Measurements of HNO3 and N2O5 using ion drift-chemical ionization mass spectrometry during the MILAGRO/MCMA-2006 campaign
Item
Title (Dublin Core)
Measurements of HNO3 and N2O5 using ion drift-chemical ionization mass spectrometry during the MILAGRO/MCMA-2006 campaign
Description (Dublin Core)
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 (HNO<sub>3</sub>) and dinitrogen pentoxide (N<sub>2</sub>O<sub>5</sub> 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, HNO<sub>3</sub> was less than 200 parts per trillion (ppt) during the night and early morning. The concentration of HNO<sub>3</sub> 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 HNO<sub>3</sub> measurements (<i>R</i><sup>2</sup>=0.75). The HNO<sub>3</sub> 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 HNO<sub>3</sub> 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, N<sub>2</sub>O<sub>5</sub> 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 N<sub>2</sub>O<sub>5</sub> 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 HNO<sub>3</sub> was primarily produced from the reaction of OH with NO<sub>2</sub> and regulated by gas/particle transfer and dry deposition. The production of HNO<sub>3</sub> from N<sub>2</sub>O<sub>5</sub> hydrolysis during the nighttime was small because of high NO and low O<sub>3</sub> concentrations near the surface.
Creator (Dublin Core)
Zheng, J.
Zhang, R.
Fortner, E. C.
Volkamer, R. M.
Molina, L.
Aiken, A. C.
Jimenez, J. L.
Gaeggeler, K.
Dommen, J.
Dusanter, S.
Stevens, P. S.
Tie, X.
Date (Dublin Core)
2018-01-15
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-8-6823-2008
https://acp.copernicus.org/articles/8/6823/2008/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
