HR: 11:05h
AN: A21G-03    [PDF]
TI: Insights into Particle Characteristics, Sources, Nucleation and Growth in Pittsburgh Based on Aerosol Mass Spectrometry
AU: * Zhang, Q
EM: zhangq@cires.colorado.edu
AF: University of Colorado at Boulder, Cooperative Institute for Research in Environmental Sciences (CIRES) 216 UCB University of Colorado at Boulder, Boulder, CO 80309 United States
AU: Jimenez, J
EM: jose.jimenez@colorado.edu
AF: University of Colorado at Boulder, Cooperative Institute for Research in Environmental Sciences (CIRES) 216 UCB University of Colorado at Boulder, Boulder, CO 80309 United States
AU: Canagaratna, M C
EM: mrcana@aerodyne.com
AF: Aerodyne Research Inc., 45 Manning Road, Billerica, MA 01821-3976 United States
AU: Jayne, J T
EM: jayne@aerodyne.com
AF: Aerodyne Research Inc., 45 Manning Road, Billerica, MA 01821-3976 United States
AU: Worsnop, D R
EM: worsnop@aerodyne.com
AF: Aerodyne Research Inc., 45 Manning Road, Billerica, MA 01821-3976 United States
AB: An Aerodyne aerosol mass spectrometer (AMS) was deployed at the Pittsburgh EPA Supersite from September 6 to September 22, 2002, as part of the Pittsburgh Air Quality Study (PAQS). The main objectives of this deployment were 2) to characterize the size-resolved chemical composition of non-refractory (NR) components in fine particles (approx. PM1.0) and 2) to investigate the chemistry and mechanism of particle growth during the nucleation events in Pittsburgh. We first compare the AMS data with measurements from a wide variety of collocated aerosol instruments, including TEOM, semi-continuous sulfate and ammonium, 2hr- and 24hr-averaged organic carbon, SMPS, and MOUDI. Good agreement is observed for particle concentrations, compositions, and size distributions. Total NR PM1.0 mass concentration in Pittsburgh accumulates over periods of several days with intermittent cleaning due to rain or air mass change. Different aerosol species show different behavior in time and size. Sulfate and organics are the major components of fine particle mass while nitrate concentrations are lower. Significant amounts of ammonium are also present in particles, which most of the time is consistent with sulfate being present as ammonium sulfate. Size distributions of particulate sulfate, ammonium, organics and nitrate vary from day to day, showing unimodal, bimodal and even trimodal characteristics. The accumulation mode (peaking around 500nm in vacuum aerodynamic diameter for the mass distribution) and the fine mode (peaking around 200nm) are most commonly observed. Periods with high sulfate and organics mass loadings are examined. The possible sources and atmospheric processes that caused the events are suggested based on the AMS results, data of gaseous pollutants and meteorological variables and back trajectory analysis. Significant formation and growth of the nucleation mode particles were observed in three days during this deployment. These events appear to be representative of the climatology of the nucleation events observed in Pittsburgh (~ 100 per year). One of the events is among the 10 most intense nucleation events observed in Pittsburgh over a period of 15 months. All these events showed distinctive growth of sulfate, ammonium, organics and nitrate in the ultrafine mode. During each of these 3 events, sulfate was always the first, and often the fastest, species that grew in the ultrafine particles. Significant increase of ultrafine ammonium was also observed, but usually lagged slightly (5 -10 min) behind that of sulfate. For this reason the ultrafine particles tend to be acidic during the initial stages of the nucleation event. Ultrafine organics also increased significantly during the growth of the nucleation mode particles at a later time, probably from the condensation of photochemically produced secondary organic compounds. Among all these four species, nitrate was always the least important in the growth.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting