AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Probing the Microphysical Properties of Single Secondary Organic Aerosol Particles
GRAZIA ROVELLI, Young-Chul Song, Kelly Pereira, Jacqueline F. Hamilton, David Topping, Jonathan P. Reid, University of Bristol
Abstract Number: 309 Working Group: Aerosol Chemistry
Abstract Secondary Organic Aerosols (SOA) can reach highly viscous and glassy states at certain RH and T conditions. This phase state can produce possible kinetic limitations to the gas-particle partitioning of semi-volatile organic compounds (SVOCs), which can affect the chemical composition and the size of SOA in the atmosphere, their CCN and ICN activity, their hygroscopic and optical properties and eventually their effects on climate.
The representation of SOA in atmospheric models needs to be improved and could greatly benefit by a systematic investigation of microphysical properties and the dynamic response of SOA to external changes in T and RH, including their dependency on temperature. Here we present a comprehensive experimental approach that will provide further insight on the volatility, on the formation of liquid-liquid phase separation and inhomogeneity in chemical composition, the hygroscopic and optical properties of single SOA particles deriving from various volatile precursors, together with correlations between the formation conditions of SOA (VOC precursor, NOx and VOC concentration, RH), the resulting chemical composition and microphysical properties.
In this work, SOA is formed in a flow reactor (300 L polyvinyl fluoride bag, controlled VOC and oxidant concentrations, controlled RH, University of York) from different precursors (e.g. α-pinene, limonene, β-caryophyllene, toluene). SOA particles are then sampled with an electrical low pressure impactor and fully extracted for offline analysis with a 1:1 mixture of ethanol and water. An extensive characterisation of the chemical composition of the collected samples can be performed (UPLC-UV/Vis-UHRMS, NMR, elemental analysis, ATR-FTIR) and the microphysical properties of individual charged SOA aqueous droplets can be investigated using an electrodynamic balance (EDB, University of Bristol), at variable RH and T conditions (0 to >90% RH, -25 to 50°C).