Comparative Analysis of Wet and Dry Deposition of Bioaerosol Tracers
JANESHTA FERNANDO, Teresa Feldman, Chamari Mampage, Claudia Mignani, Marina Nieto-Caballero, Thomas C. J. Hill, Brian Heffernan, Drew Juergensen, Christine Neumaier, Tyler Barbero, Charles Davis, Lexi Sherman, Ben Ascher, Jacob Escobedo, Nick Falk, Sean Freeman, Gabrielle Leung, Allie Mazurek, Daniel Veloso-Aguila, Leah Grant, Susan van den Heever, Russell Perkins, Paul DeMott, Sonia Kreidenweis, Elizabeth Stone, University of Iowa
Abstract Number: 626
Working Group: Bioaerosols
Abstract
The BioAerosols and Convective Storms (BACS) field campaigns examine the exchange of bioaerosols between the terrestrial biosphere and atmosphere. The objective of this study is to evaluate bioaerosol dry and wet deposition, with the latter involving precipitation. Chemical tracer analysis provides insight to three classes of bioaerosols: fungal spores by mannitol; gram-negative bacteria by endotoxins; and pollen and plant matter by fructose, glucose, and sucrose. Samples were collected in the Central Plains Experimental Range in Northern Colorado from May-June of 2022 and 2023. The cumulative precipitation in 2022 was 10 mm occurring over five rain events (18% of study days). Over a 23-day period, the fungal spore wet deposition totaled 7.0 x 107 spores/m2, which was 35 times higher than the estimated dry deposition of fungal spores (assuming a mean diameter 2.5 µm and unit density) and demonstrated the dominance of wet deposition over dry deposition. Comparison of rainwater concentrations to surface aerosol concentrations prior to rain revealed that surface aerosol concentrations accounted for less than 19% of the carbohydrates deposited in rainwater, indicating a significant enhancement of these compounds in aerosols or cloud water aloft. In the case of bacterial endotoxin, the magnitude of wet deposition was similar to the dry deposition, indicating the importance of both deposition processes. In 2023, precipitation totaled 119 mm over 21 rain events (60% of study days). In comparing across the two campaigns, the average wet deposition of pollen tracers was twice as high in the drier year, while the wet deposition of fungal spores was twice as high in the wetter year. This reflects the variability in atmospheric bioaerosol concentrations across these dry and wet years. This research provides insights into the magnitude and relative importance of wet and dry deposition for bioaerosol scavenging.