AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Development a PM2.5-Capable Aerosol Chemical Speciation Monitor
WEN XU, Philip Croteau, Leah Williams, Timothy Onasch, Manjula Canagaratna, Douglas Worsnop, John Jayne, Aerodyne Research, Inc.
Abstract Number: 173 Working Group: Instrumentation and Methods
Abstract The Aerodyne Aerosol Chemical Speciation Monitor (ACSM) measures the real-time mass loading and chemical composition of non-refractory PM1. However, since there may be interesting chemical information in particles between 1 and 2.5 µm and since air-quality standards worldwide are generally based on PM2.5, an ACSM capable of measuring PM2.5 has been developed. To achieve this, three fundamental challenges were addressed: delivery of PM2.5 to the aerodynamic focusing lens, delivery of PM2.5 through the lens to the detector, and detection of the mass from these particles. The original ACSM sampling inlet was designed to accurately sample PM1 and is less efficient for particles between 1 and 2.5 µm. Like its progenitor the Aerosol Mass Spectrometer (AMS), the ACSM size-range has been limited to about 1 µm by the aerodynamic focusing lens. And, as with the AMS, calculating mass loadings from ACSM data requires accounting for the loss of particles which are not vaporized, which is often as much as 50% of the mass and can vary with relative humidity and chemical composition, leading to uncertainty. Furthermore, this loss is greater for particles larger than 1 µm than it is for particles smaller than 1 µm. Thus, for accurate mass and chemical measurements of non-refractory PM2.5 with the ACSM three major design changes have been implemented: a sampling system which minimizes losses of large particles in transport to the aerodynamic focusing lens, a new particle lens which transmits particles up to 3 µm in diameter, and a redesigned particle vaporizer which enables detection of up to 100% of the non-refractory particle mass. Here we present the results of laboratory and ambient measurements characterizing the performance of the PM2.5 ACSM.