Acid rain- a global ecological problem

 Introduction
 Origin of the acid rain.
 Definition, forms,
formation and chemistry
of acid rain.
 Global impact of acid rain.
 Impact of acid rain in
India.
 Negative environmental
effects of acid rain.
 Beneficial effects.

Acid rain is the
Acid rain is
term used to
Acid rain is directly becoming a global
describe polluted
linked air pollution. environmental
rainfall (acid
problem.
pollution).

The main acid-
Acid rain is a forming pollutants
transboundary are sulphur dioxide
pollution problem. (SO2) and oxides of
nitrogen(NOx).

 In 1872, Robert Angus Smith
coined the term ‘acid rain’ in
his book ‘Air and Rain: The
beginning of a Chemical
Climatology’.
 Smith first found acid rain in
heavily industrialized
Manchester, England in 1852.
 He proved that acid rain has
connections to pollution in
atmosphere.

The rise in
This results in These acidic
The main driving world’s energy
more sulphur pollutants
factors are demands leads to
dioxide and contribute acidic
industrialization large scale
nitrogen oxide atmospheric
and urbanization. burning of coal
emissions. pollution.
and fossil fuels.

Acid rain is caused by human activities.

Precipitation that has a pH of less than
that of natural rain water.
• Natural rain water has a pH range of 5-7.Normal
rain is slightly acidic due to the presence of
carbonic acid formed by the mixture of CO2 and
rainwater. CO2 + H2O H2CO3

Acid rain water has a pH <5.

• Acid rain often has a pH as low as 2.4

Acid rain

Acid snow

Acid fog
Wet
deposition
Acid frost

Acid dew
Acidic deposition
Acid hail

Acid gases
Dry
deposition Acid dust/
particles

 Acid rain has a pH below
5.6 due mainly to the
reaction of water vapor
with sulfur dioxide and the
oxides of nitrogen. Acid
rain often has a pH as low
as 2.4
 2SO2 + O2 + 2H2O
2H2SO4

 4NO2 + O2 + 2H2O
HNO3
 Pure water has a pH of 7.
 The rain from an unpolluted
atmosphere has a pH close
to 6.0 (slightly acidic).

Carbon dioxide and water combine
to form carbonic acid.
CO2 + H2O H2CO3

Nitrogen dioxide and water to
form a mixture of nitrous acid and
nitric acid 2NO2 + H2OHNO2+HNO3

Sulfur dioxide combines with water SO2+H2OH2SO3
to form sulfurous acid SO3+H2OH2SO4

 Acid rain is a cocktail
mixture of 65%
sulphuric acid,30%
nitric acid and 5%
hydrochloric acid.
 Nearly 95% of the
acidity comes from
atmospheric sulfur
dioxide and nitrogen
oxides.
 The contribution of
sulfur gases to acid rain
is 60-70%.

 Forest fires
 Volcanoes

Natural sources
 Lightning
 Wet lands-organic decay
 Bacterial action in soil

 Power generation
Anthropogenic sources

 Factories
 Combustion of oil. Coal and gas
 Smelting of metals

Sulfuric acid Nitric acid deposition
• About 25% of the acidity is
deposition caused by oxides of nitrogen.
• About 75% of acidity is caused • Very reactive in the
by sulfuric acid in rain water. atmosphere.
• combustion of fossil fuels,
volcanic eruptions.

Episodic Chronic
Acidification-’Acid shocks’ acidification
• Short intense acidic events • Low, stable acidification
• Winter snowmelt, heavy rains • Loss of acid neutralizing
• Suddenly changes the pH levels capacity of streams, lakes and
of rivers and lakes. soil ecosystems.

 North eastern United
States
 South eastern Canada
 Parts of Europe-parts of
Sweden, Norway and
Germany.
 Parts of south Asia
 South Africa
 SriLanka
 Southern India

Taj Mahal in India
Temples, murals and ancient
inscriptions in Southern India

Acropolis, Parthenon in Greece

Renaissance buildings in Italy.

West Mayan Several
minister pyramids churches
Abbey in in Mexico and
England cathedrals

Acid rain does not respect political
boundaries. Emissions from one
country may be carried by wind to
a neighbouring country.

