10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Environmental Factors Affecting Biological Aerosols in Houston, TX
JOSHUA SANTARPIA, Sean Kinahan, Don Collins, Yong-Le Pan, Aimable Kalume, Matthew Tezak, Gabriel Lucero, Steven Storch, Cathryn Reyna, Danielle Rivera, Kevin Crown, Sandia National Laboratories
Abstract Number: 573 Working Group: Bioaerosols
Abstract During the summer months of 2015 and 2016 several weeks of field experiments were performed at a site in the W.G. Jones State Forest near Conroe, TX. These experiments examined changes to intentionally generated biological aerosol (Bacillus thuringiensis) when exposed to the ambient environment of this area, comparing particles fixed onto artificial spider webs and suspended in a gas and UV permeable chamber. Throughout these experiments, extensive measurements of environmental factors such as solar flux and organic and inorganic trace gas were recorded. In 2015, experiments consisted exclusively of daytime experiments, while in 2016 a mix of daytime and nighttime experiments were performed. These studies used multiple chambers to allow different environmental factors to be controlled to attempt to isolate key factors impacting the particles. For instance, in some cases one chamber would be exposed to sunlight and all ambient gas-phase species, while another chamber would be kept isolated from solar radiation with its intake filtered to remove ambient species. This would potentially allow bioaerosols generated at the same time to be exposed to different conditions during the same time period to investigate the role of sunlight and chemical aging separately. In addition, particle growth rates were measured using a co-injected mode of inorganic, sub-micron particles as an indicator of secondary growth processes activity in the chamber. Biological aerosols were measured and quantified in several ways throughout the studies. Measurements compared changes in aerodynamic size and particle fluorescence spectra, as well as viability and qPCR signature. Comparison of these data under different environmental conditions and between the two chambers led to several key findings. This study clearly indicates that biological aerosol trapped on spider webs aged at the same rate as free biological particles suspended in the rotating drum chamber. In addition, the exposure to high solar intensities in Houston led to high decay rates, which dominate the decay in viability observed during most daytime experiments. Correlation analysis between changes in biological aerosol measurements and trace species concentrations and particle growth rates indicate several potential chemical aging pathways that affect both the DNA and proteins.