Atmospheric nanoparticles constitute the greatest portion of ambient aerosol loading by number.  A major source of atmospheric nanoparticles is new particle formation (NPF), a gas to particle conversion process whereby clusters nucleate from gas phase precursors on the order of a few nanometers and then grow rapidly to climatically relevant sizes. A substantial fraction of cloud condensation nuclei (CCN) are thought to arise from NPF.  In order to better predict the frequency, growth rates, and climatic impacts of NPF, knowledge of the chemical mechanisms by which nucleated nanoparticles grow is needed.  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 are sulfate and organics.  We have shown through laboratory and field work that particle phase sulfate is adequately described by condensation of gas phase sulfuric acid.  Neutralization of sulfate by ammonia is somewhat less understood, and there appears to be an activation barrier for ammonia uptake.  Carbonaceous matter is poorly understood at a molecular level, though it is highly oxidized and in some environments contains a substantial amount of nitrogen.  This presentation will give an overview of nanoparticle growth mechanisms and will highlight current effort directed toward a detailed molecular understanding of nanoparticulate carbonaceous matter.

Mechanisms of ambient nanoparticle growth

248th National Meeting (2014)

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