On-line in-situ characterization of PM-2.5 using imaging fluorescence of aerosols

A new method, based on a novel instrument to measure fine particles in an air medium for the purpose of emission or process control has been developed and is now in evaluation at the EPA Combustion Research Laboratory. This instrument can measure PM 2.5 and ultra-fine particles in general at a rate approaching real time revealing particle size, shape, density and chemical composition. The instrument is an advanced imaging system, which uses sophisticated computer algorithms as well as unique optical features to create a two-dimensional simulation of the sample under analysis. The imaging used in this instrument, which provides target selectivity and high sensitivity, combined with the fact that it does not require any specimen pre-processing brings the analysis process close to real time and without sample destruction. The method, developed at Israel's Institute of Technology (Technion) and Green Vision Systems, is based on imaging spectroscopic analysis of the emitted fluorescence from the particle samples. The proposed method, however, enables direct measurement of solid aerosol samples. In this application, analysis is based on chemometric treatment of the collected spectra. Such mathematical treatments provide the possibility of resolution of complex mixture of fluorescing compounds. Samples can be presented to the systemmore » manually or automatically using source sampling equipment and an accurate three-axis sampling stage. The image is then processed using advanced spectral and image processing methods. The paper presents a description of the method, the instrument and the results of performance evaluations comparing this instrument to conventional methods. It also presents the possible applications for this instrument in the PM 2.5 program and other industrial applications involving the detection and control of ultrafine particles and microorganisms in gas streams and ambient air.« less