Inversion of aerosol data from the epiphaniometer

The epiphaniometer is a new instrument for continuous monitoring of the Fuchs surface of aerosol particles using the attachment of neutral radioactive 211Pb atoms to the particles. Since the 211Pb atoms have a half-life of 36.1 min, the ability of the epiphaniometer to detect short-term fluctuations in the Fuchs surface of the aerosol is limited. To overcome this drawback a general algorithm developed for the inversion of size distribution data from conventional aerosol instruments is adapted for the inversion of data from the epiphaniometer. This algorithm allows resolution of dramatic changes in the aerosol Fuchs surface occurring over a time scale of minutes. The method is applied to data collected during outdoor smog chamber experiments, with changes in aerosol concentration of several orders of magnitude occurring within a time period of 5 min. The inverted epiphaniometer data are in agreement with the corresponding data from a Scanning Electrical Mobility Spectrometer (SEMS) and an Optical Particle Counter.