Atmospheric Chemistry. Photochemical Pollutants - Ozone Formation and Degradation Global Warming Visibility. Dr. Steven Japar Ford Motor Co. – Retired March 29, 2005. TROPOSPHERIC CHEMISTRY John H. Seinfeld, Spyros N. Pandis, “Atmospheric Chemistry and Physics” (John Wiley & Sons, 1998).
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Dr. Steven Japar
Ford Motor Co. – Retired
March 29, 2005
Photochemical Cycle of NO2, NO and O3
For O atoms, O3 (very reactive), invoke pseudo-steady-state approximation, i.e., rate of formation = equals rate of loss
jNO2[NO2] = k1[O][O2][M]
Photostationary state relationship
[O3]ss = jNO2[NO2] /k2[NO]
CO + OH + O2 CO2 + HO2
HO2 + NO NO2 + OH
NO2 + hν NO + O
O + O2 + M O3 + M
CO + 2O2 + hν CO2 + O3
OH + NO2 + M HNO3 + M
OH + NO + M HONO + M
HONO + hν OH + NO
Peroxyacetyl nitrate (PAN)
CH4 + 4O2 + 2NO + OHHCHO + 2O3 + OH + 2NO2 + H2O
CH3CH3 + 2NO + OH + O2CH3CHO + 2NO2 + OH
C2H4 + OH + NO + 2O2 NO2 + 1.44 HCHO + 0.28 HOCH2CHO + OH
Relationships in the Atmosphere
O3: 100-400 ppb
O3: 50-120 ppb
O3: 20-40 ppb
O3: 20-40 ppb
All VOC/NOx regimes are not equal
Decreased [NOx] increased [O3]
Decreased [VOC] decreased [O3]
Decreased [NOx] decreased [O3]
Decreased [VOC] no change in [O3]
C = Coexp(bextx)
bext is the extinction coefficient
x is the observer-object distance.
0.02 = - exp(bextVr) and Vr = 3.912/bext
Smoke from multiple wildfires in Canada blanketed the eastern U.S. with a smoke plume nearly 200 miles wide, affecting air quality from New York to Washington D.C in July 2002. CREDIT: NASA/GSFC.
B. A. Schichtel, et al, Atmospheric Environment 35, 5205-5210 (2001)
1981-1985 1986-1990 1991-1995
bext derived from Vr
Trends in improving visibility in the eastern U.S. correlate well with the decrease in SO2 emissions (precursor to particle sulfate in the atmosphere) in the U.S.
National Air Pollutant Emissions Estimates for Major Pollutants
This image shows ocean-crossing aerosols as dust from the Sahara desert is carried over the Atlantic Ocean. Dust and pollution from Asia floats toward the Pacific Northwest. CREDIT: NASA/GSFC.
Contribution to the Natural Greenhouse
Carbon Dioxide 5-7%
Nitrous Oxide <1%
Currently ~372 ppm
8-Day Atmospheric Water Cycle
Correlation Between Solar Cycle and Surface TemperatureCourtesy of George Wolff (GM)
Dashed line is length of sun’s magnetic cycle..
S. Solanki, et al., Nature (28 Oct. 2004)
TAR (IPCC, 2001)
Medieval Warm Epoch
Little Ice Age
Australian Bureau of Meteorology
Summer-weighted, Arctic-wide (29 sites)
Annual Temperatures: Proxy Data
T = -0.942 + 0.00313(Year-1600)
~0.016 deg./yr for
Former Soviet Bloc
Growth In Developed/ Developing NationsBillion Metric Tons C/yr
(IPCC Scenario IS92a)
Accumulated CO2 emissions 1990 to 2100 is
1,500 bmt C.
T. Wigley, R. Richels, and J. Edmonds, Nature 379, 240 (1996)