Ozone

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Radiation balance for Earth
100 units corresponds to 54.4 x 1020 kJ/yr
Albedo of reflected radiation from
Earths surface varies widely from 2-90
Global albedo of 30 - reflection by clouds
reflection by atmosphere reflection from
Earth surface Absorbed by Earth (heating Earth)
44 Absorbed by atmosphere (heating atmosphere)
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Radiation balance for Earth
Heat balance on the atmosphere
Influx of solar energy minus reflection

• Maintain energy balance 70 of input solar
  energy (that is not reflected)
• must be radiated out (at IR wavelengths)
• Because of the greenhouse effect, more energy is
  in circulation in the
• outgoing IR absorbing gases (H2O, CO2, etc)
  reradiate in all directions
• (Earth emits 115 units heat balance requires
  70 units output)

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Albedo influence on heat balance

• Varies greatly over the Earths surface
• -as low as 6 in the oceans (most energy
  absorbed)
• -agricultural and forest land are low albedo
  (10-20)
• -deserts are higher (25-40)
• -clouds (35-40)
• -snow and ice cover (40-80)
• Dominant factor is clouds, which reflect incoming
  sunlight, but reradiate
• the IR radiation coming from the Earths surface
• Clouds form due to water condensation, but depend
  also on particles
• Biggest unknown in climate modeling is the effect
  of clouds, which in
• turn depend significantly on presence of aerosols

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Effects of aerosols to promote cooling
Particles in the atmosphere absorb light
depending on their albedo Size of particle is
important larger particles absorb more light,
and smaller particles tend to scatter light.
Most are submicron ? scattering (cooling)
dominates Black soot absorbs much light ?
local warming in the atmosphere Sulfate-rich
aerosols reflect light because of high albedo ?
cooling effect on the air near ground level ?
mitigation of global warming Anthropogenic
pollution increases particles in the atmosphere
by an estimated 25-50 global dimming
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H2S
DMS
FeS2
1012 gram 1 teragram (Tg)
Sulfur emission from anthropogenic sources is
similar to the biogenic rate
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Mount Pinatubo eruption, Philippines, 15 June
1991 ejected 10 Tg SO2 (1 Tg 1012 g) slowed
the rise of global warming Approximate albedo
increase of 0.5 ? T decrease of 0.5 K
SO2 (g) ? ? H2SO4 (aq)
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-2
Energy-requiring conversion from SO42- to H2S is
a bacterial process Very common in anaerobic
marine sediments SO42- 2CH2O 2H ? H2S
2H2O 2CO2 The energy is provided by oxidation
of reduced carbohydrate Sulfate-reducing bacteria
often live in consortium with methane-
oxidizing bacteria (methylotrophs) Assimilation
occurs in cells to incorporate sulfur into
proteins, nucleic acids and essential
metabolites
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• In sulfate-reducing bacteria, SO4 reduction is
  multistep and requires ATP
• Sulfide oxidation mediated by bacteria can occur
  from sulfide ores
• H2S oxidation produces an acidic environment
  acidothiobacillus also
• oxidizes Fe2 to Fe3. Oxidation can be via
  O2 or other oxidizers.

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Volatile Organic Sulfur
bacterial
bacterial
H2S is rapidly oxidized photochemically in the
atmosphere ? inorganic S does not have a
significant global effect But dimethyl sulfide
(DMS) does enter the atmosphere ? photochem
conversion to CH3SO3- (methane sulfonic acid)
? cloud condensation nuclei
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Anthropogenic generation of SO2

• Anthropogenic sources from coal (mainly) and oil
  combustion
• H2S is also an anthropogenic source (from oil and
  CH4 processing
• natural gas reservoirs often contain
  significant H2S)
• Sulfide ores are also a source of SO2 when
  processed to yield the
• elemental metal, for example
• 2NiS(s) 3O2(g) ? 2NiO(s) 2 SO2(g)
• The SO2 can be oxidized to SO3, then converted to
  commercial H2SO4
• SO2 in power plant emissions is scrubbed by
  reaction with CaCO3
• to yield CaSO4 (CO2)

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Atmospheric reactions of SO2
First step
Second step
Then SO3 H2O ? H2SO4 (g) fast H2SO4 (g)
H2O ? H2SO4 (aq)
This is the origin of acid rain
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LOSU assessed level of scientific understanding
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Everyone always complains about the weather. But
no one ever does anything about it -Mark Twain
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