. Chapter 16. Environmental Issues.

Pollution. Any undesirable change in physical, chemical or biological property of environment is called pollution. The factors that cause pollution are called pollutants. Type of pollution. Air pollution. Water pollution. Soil pollution. Radiation pollution etc.

Air pollution Any undesirable change in physical, chemical or biological property of air is called air pollution. The imp air pollutants are Oxides of sulphur, Oxides of nitrogen, Oxides of carbon, Smoke, Smog and ozone.

Effects of air pollution. Oxides of sulphur and nitrogen causes chlorosis and defoliation of leaves in plants.

In human beings Oxides of sulphur and nitrogen causes eye irritation, nasal irritation, chronic cough, bronchitis etc. Oxides of sulphur and nitrogen reacts with rain water and causes acid rain.

Oxides of carbon results in green house effects

The photochemical smog destroys plant vegetation. The ozone formed by photochemical reaction of oxides of nitrogen and hydrocarbons at lower level of atmosphere is called photochemical smog.

Control of air pollution: Electrostatic Precipitator: It removes 99% particulate matter present in the exhaust from thermal plant. It has electrode wires and a stage of collecting plates. The electrodes releases electrons. These electrons get attached to the dust and give them a net negative charge. The collecting plates attract the charged particles.

Scrubber: It removes gases like SO2 industrial exhaust. Catalytic Convertor: Used in automobiles for reducing emission of harmful gases. Vehicles fitted with catalytic converter should use unleaded petrol as leaded petrol inactivates the catalyst. Auto Fuel Policy: The Government of India laid out a road map to cut down the vehicular air policy in many cities of India

Water pollution: Undesirable change in physical, chemical or biological property of water is called water pollution. The imp water pollutants are sewage waste. Industrial waste. Chemical fertilizer and pesticides.

Effect of water pollution on biodiversity: The sewage waste directly released to water source stimulates the increase of pathogenic microbes. It causes water born disease. The nutrition enrichment in water results eutrophication and algal bloom. It increases the BOD (biological oxygen demand). The pesticides enters the water resources leads to bio-magnification. Industrial waste having heave metals and chemicals release to water destroys the aquatic organisms. The mercury that enters the human beings through food chain causes Minamata disease.

Eutrophication: The process of increase in algal production in water due to nutrition enrichment is called eutrophication.

Bio-magnification: Accumulation of non degradable chemicals, heavy metals in human beings through food chain is called bio-magnification.

BOD (Biological oxygen demand): The amount of oxygen required for microbial breakdown of biodegradable organic matter is called BOD. BOD is higher in polluted water and lesser in drinking water. Algla bloom: Excessive growth of planktonic algae on water body surface. It causes fish mortality and pollute water.

Radioactive wastes The waste produced from the nuclear fission of heavy atoms such as uranium, thorium etc for the production of power is radioactive waste. This waste is highly toxic and causes mutations and cancer. The nuclear waste should be stored after heavy treatment and packed in special containers. It should be buried deep under the ground for minimum of 60 – 80 years for the waste to stabilize. Even then there is a high chance of nuclear contamination of the surrounding areas & the ground water. Failure of nuclear power plants can have disastrous consequences. The use of nuclear fuels should be avoided if possible.

Greenhouse effect and global warming: Global warming refers to the heating up of the Earth due to greenhouse effect. Greenhouse effect is caused when gases such as CO2, CH4 etc increase in the atmosphere. This leads to the heating up of the earth as these are good absorbers of heat. These gases prevent the excess heat from leaving the Earth’s atmosphere thus resulting in greenhouse effect.

Effects: It effects Arctic polar ice cap to melt at the rate of 9% per decade. The rise is the sea level causes flood in certain countries like Bangladesh, Maldives etc. It causes food & water shortage. Destruction of underwater cities (coral reefs) & meadows result in extinction. only in the colder climatic regions global warming brings comfort but in various other places its effect is negative.

Control measures of global warming: Reforestation replaces maximum carbon dioxide by oxygen. Preventing Deforestation. Reduction of fossil fuel burning can minimize global warming. Improving the efficiency of engines & turbines can drastically reduce pollution. Planting hundreds of trees across cities & in homes. Using natural resources like wind energy, solar energy and wave energy may help to overcome global warming.  

Depletion of ozone layer Ozone is formed in the stratosphere by the effect of UV rays on O2. The thickness of ozone is measured in Dobson units. Cause of ozone depletion: Ozone degradation has increased due to chlorofluorocarbon (CFC). CFC,s reacts with UV radiation to release chlorine atoms. Chlorine atoms are catalyst that degrades ozone to oxygen. The CFCs released in the lower part of the atmosphere move upwards towards the south pole, hence depleting the ozone layer over Antarctica. Harmful effects: UV damages the DNA results in mutation. It causes skin aging and skin cancer. Control measure: Montreal protocol was signed in 1987 to crub the emission of ozone depleting substance like CFC.

Freons: Chloro-Fluoro-Carbons are called freons. Ecosan: Ecosan is ecological sanitation. This approach is useful in converting the solid human excreta into manure. E-waste: It is the electronic waste which includes irreparable components of electronic gadgets.

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