AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Size-resolved Chemical Composition of Sub-40 nm Particles during New Particle Formation and Growth Events in Beijing
XIAOXIAO LI, Yuyang Li, Chao Yan, Sabrina Chee, Jiming Hao, James Smith, Jingkun Jiang, Tsinghua University
Abstract Number: 237 Working Group: Aerosol Chemistry
Abstract The rapid growth of newly formed particles increases atmospheric CCN concentration. Direct measurement of sub-40 nm particle chemical composition helps to study the role of various physical and chemical mechanisms during atmospheric particle growth events. We carried out a field campaign in Beijing during the spring and summer of 2019 to study the growth of newly formed particles. A thermal desorption chemical ionization inlet coupled with high-resolution time-of-flight mass analyzer (TD-CI-HTOF), with O2- and C5H10NO+ as the reagent ions, was used to measure size-resolved chemical composition (sulfate, nitrate, ammonia, amine, and organics) of sub-40 nm particles. A CI-LTOF, with NO3- as the reagent ion, was used to measure gas precursors including H2SO4 and highly-oxygenated molecules (HOMs) that are potentially relevant to particle growth. Electrical mobility size spectrometers were used to measure aerosol size distributions from ~1 nm to 10 μm. Aerosol growth model was used to evaluate the role of condensational growth contributed by gas phase H2SO4 and HOMs. The modeled growth rate was compared to that directly estimated from the measured particle size distributions. Size-resolved acid/base ratio, organics/inorganics ratio, and organic O/C, H/C ratio measured by TD-CI-HTOF were compared with those predicted by aerosol growth model. The relative importance of condensational growth and other mechanisms were explored.