Chemical Engineering Seminar

The chemistry of atmospheric aerosols influences their direct and indirect effects on climate. I will present results of our recent laboratory studies showing that particle-phase chemical reactions between organics and inorganic salts can lead to secondary organic products which absorb light in the UV and visible, thus changing the optical properties of the particle. I will introduce a model of coupled gas and aqueous aerosol chemistry that we have developed in order to study the formation of secondary organic aerosol material in aerosol water and the associated changes aerosol optical properties. We have also studied the sources and properties of surface-active organic species in aerosols. Organic films at the gas-aerosol interface can reduce aerosol surface tension, potentially enhancing the ability of small particles to nucleate cloud droplets (CCN activity). Our work has shown that update of methylglyoxal, acetaldehyde, and formaldehyde from the gas phase driven by aqueous-phase oligomerization chemistry is a potentially significant source of surface-active organic material in aerosols. Aerosol chamber studies of the CCN activity of particles exposed to gas-phase surfactants will be presented.