AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
A Laboratory Inter-comparison of CPC and SMPS Measurements of Submicron Aerosols
Shouwen Zhang, ARI SETYAN, Véronique Riffault, Ecole des Mines de Douai
Abstract Number: 674 Working Group: Instrumentation and Methods
Abstract Three scanning mobility particle sizers (SMPS) and three condensation particle counters (CPC) (all commercial instruments) have been compared within the framework of this study. For the comparison in terms of particle number concentrations, one of the CPCs was used as a reference and connected to the sampling line in parallel with each of the other instruments. Measurements were carried out on monodisperse ammonium nitrate particles, which were generated by atomization of a 10$^(-2) M solution, dried using silicagel, and passed through a differential mobility analyzer (DMA) to select one size (from 50 to 300 nm in mobility diameter, Dm). The particle number concentration varied in the range 50-60000 #/cm3. For the comparison in terms of particle size distributions, measurements were performed with polystyrene latex (PSL) spheres of different sizes (from 350 to 900 nm in Dm), and one of the SMPS was connected to the sampling line in parallel with each of the two other SMPS. Diffusion loss correction was applied for all SMPS data.
All the instruments were very well correlated in terms of particle number concentrations, with a correlation coefficient r2 > 0.99. However, the scatterplots vs. the reference CPC had slopes far from 1 in some cases, and varied between 0.5 and 3.0, which means that there was a factor of 6 between the smallest and highest measured concentrations. Moreover, for one of the SMPS, the slope vs. the reference CPC increased from 1.9 to 3.0 for particles varying from 50 to 300 nm. In terms of size distributions, the agreement between the different SMPS was satisfactory.
These discrepancies in particle counting between different instruments may be a serious problem in field campaigns or lab experiments, since people often bring just one SMPS or one CPC to calibrate instruments, and to measure particle concentrations and size distributions.