Carbon Monoxide Detection
AOSC 634
Russell R. Dickerson
Finlayson-Pitts Chapt. 16
Seinfeld Chapt. 2 & 6
Wallace & Hobbs Chapt. 5
EPA 2000 Criteria Document: http://www.epa.gov/NCEA/pdfs/coaqcd.pdf
EPA 2010 ISA: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=218686
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Carbon Monoxide
Importance
• Primary Air Pollutant
• Major sink for OH (greenhouse forcing, esp. short term!)
Thompson et al. (1989); Shindell et al. (2009); Hoor et al. (2009)
• Source/Sink of O3 depending on NOx
• Toxic air pollutant
Esp. for individuals with Coronary Artery Disease (EPA 2010)
• Excellent tracer for combustion and dynamics.
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In the remote atmosphere there is often insufficient NOx to drive this
reaction to two O3; the process reduces OH. Globally, Thompson et
al. (1989) predict that increased CO increases H2O2 and the ratio of
HO2 to OH, but reduces OH. Reduced OH means a longer lifetime
for CH4 and O3 which contribute to global warming, e.g., Shindell et
al., (2009); EPA (2010)
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Chemistry
Carbon monoxide oxidation in a clean environment:
(1) O3 + h  O2 + O(1D)
(2)
O(1D) + H2O  2OH
(3) OH + O3  HO2 + O2
(4) HO2 + O3  2O2 + OH
----------------------------------------(3+4)
2O3  3O2
NET
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Chemistry, continued
Carbon monoxide oxidation in a dirty (polluted)
environment:
(3')
OH + CO  H + CO2
(4') H + O2 + M  HO2 + M
(5') HO2 + NO  NO2 + OH
(6')
NO2 + h  NO + O
(7')
O + O2 + M  O3 + M
------------------------------------------------(3'-7') CO + 2 O2  CO2 + O3
NET
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Detection Methods
• Cavity Ringdown
• GC-FID
• Hg Liberation (CO + HgO → CO2 + Hg↑)
• Gas Filter Correlation NDIR
• FTIR
• Fluorescence
• Tunable Diode Laser Spectroscopy
• Remote sensing NDIR
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Non-Dispersive Gas-Filter Correlation
Detection of Carbon Monoxide
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Tunable Diode Laser Spectroscopy: Schematic Diagram
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A TDL can be finely tuned to the
precise wavelength that
characterizes whatever chemical
its users wish to detect. By
measuring how much light has
been absorbed, the TDL-based
detector can determine how
much carbon monoxide is
present. The laser is tuned on
and off a single rotational line
around 4.6 mm to generate an
AC signal. The signal is most
easily seen as the second
derivative.
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MOPITT (Measurement of Pollution in the Troposphere):
MOPITT is the first satellite
sensor to use gas
correlation spectroscopy.
GCS is a non-dispersive
technique to increase the
sensitivity of the instrument
to the gas of interest by
separating out the regions
of the spectrum where the
gas has absorption lines
and integrating the signal
from just those regions.
The specific wavelengths
are located using a sample
of the gas as a reference
for the spectrum. By using
correlation cells of differing
pressures, some height
resolution can be obtained.
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MOPITT (Measurement of Pollution in the Troposphere)
http://terra.nasa.gov/
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MOPITT CO image
from EPA ISA.
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Sources
Natural: Methane oxidation. Biogenic hydrocarbon (esp. isoprene) oxidation.
Direct emission from plants and oceans, although plants may absorb CO as well
as emit it. In any case, only direct emission is small relative to HC oxidation.
Anthropogenic: Internal combustion engines emit CO, especially when they run
rich. Even at a stoichiometric air/fuel mixture, CO is produced because of hightemperature dissociation of CO2.
CO2 → CO + ½O2
CO + ½O2 → CO2
H = -67.6
Coal combustion does not generate much CO because the power plants run
lean in order to extract as much energy from the coal as possible. Biomass
burning is a major source, as is oxidation of anthropogenic hydrocarbons in the
presence of NOx.
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American CO Emissions 2008
MISCELLANEOUS
17%
c
OFF-HIGHWAY
26%
HIGHWAY VEHICLES
57%
Direct anthropogenic emissions only, based on the
Mobile6 model. (EPA, 2009)
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Na onal US CO emissions
Thousands of tons CO per year
250,000
200,000
150,000
100,000
50,000
0
1970
1975
1980
1985
1990
1995
2000
2005
2010
2015
Year
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The global distribution
of CO reflects the
dominance of
emissions in the
Northern Hemisphere,
the seasonal cycle of
OH, and the short
lifetime relative to
transport across the
ITCZ.
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From the NOAA CMDL Trends Network Available almost real time.
http://www.esrl.noaa.gov/gmd/ccgg/iadv/
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CO/NOx ratio from observations indicates a ratio of ~6:1 (Luke et al., 2010).
Emissions inventories (http://www.epa.gov/ttnchie1/trends/) indicate a ratio of
12:1.
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References
Bishop, G. A. and D. H. Stedman (2008), A decade of on-road emissions measurements, Environmental Science & Technology,
42, 1651-1656.
