Atmospheric Chemistry

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Nonmethane hydrocarbons
Alkanes (C-C single bonds)
Alkenes (C-C double bonds)
ethane
ethene
Alkynes (C-C triple bonds)
Aromatic compounds
ethyne
Benzene
Oxygenated hydrocarbons Aldehydes, alcohols,
ketones, etc
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Global emissions of non-methane hydrocarbons
ANTHROPOGENIC SOURCES 100 TgC/yr Energy
use and transfer 43 TgC/yr Biomass burning 45
TgC/yr Organic solvents 15 TgC/yr NATURAL
SOURCES 1170 TgC/yr Emissions from
vegetation isoprene (C5H8) 500
TgC/yr monoterpenes 125 TgC/yr other
VOC 520 TgC/yr Oceanic emissions 6-36 TgC/yr
Brasseur et al., 1998
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Satellite observations of HCHO
OH
HCHO
NMHC
CO
hours
hours
Isoprene emissions
Trees cause more pollution than automobiles do.
Ronald Reagan, 1981
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Carbon monoxide, CO
CH4
CO2
Fluxes in TgC/year
CO sources 25 Fossil fuel, 25 Biomass
burning 25 CH4 oxidation,
25 NMHC oxidation
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GLOBAL DISTRIBUTION OF CONOAA/CMDL surface air
measurements
CO lifetime 1-2 months
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Transport from the Stratosphere 475 Tg/yr
Chem prod in trop 4920 Tg/yr
Chem loss 4230 Tg/yr
O
Deposition 1165 Tg/yr
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Tropospheric ozone column seen from space
Figure 3.
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Historical records imply a large anthropogenic
contribution to the present-day ozone background
at northern midlatitudes
Ozone trend from European mountain observations,
1870-1990
Marenco et al.,1994
? Increase is important from pollution and
climate perspectives
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Some important Trace gases

• Hydroxyl radical (OH)
• Reactive nitrogen species and the nitrogen cycle
• Hydrocarbons, Carbon monoxide
• Ozone
• Sulfur compounds and the sulfur cycle

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Sulfur gases
Increasing oxidation number (atmospheric
oxidation)
Decreasing oxidation number (reduction reactions)
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The sulfur cycle
Sources of SO2 Natural 42 Tg(S)
Anthropogenic 78 Tg (S)
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GLOBAL SULFUR EMISSION TO THE ATMOSPHERE1990
annual mean
Chin et al. 2000
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ORIGIN OF TROPOSPHERIC AEROSOL
Aerosol dispersed condensed phases suspended in
a gas Size range 0.001 mm (molecular cluster) to
100 mm (small raindrop)
Soil dust Sea salt
Environmental importance health (respiration),
visibility, radiative balance, cloud formation,
heterogeneous reactions, delivery of nutrients
Jacob, Introduction to Atmospheric Chemistry,
2000.
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AEROSOL OPTICAL DEPTH (GLOBAL MODEL)
Annual mean
IPCC 2001, Chapter 5.