Background Aerosol Characteristics Measured with a Fluorescence AerodynamicParticle Sizer: Sensitivity of FLAPS Performance

摘要

The Fluorescence Aerodynamic Particle Sizer (second generation FLAPS2) measuresparticle size as well as intrinsic fluorescence characteristics of individual particles in an aerosol stream. Laser light at UV wavelength is used to preferentially excite aerosol material of a selected size range. The measured fluorescence signals represent intrinsic biological properties of the particles. By this method, it has been shown that inert particles like sand can be distinguished from biological particles like spores and vegetative bacteria. This instrument and its prototype have been demonstrated to effectively detect and characterize biological aerosols during joint field trial exercises in both 1995 and 1996. Integral with the FLAPS design is an aerosol concentrator that provides about 400-500 times normal ambient concentration. This makes it possible to sample at a rate of 3 seconds and within this period, about 300-3000 total particles are processed. To function effectively as a biological detector, the instrument compares background or ambient data to that of an unknown cloud. An ambient aerosol database from diverse localities will greatly enhance data analysis. To this end, the instrument has been use to collect data on ambient aerosols in different geographical sites, for example at DRES, Calgary, Dugway, Cornwall and a spot downwind from a cattle feedlot. The results show that FLAPS can distinguish between clean and dirty environments with respect to the fraction of fluorescent particles measured in a given aerosol population.