Castellanos, P., L. T. Marufu, B. G. Doddridge, B. F. Taubman, S. H. Ehrman, and R. R. Dickerson (2010), Evaluation of Vertical
Mixing and Emissions in the CMAQ Model Using Measured Vertical Profiles of CO and O3, J. Geophys. Res., in preparation.
Hoor, P., J. Borken-Kleefeld, D. Caro, O. Dessens, O. Endresen, M. Gauss, V. Grewe, D. Hauglustaine, I. S. A. Isaksen, P. Jockel,
J. Lelieveld, G. Myhre, E. Meijer, D. Olivie, M. Prather, C. S. Poberaj, K. P. Shine, J. Staehelin, Q. Tang, J. van Aardenne, P.
van Velthoven, and R. Sausen (2009), The impact of traffic emissions on atmospheric ozone and OH: results from
QUANTIFY, Atmospheric Chemistry and Physics, 9, 3113-3136.
Hudman, R. C., L. T. Murray, D. J. Jacob, D. B. Millet, S. Turquety, S. Wu, D. R. Blake, A. H. Goldstein, J. Holloway, and G. W.
Sachse (2008), Biogenic versus anthropogenic sources of CO in the United States, Geophysical Research Letters, 35.
Hudman, R. C., L. T. Murray, D. J. Jacob, S. Turquety, S. Wu, D. B. Millet, M. Avery, A. H. Goldstein, and J. Holloway (2009),
North American influence on tropospheric ozone and the effects of recent emission reductions: Constraints from ICARTT
observations, Journal of Geophysical Research-Atmospheres, 114, DOI: 10.1029/2008JD010126
Kuhns, H. D., C. Mazzoleni, H. Moosmuller, D. Nikolic, R. E. Keislar, P. W. Barber, Z. Li, V. Etyemezian, and J. G. Watson (2004),
Remote sensing of PM, NO, CO and HC emission factors for on-road gasoline and diesel engine vehicles in Las Vegas, NV,
Science of the Total Environment, 322, 123-137, DOI: 10.1016/j.scitotenv.2003.09.013
Luke, W. T., P. Kelley, B. L. Lefer, and M. Buhr (2010), Measurements of primary trace gases and NOy composition in Houston,
Texas, Atmospheric Environment, in press, DOI: 10.1016/j.atmosenv.2009.08.014.
Marmur, A., W. Liu, Y. Wang, A. G. Russell, and E. S. Edgerton (2009), Evaluation of model simulated atmospheric constituents
with observations in the factor projected space: CMAQ simulations of SEARCH measurements, Atmospheric Environment,
43, 1839-1849, DOI: 10.1016/j.atmosenv.2008.12.027.
Novelli, P. C., K. A. Masarie, P. M. Lang, B. D. Hall, R. C. Myers, and J. W. Elkins (2003), Reanalysis of tropospheric CO trends:
Effects of the 1997-1998 wildfires, Journal of Geophysical Research-Atmospheres, 108.
Parrish, D. D. (2006), Critical evaluation of US on-road vehicle emission inventories, Atmospheric Environment, 40, 2288-2300.
Shindell, D. T., G. Faluvegi, D. M. Koch, G. A. Schmidt, N. Unger, and S. E. Bauer (2009), Improved Attribution of Climate Forcing
to Emissions, Science, 326, 716-718.
Thompson, A. M., R. W. Steward, M. A. Owens, and J. A. Herwehe (1989), Sensitivity of tropospheric oxidants to global chemical
and climate change, Atmos. Environ., 23, 519-532.
Warneke, C., J. A. de Gouw, A. Stohl, O. R. Cooper, P. D. Goldan, W. C. Kuster, J. S. Holloway, E. J. Williams, B. M. Lerner, S. A.
McKeen, M. Trainer, F. C. Fehsenfeld, E. L. Atlas, S. G. Donnelly, V. Stroud, A. Lueb, and S. Kato (2006), Biomass burning
and anthropogenic sources of CO over New England in the summer 2004, Journal of Geophysical Research-Atmospheres,
111, DOI: 10.1029/2005JD006878.
Yu, S. C., R. Mathur, D. W. Kang, K. Schere, and D. Tong (2009), A study of the ozone formation by ensemble back trajectoryprocess analysis using the Eta-CMAQ forecast model over the northeastern US during the 2004 ICARTT period,
Atmospheric Environment, 43, 355-363.
Yu, S. C., R. Mathur, K. Schere, D. W. Kang, J. Pleim, and T. L. Otte (2007), A detailed evaluation of the Eta-CMAQ forecast
model performance for O-3, its related precursors, and meteorological parameters during the 2004 ICARTT study, Journal of
Geophysical Research-Atmospheres, 112.
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Take Home Messages
• Carbon Monoxide is a relatively well understood
trace gas with important roles in human health,
the oxidizing capacity of the atmosphere and in
global climate.
• CO is a useful tracer for dynamical processed in
the atmosphere such as convective mixing.
• The uncertainty in the emissions is larger than
can be explained by measurement uncertainty.
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