Factories, power stations and motor vehicles pump large quantities of CO2 and other waste gases into the air. This is a major cause of the greenhouse effect. A lot of petrols contains lead, which is very poisinous and can couse brain damage in children. Many people now prefer to use unleaded petrol.
Some poisonous gases dissolve in water in the atmosphere and then fall to the earth acid rain. Acid rain damages trees and buildings and can kill fish in lakes and rivers. Rivers can also be polluted by industrial waste from facrories and chemical fertilizers and pesticides used by farmers.
Global warming is caused by the greenhouse effect. Normally, heat from the sun warms the Earth and then C escapes back into space. But CO2 and other gases in the atmosphere trap the sun’s heat, and this is slowly making the Earth warmer. The glass of greenhouse conserves heat by the same principal, that’s why this phenomenon is known as the greenhouse effect. It’s very important because without it, the temperature of our planet would be 40 degrees lowers and the oceans would freeze. On the other hand, an increase in the greenhouse effect, which is caused by an increase in the concentration of greenhouse gases in the atmosphere, may lead global warming, with disastrous consequences: sea levels would rise as the world gets warmer beacuse the heat would melt ice and expand the water in oceans. Scientist say the temperature of the earth could rise by 3 °C over the next 50 years. This may cause drought is some parts of the world, and floods in others, as ice at the North and South Poles begins to melt and sea levels rise.
The ozon layer
O3 , a form of O with 3 atoms instead of the normal two, is highly toxic. Near ground level, it’s a pollutant which helps form photochemical smog and acid rain. But far overhead stratosphere, 15-20 km up in the sky, it forms the life-saving ozon-layer, It’s life-saving because it screens out the lethal UV rays of the sun which can cause skin cancer and major cause of cataracts. The greatest danger to the ozone layer comes from CFCs. CFCs are used in frigiders, aerosols cans and in the manufacture of some plastice products. Some companies now make aerosols that don’t contain CFCs and these are often marked „ ozone friendly” .
Rainforests help control global warming beacuse they absorb CO2. In recents years, large areas have been destroyed, only about half of the mature tropical forests that once graced the planet still stand. The Nr.1 reason is the popilation of the world, which is increasing – especially in the third world. We need new corpland so trees have been cut down, new areas must be used to build new cities, towns, villages, which means that the living area of animals and plants- their habitat – is taken over by a man. A lots of animals are hunted fot the skin, food or horn as well. The burning releases large amounts of CO2 into the atmosphere.
With the destruction of the forests the exposed soil erodes rapidly and becomes incapable of supporting any kind of vegetation, so that the area may turn to desert. Many plant any animal species that live there could become extinct
Energy resources can be classified in two groups: renewable and non-renewable. Non-renewable energy resources are those which cannot be used forever – their supplies are limited, for e.g. fossil fuels. Fossil fuels are buried under the ground: oil, coal, and natural gas. When a fossil fuel nurned from carbohydrate and the O of the air, CO2, water, heat energy and light energy formed. All fossil fuels produce CO2, the most important greenhouse gas, when they burn. As fossil fuels are very polluting people started to use other forms of resources, which can be used forever and not polluting the environment.
Energy comes in many forms – heat, light, sound, electrical and mechanical.A device that converts one form of energy into another is called a generator. The traditinal generatot converts heat enegry from coal or gas into electrical energy. The new generators harness renewable forms of energy like the nergy ot the wawesm of the sun and wind and geothermal power. Wind power has been used hundreds of yeras in the form of windmill. The modern verion of the windmill is the aerogenerator, which converts wind energy.
Solar energy powers the world. The only problem is that it is spread so widely that it’s hard to collect and concentrate in large amount. The simplest way of using this kind of energy is to heat water, in fact, 1500 homes world-wide are powered by solar cells.
The top 5 km of the earth’s crust contain 40 million times as much energy as its oil and gas reserves but geothermal energy is widely dispersed and is only used when concentrated by hot water, trapped in rock. If the water is hot enough, it can generate electricity.
There are several types of water-power river water in mountainous areas can be used to generate hydroelectric power, and we can also create electricity from sea water flowing in and out with the tides.
Recycling is the processing of used objects and materials so that they can be used again. About 60% of rubbish from homes and factories contain materials that could be recycled. Recycling saves energy and raw materials, and also reduces damage to the countryside.
Glass, paper and Al cans can call be recycled very easily. Many towns have bottle banks where people can leave their empty bottles and cans for recycling. A lot of paper bags, writing paper and greetings cards are now produced on recycled paper.
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