AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Characterization of the 8-stage Rotating Drum Impactor under Low Concentration Conditions
MELISSA VENECEK, Yongjing Zhao, Jose Mojica, Charles McDade, Peter Green, Michael Kleeman, Anthony Wexler, University of California, Davis
Abstract Number: 419 Working Group: Instrumentation and Methods
Abstract The Rotating Drum Impactor (RDI) is designed to collect samples of airborne particulate matter that are resolved by aerodynamic particle diameter as a function of time. The purpose of this study is to characterize the performance of the RDI sampler for use in relatively low concentration environments. Airborne particulate matter was collected at the University of California, Davis during the winter and summer of 2013 by two IMPROVE samplers, two RDI samplers and two MOUDI samplers. X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS) were used as the chemical analyses. The IMPROVE XRF analysis gave similar repeated measurements for 78% of the elements present above stated Minimum Detection Limits (MDLs) in winter and 42% in summer. The MOUDI XRF analysis gave similar repeated measurements for 33% and 37% of the elements in winter and summer, respectively. The MOUDI, ICP-MS analysis was the most repeatable method tested, yielding similar repeated measurements for 62% and 91% of elements above stated MDLs in winter and summer, respectively. The RDI, XRF analysis was the least repeatable method tested, yielding similar repeated measurements for 35-40% and 5-20% in winter and summer, respectively. These results indicate that MDLs should be reassessed for all methods and a longer collection time should be considered under low concentration conditions. PM2.5 measurements from IMPROVE samplers were in better agreement with integrated size-resolved measurements made by MOUDI samplers than RDI samplers, suggesting that the absolute accuracy of the RDI method needs further improvement. Also, the RDI size distributions were implausible because they had a consistent gap between 0.34 – 0.56 μm that was not present in MOUDI measurements and does not match expected size distribution patterns in the atmosphere. The collection efficiency of all RDI stages should be verified before this instrument is used for size distribution measurements.