AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Quantifying the Effect of Relative Humidity and Ozone on the Viability of Aged Bacillus Thuringiensis Al Hakam and MS-2 Bacteriophage Biological Aerosols
SEAN KINAHAN, Elizabeth Corson, Shanna Ratnesar-Shumate, Yong-Le Pan, Jonathan Eshbaugh, Christopher Bare, Joshua Santarpia, Johns Hopkins University Applied Physics Laboratory
Abstract Number: 345 Working Group: Bioaerosols: Characterization and Environmental Impact
Abstract The viability of primary biological aerosols (PBA) is a complex function of the particle properties and atmospheric conditions surrounding their release. The type of organism, aerosolization method, relative humidity, oxidation, irradiation, and the presence of secondary organic aerosol forming constituents may each or cumulatively alter an organism’s survivability and fate as an aerosol particle. To isolate and better understand the effects of any individual variable over time, it is essential to contain these particles in a controlled environment. JHU/APL developed a rotating drum system (RDS) to simulate an increased residence time of biological aerosols in the atmosphere, in order to observe changes due to controlled levels of relative humidity and ozone concentration. The viability of two biological aerosols, Bacillus thuringiensis Al Hakam (Bt) and the bacteriophage MS-2, was investigated. A Sono-tek ultrasonic nozzle generated each biological particle of interest into the RDS until a target concentration of 200 particles cc$^(-1) was achieved, as monitored by a TSI Inc. Ultraviolet Aerodynamic Particle Sizer (UV-APS) spectrometer. All glass impingers (AGI) sampled the biological aerosol immediately after reaching the target concentration and after four hours of aging. Experiments consisted of three humidity targets (~20%, 50%, and 85% RH) to which the drum was preconditioned before aerosolization of the biologicals in HEPA-filtered laboratory air. Each relative humidity condition was coupled with trials at background (<5 ppb) and high ozone concentrations (~150 ppb), introduced after the initial time-zero sample was collected. Viability was quantified using culture for the Bt and an E. Coli plaquing assay for MS-2. These culture numbers were normalized to total sampled genomic content, using quantitative polymerase chain reaction (qPCR), to account for losses in particles over time and improve percent viability correlations.