(673c) Design and Application of Ultra-Fine V-Tdma to Atmospheric Aerosols

Volatility of freshly nucleated particle provides important information to understand the balance of volatile, semivolatile, and nonvolatile particle components, as well as the mixing state of these components.

The design, construction, testing, and field application of a Volatility Tandem Differential Mobility Analyzer system (V-TDMA) will be presented.  The system is designed to study the volatility of ambient aerosols, including those recently created from new particle formation and growth.   Our V-TDMA has two nano-DMAs (Nano-DMA, TSI model 3085) in tandem, and a thermodenuder for thermal treatment of sub-30 nm aerosols.  The V-TDMA system was tested in laboratory using mono-disperse ammonium sulfate, sodium chloride, and secondary organic aerosol components (e.g., pinic acid, pinonic acid, and adipic acid) to understand system performance and benchmark behavior against published volatility data. Performance was tested as a function of size, concentration, residence time, Reynolds number, chemical composition (pure component vs. mixture), and thermodenuder design parameters such as dimension of heating and denuder, choice of denuder type (activated charcoal and without activated charcoal) , and whether the denuding section was cooled.   Details regarding these different aspects of thermodenuder design will be presented.