AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Resolution Limitations to Tandem Differential Mobility Analyzer-Aerosol Particle Mass Analyzer Measurements
JAMES RADNEY, Christopher Zangmeister, National Institute of Standards and Technology
Abstract Number: 403 Working Group: Instrumentation and Methods
Abstract The use of a tandem differential mobility analyzer (DMA), aerosol particle mass analyzer (APM) and condensation particle counter to measure the mass and effective density of aerosol particles is becoming increasingly common; in some studies, including an optical measurement provides another level of classification. Both DMAs and APMs separate particle by net charge in the form of electrical mobility and the balance of electrostatic and centripetal forces, respectively. Here, we provide an in-depth study of how net charge can affect measurement interpretation using 3 aerosols with unique physical characteristics: ammonium sulfate (AS), soot and Aquadag which represent a dense, nearly spherical particle; a lacey fractal agglomerate and a medium density oblate to prolate spheroid. In the case of AS, multiple charging does not affect measurement resolution or interpretation. For soot, multiple charging severely affects measurement resolution and can cause the measured peak mass and extinction cross-section to deviate by as much as 21% and 160%, respectively, versus when only the singly charged particle is isolated. For Aquadag, multiple charging does not affect peak mass, but the range of morphologies does affect the interpreted relationship between mass and optical signal which could have serious implications when being used for calibrations as is common with the single particle soot photometer.