Insights into the Chemistry of New Particle Formation and Growth Events in Pittsburgh Based on Aerosol Mass Spectrometry

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• 作者：Qi Zhang ; Charles O. Stanier ; Manjula R. Canagaratna ; John T. Jayne ; Douglas R. Worsnop ; Spyros N. Pandis ; and Jose L. Jimenez
• 刊名：Environmental Science & Technology
• 出版年：2004
• 出版时间：September 15, 2004
• 年：2004
• 卷：38
• 期：18
• 页码：4797 - 4809
• 全文大小：4586K
• 年卷期：v.38,no.18(September 15, 2004)
• ISSN：1520-5851

文摘

New particle formation and growth events have beenobserved in several urban areas and are of concern dueto their potential negative effects on human health. The mainpurpose of this study was to investigate the chemistry ofultrafine particles during the growth phase of the frequentlyobserved nucleation events in Pittsburgh (~100 eventsper year) and therefore infer the mechanisms of new particlegrowth in the urban troposphere. An Aerodyne aerosolmass spectrometer (AMS) and two SMPS systems weredeployed at the U.S. EPA Pittsburgh Supersite duringSeptember 2002. Significant nucleation events were observedin 3 out of the 16 days of this deployment, including oneof the 10 strongest nucleation events observed in Pittsburghover a period of 15 months. These events appear to berepresentative of the climatology of new particle formationand growth in the Pittsburgh region. Distinctive growthof sulfate, ammonium, organics, and nitrate in the ultrafinemode (33-60 nm in a vacuum aerodynamic diameter or ~18-33 nm in physical diameter) was observed during eachof these three events, with sulfate always being the first(and the fastest) species to increase. Ultrafine ammoniumusually increased 10-40 min later than sulfate, causingthe ultrafine mode particles to be more acidic during theinitial stages of the nucleation events. Significant increaseof ultrafine organics often happened after 11:00 a.m.,when photochemistry is more intense. This observationcoupled with a parallel increase of ultrafine m/z 44, a massfragment generally representative of oxygenated organiccompounds, indicates that secondary organic speciescontribute significantly to the growth of particles at arelatively later time of the event. Among all these four species,nitrate was always a minor component of the ultrafineparticles and contributed the least to the new particlegrowth.