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Acid in the Atmosphere

• Pollution and Impact on Ecosystems

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Three Problems

• Acid deposition
• Nitrogen Eutrophication
• Ground-level Ozone

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What causes acid rain?

• sulphur dioxide, mainly from power stations,
•  
• oxides of nitrogen from motor vehicles and the
  industrial burning of fossil fuels (gas, oil and
  coal).
•  
• Another form of nitrogen pollution, ammonia, is
  emitted especially in rural areas, e.g. from
  manure spread on farmland and from farm animals.

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  UK Sources of SO2
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UK Sources of NOx
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Total deposition 1988 - 1992 Source The critical
load / NILU. Maps SKMe Norwegian Mapping
Authority - Environmental unit
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Map Regional distribution of areas with fish
stocks affected by acidification in Norway
1950-1990. Source DN, Directorate for Nature
Management.
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Capacity   (to neutralise inputs) ie amounts
of Na K Ca Mg Al
Intensity
Sensitivity
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Critical Loads

• To help quantify effects and relate them to the
  acid deposited, an "effects based" approach,
  known as critical loads, has been developed.
•  
• The critical load is a measure of sensitivity of
  the environment to pollutants.

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Areas where excess deposition over the
sensitive acidity critical loads is unlikely
(pink), where excess is likely (red) and where
the excess is high (black) as given by the
deposition of sulphur, nitrogen oxide and
ammonia
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The Critical Load
"the quantity of pollution that a part of the
environment can tolerate without harmful effects
occurring".   Deposition above that limit may
damage plants and animals. Where acidity critical
loads are large, more acid deposition can be
tolerated, but areas with small acidity critical
loads are very sensitive to acidification.
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Total deposition 1988 - 1992 Source The critical
load / NILU. Maps SKMe Norwegian Mapping
Authority - Environmental unit
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2010 (estimated)
1992-94
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  The sensitivity of Acid Heathland to further
inputs of acidity  
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Treating the Symptoms

• In 1995 lime was used over 2,500 locations in
  Norway covering a precipitation area of about
  6,400 square kilometres      
•  
• In 1994 NOK 58 million were used on liming. The
  amount increased to 93 million in 1995 and then
  to NOK 118 million in 1996

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1,000 tonnes of lime used Calculated from
government expenditure on lime, (with a fixed
price of NOK 1,000 per tonne through the whole
period. Source Directorate for Nature
Management).
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Treatment High Costs

• If the entire area of Southern Norway where the
  critical load has been exceeded should receive
  sufficient lime, the costs would be approximately
  NOK 340 million according to the Norwegian
  Institute for Water Research.

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What is being done?

• 1979 Convention on Long Range Transboundary Air
  Pollution (LRTAP
• 43 Signatories around the Northern Hemisphere

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Legislation for Reductions in Acid Emissions (I)

• Early Protocols for sulphur dioxide and oxides of
  nitrogen set simple targets for all countries
•  
•    a 30 reduction of sulphur emissions by 1993
•  
•   decreasing emission levels of oxides of
  nitrogen to those of 1987 (by 1994)

   
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Emissions of SO2 in 1000 tons, and by source.
Source Statistics Norway ("Natural Resources
and the Environment 1997") / SFT
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Emissions of NOx in 1000 tons, and by
source Source Statistics Norway ("Natural
Resources and the Environment 1997") / SFT
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Legislation for Reductions in Acid Emissions (II)

• In 1994, the new 'effects based' Protocol for
  sulphur, based on critical loads, was agreed in
  Oslo.
• This defined a target for each European country
  based on its pollutant emissions, the costs of
  abatement and the contribution those emissions
  made to acid deposition on sensitive ecosystems
  across Europe.

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Excess depositions of SO2 in Europe (in tons per
square kilometer). No colourno data. Source
EMEP
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The Multi-pollutant, Multi-effect Protocol

• was signed in Gothenburg in 1999.
• It takes into account effects of acidity, excess
  nutrient nitrogen and also photochemical oxidants
  (low level ozone).

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Recovery

• Slow processes are involved
• Calculations show that to achieve recovery at the
  most sensitive sites, emissions of sulphur,
  oxides of nitrogen and ammonia must be decreased
  further still.

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• For some sensitive areas, however, critical loads
  may be unattainable with current emission control
  technology, so recovery may not be possible
  through emission decreases alone in the
  foreseeable future
• Other methods may be used to aid their recovery.
  For example, in many lakes in Scandinavia, the
  addition of lime has been used as an interim
  measure for neutralising acidification.