AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
AEESP Lecture: This is Getting Dynamic: How the Volatility Basis Set Informs Particle Formation and Growth
NEIL DONAHUE, Carnegie Mellon University
Abstract Number: 63 Working Group: Invited by Conference Chair
Abstract A large fraction of atmospheric nanoparticle growth is driven by condensation of organic compounds. Especially below 10 nm there is a fine dance between curvature induced volatility enhancement (the Kelvin effect) and mixing (the Raoult effect). In addition to Koehler and nano-Koehler behavior, the distribution of organic volatility over a very wide range plays a key role in particle growth. A major contribution comes from the new (to atmospheric chemistry) process of peroxy-radical auto oxidation, which forms highly oxygenated organic molecules (HOMs) rapidly during the initial stages of oxidation. In the CERN CLOUD experiment we have been able to measure the full distribution of organic products in both the gas and particle phases, establishing closure between observed vapor concentrations, growth rates, and particle composition at temperatures ranging from 250 to 320 K. Finally, we observe interesting and potentially critical couplings between different organic peroxy radicals that may have major implications for the behavior of atmospheric organics in low-NOx environments. All of these issues are well-suited to a dynamical version of the Volatility Basis Set that resolves peroxy-radical chemistry and provides a framework to describe the dynamics of organic particle nucleation and growth.