REAL-TIME MEASUREMENT OF CORRELATED SIZE AND COMPOSITION PROFILES OF INDIVIDUAL ATMOSPHERIC AEROSOL-PARTICLES

In this paper, the unique real-time measurement capabilities of aeroso l time-of-flight mass spectrometry (ATOFMS) for characterizing atmosph eric aerosol particles are demonstrated. ATOFMS is used to obtain the aerodynamic size and chemical composition of individual aerosol partic les sampled directly into the instrument from outdoors. Such measureme nts are made in-situ by combining a unique dual-laser aerodynamic part icle sizing system to size and track individual particles through the instrument and laser desorption/ionization time-of-flight mass spectro metry to obtain correlated single particle composition data. At typica l ambient concentrations, the size and chemical composition of 50-100 particles per minute can be measured (up to 600 per minute at high par ticle concentrations). Presented here for the first time are compositi onally resolved particle size distributions of ambient aerosol particl es, showing definitive size/composition correlations. A goal of these studies is to ultimately couple data obtained from the dynamic monitor ing of individual particles in atmospheric systems with that obtained using conventional ambient aerosol sampling to assist in sorting out c omplex field data on atmospheric processes.