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| Titel |
Measurements of HNO3 and N2O5 using ion drift-chemical ionization mass spectrometry during the MILAGRO/MCMA-2006 campaign |
| VerfasserIn |
J. Zheng, R. Zhang, E. C. Fortner, R. M. Volkamer, L. Molina, A. C. Aiken, J. L. Jimenez, K. Gaeggeler, J. Dommen, S. Dusanter, P. S. Stevens, X. Tie |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 8, no. 22 ; Nr. 8, no. 22 (2008-11-28), S.6823-6838 |
| Datensatznummer |
250006468
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| Publikation (Nr.) |
 copernicus.org/acp-8-6823-2008.pdf |
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| Zusammenfassung |
| An ion drift-chemical ionization mass spectrometer (ID-CIMS) was deployed in
Mexico City between 7 and 31 March to measure gas-phase nitric acid
(HNO3) and dinitrogen pentoxide (N2O5 during the Mexico City
Metropolitan Area (MCMA)-2006 field campaign. The observation site was
located at the Instituto Mexicano del Petróleo in the northern part of
Mexico City urban area with major emissions of pollutants from residential,
vehicular and industrial sources. Diurnally, HNO3 was less than 200
parts per trillion (ppt) during the night and early morning. The
concentration of HNO3 increased steadily from around 09:00 a.m. central
standard time (CST), reached a peak value of 0.5 to 3 parts per billion (ppb)
in the early afternoon, and then declined sharply to less than half of the
peak value near 05:00 p.m. CST. An inter-comparison between the ID-CIMS and
an ion chromatograph/mass spectrometer (ICMS) showed a good agreement between
the two HNO3 measurements (R2=0.75). The HNO3 mixing ratio
was found to anti-correlate with submicron-sized aerosol nitrate, suggesting
that the gas-particle partitioning process was a major factor in determining
the gaseous HNO3 concentration. Losses by irreversible reactions with
mineral dust and via dry deposition also could be important at this site.
Most of the times during the MCMA 2006 field campaign, N2O5 was
found to be below the detection limit (about 30 ppt for a 10 s integration
time) of the ID-CIMS, because of high NO mixing ratio at the surface
(>100 ppb) during the night. An exception occurred on 26 March 2006, when
about 40 ppt N2O5 was observed during the late afternoon and
early evening hours under cloudy conditions before the build-up of NO at the
surface site. The results revealed that during the MCMA-2006 field campaign
HNO3 was primarily produced from the reaction of OH with NO2 and
regulated by gas/particle transfer and dry deposition. The production of
HNO3 from N2O5 hydrolysis during the nighttime was small
because of high NO and low O3 concentrations near the surface. |
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