INERTIAL COLLECTION OF FINE PARTICLES USING A HIGH-VOLUME RECTANGULARGEOMETRY CONVENTIONAL IMPACTOR

This paper presents the development and evaluation of a high-volume re ctangular geometry conventional impactor. Operating with a preselectiv e inlet that removes particles larger than 2.5 mu m in aerodynamic siz e, the impactor has been designed to sample ambient fine particles in the accumulation mode range (0.1 < d(p) < 2.5 mu m). Particles are acc elerated in a rectangular nozzle, 0.032 cm wide and 28 cm long, and im pact on a filler medium attached on a porous glass frit, which is soak ed in mineral oil. The impactor operates at a how rate of 1000 1 min(- 1) with a total pressure drop of 30 kPa. The performance of the slit-n ozzle impactor was validated in laboratory and field tests. Laboratory experiments conducted with monodisperse fluorescent PSL particles sho wed that the aerodynamic diameter of the 50% cutpoint of the impactor is approximately 0.09 mu m. Laboratory and field intercomparisons betw een the high-volume slit impactor and the microorifice uniform deposit impactor (MOUDI) showed that particulate nitrate and sulfate concentr ations obtained with the two samplers are in good agreement (within 10 %). Finally, a comparison between the particulate nitrate concentratio ns obtained with high volume impactor and the Harvard/EPA annular denu der system (HEADS) was conducted, using indoor air as the rest aerosol . Results from this comparison indicated that losses of nitrate from t he impactor are not substantial and range between 5 and 15%. Results f rom the laboratory and field tests suggest that the high-volume impact or presented in this study constitutes a major improvement in the fiel d of high-volume line particle sampling. (C) 1997 Elsevier Science Ltd .