Atmospheric aerosols play important roles in climatology and visibility by absorbing and scattering solar radiation and also adversely affect human health in ways that are not fully understood. Motivated primarily by the health concerns associated with airborne particulates, there have been increased efforts over the past decade to better characterize aerosol chemical and microphysical properties to help provide guide lines for the legislation of appropriate particulate matter emission standards. Thus, in addition to intensive air quality measurement campaigns, there has also been a focused effort on developing and testing advanced technology aerosol instrumentation.

Presented here are results obtained from national and international deployments of the Aerodyne Aerosol Mass Spectrometer (AMS) system by different research groups. The AMS is capable of providing size and compositionally resolved mass loadings of non-refractory aerosol components in real time. Recent deployments of the AMS include field campaigns in Houston (TEXAQS 2000), New York City (PMTACS 2001), Michigan (PROPHET 2001), Vancouver (PACIFIC 2001), Pittsburg (PAQS 2002), New England (NEAQS 2002), and Mexico City (2002 and 2003). An analysis of aerosol mass, size, and composition trends obtained during these campaigns reveal diurnal variations in the photochemically driven formation of sulfate, nitrate, and oxidized organic aerosols. The chemical composition of these aerosols can be clearly distinguished from those observed during vehicular exhaust or biomass burning pollution events. These results, when combined with airmass backtrajectory calculations and ancillary gas phase measurements allow for the characterization of particle sources. Similarities and differences in aerosol size and chemical composition as well as aerosol formation and transformation at these widely varying sampling locations will be discussed.