THE CALIBRATION OF A CALIFORNIA MEASUREMENTS PC-2 QUARTZ CRYSTAL CASCADE IMPACTOR (QCM)

The California Measurements 10-stage Quartz Crystal cascade impactor (QCM) has been widely used for near real-time monitoring of the aerodynamic particle size distribution of aerosols in the size range from 0.05 to 25-mu-m aerodynamic diameter. Calibration data for this impactor are limited, especially at particle sizes smaller than 0.5-mu-m aerodynamic diameter. A QCM impactor has therefore been calibrated with monodisperse aerosols throughout its operating range, particular attention being paid to internal deposition. This study has also highlighted that electrostatic charge equilibration of aerosols entering the QCM impactor is essential if reliable data are to be obtained. The collection stages are electrically insulated from their supports so that the mass of particles collected can be sensed; this requirement renders it possible for electrostatic charge to build up on the surface of the sensing crystals, interfering with the subsequent collection of further charged particles.