8th Class Science Pollution of Air and Water Water Pollution

       Water Pollution

Water is a natural resource. A large number of substance are obtained from water. Apart from air, the most abundant source on earth is water. There are about 1.4 billion cubic kilometers of water on earth. About seventy one per cent surface of the earth is covered with water and is called hydrosphere.

The amount has not changed at all in the million year of earth's existence. There is plenty of water on our planet, but its distribution is not uniform. About 97.4% of the total water on the earth is present in oceans. Of the remaining 2.6%, only is in liquid form, the rest is frozen in polar caps and glaciers like those of the HIMALAYAS. If the surface of India were flat, and all the ice was packed on the surface of India, it would reach an incredible height of 9 km . thus, only 0.01% of the total water on the earth, which is available freshwater, is used by us and other living beings. The water in the oceans is so salty that it cannot be used for most purposes.

           Sources of Water Pollution

• Domestic waste
• Industrial waste
• Agricultural waste

              Effect of Pollution on Water Bodies

• Oxygen Depletion
• Toxicity
• Algal bloom
• Water borne diseases
• Soil contamination

            Purification of Waste Water

• Coagulation
• Sedimentation and decantation
• Biochemical treatment

       Which one of the following is a cause of air pollution?

(a) Burning of fossil fuel

(b) Smokes from motor vehicles

(c) Volcano eruption

(d) All of these

(e) None of these

         The water which is fit for drinking is called:

(a) Sewage

(b) Black water

(c) Potable water

(d) All of these

(e) None of these

Answer: (c)

• Our environment comprises both living and non-living things.
• A pollutant is a waste material that pollutes air, water or soil.
• Any undesirable change into air is known as air pollution.
• Any undesirable change into water is called water pollution.
• Acid rain occurs because of air pollution..