The presence of carbon-di-oxide, methane, CFCs, nitrous oxide, and ground level ozone gases in the atmosphere which surrounds the earth enables to form a greenhouse for earth by retaining the heat that are radiating from earth.
Increase in carbon-di-oxide in the atmosphere is a major challenge, facing mankind today. CO2 is a natural constituent in atmosphere. It is 0.032% by volume, having a ratio of 1:450 with oxygen. Inspite of its relatively small proportion, CO2 plays a very important role in the biosphere. On account of industrialization, fossil fuel consumption is growing. As a result CO2 concentration in the atmosphere is steadily increasing. CO2 absorbs heat radiations. It lets the sun rays to the earth but retains the heat radiation from the earth. Thus the global warming phenomenon exists.
Due to burning of fossil fuels and deforestation, the quantity of green house gases has grown by about 50%. The release of chloro floro carbon (CFC) from refrigerators into the atmosphere has also aggrevated the green house effect. If the increase of green house gases continues, it is anticipated that global temperature will rise by 1.5°C to 4.5°C by the year 2030. This in turn, will lead to melting of polar ice caps which may result in rise of sea level, salt water inrusion into acquifers and submerge coastal wetlands.
Economic productivity will be lost with rising sea level. The proposed location or expansion of ports, cities, agricultural activities, coastal developments, etc. should be reconsidered.Warmer climate will promote evaporation of water and increase cloudiness and rainfall. Tropical cyclones will become more intensive and their ferocity will increase. Greenhouse effect will sweep changes in the biosphere. To manage this conditions, people are encouraged to use less polluting fuels.
Acid rain is an increasing threat to India, where emission of acidic gases is sharply increasing. The term acid rain is used to describe all forms of precipitation, rain, snow, sleet, dew which is more acidic than normal.Acid rain is a man made phenomenon. Emission of sulpher di oxide and oxides of nitrogen and carbon di oxide are prime contributors to atmosphericacidification, as they readily dissolve in the atmosphere moisture forming sulphuric and nitric acids which make the rain acidic.
Acid rain often produces irreversible changes. It has corroding effect on the plant leaves and predisposes them to pests and insects. The soil become thus acidic, a condition which releases toxic heavymetal ions in the soil and promotes the loss of calcium,magnesiumfromthe soil which are essential plant nutrients. The cumulative effect is the gradual decline in soil and forest productivity. In acquatic systems, the acidic rain raises the level of toxic heavy metals, resulting fish killings and reproductive failure.Acid rain contaminates surface waters by direct deposition of pollutants.
It is very essential that smoke precipitators should be used in every factory so that smoke is devoid of all solids like ash.
Earth is surrounded by atmosphere. In the atmosphere, between 15 to 50 kms above the earth’s surface, there is a protective layer of ozone which protects the earth from harmful ultra violet rays of the sun. Ultra violet rays damages the genetic material DNA and is a main cause for skin cancer.
Damage to ozone layer is fatal to all life on earth. The major threat to ozone layer is from CFCs (chloro floro carbons) which are the family of human made carbons. CFCs are being used extensively for refrigeration aerosols, foams and solvents. Once the CFCs reach the stratosphere, the chlorine atoms of the CFCs do damage. The UV radiation in the stratosphere is strong enough to split the chlorine atoms of the CFC molecule. The free chlorine atom then attaches the ozonemolecule, resulting in the splitting of an oxygen atom. Thus, results in the ozone (O3) molecule being reduced to plain oxygen (O2) and the chlorine atom joining with split of oxygen atom to form chlorine monoxide. It is estimated that a single chlorine atom can destroy upto 100,00 ozone molecule.
The vienna convention between various countries was signed in 1985 to protect ozone layer by limiting and phase out the use and manufacture of CFCs.