The nighttime P-3 flights during TexAQS 2006 were aimed at characterizing the nocturnal reactions, transport and loss of NOx, VOC and O3, with an emphasis on the role of the nighttime nitrogen oxides, NO3 and N2O5. Mixing ratios of NO3 and N2O5 were highly variable and occasionally quite large, consistent with previous aircraft measurements of these compounds. Analysis of these data showed that hydrolysis of N2O5, the most important reaction in the nocturnal conversion of NOx to HNO3, was generally inefficient in air masses around Houston and elsewhere in Texas. As a result, NOx emissions occurring late in the day or at night could be transported overnight in the form of N2O5 to regions distant from the NOx source regions. Transport of O3 was also efficient since N2O5 is a reservoir for odd oxygen (Ox) as well. The reduced rate of N2O5 hydrolysis enhanced the availability of NO3, which is a strong oxidant for highly reactive VOC (HRVOC such as alkenes, some aromatics and oxygenates). This was important in plumes containing both NOx and HRVOC from industrial sources in the Houston area.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 0322 Constituent sources and sinks;
- 0345 Pollution: urban and regional (0305;
- 0365 Troposphere: composition and chemistry;
- 0368 Troposphere: constituent transport and chemistry