ONLINE CHARACTERIZATION OF INDIVIDUAL PARTICLES FROM AUTOMOBILE EMISSIONS

This paper presents results from a study showing the first on-line mea surement of the size and chemical composition of individual particles emitted in automobile exhaust. Particles sampled directly from the exh aust pipes of a number of vehicles upon startup were analyzed using ae rosol time-of-flight mass spectrometry (ATOFMS). Both organic and inor ganic chemical species including lead, cerium, platinum, molybdenum, c alcium, and sodium were observed in individual exhaust particles. In g eneral, a qualitative correlation exists between particle size and com position, typified by the presence of predominately organic species in particles in the fine size mode (<1 mu m) and inorganic species in pa rticles in the coarse size mode (>1 mu m). This study demonstrates the potential of using ATOFMS for analyzing vehicular exhaust in an on-li ne matter. Ultimately, ATOFMS can be used as a real-time monitor, char acterizing particles produced from vehicles under a variety of well-de fined operating conditions that will allow for further development of the understanding of particle formation and reaction processes. Furthe rmore, determination of chemical tracers in individual exhaust particl es will allow for more accurate source allocation of atmospheric parti cles.