AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Chemical Mechanisms of Nanoparticle Growth Studied through a Combination of Ambient and Laboratory Measurements
MURRAY JOHNSTON, Bryan R. Bzdek, Joseph DePalma, Andrew J. Horan, University of Delaware
Abstract Number: 202 Working Group: Advances in the Physics and Chemistry of New Particle Formation and Growth
Abstract Improved predictions of the frequency, growth rates, and climatic impacts of new particle formation (NPF) require knowledge of the chemical mechanisms by which nucleated nanoparticles grow. Our group has performed a combination of ambient measurements, laboratory experiments and computational work to study growth mechanisms of nanoparticles. The two main contributors to growth during NPF are sulfate and organics. Quantitative elemental composition measurements with the nano aerosol mass spectrometer allow the relative amounts of each to be quantified. Both laboratory and field measurements show that particle phase sulfate is adequately described by condensation of gas phase sulfuric acid. Neutralization of sulfate by either ammonia or amines is somewhat less understood, and recent work suggests that it is dependent on particle water content. Carbonaceous matter is poorly understood at a molecular level, although elemental and molecular composition measurements of ambient particles show that it is highly oxidized. Recent ambient measurements show that this carbonaceous matter often contains a substantial amount of nitrogen. This important discovery is the subject of current laboratory experiments of nanoparticle growth under controlled conditions where nitrogen incorporation might be expected to occur. This work is aided by the use of a new method for nanoparticle collection that allows molecular analysis of size-selected particles down to 10-nm in diameter.