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Title: Comparison of secondary organic aerosol formed with an aerosol flow reactor and environmental reaction chambers: effect of oxidant concentration, exposure time and seed particles on chemical composition and yield

We performed a systematic intercomparison study of the chemistry and yields of SOA generated from OH oxidation of a common set of gas-phase precursors in a Potential Aerosol Mass (PAM) continuous flow reactor and several environmental chambers. In the flow reactor, SOA precursors were oxidized using OH concentrations ranging from 2.0×108 to 2.2&times1010 molec cm-3 over exposure times of 100 s. In the environmental chambers, precursors were oxidized using OH concentrations ranging from 2×106 to 2×107 molec cm-3 over exposure times of several hours. The OH concentration in the chamber experiments is close to that found in the atmosphere, but the integrated OH exposure in the flow reactor can simulate atmospheric exposure times of multiple days compared to chamber exposure times of only a day or so. A linear correlation analysis of the mass spectra (m=0.91–0.92, r2=0.93–0.94) and carbon oxidation state (m=1.1, r2=0.58) of SOA produced in the flow reactor and environmental chambers for OH exposures of approximately 1011 molec cm-3 s suggests that the composition of SOA produced in the flow reactor and chambers is the same within experimental accuracy as measured with an aerosol mass spectrometer. This similarity in turn suggests that both in the flow reactor andmore » in chambers, SOA chemical composition at low OH exposure is governed primarily by gas-phase OH oxidation of the precursors, rather than heterogeneous oxidation of the condensed particles. In general, SOA yields measured in the flow reactor are lower than measured in chambers for the range of equivalent OH exposures that can be measured in both the flow reactor and chambers. The influence of sulfate seed particles on isoprene SOA yield measurements was examined in the flow reactor. The studies show that seed particles increase the yield of SOA produced in flow reactors by a factor of 3 to 5 and may also account in part for higher SOA yields obtained in the chambers, where seed particles are routinely used.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [4] ;  [5] ;  [5] ;  [5] ;  [2] ;  [2] ;  [5]
  1. Boston College, Chestnut Hill, MA (United States); Aerodyne Research Inc., Billerica, MA (United States)
  2. Aerodyne Research Inc., Billerica, MA (United States)
  3. Pennsylvania State Univ., State College, PA (United States)
  4. MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States)
  5. Boston College, Chestnut Hill, MA (United States)
Publication Date:
OSTI Identifier:
1197855
Grant/Contract Number:
FG02-05ER63995; SC0011935; SC0006980
Type:
Published Article
Journal Name:
Atmospheric Chemistry and Physics Discussions (Online)
Additional Journal Information:
Journal Name: Atmospheric Chemistry and Physics Discussions (Online); Journal Volume: 14; Journal Issue: 22; Journal ID: ISSN 1680-7375
Publisher:
Copernicus GmbH
Sponsoring Org:
USDOE
Country of Publication:
Germany
Language:
English