Executive Summary- Project 10-021
Dry Deposition of Ozone Built Environment Surfaces
In January of 2010 the USEPA proposed to strengthen the 8-hour primary National Ambient Air Quality Standards (NAAQS) for ozone to between 0.060 and 0.070 ppm and established a new seasonal secondary standard. The increased stringency of the primary and secondary NAAQS is expected to result in nonattainment designations for many more counties throughout the United States, including Texas. Photochemical grid models, such as the Comprehensive Air Quality Model with extensions (CAMx) that is used by the State of Texas, have a central role in the design of emission control strategies for attainment demonstrations and air quality planning. Dry deposition is the most important physical removal mechanism for ozone in Texas. Consequently, it is critical that related model algorithms be as accurate as possible in order to reduce uncertainties in predictions that will be used to implement ozone reduction strategies. Improvements in the dry deposition algorithms in CAMx are particularly important given the rapidly changing nature of urban landscapes, including increases in built environment surfaces such as roofing, building façades, and roadways.
The overall objective of this project is to improve existing knowledge of the effects of the urban built environment on dry deposition of ozone and predicted ozone concentrations. This project uses Austin, Texas, as the case study area but the experimental data and air quality modeling approach will be applicable to other ozone nonattainment and near nonattainment areas in eastern Texas. The project has the following objectives:
1. To conduct laboratory and field experiments to better characterize ozone removal by large-area outdoor built environment surfaces.
2. To characterize built environment surfaces in the Austin, Texas urban landscape using geospatial data.
3. To modify the dry deposition algorithms in CAMx, the air quality model used in regulatory applications for Texas, to include information from (1) and (2).
4. To conduct CAMx simulations to investigate the impacts of improvements in the characterization of dry deposition to built environment surfaces and of potential increases in built environment surfaces due to future urbanization on predicted ozone concentrations in Austin, Texas.
The deliverables to TCEQ will include revised deposition information, obtained from laboratory experiments, for a minimum of sixteen materials representing a range of urban built environment surfaces. Modified CAMx code to recognize these new urban land use categories will be provided, as well as an updated land use database for Austin, Texas, based upon the latest available geospatial information. Collectively, these deliverables should allow the TCEQ to readily adapt this work to photochemical modeling of other urban areas in Texas with similar built environment surfaces to that of Austin.