ACID
PRECIPITATION
Table Of Contents
 Introduction
 What is Acid precipitation
 Causes of Acid precipitation
 Acid Deposition
 Effects of Acid precipitation
 Solutions to the problem of acid rain
 A global problem
Introduction
 Acid rain is one of the most dangerous and widespread
forms of pollution. Sometimes called "the unseen
plague," acid rain can go undetected in an area for
years.
 Technically, acid rain is rain that has a larger amount
of acid in it than what is normal.
 The acidity of rain in parts of Europe and North
America has dramatically increased over the past few
decades. It is now common in many places for rain to be
ten to seventy times more acid than unpolluted rain.
 Many living and non-living systems become harmed
and damaged as a result of acid rain.
What is Acid Rain?
The term "acid rain" is commonly used to mean the
deposition of acidic components in rain, snow, fog, dew,
or dry particles. The more accurate term is "acid
precipitation." Acid rain is mostly caused by human
emissions of sulphur and nitrogen compounds which
react in the atmosphere to produce acids
Causes of Acid Precipitation
Natural Phenomenon
 The principal natural phenomenon that contribute acidproducing gases to the atmosphere are emissions from
volcanoes and those from biological processes that occur
on the land, in wetlands, and in the oceans.
 The major biological source of sulfur containing
compounds is dimethyl sulfide.
 The effects of acidic deposits have been detected in
glacial ice thousands of years old in remote parts of the
globe.
Human Activity
 The principal cause of acid rain is sulphuric and
nitrogen compounds from human sources, such as
electricity generation, factories and motor vehicles.
 Coal power plants are one of the most polluting.
 The gases can be carried hundreds of kilometres in the
atmosphere before they are converted to acids and
deposited.
Equations
Acid Deposition
Wet deposition
 Wet deposition of acids occurs when any form of
precipitation (rain, snow, etc) removes acids from the
atmosphere and delivers it to the Earth's surface.
 This can result from the deposition of acids produced
in the raindrops or by the precipitation removing the
acids either in clouds or below clouds.
Dry deposition
 Acid deposition also occurs via dry deposition in the
absence of precipitation. This can be responsible for as
much as 20 to 60% of total acid deposition.[8] This
occurs when particles and gases stick to the ground,
plants or other surfaces.
Adverse Effects of Acid Rain
Acid rain has been shown to have adverse impacts
on forests, freshwaters and soils, killing off insect
and aquatic lifeforms as well as causing damage to
buildings and having possible impacts on human
health.
The Effects of Acid Rain
 The lower pH and higher aluminum concentrations in
surface water that occur as a result of acid rain can
cause damage to fish and other aquatic animals.
 Soil biology can be seriously damaged by acid rain.
The hydronium ions of acid rain also mobilize toxins
and leach away essential nutrients and minerals.
 Acid rain can slow the growth of vulnerable forests
and cause leaves and needles to turn brown and fall
off.[High altitude forests are especially vulnerable as
they are often surrounded by clouds and fog which are
more acidic than rain. Also, acid Rain depletes
minerals from the soil and then it stunts the growth of
the plant.
 Human Health- Fine particles a large fraction of
which are formed from the same gases as acid rain
(sulphur dioxide and nitrogen dioxide), have been
shown to cause illness and premature deaths such as
cancer and other deadly diseases. Visibility is also
reduced by sulfate and nitrate in the atmosphere.
 Acid rain can also cause damage to certain building
materials and historical monuments.
 This is because the sulfuric acid in the rain chemically
reacts with the calcium compounds in the stones
(limestone, sandstone, marble and granite) to create
gypsum, which then flakes off.
CaCO3 (s) + H2SO4 (aq) ⇌ CaSO4 (aq) + CO2 (g) + H2O (l)
Leaching Effects of Acid Rain
Practical andTechnical Solutions
 Use less energy! When less energy is used, less coal is
burnt, and as a result, there is less acid rain. Experts say
that if energy was used more carefully, we could cut the
amount of fuel burned in half!
 Also, if coal was cleaned before it was burnt, the
dangerous pollutants that cause acid rain would be
cleaned away. If coal is crushed and washed in water, the
sulfur washes out. However, this is a very costly method.
 In the United States, many coal-burning power plants use
Flue gas desulfurization(FGD) to remove sulphurcontaining gases from their stack gases.
 Automobile emissions control reduces emissions of
nitrogen oxides from motor vehicles.
International treaties
 A number of international treaties on the long range
transport of atmospheric pollutants have been agreed
e.g. Sulphur Emissions Reduction Protocol under the
Convention on Long-Range Transboundary Air
Pollution.
Emissions trading
 In this scheme, every current polluting facility is given
an emissions license that becomes part of capital
equipment. Operators can then install pollution
control equipment, and sell parts of their emissions
licenses. The intention of this is to give operators
economic incentives to install pollution controls.
A Global Problem
 Acid rain is truly global phenomenon that is causing
problems for humans, plant and animal species and the
environment. Here are a few of the major problems
caused by acid rain around the world:
 In Brazil,fish are dying in the reddish water due to acid
deposition , trees are turning to skeletons, and human
health has suffered immensely.
 Poland is one of the most polluted in the world, and
burns coal with much sulfur in it. There is much human
illness in cities close to coal burning factories, and in
Crakow, the golden roof of a chapel is quickly
dissolving.
 In South Africa, There is lots of coal burning near Kruger
National Park, and the park is currently facing the
threat of acid rain.
 In the country of Czechoslovakia, the sickness rate for
children is quite high because of acid rain, especially in
the form of breathing problems. Much of the fresh water
there is too acidic to drink.
 North America is a huge contributer to the world's
pollution and acid rain. Back in 1982, in the United
States and Canada alone, 51,000 people died from sulfur
pollution (a number which has increased considerably
ove r the years) In 1967, a bridge over the Ohio River
collapsed due to corrosion from acid rain, and killed 46
people.