Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions.

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 electricity.

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

DEPOSITION:

1)WET:RAIN;SNOW;

2)DRY:PARTICLES

POLLUTANTS

RESPONSIBLE:

1)OXIDES OF SULPHUR (SO2)

2)OXIDES OF NITROGEN(NO2)

FORMATION OF

ACID RAIN :

1)NATURAL SOURCE

2)MAN-MADE SOURCE

FACTORIES/AUTOMOBLIES(OXIDES OF SULPHUR/NITROGEN) WATER(H2O) SULPHURIC / NITRIC ACID (H2SO4/HNO3) 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 POWER GENERATION.

1. Sulphur [S] impurities in the coal-form pollutant sulphur dioxide [SO2] S + O2SO2

2. Sulphur dioxide [SO2] reacts with water vapour to form sulphurous acid[H2SO3] H2O+SO2=H2SO3 [aq.]

3. Sulphur dioxide [SO2] can also be oxidised to sulphur trioxide[SO3] 2SO2 +O2=2SO3

[The reaction catalysed by dust particles and water droplets]

4. Sulphur trioxide [SO3]reacts with water vapour in air forming sulphuric acid [H2SO4]

5. H2O +SO=H2SO4[aq.]

6. 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 Automobiles.

19

20

4.8%

79.8%

15.2%

Transportation Fuel Combustion

Industrial Processes

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Total emissions - 22.7 Million tons in 1992

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Industri

al

Sources

5%

Other

18%Off

Road

Vehicles

12%

Highway

Vehicles

33%

Electric

Utilities

32%

On a global scale, agricultural practices contribute

approximately 70 percent of anthropogenic nitrous oxide

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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

United States. ◦ 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 4.2.

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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

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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 visibility impairment, meaning we can't see as far or as clearly through the air. Sulfate particles account for 50 to 70 percent of the visibility reduction

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Elevated levels of fine particles increase 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 form ozone

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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 whenever possible

Buy vehicles with low NOx emissions, and maintain all vehicles well.

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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.

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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 O2 molecule.

Thus the oxides of nitrogen which are pollutants are converted to free nitrogen.

GROUP II

ARPIT(Roll no. 7) –PREVENTION OF ACID RAIN ANS COMPOSITION

DHRUV(Roll no. 8)- FORMATION OF ACID ACID RAIN

DIVYANSHU(Roll no. 9)- EDITOR OF PPT AND CAUSES OF ACID RAIN

KRATI(Roll no. 13)- FORMATION OF POLLUTANTS

HERRSH(Roll no. 10)- IMPACT