Abstract View
Integrated Aerosol Mass and Number Measurements with the Mass and Mobility Aerosol Spectrometer (M2AS)
KINGSLEY REAVELL, David Walker, Cambustion Ltd
Abstract Number: 396
Working Group: Instrumentation and Methods
Abstract
The Mass and Mobility Aerosol Spectrometer (M2AS) is an instrument which combines a unipolar diffusion charger, CPMA (Centrifugal Particle Mass Analyzer) mass classifier, Condensation Particle Counter, Electrometer and a novel mobility classifier. The M2AS allows the mass and mobility distributions of an aerosol to be simultaneously measured in a single scan. Currently we have demonstrated the measurement of aerosols between approximately 50 nm and 3 microns, depending on the particle density. The aerosol is first charged and then selected by mass : charge ratio in the CPMA. The aerosol charge level is determined by the ratio of particle count and electrometer measurements which avoids the need to make assumptions about the charge level. Direct measurement of the electrical mobility of the selected aerosol allows compensation for the width of the CPMA transfer function and provides a measurement of mobility diameter up to a larger particle size than traditional techniques. The particle effective density is thus directly measured.
In order for the integrated distributions from the M2AS to accurately match conventional measurements of the aerosol number and mass, it is necessary to characterise the particle losses and transfer functions of the constituent instruments. We describe a new technique for the measurement of the CPMA transfer function based on passing the sample aerosol twice through the same classifier.
We present validation of the accuracy of the M2AS measurement of total aerosol parameters by measurement of the density of aerosols of known density, comparison with weighing of samples collected on filter paper, and comparison with a condensation particle counter. Typically, the integrated distributions agree with the total aerosol measurements within approximately 10%.