5.8 Acid Rain and Acid
Deposition
5.8.1: Outline the chemistry leading to the formation of acidified precipitations.
5.8.2: Describe three possible effects of acid deposition on soil, water and living organism.
5.8.3: Explain why the effect of acid deposition is regional than global.
5.8.4: Describe and evaluate pollution management strategies for acid deposition.
Kolap
ESS -2014/2015
Definitions
Acid Deposition:
Wet deposition includes all forms of acid precipitation such as acid rain, snow, and
fog. The accumulation of acidic particles that settle out of the atmosphere or of acidic
gases that are absorbed by plant tissues or other surfaces is known as dry deposition.
● Wet deposition - acidic rain, snow, or other precipitation
● Dry deposition - acidic gas or dry particles, not mixed with water
Acid Rain:
Rainfall made so acidic by atmospheric pollution that it causes environmental harm,
chiefly to forests and lakes. The main cause is the industrial burning of coal and other
fossil fuels, the waste gases from which contain sulphur and nitrogen oxides which
combine with atmospheric water to form acids.
Process:
Primary pollutants - those
directly emitted by a factory or
automobile, such as...
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SO2 - sulfur dioxide
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NO and NO2, usually
identified as NOx
Secondary pollutants - primary
pollutants react with other
substances in the atmosphere and
create different pollutants, such
as...
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H2SO3 - sulfurous acid
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H2SO4 - sulfuric acid
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HNO3 - nitric acid
5.8.1: Outline the chemistry
leading to the formation of
acidified precipitations.
Sources Of Acid Rain
● The acidic materials come from sulfur dioxide (SO2),
ammonia (NH3), nitrogen oxides (NOx) and acidic
particles emitted
● Carried into the atmosphere by burning of fossil
fuels in power plants and cars.
Example:
In the United States, roughly 2/3 of all SO2 and 1/4 of all
NOx come from burning of fossil fuels, especially coal, in
electric power plants.
Acidity of Rain
Acidity of precipitation is measured in pH
units, where
pH ≈ –log[H+]
where H+ is the dissolved hydrogen ion
concentration in a weak solution in water.
The lower the pH the more acidic the
precipitation, the higher the pH the more
basic the precipitation.
Pure water water has a pH of 7.0, and pure
rain has a ph of 5.6 because carbon dioxide
dissolved in water forms a weak acid,
carbonic acid,
H2CO3.H2O + CO2 –> H2CO3
5.8.2 Describe three possible effects of acid deposition on
soil, water and living organisms.
Effects on Water quality
Killing Aquatic life:
● Fish and plants may end up dying
● Tiny plants and animals are unable to survive
● Toxic to many aquatic animals especially young animals including eggs and larves
● Most fish killed if pH falls below 5.2
Acidified lakes are characterized by
● An impoverished species structure
● Visibility several times greater than normal
● White moss spreading across the bottom of lake
● Increased levels of dissolves metals such as cadmium, aluminium, zinc and lead
Effects on soil pollution & vegetation
Direct effects on Coniferous Trees:
Rocks and Limestone
Leaching of Nutrients
Loss of Chlorophyll
Burnt Trees
>Weak and Loss of strong struction system
● Acid leach nutrients from soil
Trees and forests: It breaks down lipids in the foliage and damages membranes which
can lead to plant death. Sulfur dioxide interfere with the process of photosynthesis.
Example: Coniferous Trees
These trees do not shed their needles at the end of every year
● On a healthy conifer , needs can be up to 7 years old
● Hence trees affected by acid rain often have needles that are up to 2 or 3 years
● The conifer loses over 65% of its needles, or will most likely die
● This damages the roots, decreases tree growth, increasing development of
abnormal cells and premature loss of needles.
Effects on Air Quality
Human health:
● Breathing problems
● Overtime can cause cancer
● Water we drink from taps can be
contaminated by acid rain which
then damages the brain
● Risk for those who have asthma
5.8.3: Explain why the effect of acid deposition is
regional than global.
● Acid precipitation falls back to Earth rather than entering
stratospheric jet stream
● Most areas are downwind of pollution sources
● Canadian forests damaged by coal-fired power plants in
USA
● Scandinavian and German forests damaged by British
coal plants
5.8.4: Describe and
evaluate pollution
management
strategies for acid
deposition.
Replace
• switch to renewable energy sources (reduce fossil fuel use)
• increase energy efficiency (better light bulbs and appliances)
• more public transportation (fewer automobiles on the road)
• use low-sulfur fuels
Regulate
• install ‘scrubbers’ on smokestacks of coal-fired power plants to remove SO2
• catalytic converters installed on automobiles (required by law in the US, Canada,
and Europe)
Restore
• add lime to acidified lakes and streams
• add lime to forestry plantations (why not natural forests?)
• UN Convention on Long-Range Transboundary Air Pollutants (LRTAP) - 1979;
subsequently amended and modified by US, Canada, and Europe
Acid Fog in London 1952
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December 1952 -March 1953 heavy smog to London,
Coal combustion and many people travelled only by car, which caused the
occurrence of a combination of black soot, sticky particles of tar and gaseous
sulphur dioxide.
Air had reached 56 times its normal level. Sulphur dioxide concentrations
increased to seven times its peak level.
The smoke particles trapped in the fog gave it a yellow-black colour. Sulphur
dioxide reacts with substances in foggy droplets to form sulphuric acid,
adding an intense form of acid rain to the process.
Smog easily entered buildings, causing cinemas, theatres and stores to be
closed. Transport became largely impossible. Motor vehicles were
abandoned, trains were disrupted and airports were also closed.
Killed 12.000 people, mainly children, elderly people and people suffering
from chronic respiratory or cardiac disease.
Could be attributed to lung disease, tuberculosis and heart failure. Mortality
from bronchitis and pneumonia increased more than sevenfold.
Most deaths occurred because of breathing in acid aerosols, which irritates
or inflames the bronchial tubes. Acidity was not measured, but estimates
show that the pH probably fell to 2 during the peaks in the smog episode.
Personal questions to answer
● Did you ever put an empty bucket and let the rain drop… if you did
why?
● Have you’ve ever tasted rain drops?
● Do you like or dislike rain? why?
● Are you worried about your health when you breathe in air knowing
that it is very polluted… if so… do you think considering wearing a
masks would be beneficial?
Sources
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http://www.air-quality.org.uk/16.php
http://www.clean-air-kids.org.uk/acidrain.html
http://oceanworld.tamu.edu/resources/environment-book/acidrain.html
http://www.lenntech.com/acid-deposition.htm
https://iboess.wikispaces.com/5.8+Acid+deposition
http://www.youtube.com/watch?v=26T8HDQBfGY 5.8 Acid deposition
https://www.youtube.com/watch?v=UIWY-0Xqj_s What is Acid deposition
https://www.youtube.com/watch?v=SyEr17yFX-Y Acid deposition
http://www.youtube.com/watch?v=Vkx-2mT1-q4 Acid Smog in London Documentary
http://www.youtube.com/watch?v=6pwQlHl6Ofw AR+AD