AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Development of a Rotating Drum System for Studying the Effects of Humidity and Ozone on Biological Aerosols
Shanna Ratnesar-Shumate, ELIZABETH CORSON, Jonathan Eshbaugh, Christopher Bare, Sean Kinahan, Joshua Santarpia, Johns Hopkins University Applied Physics Laboratory
Abstract Number: 276 Working Group: Homeland Security
Abstract Biological aerosols may undergo physical and chemical changes in the atmosphere due to many different processes. Chemical modifications via oxidation with ozone, uptake of water, solar irradiation, and interactions with atmospheric pollutants may change the viability as well as the physical properties of these aerosols as a function of time of exposure. The ability to observe these changes during time periods on the order of hours in a laboratory setting is difficult. Physical loss of aerosols suspended in static or stirred (mixed) chambers due to settling, deposition, and inertial forces create difficulty in attempting to recreate exposure on time scales that are representative of real world conditions. A rotating drum system was developed that allows for biological aerosols to be generated into a sealed chamber and exposed to varying concentrations of ozone at different relative humidity settings for 4 hour experiments. An automated control system was developed to maintain stable ozone concentration and RH in the drum. Experiments were performed with Bacillus thuringiensis kurstaki spores, Phosphate Buffer Solution (PBS) aerosols, and Arizona Road Dust in order to characterize the physical losses associated with the drum during a four-hour experiment. RH in the drum can be controlled from 20 to 85% via dry air input and a piezoelectric generator. Ozone concentrations from < 5 to 150 ppb were achieved. A standard operation procedure was developed that allows for input of ozone and water vapor in order to maintain the required levels for experiments while minimizing losses due to sampling. Examples of data sets generated using the system will be presented.