II Прочтите 2-ой абзац текста и письменно ответьте на следующий вопрос:

What gases are considered to be the primary culprit in the ozone depletion process?

Контрольная работа № 5

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Вариант 3

I Прочтите и устно переведите с 1-го по 5-ый абзацы текста.

Перепишите и письменно переведите 1, 2, 4 абзацы текста.

AIR POLLUTION

1. Pollution of the air by certain industrial processes, particularly by burning of coal, has been a concern for many years. However, it was not until thousands died because of air pollution, in such cities as London in the 1950s, that the first steps were taken to reduce the poisons that were routinely being emitted into the air we breathe. Two major sources of harmful emissions became the targets for initial action: utilities and industries, and motor vehicles. Steps were first taken to clean up smokestack emissions around power plants and industrial complexes. Attention was then focused on the sulfur oxides emitted from utility, commercial, and industrial stacks. At the same time devices were developed to cut back on emissions from motor vehicles.

2. Air quality management is a complex undertaking. It is complicated by the nature of air, and by the gases that are commonly considered its basic components. It is further complicated by the continual chemical changes that take place in the air as it moves from one location to another and by atmospheric forces.

3. Special understanding of city air pollution is needed because of great potential health hazards. Sources of pollution are more abundant in major cities than in small towns or rural areas. Often there are coal-fired power plants nearby; schools, universities, hospitals, and other institutions often burn oil as their heat source; industries use fossil fuels as a vital part of industrial processes; each individual home, burning oil, gas, or wood, adds to the pollution entering the city's air.

4. There are many other sources of pollution: motor vehicles, construc­tion activities, dust generated in the city and from agricultural activi­ties nearby, and thousands of vaporized chemicals, some of them toxic and hazardous.

5. Each year millions of dollars are spent to reduce the amount of pol­lution emitted into the atmosphere. Some control devices are already used to reduce emissions from smokestacks and automobile exhausts. However, even tighter controls may be needed in the future. It is an endless battle, one that is essential to safeguard human health and the natural environment.

II Прочтите 5-ый абзац текста и письменно ответьте на следующий вопрос:

Where are control devices already used?

Контрольная работа № 5

(для специальностей ЭТФ)

Вариант 4

I Прочтите и устно переведите с 1-го по 7-ой абзацы текста.

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ACID RAIN

1. Precipitation absorbs carbon dioxide from the atmosphere and falls to earth as an extremely weak solution of carbonic acid. This is a natural occurrence that poses no threat to the environment. However, when sulfur and nitrogen oxides from industrial pollution chemically combine with the precipitation it becomes dangerously acidic and is termed “acid precipitation” or as it is more com­monly called, “acid rain”.

2. To understand acid rain, we first must understand what an acid is. Acidity or alkalinity is measured on a pH scale which ranges from 1 to 14. A substance with a pH of 7 is considered neutral. Low pH values indicate acidity while high values indicate alkaline conditions, the lower the number, the stronger the acid.

3. Unpolluted rain is slightly acidic with a pH of 5.0 to 5.2. In areas of central and northern Europe, the eastern United States, and Russia the annual average pH of precipitation is now between 4 and 4.5 which is 5 to 8 times more acidic than unpolluted rain.

4. The acid-forming compounds come from natural as well as manmade sources. A volcanic eruption can cause acidic conditions covering half the globe. Decay processes involving both plant and animal materials, which occur in marshes, swamps, and oceans, can also produce chemicals that can increase acidic deposits. Many researches, however, believe that a major source of increased acid in rainfall is such industrial activity as the burning of fossil fuels like coal, gasoline, fuel oil, and natural gas.

5. The effects of acid rain are difficult to pinpoint. We know that when a stream or lake becomes too acidic, fish and their food sources are effected. Acid stress can cause fish to die. Small amounts of acid can also affect the ability of fish to reproduce.

6. Acid rain is also believed to reduce crop yields and deteriorate buildings and roads. There are also indications that acid precipitation also may be causing a reduction in forest production.

7. Since air moves without restriction from region to region, from nation to nation, and from continent to continent, any solution to the problem will require international cooperation.