AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
A Study on Mixing Structure of Atmospheric Ultrafine Particles by Using the Thermo-Denuder HTDMA System
Kihong Park, JAE-SEOK KIM, School of Environmental Science and Engineering, Gwangju Ins
Abstract Number: 294 Working Group: Aerosol Physics
Abstract A hygroscopicity tandem differential mobility analyzer (HTDMA) system with a thermo-denuder (heated tube and charcoal absorber) system was applied to determine mixing structure of the size-selected ultrafine particles at urban Gwangju in Korea. Number concentration of particles of 20-600 nm was continuously measured with a scanning mobility particle sizer (SMPS). When formation of ultrafine particles was observed (e.g., photochemical and combustion events), the tandem system was triggered to measure the mixing structure of the size-selected ultrafine particles. The size-selected ultrafine particles by the first DMA were introduced into the thermo-denuder system to remove volatile species with varying temperature (20-250 oC), and the remaining particles (i.e., core particles) were exposed to increased RH to determine the hygroscopicity of the remaining particles. It was found that a distinct difference of the hygroscopicity of the remaining particles was observed between photochemical and combustion events. In the combustion event, non-volatile core was identified (i.e., no more size change with increasing the thermo-denuder temperature up to 250 oC), and the hygroscopicity of particles decreased after removing volatile species, suggesting that the core particles mainly consist of non-hygroscopic black carbon species and that the volatile species included hygroscopic species. In the photochemical event, after removing volatile species, the hygroscopicity of the remaining particles was not changed and the non-volatile core was not observed (i.e., particles were completely evaporated at 200 oC).