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<front>
<journal-meta>
<journal-id journal-id-type="publisher">ACPD</journal-id>
<journal-title-group>
<journal-title>Atmospheric Chemistry and Physics Discussions</journal-title>
<abbrev-journal-title abbrev-type="publisher">ACPD</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1680-7375</issn>
<publisher><publisher-name>Copernicus GmbH</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/acpd-9-19641-2009</article-id>
<title-group>
<article-title>Comparison of aromatic hydrocarbon measurements made by PTR-MS, DOAS  and GC-FID in Mexico City during the MCMA 2003 field experiment</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Jobson</surname>
<given-names>B. T.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Volkamer</surname>
<given-names>R.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Velasco</surname>
<given-names>E.</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Allwine</surname>
<given-names>G.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Westberg</surname>
<given-names>H.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Lamb</surname>
<given-names>B.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Alexander</surname>
<given-names>M. L.</given-names>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Berkowitz</surname>
<given-names>C. M.</given-names>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Molina</surname>
<given-names>L. T.</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Department of Civil and Environmental Engineering, Washington State  University, Pullman, WA, USA</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Department of Chemistry and  Biochemistry and CIRES, University of Colorado, Boulder, CO, USA</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Molina Center for Energy and the Environment (MCE2), La Jolla, CA,  USA</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>Departmnet of Earth, Atmospheric, and Planetary Science, Massachusetts Institute of Technology, Cambridge, MA, USA</addr-line>
</aff>
<aff id="aff5">
<label>5</label>
<addr-line>Battelle Pacific Northwest, P.O. Box 999, Richland, WA, USA</addr-line>
</aff>
<pub-date pub-type="epub">
<day>23</day>
<month>09</month>
<year>2009</year>
</pub-date>
<volume>9</volume>
<issue>5</issue>
<fpage>19641</fpage>
<lpage>19681</lpage>
<permissions>
<license xlink:type="simple">
<license-p>This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</license-p>
</license>
</permissions>
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<abstract>
<p>A comparison of aromatic hydrocarbon measurements is reported for the
CENICA supersite in the district of Iztapalapa during the Mexico City
Metropolitan Area field experiment in April 2003 (MCMA 2003). Data
from three different measurement methods were compared, a proton
transfer reaction mass spectrometer (PTR-MS), long path measurements
using a UV differential optical absorption spectrometer (DOAS), and
gas chromatography-flame ionization analysis (GC-FID) of canister
samples. Lab tests established that the PTR-MS and DOAS calibrations
were consistent for a suite of aromatic compounds including benzene,
toluene, p-xylene, ethylbenzene, 1,2,4-trimethylbenzene, phenol, and
styrene. The point sampling measurements by the PTR-MS and GC-FID
showed good correlations (&lt;i&gt;r&lt;/i&gt;=0.6), and were in reasonable agreement
for toluene, C&lt;sub&gt;2&lt;/sub&gt;-alkylbenzenes, and
C&lt;sub&gt;3&lt;/sub&gt;-alkylbenzenes. The PTR-MS benzene data were consistently
high, indicating potential interference from fragmenting alkyl
aromatics for the 145 Td drift field intensity used in the
experiment. Correlations between the open-path data measured at
16-m height over a 860 m path length (retroreflector in
430 m distance), and the point measurements collected at
37-m sampling height were best for benzene (&lt;i&gt;r&lt;/i&gt;=0.61), and
reasonably good for toluene, C&lt;sub&gt;2&lt;/sub&gt;-alkylbenzenes, naphthalene,
styrene, cresols and phenol (&lt;i&gt;r&lt;/i&gt;&amp;gt;0.5). While the DOAS data agreed
within 20% with both point measurements for benzene, concentrations
measured by DOAS were on average a factor of 1.7 times greater than
the PTRMS data for toluene, C&lt;sub&gt;2&lt;/sub&gt;-alkylbenzenes, naphthalene, and
styrene. The level of agreement for the toluene data was a function of
wind direction, establishing that spatial gradients – horizontal,
vertical, or both – in VOC mixing ratios were significant, and up to
a factor of 2 despite the fact that all measurements were conducted
above roof level. Our analysis highlights a potential problem in
defining a VOC sampling strategy that is meaningful for comparison
with photochemical transport models: meaningful measurements require
a spatial fetch that is comparable to the grid cell size of models,
which is typically few 10 km&lt;sup&gt;2&lt;/sup&gt;. Long-path DOAS measurements
inherently average over a larger spatial scale than point
measurements. The spatial representativeness can be further increased
if observations are conducted outside the surface roughness sublayer,
which might require measurements at altitudes as high as few
10 m above roof level.</p>
</abstract>
<counts><page-count count="41"/></counts>
</article-meta>
</front>
<body/>
<back>
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