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Big Bend (TX) Environmental Study; Report Nearing Publication


April 19, 2004

The Air Resources Laboratory, in collaboration with the Cooperative Institute for Atmospheric Sciences and Terrestrial Applications, participated extensively in the multi-agency Big Bend Regional Aerosol and Visibility Observational (BRAVO) Study of 1999. The results are now ready for publication. The BRAVO Study involved a four-month intensive monitoring period from July through October, followed by a four-year data analysis and modeling effort to assess the causes of haze in Big Bend National Park, TX. The BRAVO Study was specifically designed to relate haze contributions from different source regions and source types.

Visibility at Big Bend National Park is reduced due to haze caused by particles in the atmosphere (particulate haze). Particles contributing to haze originate from numerous sources across various geographic regions. The key points are that:

  • Sulfate compounds are the largest contributor to particulate haze at Big Bend.
  • Other particulate components, such as dust and carbonaceous compounds, comprise the majority of the remaining particulate haze annually.
  • Dust or smoke from local and international sources (Mexico and beyond) is the largest contributor on some of the haziest days, particularly during the spring.
  • SO2 emissions from sources in the U.S. and Mexico were estimated to contribute about 26% and 18%, respectively, of the particulate haze during the four-month BRAVO Study period. The split among U.S. source regions was Texas - 8%, eastern U.S. - 15%, and western U.S. - 4%.
  • SO2 emissions from sources in the U.S. and Mexico were estimated to contribute about 35% and 17% respectively of the particulate haze on the haziest 1/5 of the days during the four-month BRAVO Study period. The split among U.S. source regions was Texas - 11%, eastern U.S. - 20%, and western U.S. - 4%.
  • Two large power plants in northern Mexico contributed a total of about 9% of the particulate haze during the four-month BRAVO Study period, making them the single largest contributing SO2 emissions facility. Throughout the year transport is often from the western U.S. and Mexico on the least hazy days when the appearance of scenic vistas are especially sensitive to small increases in particle concentrations.

Contact information: Bruce B. Hicks
Phone: (301) 713-0684
e-mail: bruce.hicks@noaa.gov