlin, Ewan Crosbie, Mojtaba Aghdam, Ali Mardi, Armin Sorooshian, University of Arizona
Abstract Number: 54 Working Group: Aerosol Chemistry
Abstract This presentation will report on findings related to particulate chloride (Cl-) and bromide (Br-) depletion in marine aerosol particles influenced by wildfires at a coastal California site in the summers of 2013 and 2016. Novelties of this work include: (i) presentation of rare data for size-resolved aerosol composition at a coastal site impacted by wildfires from two source regions in separate summers; (ii) contrasting size-resolved characteristics of Cl- and Br- concentrations and their degree of depletion between non-fire and fire periods; and (iii) quantification of species most responsible for Cl- depletion during non-fire and fire periods. Chloride exhibited a dominant coarse mode due to sea salt influence, with substantially diminished concentrations during fire periods as compared to non-fire periods. Bromide exhibited a peak in the submicrometer range during fire and non-fire periods, with an additional supermicrometer peak in the latter periods. Chloride and Br- depletions were enhanced during fire periods as compared to non-fire periods. The highest observed %Cl- depletion occurs in the submicrometer range, with maximum values of 98.9% (0.32 – 0.56 µm) and 85.6% (0.56 – 1 µm) during fire and non-fire periods, respectively. The highest %Br- depletion occurred in the supermicrometer range during fire and non-fire periods with peak depletion between 1.8 – 3.2 μm (78.8% and 58.6%, respectively). When accounting for the neutralization of sulfate and nitrate by ammonium, organic acid particles showed the greatest influence on Cl- depletion in the submicrometer range.
As wildfire research is growing in importance, the results of this work highlight the need for considering how aerosol properties and effects, such as hygroscopicity and radiative forcing, can be modified as a result of acidic species depleting Cl- and Br- in sea salt particles.