Houston-Galveston-Brazoria area is in severe non-attainment status for ozone compliance.
Source-oriented mechanistic modeling was used to determine the major sources of VOCs that
contributes to ozone formation during the Texas Air Quality Study (TexAQS) from August 16,
2000 to September 7, 2000. Environmental Protection Agency (EPA)?s Community Scale Air
Quality Model (CMAQ) version 4.6 was used as a host model to include a revised Statewide Air
Pollution Research Center (SAPRC99) photochemical mechanism with source-oriented
extensions to track the contributions of Volatile Organic Compounds (VOCs) emissions from
diesel engines, biogenic sources, highway gasoline vehicles, fuel combustion, off-highway
gasoline engines, solvent utilization and petrochemical industries to ozone formation in the
atmosphere. Source-oriented emissions needed to drive the model were generated using a revised
Sparse Matrix Operator Kernel Emissions (SMOKE) model version 2.4. VOC/NOx ratios are
found to be a critical factor in the formation of ozone. Highest ozone formation rates were
observed for ratios from 5-15. The contributions of VOC to ozone formation were estimated
based on the linear relationship between the rate of NO to NO2 conversion due to radicals
generated from VOC oxidation and the rate of net ozone formation. Petroleum and other industrial sources are the largest anthropogenic sources in the urban Houston region and
contribute to 45% of the ozone formation in the HGB area. Highway gasoline vehicles make
contributions of approximately 28% to ozone formation. Wildfires contribute to as much 11% of
ozone formation on days of high wildfire activity. The model results show that biogenic
emissions account for a significant amount of ozone formation in the rural areas. Both highway
and off-highway vehicles contribute significantly to ozone formation especially in the downwind
region. Diesel vehicles do not contribute significantly to ozone formation due to their low VOC
emissions.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2010-05-7933 |
| Date | 2010 May 1900 |
| Creators | Krishnan, Anupama |
| Contributors | Ying, Qi |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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