The composition of sea water

Sea water is a "water" only in the sense that water is dominant substance present. Actually it is a solution of many salts and gases, not to mention a tremendous number of living organisms, most of which are very minute. Throughout the ages there has been the steady movement of enormous quantities of materials both in solution and suspension from the land into the ocean. According to the estimation made by scientists 451,702 km² of sea water evaporate and return to the осеаn in the form of rain or water from the rivers every year. The latter amounts to about 132,297 cubic kilometers of water annually, which brings 2,735,000,000 metric tons of salts to the ocean. In addition vast quantities of suspended mud and silt are carried into the ocean and deposited near the mouths of rivers.

The total quantity of soluble salts in the ocean is very great – about 510¹⁶ metric tons, which is enough to form a layer of dry salts about 180 metres deep over the surface of the land. Sea water is mainly the solution of clorides and sulphates sodium, magnesium and potassium; yet it contains the appreciable amount of bromine, iodine, iron, silicon, carbonate and phosphate. Gold, silver and radium have been found among the elements contained in sea water. Biological activity is undoubtedly of great importance controlling the concentrations of many of the elements in the ocean. For example, the growth of plants in the surface layers greatly reduces the quantity of nitrates and phosphates. Yet these compounds tend to accumulate in the comparatively stagnant depths. Large portion of marine animals use phosphate and carbonate of lime to construct their shells and bones and thus remove quantities of carbon dioxide, phosphate and lime from sea water. The calcium, carbonate and phosphate of their shells and bones are deposited on the ocean floor.

As to the salinity of sea water it should be said that it is not identical in various seas. There is bitter salt water, for example, and there is brackish water. There is also semi-fresh water though it tastes a little bitter. The strongest salinity is observed in the zone of trade winds between 20°–30° of the latitude. It diminishes towards the equator and in the polar regions. The degree of salinity depends upon the barometrical pressure, the direction of winds, the quantities of precipitation and, in the shore zone, upon the freshening of sea water by rivers.

Notes on the text

1. not to mention a tremendous number of living organisms – не говоря уже об огромном количестве живых организмов;

2. throughout the ages – веками (на протяжении столетий);

3. trade winds – пассаты.

Exercise 4. Answer the following questions:

1. What minerals can we find in sea water?

2. Which layer of the sea water contains more salt, the surface layer or the bottom one?

3. What does the degree of salinity of sea water depend on?

4. What substances do rivers carry into the ocean?

5. In which zone is the strongest salinity ob­served?

Exercise 5. a) Form adjectives of the following nouns using the suffix -al:

monument, nation, profession, centre, finance, commerce, addition.

b) Read and translate the words, say what part of speech they are:

fresh – fresh­ening; identify – identical; construct – construction; deposit – deposition; direct – direction; accumulate – accumulation; compare – comparatively; grow – growth; press – pressure; concentrate – concentration; biology – biological; active – activity; suspend – suspension.

Exercise 6. Change the following sentences into the Passive Voice:

1. They have estimated that 451,702 cubic kilometres of sea water evaporate every year.

2. The river water brings 2,735,000,000 metric tons of dissolved salts to the ocean annually.

3. Rivers carry vast quantities of suspended mud and silt into the ocean.

4. We can find gold, silver and radium in sea water.

5. Large portion of marine animals use phosphate and carbonate of lime to form their shells or bones.

6. Marine animals also absorb nitrogen compounds and oxygen.

Exercise 7. Translate the following sentences into Russian:

1. The salinity of the Azov Sea is a half of the common salinity of seas.

2. The Red Sea which is located between the two torrid deserts – the Nubian and the Arabian ones is the saltiest sea in the world.

3. It is a well-known fact that the water in the Caspian Sea is greatly freshened by the river water.

4. Big rivers freshening sea water enrich it with "living salts".

5. In the slightly salt water life devel­ops much better than in salt or fresh water.

Exercise 8. Translate the following sentences into English:

1. Морская вода – это раствор многих солей и газов, а не просто вода в обычном понимании.

2. Ученые подсчитали, что ежегодно испаряется 451 702 км³ морской воды, которая возвращается в море в виде дождя и речной воды.

3. Морские водоросли, произрастающие в верхних слоях морской воды, поглощают из нее большое количество нитратов и фосфатов.

4. Панцири и кости морских животных образуются из фосфатов, карбонатов и извести, которые являются составной частью морской воды.

5. Степень солености морской воды зависит от многих причин.

TEXT 4

Exercise 1. Read and translate the texts with the help of a dictionary.