8th Class Science Pollution of Air and Water

Pollution of Air and Water

Synopsis

• Pollution is the introduction of harmful substances into the environment, which can harm the health, survival or activities of living organisms. Pollutants may be biodegradable or non-biodegradable. Biodegradable pollutants can be broken down by biological agents, whereas non-biodegradable pollutants cannot be broken down by any agents and remain in the environment for a long time.

• The major causes of air pollution are industries and automobiles. The burning of fossil fuels releases carbon dioxide, carbon monoxide, sulphur dioxide, oxides of nitrogen, hydrocarbons and particulate matter. Industrial processes release polluting gases and particulate matter.

• The oxides of nitrogen and sulphur combine with rainwater to form acid rain, which affects soil fertility, vegetation, buildings and monuments.

• Carbon dioxide and some other gases, like methane are called greenhouse gases. They trap radiations from the earth and are considered to be the cause of global warming.

• Air pollution can be reduced by modifying automobile engines, using CNG in the place of petrol or diesel, using unleaded petrol, removing pollutants from industrial waste gases before their release into the atmosphere and using cleaner sources of energy.

• Water pollution can be classified into two types - chemical and biological.

• Chemical pollution of water is caused by the discharge of unwanted chemicals into water bodies.

• Biological pollution of water bodies is caused by oxygen-demanding wastes and disease- causing micro-organisms.

• The major causes of water pollution are industrial effluents and urban sewage. Disease- causing organisms, agricultural and industrial chemicals, oxygen-demanding brganic wastes and hot water are some of the major categories of pollutants.

• The accumulation of plant nutrients in water bodies enhances the rapid growth of algae. The algae cut off the supply of light to organisms and their decomposition by bacteria uses up dissolved oxygen from water.

• Eutrophication is an increase in the rate of supply of organic matter in an ecosystem.
• Water pollution can be prevented or reduced by the treatment of sewage, treatment of industrial wastes, limited use of pesticides and fertilisers, burning of hospital wastes and proper disposal of dead bodies.

• Water fit for drinking is called potable water.

• Alum facilitates the removal of suspended particles from water by sedimentation.

• Water can be disinfected by boiling, chlorination, ozonisation or irradiation with ultraviolet rays.

• Sustainable development implies a change in all aspects of life. The public must be educated on the 3 Rs concept that is recycle, reuse and reduce to conserve and preserve resources.