AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Surface Activity in Secondary Organic Aerosol Liquid Samples
ANDREW METCALF, Cari Dutcher, University of Minnesota, Twin Cities
Abstract Number: 399 Working Group: Aerosol Chemistry
Abstract Recent experimental evidence suggests that ambient aerosol particles, particularly aged secondary organic aerosol (SOA), can be phase-separated into multiple liquid phases. One potential particle configuration is a core-shell morphology, where the presence of an organic surface film may inhibit species uptake and evaporation by providing a mass transfer barrier (kinetic effect) or by mixing with components in the aerosol, reducing the overall particle hygroscopicity (chemical effect). Organic films acting as surfactants affect particles’ ability to act as cloud condensation nuclei (CCN) and can, therefore, introduce large variability in cloud droplet number resulting from these CCN. However, we currently lack the ability to accurately predict the formation of these films under most natural conditions. Thus, it is necessary to assess the presence of these organic films in ambient aerosol.
In this talk, our microfluidic platform will be used to measure the presence of surface-active species in aerosol liquid samples. The presence of surface-active constituents will change (usually reduce) the surface (liquid-vapor) and interfacial (liquid-liquid) tension relative to a reference state, resulting in a change in the mixing state of ambient particles and their tendency for growth and activation. We derive aerosol liquid samples from a variety of sources, including laboratory-generated SOA and SOA intermediates. The intermediates are isoprene-SOA intermediates synthesized in the laboratory. SOA liquid is extracted from filters collected during flow-tube or environmental chamber experiments. Sources of SOA liquid examined in this study include photooxidation of naphthalene and both photooxidation and ozonolysis of caryophyllene.