Acid rain is a rain or any other form of
precipitation that is unusually acidic, meaning
that it possesses elevated levels of hydrogen
It can have harmful effects on plants, aquatic
animals and infrastructure.
Human activities are the main cause of acid rain.
Over the past few decades, humans have released
so many different chemicals into the air that they
have changed the mix of gases in the atmosphere.
Power plants release the majority of sulfur dioxide
and much of the nitrogen oxides when they
burn fossil fuels, such as coal, to produce
In addition, the exhaust from cars, trucks, and
buses releases nitrogen oxides and sulfur dioxide
into the air. These pollutants cause acid rain.
TWO FORMS OF
ACID RAIN :
Normal unpolluted rain water is only slightly
acidic because. This is because it contains
carbonic acid. The carbon dioxide naturally
present in the air is dissolved in rain water.
Unpolluted rain water has a pH of about 5.6.
The carbon dioxide present in traces in
UNPOLLUTED AIR dissolves in rain water
forming weak carbonic acid[H2CO3].
Acid rain refers to rain[or any precipitation i.e.
snow or fog] which has pH less than 5.6.
Since it is mainly caused by atmospheric
pollutants like sulphur dioxide and nitrogen
oxides , it is a complex mixture of sulphuric
acid [H2SO4]nitric acid [HNO3] (and
sulphurous[H2SO3] and nitrous [HNO2] acids)
ELECTRIC POWER STATIONS BURN COAL[fossil fuel] FOR
Sulphur [S] impurities in the coal-form pollutant sulphur
S + O2SO2
Sulphur dioxide [SO2] reacts with water vapour to form
sulphurous acid[H2SO3] H2O+SO2=H2SO3 [aq.]
Sulphur dioxide [SO2] can also be oxidised to sulphur
trioxide[SO3] 2SO2 +O2=2SO3
[The reaction catalysed by dust particles and water droplets]
Sulphur trioxide [SO3]reacts with water vapour in air forming
sulphuric acid [H2SO4]
Thus the acidity in rain is due to reaction of oxides of sulphur
with water vapour forming dilute acids
Nitrogen in air at temperature above 1300
degree Celsius combines with oxygen to form
nitrogen monoxide .
The high temperature can be achieved
during Natural Sources - Lighting Bolts
Human Source - Combustion of Gasoline in
Total emissions - 22.7 Million tons in 199
On a global scale, agricultural practices contribute
approximately 70 percent of anthropogenic nitrous oxide
Several regions in the U.S. were identified as
containing many of the surface waters sensitive to
acidification. They include
◦ the Adirondacks and Catskill Mountains in New York state,
◦ the mid-Appalachian highlands along the east coast,
◦ the upper Midwest, and mountainous areas of the Western
◦ In areas like the Northeastern United States, where soil
buffering capacity is poor, some lakes now have a pH value of
less than 5. One of the most acidic lakes reported is Little
Echo Pond in Franklin, New York. Little Echo Pond has a pH of
Acid rain and the dry deposition of acidic
particles contribute to the corrosion of metals
(such as bronze) and the deterioration of paint
and stone (such as marble and limestone).
These effects seriously reduce the value to
society of buildings, bridges, cultural objects
(such as statues, monuments, and
tombstones), and cars
An example of acid precipitation damage to an outdoor statue. The statue, made of porous sandstone, was created in 1702 as
part of the gable of the entrance of the Castle at Herten, near Reclinhausen, Germany. The left photo, taken in 1908, shows
some stains and the loss of the left hand, but most of the face and right hand were intact after 206 years of exposure. The
right photo, taken in 1969, shows the loss of most of the detail of the statue over 61 years
Sulfates and nitrates
that form in the
atmosphere from sulfur
dioxide (SO2) and
nitrogen oxides (NOx)
emissions contribute to
impairment, meaning we
can't see as far or as
clearly through the air.
account for 50 to 70
percent of the visibility
Elevated levels of fine
illness and premature
death from heart and
lung disorders, such as
asthma and bronchitis.
reducing the nitrogen
oxides available to
react with volatile
organic compounds and
Turn off lights, computers, and other appliances when you're
not using them
Use energy efficient appliances: lighting, air
conditioners, heaters, refrigerators, washing machines, etc.
Only use electric appliances when you need them.
Keep your thermostat at 68 F in the winter and 72 F in the
summer. You can turn it even lower in the winter and higher in
the summer when you are away from home.
Insulate your home as best you can.
Carpool, use public transportation, or better yet, walk or bicycle
Buy vehicles with low NOx emissions, and maintain all vehicles
EPA's Acid Rain Program limits, or "caps,"
sulfur dioxide (SO2) emissions from power
plants at 8.95 million tons annually, allows those
plants to trade SO2 allowances, and reduces
nitrogen oxide emission rates.
A catalytic convertor in internal combustion
engines- helps reduce pollution.
The reduction catalyst in a converter
separates the nitrogen atom from NO and
NO2 molecules freeing oxygen in the form of
Thus the oxides of nitrogen which are
pollutants are converted to free nitrogen.
ARPIT(Roll no. 7) –PREVENTION OF ACID RAIN
DHRUV(Roll no. 8)- FORMATION OF ACID
DIVYANSHU(Roll no. 9)- EDITOR OF PPT AND
CAUSES OF ACID RAIN
KRATI(Roll no. 13)- FORMATION OF
HERRSH(Roll no. 10)- IMPACT