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Characterization of Pollen Fragments in Atmospheric Aerosol Using Chemical Tracers
CHAMARI MAMPAGE, Dagen Hughes, Lillian Jones, Nervana Metwali, Peter Thorne, Elizabeth Stone, University of Iowa
Abstract Number: 229
Working Group: Bioaerosols
Abstract
Pollen grains contain allergens that can trigger allergic responses. In the presence of water, pollen grains (10-100 µm) can osmotically rupture to produce pollen fragments (<3 µm). The current study examines pollen fragments, fungal spores, and bacteria in size-resolved atmospheric aerosols. During springtime in Iowa City, Iowa, fine particle (PM2.5) concentrations of fructose (a chemical tracer of pollen) increased on rainy days, especially heavy thunderstorms, and peaked when a tornado struck nearby. PM samples size-separated across 5 impactor stages revealed mass distributions that ranged 0.25-2.5 µm, consistent with pollen fragments that were also detected in collocated measurements. Meanwhile, mannitol (a fungal spore tracer) in PM2.5 peaked on a warm day following rain and was primarily in supermicron particles, in agreement with the intact diameters of fungal spores (1-30 µm). Bacterial endotoxins in PM2.5 also peaked on rainy days, with their mass primarily distributed to coarse PM. While the PM2.5 concentrations of fructose, mannitol, and endotoxin all increased on rainy days, the greatest relative increase in concentration and decrease in particle size was observed for the pollen tracer. Together, these observations suggest that pollen grains ruptured into pollen fragments in the atmosphere. Compared to intact pollen grains, pollen fragments have longer atmospheric lifetimes, greater deposition in the lower lung, undergo longer range transport, and have greater potential to impact cloud and ice formation and precipitation.