Real-time measurement of correlated size and composition profiles of individual atmospheric aerosol particles

In this paper, the unique real-time measurement capabilities of aerosol time-of-flight mass spectrometry (ATOFMS) for characterizing atmospheric aerosol particles are demonstrated. ATOFMS is used to obtain the aerodynamic size and chemical composition of individual aerosol particles sampled directly into the instrument from outdoors. Such measurements are made in-situ by combining a unique dual-laser aerodynamic particle sizing system to size and track individual particles through the instrument and laser desorption/ionization time-of-flight mass spectrometry to obtain correlated single particle composition data. At typical ambient concentrations, the size and chemical composition of 50-100 particles per minute can be measured (up to 600 per minute at high particle concentrations). Presented here for the first time are compositionally resolved particle size distributions of ambient aerosol particles, showing definitive size/composition correlations. A goal of these studies is to ultimately couple data obtained from the dynamic monitoring of individual particles in atmospheric systems with that obtained using conventional ambient aerosol sampling to assist in sorting out complex field data on atmospheric processes.