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Title: Validation of concentrations estimated from air dispersion modeling for source-receptor distances of less than 100 meters.

Principal Investigator / Author(s): Venkatram, Akula

Contractor: UC Riverside

Contract Number: 99-319

Research Program Area: Atmospheric Processes

Topic Areas: Area Sources, Field Studies, Modeling, Monitoring, Stationary Sources


Currently available dispersion models used to estimate dispersion in urban areas were developed using data from experiments conducted at source-receptor distances ranging from 50 m to 16km. The rural dispersion curves are based on the Prairie Grass experiment (Barad, 1958) where the source-receptor distances ranged from 50 m to 800 m. The urban dispersion curves are based on the St. Louis Dispersion Study (Mc. Elroy and Pooler, 1968) where the nearest receptor was 800 m from the source. Regulatory programs require the assessment of potential health impacts from exposures to air toxics from urban sources, such as gasoline stations, dry cleaners, and automotive repair facilities, where human receptors are typically within fifty meters from the critical need to validate dispersion tools at this distance. ARB has responded to this need by sponsoring UCR to develop a new dispersion model that can be used to estimate the impact of urban sources at source-receptor distances of tens of meters. The model has been developed using data from the Prairie Grass experiment (Barad, 1958), and an experiment conducted in this project have been compared with tracer concentrations measured under a variety of meteorological conditions in the vicinity of an urgan source located at a parking lot on the College of Engineering, Center for Environmental Research and Technology (CE-CERT) at the University of California, Riverside. In addition, the performance of the model has been compared with those of ISC, ISC-PRIME, and AERMOD-PRIME, models that are currently used in regulatory practice. The statistics used to quantify model performance ranks the models in the following order: Proposed model, AERMOD-PRIME, ISC, and ISC-PRIME. The relative performance of these models indicates that a reliable model for near source dispersion in urban areas needs to use site-specific meteorology, incorporate upwind dispersion under low wind speed conditions, and reduce source height to account for building downwash.


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

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