Determining VOC boundary values for simulations of Phoenix, AZ ozone with limited ambient measurements
- Arizona Dept. of Environmental Quality, Phoenix, AZ (United States)
For Urban Airshed Model simulations of ozone episodes in 1992 and 1996 for Phoenix, AZ, numerous attempts to better characterize boundary conditions were made. The early boundary values relied on concentrations from urban sites that were adjusted to rural values, and ended with background VOC monitoring 50 miles west of Phoenix. Early attempts at specifying lateral boundary values for VOC depended on adjusting central city concentrations to boundary values based on simultaneous measurements with a limited analytical suite of 20 samples at a single boundary location and at three locations in the central city in 1992. Although these boundary values were refined and revised, their values proved to be too high to give a realistic boundary contribution to metropolitan ozone. These boundary values were lowered by incorporating hourly wind directions. Wind from the urban area led to a higher VOC value at a boundary segment, while wind from the rural area led to a lower VOC value at the boundary segment. These wind-directional dependent, spatially-varying boundary values were used in the final UAM model validation for a March, 1997 report. Evidence that these values were still too high, however, prompted a test with data from the remote location of Hillside, AZ, 80 miles northwest of Phoenix. These data consisted of only 53 hydrocarbons and 10 aldehydes, with no measurement of ethene. Boundary values based on these data produced ozone concentrations about 5% lower than the rural-urban, wind-direction dependent scheme. A special sampling program, conducted in May and June, 1997 at a site 50 miles west of Phoenix, provided data, that, when combined with the full Hillside data set, were sufficient to calculate optimal boundary concentrations for an October, 1997 report.
- OSTI ID:
- 362030
- Report Number(s):
- CONF-980632--
- Country of Publication:
- United States
- Language:
- English
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