Environmental Engineering Reference
In-Depth Information
0.1
1
0.08
0.8
0.06
0.6
s(1)03 to Nox
s(2)03 to Nox
03 concentration
α
=0.5* 5(2)/s(1)
0.04
0.4
0.02
0.2
0
0
0
50
100
150
Distance from Power Plant (km)
Fig. 2.
Surface layer baseline ozone concentration and its first- and second-order sensitivity to
Martin Lake NO
x
at the center of the plume (defined by maximal ZOC
NOy
) on June 4, 2006, at
14:00 (S
(2)
is negative, plot shows |S
(2)
|)
4. Conclusion
The nonlinear formation of ozone from six Texas power plants has been charac-
terized for a summertime air pollution episode. The spatial extent of the ozone
impacts tends to increase with the size of the NO
x
source, as ozone production
occurred more quickly in the smaller NO
x
plumes. However, the large power plant
plumes considered here achieved relatively high OPE's downwind, likely ref-
lecting the rich biogenic emissions near those facilities.
The nonlinearity of ozone impact tended to be greatest for the largest NO
x
emitters and to sharply decrease with time as each plume dispersed downwind.
This suggests that while power plant impacts are highly nonlinear near the facility,
responsiveness to controls will be nearly linear at large distances downwind.
One limitation of this study is the use of 12-km resolution, which may unrealisti-
cally dilute the initial intensity of the NO
x
plumes and thus fail to capture ozone
titration near the facilities. Future work could apply finer resolution or plume-
in-grid modeling to better resolve the near-facility features of ozone formation.
References
Cohan DS, Hakami A, et al. (2005) Nonlinear response of ozone to emissions: Source apportion-
ment and sensitivity analysis,
Environ Sci Technol
,
39
(17), 6739-6748.
Dunker AM (1984) The decoupled direct method for calculating sensitivity coefficients in
chemical kinetics,
J. Chem. Phys.
,
81
(5), 2385-2393.
Hakami A, Odman MT, et al. (2003) High-order, direct sensitivity analysis of multidimensional
air quality models,
Environ Sci Technol
,
37
(11), 2442-2452.
Koo B, Yarwood G, et al. (2007) Incorporation of High-order Decoupled Direct Method (HDDM)
Sensitivity Analysis Capability into CAMx, Prepared for Texas Commission on Environmental
Quality.
