Abstract
Dallas-Fort Worth Metroplex is one the most populated areas in
the United States with a long history of ground level ozone
pollution. In this research, Comprehensive Air Quality Model with
Extensions (CAMx) is used to develop a photochemical model of
DFW area. The impact of NOx and VOC emission from regional
shale gas activities (in Barnett Shale) is studied. Results show that
in order to effectively control ozone level to attain the national
standard level it is necessary to include strategies and techniques
to lower the emission levels of all shale gas production activities.
Background
Ozone is one of the criteria pollutants with negative health effects
on humans. Ground level ozone is formed by photochemical
reactions of nitrogen oxides (NOx) and volatile organic compounds
(VOC) in the atmosphere. Different facilities and activities involved
in shale gas development are significant sources of NOx and VOC.
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Results
Method
Complex cycles of photochemical reactions turn NOX and VOC molecules under sunlight into ozone. To evaluate the impact
of shale gas activities on ozone level we developed a photochemical modeling based on TCEQ (Texas Commission on
Environmental Quality) official CAMx model. Two hypothetical simulation cases were conducted with 50% and 100%
reduction in NOX and VOC area emission loads from shale gas activities. Simulations were performed for two ozone
episodes: June and August-September. Study area, Continuous Ambient Monitoring Sites (CAMS), and the location of gas
and oil wells are shown in Fig. A. Maximum reduction in 8hr mean ozone value in year 2018 near-by CAMS is calculated for
each case. Results are prepared in tabulated format, dispersion and concentration maps and animated GIFs.
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Fig. A. Study site: location of oil and gas wells and monitoring sites
Results
Impact of different emission reduction cases on predicted ozone
I
50% Reduction Oil/Gas Area Emission 100% Reduction Oil/Gas Area Emissions
CAMS
June August-September June August-September
Ft. Worth Northwest-C13 1.3 0.6 2.7 1.2
Keller-C17 1.5 1.0 3.1 2.1
Frisco - C31 0.5 0.5 1.1 0.9
Midlothian OFW - C52 0.2 0.5 0.4 1.0
Denton Airport South - C56 1.1 1.1 2.2 2.4
Arlington - C61 0.2 0.4 0.5 0.8
Dallas North - C63 0.2 0.5 0.4 1.1
Rockwall - C69 0.2 0.3 0.4 0.3
Grapevine - C70 0.5 1.1 1.1 1.1
Kaufman - C71 0.1 0.4 0.3 0.7
Granbury - C73 0.7 0.6 1.4 1.3
Eagle Mt. Lake - C75 1.4 1.4 2.8 2.9
Parker County - C76 0.8 1.0 1.7 2.0
Cleburne Airport - C77 0.8 0.5 1.6 1.1
Midlothian Tower - C94 0.2 0.5 0.4 1.0
Dallas Hinton St. - C401 0.2 0.4 0.3 0.8
Dallas Exec. Airport - C402 0.2 0.5 0.5 1.0
Itally/Ellis - C650 0.1 0.3 0.1 0.6
Greenville - C1006 0.3 0.2 0.6 0.5
Pilot Point - C1032 0.5 0.8 0.9 1.5
Numbers represent maximum predicted reduction in daily 8hr mean ozone (part per billion) in the year 2018
in each hypothetical emission reduction case
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Fig. C and D. Reduction in maximum daily u-hr ozone: 1ZD0% oil and
gas area emission reduction case
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Fig. E Fredicte"d hr oz ne
map reduction on June 17th
Fig F Predicted 'hr ozon e
map reduction on .August t
Conclusion
Results for 100% reduction in oil and gas area emission show that most
of the ozone reduction will happen in western portion of the metroplex
were oil and gas wells are located. Considering the size and location of
these area emission sources, local effect on ozone level is predicted.
Reduction in 8hr mean ozone value for 50% reduction in oil and gas area
emission reduction is as high as 1.5 (ppb) and with 100% reduction case,
this can be as high as 3.1 (ppb).
Findings of this research are useful for air quality improvement
strategies in DFW area. This can be very helpful considering the fact that
several counties in DFW area have been designated ozone non-
attainment for more than a decade.
ACKNOWLEDGMENT
The authors wish to thank the Downwinders at Risk Educational
Foundation for the financial support of this work.
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