Transport and Evolution of Aerosol Plumes From Urban and Industrial Sources in the Eastern U.S.

In situ measurements of particle size distributions and bulk, size resolved, and single particle composition, as well as reactive and trace gas species, were made aboard the NOAA WP-3D aircraft as part of the ICARTT field program in summer 2004. Plumes of pollution originating from industrial and urban sources along the heavily populated Atlantic coastline of the northeastern U.S. were studied as they propagated over Atlantic coastal waters toward the northeast over a three-day period. Particle mass loadings exceeding ~10 μg/m3 were associated with sources of sulfur dioxide and with forest fire smoke. Ratios of gas-phase precursors to particle mass in plumes originating from non-forest-fire sources decreased with plume age, consistent with to gas-to-particle conversion. The water-soluble organic carbon content of the aerosol particles did not appreciably increase with plume age once the plumes were more than one day old, while the sulfate content continued to increase. Particle size distributions in the urban/industrial plumes evolved with time from complex, multimodal distributions having significant numbers of particles with diameters <0.1 μm, to a unimodal distribution with a mass mean diameter near 0.5 μm. These mixed sulfate/organic, accumulation-mode particles exported to the North Atlantic lower troposphere would be efficient cloud condensation nuclei.