Project Summary

Title:	Daytime and Nighttime Atmospheric Nitrogen Cycling
Scholar:	James Flynn
School:	University of Houston
Mentor:	Dr. Barry Lefer and Dr. Bernhard Rappenglueck	[View Presentation ( 1.00 MB)]

In August and September of 2006 the University of Houston (UH) will host numerous federal and university scientists as part of the TexAQS Radical Measurement Program (TRAMP). UH and the visiting scientists will measure the following nitrogen species: NO, NO₂, NO₃, HONO, N₂O₅, HNO₃, PANs, and total reactive nitrogen. In addition, O₃, CO, HCHO, HOOH, photolysis frequencies and meteorological parameters will also be measured as well as many other ozone precursors and photochemical products. This comprehensive suite of measurements will help to quantify the concentrations and effects of nitrogen cycling on ozone formation and destruction processes.

As part of the preparations for the UH campaign a data system was developed, the UH O₃, NO_x, and CO instrumentation was calibrated, a heated Mo converter was replaced with a selective photolytic NO₂ converter on the NO_x instrument, and multiple spectral radiation instruments was installed. Additional infrastructure enhancements included the construction of a permanent radiation tower and a temporary walk-up tower for visiting scientists.

Although the campaign does not start until August 14, measurements from the weeks preceding the campaign were collected. These data show how meteorology controls whether Houston air quality will exceed EPA National Ambient Air Quality Standards for ozone. Temporally and spatially heterogeneous events such as rain showers also impacted ozone levels at the UH- Moody Tower site. Diurnal cycles of these chemical species highlighted the relative importance of point versus mobile sources at different times of the day and the influence of boundary layer dynamics on atmospheric nitrogen chemistry.