Atmospheric Chemistry and Physics
www.atmos-chem-phys.net
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7
20
2007
10.5194/acp-7-5309-2007
http://www.atmos-chem-phys.net/7/5309/2007/
http://www.atmos-chem-phys.net/7/5309/2007/acp-7-5309-2007.html
http://www.atmos-chem-phys.net/7/5309/2007/acp-7-5309-2007.pdf
5309
5325
2007-10-16
Influence of trans-Pacific pollution transport on acyl peroxy nitrate abundances and speciation at Mount Bachelor Observatory during INTEX-B
G. M. Wolfe
J. A. Thornton
thornton@atmos.washington.edu
V. F. McNeill
D. A. Jaffe
D. Reidmiller
D. Chand
J. Smith
P. Swartzendruber
F. Flocke
W. Zheng
Chemistry Department, University of Washington, Seattle, WA, USA
Atmospheric Sciences Department, University of Washington, Seattle, WA, USA
Interdisciplinary Arts and Sciences Department, University of Washington, Bothell, WA, USA
Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO, USA
Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
now at: Department of Chemical Engineering, Columbia University, New York, NY, USA
now at: UNAVCO, Boulder, CO, USA
We present month-long observations of speciated acyl peroxy nitrates (APNs),
including PAN, PPN, MPAN, APAN, and the sum of PiBN and PnBN, measured at
the Mount Bachelor Observatory (MBO) as part of the INTEX-B collaborative
field campaign during spring 2006. APN abundances, measured by thermal
dissociation-chemical ionization mass spectrometry (TD-CIMS), are discussed
in terms of differing contributions from the boundary layer (BL) and the
free troposphere (FT) and in the context of previous APN measurements in the
NE Pacific region. PAN mixing ratios range from 11 to 3955 pptv, with a mean
value of 334 pptv for the full measurement period. PPN is linearly
correlated with PAN (<I>r</I><sup>2</sup>=0.96), with an average abundance of 6.5%
relative to PAN; other APNs are generally <1% of PAN. Diurnal cycles
and relationships of APNs with ozone reveal a gradient in hydrocarbon
chemistry between the BL and the FT. On average, levels of APNs, ozone and
PPN/PAN are substantially higher in FT air relative to BL air, suggesting
that this site is strongly influenced by distant pollution sources. To
estimate the impact of long-range transport of Asian pollution on
atmospheric composition at MBO, we perform a detailed analysis utilizing
HYSPLIT back trajectories. This analysis suggests that trans-Pacific
transport of Asian pollution leads to substantial increases in APN and ozone
mixing ratios at MBO, especially when transport occurs via the free
troposphere. The ensemble of trajectories indicate that Asian-influenced
free tropospheric air was sampled in ~16% of our data and contained
a median PAN mixing ratio double that of the full dataset.
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