AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Particle Formation in Power Plant Plumes in the Southeastern United States
CHARLES BROCK, Steven G. Brown, Timothy Gordon, Joost de Gouw, John Holloway, Jin Liao, Ann M. Middlebrook, J. Andrew Neuman, John B. Nowak, Jeff Peischl, Ilana Pollack, Thomas Ryerson, Michael Trainer, Nick Wagner, Jeffrey Pierce, Robin Stevens, André Welti, NOAA Earth System Research Laboratory, Boulder, CO
Abstract Number: 361 Working Group: Aerosol Chemistry
Abstract Measurements of particle size distribution and composition and of gas-phase particle reactive and precursor species were made in the plumes downwind of more than 30 power plants in the southeastern United States in summer 2013 as part of the Southeast Atmosphere Study. Substantial reductions in emissions of SO2 from many of these sources over the last two decades have resulted in smaller regional sulfate concentrations, as is evident in compositional measurements at long-term surface monitoring sites. Despite the impressive reductions in sulfate mass production, however, large numbers of submicron particles are still generated in power plant plumes. In addition to being a potential human health hazard, these particles may also grow to sizes large enough to be active as cloud condensation nuclei (CCN), subsequently affecting cloud microphysical properties, extent, and lifetime. Airborne measurements made on the NOAA WP-3D aircraft are used to quantify the number of particles of cloud-active size formed as a function of plume age and chemical processing. A systematic relationship between chemical age of the plume and CCN-sized particle abundance is evident. Enhanced number concentrations of ultrafine particles were found in some of the plumes emitted after sunset that were measured during SAS and earlier projects, suggesting direct emissions of SO3 or ultrafine particles in these cases. These cases of nighttime particle production will be examined for their importance to downstream particle size and number and for evidence of formation of secondary organic species.