1. Simple Chemical modeling of ozone sensitivity
to NOx and VOCs in Atlanta
Jin Liao
EAS 6410
04/24/2007

2. Outline 1.Introduction 2. Troposphere ozone production mechanism
in urban region
3. Simple Chemical modeling of ozone sensitivity
to NOx and VOCs in Atlanta
4. Modeling result and ozone control in Atlanta
5. Conclusion

3. The importance to control ozone in Atlanta
Tropospheric Ozone :
1. Cause photochemical smog, toxic to ecosystem,
destroy material such as rubber… Increase ground-level
2. A primary source of hydroxyl radicals ozone concentration
3. Greenhouse gas
Ozone ---- one of the U.S. EPA’s six criteria pollutants
and is regulated by a National Ambient Air Quality Standard.
Atlanta---One of 77 nonattainment areas in former U.S. EPA standard
The new U.S. EPA standard is more stringent.

4. The budget of ozone in Troposphere
Global models of tropospheric chemistry in a three-dimensional
frame-work to estimate tropopheric O3 budget
Dry Deposition
Chemical loss
Sinks
Transport from Stratosphere
Chemical Production
Sources
Tg O3 yr-1
Chemical Production = Chemcial Loss
Model only consider
Chemical Process

5. Troposphere O3 Production and Loss Mechanism in Urban Region
Emission
HNO3
Ozone NO
NO2 OH
HO2
VOCs hv
The emissions of NO and
VOCs from the surface drive
this cycle to produce o3.
To control the local ozone concentration, it is necessary to quantify the ozone
concentration relative to NOx and VOCs concentration.

6. Simple Chemical modeling of ozone sensitivity to NOx and VOCs in Atlanta
Basic modeling conception:
Only consider chemical production and loss reaction processes
We can determine the maximum ozone concentration with initial
NOx ,VOCs concentrations and photolysis rate
Acuchem
Input File(reaction mechanism and reaction rates)
Process(solves differential equations)
Output File(species concentration VS. reaction time)
MATLAB
Peak Ozone concentration Isopleths

7. This input file includes 37 chemical reactions for ozone formation and loss.
The photolysis rates for Atlanta come from
Other reaction rates come from IUPAC :
(John H. Seinfeld et al.,1998) Atmospheric chemistry and physics
The unit of photolysis rate : min-1
The unit of other reaction rates : ppm-1min-1.
The initial concentration for NOx :0.01ppm~ 0.2ppm
The initial concentration for VOCs :0~2ppmC.
CH4 concentration : 1.7ppm
CO concentration : 0.3ppm.
The Integration Tolerance : 10-8.
The reaction time for every cases changes from 5000~106mins.

8. Atlanta
(ppm)
NOx limited region
VOCs limited region

9. NOx concentration in Atlanta 2003~2005
0.0329
0.693
8179
2005
0.795
8407
2004
0.0336
0.626
8483
2003
Annual Arithmetic Mean (ppm)
1st Max (ppm)
Hours measured
Year
Oxides of Nitrigen concentration in Atlanta
(fulton county)
Cited from Georiga Department of Natural Resources Ambient Monitoring Program
2003~2005 annual reports

10. VOCs concentration in Atlanta from 2003 to 2005
2003: ~95ppb
2004:~110ppb
2005:~165ppb
Isoprene is by far the largest contributor
to ozone formation at every site.
VOCs(ppmc)=VOCs(ppm) * 5( for isoprene)
Georiga Department of Natural Resources
Ambient Monitoring Program 2005 report

11. Atlanta
(ppm)
NOx limited region
VOCs limited region

12. Compare modeling ozone concentration to the measurement
Cited from Georiga Department of Natural Resources Ambient Monitoring Program 2005 annual report

13. Ozone concentration control in Atlanta
Ozone control in Atlanta is
in the NOx limited region.
Peak ozone concentration
can be reduced to from
about 0.09ppm to 0.08ppm
by decrease NOx
concentration from 0.03ppm
to 0.02ppm.
Peak ozone concentrations depend on
different NOx levels with VOCs in 0.8ppmC

14. Conclusion
1.The modeling result of peak ozone isopleths plot of Atlanta makes
sense for ozone production is suppressed by the relationship between
VOCs and NOx concentrations indicated in the chemical mechanism.
2. According to the modeling result and the measurement of NOx,
VOCs concentration in Atlanta, ozone control in Atlanta is in the NOx-
limited region .
3. There are also some uncertainties in the modeling and result.
Software
Modeling: only consider chemical process
Measurement of NOx, VOCs and photolysis rates
(4) Detail VOCs compounds in Atlanta