Modeling of the signals of an optical particle counter for real nonspherical particles.
An optical particle counter (OPC) was exposed to atmospheric particles of diameters of 200, 300, and 400 nm. The OPC data were combined with the results of single-particle analysis with a transmission electron microscope (TEM) on samples taken in parallel with the OPC measurements. With a T-matrix-based optical model the measured OPC spectra of scattered light pulses could be approximated with good precision. With an algorithm that simulated the response of the OPC to a given population of model particles derived from the TEM results, average absorption properties of different particle types were retrieved. For mobility sizes of 400 nm, higher light absorption was retrieved with the optical model for soot aggregates than for the rest of the morphological particle types. At smaller mobility sizes no compositional information could be derived from the model particles derived from the TEM data. Despite the limited success of the new methodology applied to the present experiment the results encourage the use of OPCs in combination with electrical mobility analyzers to derive more than aerosol-size distributions. With state-of-the-art pulse-height analysis the light-scattering pulses could be resolved with much finer resolution than in the instrument used.
Heintzenberg
Jost
J
Leibniz-Institute for Tropospheric Research, Permoserstrasse 15, D-04318 Leipzig, Germany. jost@tropos.de
Okada
Kikuo
K
Trautmann
Thomas
T
Hoffmann
Peter
P
D000336:Aerosols / Q000032:analysis*; D000393:Air Pollutants / Q000032:analysis*; D000465:Algorithms; D016880:Anisotropy; D003198:Computer Simulation; D004784:Environmental Monitoring / Q000379:methods*; D046529:Microscopy, Electron, Transmission / Q000379:methods; D008962:Models, Theoretical; D043942:Nanotubes / Q000032:analysis* / Q000648:ultrastructure; D010316:Particle Size; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis / Q000379:methods*
D000336:Aerosols; D000393:Air Pollutants