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Nitrogen Cycle. Living things need nitrogen to manufacture proteins




Living things need nitrogen to manufacture proteins. Thus the growth of many plants can be limited by a lack of nitrogen from the soil. Too little nitrogen can also cause malnutrition in people, because many of the body’s essential functions require nitrogen-containing molecules such as proteins, DNA, and some vitamins.

The nitrogen gas that makes up about 78%of the volume of the earth’s atmosphere is useless to most plants and animals. Fortunately, nitrogen gas is converted into water-soluble ionic compounds containing nitrate ions, which are taken up by plant roots as part of the nitrogen cycle. This nitrogen fixation – that is, the conversation of atmospheric nitrogen gas into forms useful to plants – is accomplished by (1) soil bacteria; (2) rhi-zobium bacteria living in small swellings; (3) blue-green algae in water and soil; (4) lightning which converts nitrogen gas and oxygen gas in the atmosphere to forms that return to the earth as nitrate ions in rainfall and other types of precipitation.

Plants convert nitrates obtained from soil water into large, nitrogen-containing molecules such as the proteins and nucleic acids necessary for life and good health. Animals get most of the proteins and other nitrogen-containing molecules they need by eating plants or other animals that have eaten plants. When plants and animals die, decomposers break down the nitrogen-containing molecules into ammonia gas and water-soluble salts containing ammonium ions. Other specialized groups of bacteria then convert these forms of nitrogen back into nitrate ions in the soil and into nitrogen gas, which is released to the atmosphere to begin the cycle again.

Human beings intervene in the nitrogen cycle in several important ways. First, large quantities of NO and NO2 are added to the atmosphere when fossil fuels are burned in power plants and vehicles. These oxides of nitrogen can react with other chemicals in the atmosphere under the influence of sunlight to form photochemical smog and nitric acid, a major component of acid deposition, commonly known as acid rain. Second, nitrogen gas and hydrogen gas are converted by an industrial process into ammonia gas, which is then converted to ammonium compounds used as commercial fertilizer. Third, mineral deposits of compounds containing nitrate ions are mined and used as commercial fertilizers. Fourth, excess nitrate ions are added to aquatic ecosystems via the runoff of animal wastes from livestock feedlots, the runoff of commercial nitrate fertilizers from cropland, and the discharge of untreated and treated municipal sewage. This excess supply of nitrate plant nutrients can stimulate extremely rapid growth of algae and other aquatic plants, which can deplete the water of dissolved oxygen gas and cause massive fish kills.

Упражнение 2

Составьте 5 специальных вопросов к тексту Nitrogen Cycle

 

 

Упражнение 3

(Парная работа) Ответьте на вопросы, составленные в упражнении 2

 

Упражнение 4

Выберите из текста Nitrogen Cycle 10-15 ключевых слов. Какие из Ваших предположений оправдались?

 

Упражнение 5

Определите к каким частям речи относятся выбранные Вами слова

 

Упражнение 6

Найдите в тексте Nitrogen Cycle примеры этих частей речи.

 

v. n. adj. adv. prep.
         

 

Упражнение 7

Используя суффиксы, образуйте глаголы или существительные и заполните пропуски в предложениях: ~(at)ion, ~sion, ~ise.

Примеры: to vary - variation; to divide - division; character - to characterise.

Verbs Nouns
1. It is cheaper to regulate the temperature automatically.   2. If gases … very rapidly cryogenic temperatures are attained.   3. The committee was set up to standardise civil aviation procedures.   4. People get old because the body … genetic damage.   5. The first atomic bomb exploded on August 6, 1945.   6. The astronauts are provided with a 14-day supply of pressurised oxygen.   7 Solar energy is … from hydrogen.     8. Heat losses can be … by thermal protection.   9. It was necessary to extend the research facilities   Automatic temperature.... is more economical.   Rapid expansion of the gases produces temperatures of below 120 Kelvin.   His job involves the … of aviation safety procedures.   Ageing is a result of the accumulation of genetic damage.   80,000 people were killed in the Hiroshima …   The oxygen supply is stored under …     The generation of solar energy involves the conversion of hydrogen.   Efficient insulation reduces heat losses to a minimum.   Because of the increase in staff, an … had to be built  

 

Упражнение 8

В тексте Nitrogen Cycle найдите слова с суффиксами ~(at)ion, ~sion, ~ise

Упражнение 9

В правой колонке найдите русские эквиваленты следующих английских словосочетаний:

1 lack of nitrogen 2 essential functions 3 make up 4 plant roots 5 rapid growth 6 blue-green algae 7 nucleic acids 8 water-soluble salts 9 power plants 10 nitric acid 11 photochemical smog 12 commercial fertilizers 13 municipal sewage a растворимые в воде соли b быстрый рост c азотная кислота d сине-зеленые водоросли e жизненно важные функции f электростанции g городские сточные воды h фотохимический смог i промышленные (химические) удобрения j корни растений k составлять l недостаток азота m нуклеиновые кислоты

 

Упражнение 10

Слова, которые встретятся в тексте

conventional removal – стандартное удаление

reside in - возлагаться

replenish – наполнять

 

Прочитайте текст. Контрольное время – 5 минут

 

Nitrification is the biological oxidation of ammonia with oxygen into nitrite followed by the oxidation of these nitrites into nitrates. Degradation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an important step in the nitrogen cycle in soil. This process was discovered by the Russian microbiologist, Sergei Winogradsky.

Nitrifying organisms are chemoautotrophs, and use carbon dioxide as their carbon source for growth.

Nitrification also plays an important role in the removal of nitrogen from municipal wastewater. The conventional removal is nitrification, followed by denitrification. The cost of this process resides mainly in aeration (bringing oxygen in the reactor) and the addition of an external carbon source (e.g. methanol) for the denitrification.

Together with ammonification, nitrification forms a mineralisation process which refers to the complete decomposition of organic material, with the release of available nitrogen compounds. This replenishes the nitrogen cycle.

 

Упражнение 11

Ответьте на следующие вопросы, исходя из информации в тексте из упражнения 10

12. Что такое нитрификация?

13. Где нитрификация играет важную роль?

14. За что отвечает процесс минерализации?

 

Упражнение 12

Выпишите 10 ключевых слов из текста в упражнении 10

 

Упражнение 13

Найдите в тексте упражнения 10 слова с суффиксами ~(at)ion, ~sion, ~ise и переведите их.

 

Упражнение 14

Письменно переведите текст. Контрольное время – 25 минут.




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