Docstoc

Acid Rain - Download as PowerPoint

Document Sample
Acid Rain - Download as PowerPoint Powered By Docstoc
					Acid Rain
1970   1985
• Our atmosphere contains many pollutants from
  human activities. Some of these come from
  fossil fuels, which release large amounts of
  sulphur dioxide (SO2) and nitrogen oxides
  (NOX) into the air. Combined with water and
  powerful oxidants like ozone, sulphur and
  nitrogen oxides become sulphuric and nitric
  acid. These acids may travel long distances
  before falling to the earth as rain, snow, sleet,
  hail, fog, dew or dust.
    Effect of acidic precipitation on
          aquatic ecosystems
•
    Most biological life thrives best within a narrow range of
    pH levels, near neutral or 7.0. Aquatic vegetation and
    animal life vary in their susceptibility to changes in pH;
    some species are more acid-tolerant than others.
    Aquatic systems that are well-buffered may not be as
    affected by acidic runoff as those that lack a buffering
    capacity. In lakes and streams whose waters become
    acidified, micro-organisms may be affected. As
    organisms lower in the food chain are reduced, species
    higher up the food chain that rely on these organisms for
    food will be affected. Plankton and invertebrates are
    most sensitive to changes in pH. If the pH levels drop
    below 5.0 most fish species are affected.
 Effect of acidic precipitation on
     soils and plant growth
• Some plants are tolerant of acidic conditions,
  while others are not. Acidic soils may affect
  micro-organisms in the soil, which play important
  roles in plant growth. Acidity affects the
  availability of nutrients that are essential for plant
  growth and increases leaching of aluminium and
  mercury, which are toxic to plants at high levels.
  Nitrogen is a nutrient and at certain levels,
  nitrogen deposition from air emissions has
  increased growth of vegetation; however, at
  higher levels, excess nutrients can reduce plant
  growth.
 Effect of acid rain on buildings
          and materials
• Acidic precipitation is corrosive of metals
  and alkaline building materials such as
  marble and limestone. Urban areas
  subject to high levels of exhaust fumes
  and other sources of acidic precipitation
  have experienced significant weathering of
  statues and building materials
• in Germany's "Black Forest" or "Schwarzwald," more
  than 50% of the forest has been severely damaged by
  acid rain. Many trees have dried out and died already,
  while many others have discoloured leaves. Even tree
  planting has failed to halt this destruction, since the soil
  is already acidic.
  Ironically, countries like Sweden, Norway, and other
  Scandinavian countries do not contribute much to
  atmospheric pollution, but they are suffering extensive
  damage from atmospheric pollutants carried there from
  other countries. For example, it has been reported that
  fish have disappeared from one-third of the lakes and
  marshes of Norway.
The origin of the deposition
   of sulphur (left) and
 oxidized nitrogen (right)
  over Germany (above)
   and Sweden (below)
          in 2003.
              Legislative controls
•   The UK, as a member country of the European Union, is under obligation to
    comply with the Large Combustion Plant Directive of 1988 which concerns
    reductions in emissions of SO2 and NOx from plants over 50MW in size
•   The UK is, under this Directive, required to reduce SO2 by 60% by 2003
    and NOx by 30% by 1998 (from 1980 levels).
•   The UK is also a Party to the Gothenburg Protocol, designed to Abate
    Acidification, Eutrophication and Ground-level Ozone. The UK is committed
    to reducing 1990 emissions of sulphur dioxide by 75% by 2010 and nitrogen
    oxides by 50% over the same period. In addition, the UK National Air
    Quality Strategy sets out standards and objectives for reducing key air
    pollutants to be achieved by year 2005. To meet the objectives for the acid
    deposition pollutants (largely SO2 and NOx), industry will have a significant
    part to play in reducing emissions.
•   As most of the SO2 emitted in the UK is from industry and power
    generation, reductions in annual emissions will be necessary from industrial
    sources. The use of cleaner fuels and the use of control technologies will be
    required at all new industrial plants if SO2 levels are to continue in a
    downward trend.
                     Contribution to UK
                                          Total UK emissions 1999
                        emissions
                                               million tonnes
                    from road transport


 Nitrogen Oxides
                           44%                      1.6
 (NOx)


 Carbon Monoxide
                           69%                      4.8
 (CO)


 Hydrocarbons
                           27%                      1.7
 (VOCs)


 Black Smoke               48%                      0.3




Vehicle pollution can be
significantly reduced by fitting a
catalytic converter to the exhaust
system. This is a relatively low
cost method of pollution control
(around £350) which has little
effect on vehicle performance
and fuel consumption. All new
cars sold in Britain from January
1993 onwards have catalytic
converters
• In 1988 a Directive was introduced for
  European Community (EC) countries
  which required power stations to reduce
  emissions of sulphur dioxide and nitrogen
  oxides. This was helped through new gas-
  fired power stations (which have lower
  emissions) replacing coal fired power
  stations, and flue gas desulphurisation
  equipment fitted to some of the existing
  coal-fired power stations.

				
DOCUMENT INFO