Britain • smog episodes around London, (1952)

Germany • acid mists in central Germany

Poland • acid cold smog (1985)

Greece • Deterioration of the Parthenon in the
Athens area.

Italy • Damage to Venice structures

Scandinavia • 15% of acid rain caused by Great-Britain

• black acid snow-the Cairngorm mountains
Scotland (1984)
•corrosion of bells of the Utrecht Dom tower since
Netherlands 1951

United states •disrupts forest ecosystems and pollutes surface
waters.

 Coal consumption
 Road traffic

sources
 Fertilizer plants
 Refineries
 Thermal power plants
 Petrochemical industries
 Metal smelting industries

 pH of acid rain in Bombay and
Trombay=4.45
effects

 pH of acid rain in Kolkata = 5.85
 pH of acid rain in Chennai= 8.85
 pH of acid rain in Delhi = 6.2 1

 Localized effects-few kilometers range
 Effects decrease with increasing

Direct effects
distance from emission source.
 Effects based on concentration of
pollutants in the air.

 Widespread effects –hundreds and
thousands of kilometers.
Indirect effects

 Secondary and tertiary effects

Atmospheric Harm or kill
acid input individual fish

Acidic surface Reduce population
waters numbers

Toxic elements
Complete elimination
-acid of particular fish
molecules species

Affects the soil buffering capacity of
watersheds.
Restrict flora of aquatic macrophytes
and phytoplankton.
Reduce fish diversity and
abundance.
Cause biotic depletion.
Implicate metal pollution.
Limit aquatic productivity.
Retard recycling of cations from
sediments.

 Decrease the acid neutralizing capacity
(ANC) of soils.
 Leach macro- and micro-nutrients from
the soil.
 Mobilize aluminium leaching into the soil
water.
 Increase the accumulation of sulphur and
nitrogen in soil.
 Harms the microbes of the soil.
 Reduces fertility of the soil.

 Directly harm leaf tissues: cuticle,
waxy layer and needles.
 Damages roots and bark.
 Reduce forest canopies at high
elevations.
 Poison tree with toxic substances and
make trees vulnerable to diseases.
 Reduce tree growth and increase tree
mortality.

 Cause gradual yellowing (chlorosis) of
leaves.
 Burn leaf tissues and cause
depigmentation.
 Disrupt the process of photosynthesis.
 Affect the water retaining ability of plants.
 Leach nutrients from plant tissues.
 Reduce plant germination and
reproduction.

Cause extensive gill damage.
Increase fish morbidity(sickness) and
mortality(death).
Reduce age distribution and size.
Reduce growth rate and condition factor.
Induce skeletal deformities in young
ones.
Enhance uptake of heavy metals.
Cause reproductive failure.

Direct effects Indirect effects
 Increased morbidity  Pain
(sickness).  Discomfort
 Asthma, bronchitis  Aggravate heart
 Dry coughs disease
 Headaches
 Eye, nose and
throat irritations.
 Mortality from lung
diseases.

 Cause physical damage by corrosion of
limestone, marble, carbon-steel, zinc,
nickel, paint and some plastics.
 Reduce life usefulness and aesthetic
appeal of structures.
 Acid smoke solids soiling building
materials.
 Accelerate chemical degradation of
metals, paints stone cement etc.

 Sulfate aerosols diminish visibility and
augment global warming.
 Nitrogen oxides contribute to the
formation of ozone.
 Mercury contamination in fish.
 Over-fertilization of coastal waters 9
coastal eutrophication).
 Decrease bacterial flora and other
beneficial micro-organisms.
 Offset mineral balance in forests, rivers,
fields and lakes.

 Stimulates growth of fine
range grasses in iron
deficient calcareous soils
 Improve water penetration
in sodic soils.
 Increase micro-nutrient
availability in calcareous
soils.

 Dr.B.Victor is a highly experienced
professor, recently retired from the reputed
educational institution- St. Xavier’ s College,
Palayamkottai, India-627001.
 He was the dean of sciences, IQAC
coordinator and assistant controller of
examinations.
 He has more than 32 years of teaching and
research experience
 He has taught a diversity of courses and
guided 12 Ph.D scholars.
 send your comments to :
bonfiliusvictor@gmail.com

Acid rain- a global ecological problem

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Acid rain- a global ecological problem