During the past few years, Houston, Texas, has surpassed Los Angeles in having the highest levels of ozone in an urban area. The Texas 2000 Air Quality Study was conducted during the summer of 2000 to assess the sources for this high ozone production. One possible source is ozone transported from aloft. Beryllium-7 can be an indicator of upper tropospheric and lower stratospheric folding events, because it is produced in this region of the atmosphere. The isotope attaches itself to fine aerosols and can be a useful tracer of air masses containing the aerosols. Filter samples were collected at 12-hour intervals for approximately six weeks at the Deer Park site to investigate this source of ozone. A comparison of the maximum and 12-hour-average ozone levels with the beryllium-7 levels found at this site will be presented and discussed. An upper limit will be given for the ozone background in the Houston area due to this ozone source.

This work was supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Atmospheric Chemistry Program, and by the Texas Natural Resource and Conservation Commission via the University of Texas, Austin, under contract W-31-109-Eng-38. This work was performed at Argonne National Laboratory.