2. What is an Acid rain?
Acid rain is a rain or any other form of precipitation
that is unusually acidic, meaning that it possesses
elevated levels of hydrogen ions (low pH).
Refers to a mixture of deposited material, both wet
and dry, coming from the atmosphere containing
more than normal amounts of nitric and sulfuric
acids. Simply put, it means rain that is acidic in
nature due to the presence of certain pollutant in the
air due to cars and industrial processes .
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5. Acidity is determined on the basis of the
pH level of the water droplets. Normal rain
water is slightly acidic with a pH range of
5.3-6.0, because carbon dioxide and water
present in the air react together to form
carbonic acid, which is a weak acid. When
the pH level of rain water falls below this
range, it becomes acid rain.
7. How acid rain is formed?
It occurs due to natural and human
activities. Erupting volcanoes contains
some chemicals that can cause acid rain.
Apart from this, burning of fossil fuels,
running of factories and automobiles due
to human activities are few other reasons
behind this activity.
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9. Formed in Acid rain
Sulfuric acid is a highly corrosive strong mineral acid with
the molecular formula H2SO4.
Nitric Acid – acid that contains nitrogen and that is used in
making fertilizers.
Causes Acid rain
Sulfur dioxide (also sulphur dioxide) is the chemical
compound with the formula SO2.
it is a toxic gas with a pungent, irritating, and rotten smell.
Nitrogen oxide In areas of high motor vehicle traffic, such
as in large cities, the amount of nitrogen oxides emitted
into the atmosphere as air pollution can be significant.
gases react to form smog and acid rain
10. Human Activity
Sulphur and nitrogen compounds
from human sources such as:
a) Electricity generations
b) Motor vehicles
c) Air pollution
d) Factories
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13. Human Attribution
• Human emissions of sulfur dioxide and nitrogen
oxides contribute to the acidification of rain
• Emissions began during the industrial
revolution, remaining unchecked until the 1970s
• Biggest contributor is the burning of coal
• Annually 70Tg (1012 g) of Sulfur emissions comes
from fossil fuel burning, compared to 8Tg from
volcanoes and 2.8Tg from wildfires
14. Burning of coals in power plants.
Oil and natural gas in power stations
makes electricity, giving off sulphur
dioxide.
Burning petrol and oil in vehicle engines
give off nitrogen oxides as gases.
15. The Coal Power Plant Problem
Burning coal is extremely cheap and efficient
but dirty, releasing sulfur dioxide which
becomes sulfuric acid in the atmosphere
Areas downwind of power plants receive heavy
acid rain
Smoke stacks built to counteract direct
deposition of sulfuric acid only spread the
problem
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19. Natural Activities
Natural acid rain can be caused by volcanic
emissions and biological processes
Eruption of Volcanoes
Lightning
24. Effects on Human
Contribute heart and lung problem
including Asthma and Bronchitis.
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27. On Nature
It can have harmful effects on plants, aquatic
animals and infrastructure.
Not many things can grow in acidic conditions
Low pH and high aluminum concentrations can
damage or kill fish and aquatic populations
Soils can be damaged by the hydronium ion, which
mobilizes aluminum and encourages leaching of
minerals such as magnesium essential for plant life
Forests suffer from soil damage, however most food
crops are unharmed because the nutrients lost are
replaced in fertilizer
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34. Effects on Infrastructure
Effect on Architecture and Buildings – Acid rain on
buildings, especially those constructed with
limestone, react with the minerals and corrode them
away. This leaves the building weak and susceptible
to decay. Modern buildings, cars, airplanes, steel
bridges and pipes are all affected by acid rain.
Irreplaceable damage can be caused to the old
heritage buildings.
35. Other Effects
• Monuments made of
Calcium Carbonate
(limestone and marble)
will react with acid rain
to form Gypsum
• Increases the oxidation
rate of metals such as
copper and bronze
40. Acid rain can occur in form of rain, snow, fog or dry
material that settle to earth.
41. Wet Deposition
When the wind blows the acidic chemicals in the air
to the areas where the weather is wet, the acids fall
to the ground in the form of rain, sleet, fog, snow or
mist. It removes acid from the atmosphere and
deposit them on the earth’s surface. When this acid
flows through the ground, it affects large number of
plants, animals and aquatic life. The water from drain
flows into rivers and canals which is them mixed up
with sea water, thereby affecting marine habitats.
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44. Dry Deposition
If the wind blows the acidic chemicals in the air to
the areas where the weather is dry, the acidic
pollutants slip into dust or smoke and fall to the
ground as dry particles. These stick to the ground
and other surfaces such as cars, houses, trees and
buildings. Almost 50% of the acidic pollutants in the
atmosphere fall back through dry deposition. These
acidic pollutants can be washed away from earth
surface by rainstorms.
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47. Areas of Highest Concern
Current problem areas are:
Eastern United States
South Western Canada
Eastern Europe
East Coast of China
Potential future problem areas:
Southern India
West Africa
Indonesia
Thailand
48. Prevention
• Coal burning power plants use Flue gas
desulfurization requiring a reaction tower that
extracts the sulfuric acid by reacting it with lime or
limestone slurry and removing the product with
scrubbers
• Reduction in automotive emissions cuts down on
nitrogen oxides
• Emissions trading put into practice to put economic
incentive into cleaning industrial activities
