On-line characterization of individual particles from automobile emissions

This paper presents results from a study showing the first on-line measurement of the size and chemical composition of individual particles emitted in automobile exhaust. Particles sampled directly from the exhaust pipes of a number of vehicles upon startup were analyzed using aerosol time-of-flight mass spectrometry (ATOFMS). Both organic and inorganic chemical species including lead, cerium, platinum, molybdenum, calcium, and sodium were observed in individual exhaust particles. In general, a qualitative correlation exists between particle size and composition, typified by the presence of predominately organic species in particles in the fine size mode (<1 mu m) and inorganic species in particles in the coarse size mode (>1 mu m). This study demonstrates the potential of using ATOFMS for analyzing vehicular exhaust in an on-line matter. Ultimately, ATOFMS can be used as a real-time monitor, characterizing particles produced from vehicles under a variety of well-defined operating conditions that will allow for further development of the understanding of particle formation and reaction processes. Furthermore, determination of chemical tracers in individual exhaust particles will allow for more accurate source allocation of atmospheric particles.