CIASTA-Led Program Attributes Haze In Texas Among US and Mexican Sources
March 12, 2004
The Big Bend Regional Aerosol and Visibility Observational (BRAVO) Study involved a four-month intensive monitoring period from July through October 1999, 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 use extensive measurements with a variety of attribution methods to estimate haze contributions from source regions and source types. Several ARL groups were heavily involved. Coordination of the overall effort was through the Cooperative Institute on Atmospheric Sciences and Terrestrial Applications (CIASTA) in Nevada. 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 findings of the BRAVO program are:
- Sulfate compounds are the largest contributor to particulate haze at Big Bend.
- 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 on average 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%.
- The two Carbón power plants in northern Mexico contributed a total of about 9% of the particulate haze on average 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 particulate concentrations.
Contact information: Bruce B. Hicks
Phone: (301) 713-0684