Topic outline

    • Pollution of Air and Water

      Q41. What is Ganga Action Plan? When was it launched? What was its purpose?

      Ans. An ambitious plan to save the river, called the Ganga Action Plan was launched in 1985. It aimed to reduce the pollution levels in the river. Recently a study by the World Wide Fund for Nature (WWF) found that Ganga is one of the ten most endangered rivers in the world. The pollution levels have been rising for many years. This stage is reached because the towns and cities, through which the river flows, throw large quantities of garbage, untreated sewage, dead bodies, and many other harmful things, directly into the river. In fact the river is “dead” at many places where the pollution levels are so high that aquatic life cannot survive.

      Q42. Prepare a brief speech on global warming that you have to make in your class.

      Ans. CO2 is one of the gases responsible for this effect. Carbon dioxide is needed by plants. But if there is excess of CO2 in the air, it acts as a pollutant. On the one hand, CO2 is continuously being released because of human activities. On the other hand, area under forests is decreasing. Plants utilise CO2 from the atmosphere for photosynthesis, thereby decreasing the amount of CO2 in the air. Deforestation leads to an increase in the amount of CO2 in the air because the number of trees which consume CO2 is reduced. Human activities, thus, contribute to the accumulation of CO2 in the atmosphere. CO2 traps heat and does not allow it to escape into space. As a result, the average temperature of the earth’s atmosphere is gradually increasing. This is called global warming.


      Q43. What are the harmful effects of water pollution?

      Ans. Following are the harmful effects of water pollution:

                                i.        Water contaminated with sewage may contain bacteria, viruses, fungi and parasites which cause diseases like cholera, typhoid and jaundice.

                               ii.        Excessive quantities of chemicals which get washed from the fields act as nutrients for algae to flourish. Once these algae die, they serve as food for decomposers like bacteria. A lot of oxygen in the water body gets used up. This results in a decrease in the oxygen level which may kill aquatic organisms.

                              iii.        Hot water released by power plants and industries raises the temperature of the water body and adversely affecting the animals and plants living in it.

                              iv.        The chemicals released include arsenic, lead and fluorides which lead to toxicity in plants and animals.

      Q44. What are the main sources of air pollution?


      How does air get polluted?

      Ans. Sources of air pollution

                                 i.        Natural sources like smoke and dust arising from forest fires or volcanic eruptions causes air pollution.

                                ii.        Pollutants are also added to the atmosphere by human activities. The sources of air pollutants are factories, power plants, automobile exhausts and burning of firewood and dung cakes.

                               iii.        Pollutants like sulphur dioxide and nitrogen dioxide gases react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid and causes acid rain.

                              iv.        Carbon monoxide is produced from incomplete burning of fuels such as petrol and diesel. It is a poisonous gas.

                               v.        Chlorofluorocarbons (CFCs) which are used in refrigerators, air conditioners and aerosol sprays cause air pollution.

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