Sometimes I like to go to the sea. As you know, the local water is characterized by high salinity. But recently I wondered: "How much exactly salts are dissolved in sea water?" Finding the average salinity of ordinary sea ​​water didn't take me long. And that's what I would like to talk about.

Average salinity of sea water

As you know, sea water fills the seas and oceans of the Earth. It is best to consider the average salinity of sea water using an example oceans. Middle level salts in it is about 34.7‰ (ppm) or 3,47% (percent). This indicator can range from 3.4 to 3.6% (or 34-36‰ ppm).

Simply put, every liter of ordinary sea water contains an area 35 grams of various salts(most of which are sodium chloride).

It is worth noting that the salinity in the oceans is almost everywhere equal to 35‰. But the water in the seas is more different uneven distribution of salts. So, the least salty can be called water Gulf of Finland , plus northern part Gulf of Bothnia. And the most salty are Red and Dead Sea.

Differences between salt and fresh water

• greater density;
• increased viscosity;
• lower freezing point;
• reduced heat capacity;
• reduced steam pressure;
• and increased speed of sound.

But the main difference between sea water can be called its unsuitable for drinking. The fact is that sea water contains much more salts than our body needs to remove it. And before drinking sea water, it must be desalinate.

It is noteworthy that in the 1950s, Alain Bombard (the notorious French doctor and wanderer) proved that a person can, without harm, drink sea water in small quantities (approx. 700 ml per day) for 5-7 days.

Sea water is also used in some countries for work drain systems(particularly in Hong Kong). This is done to save fresh water, the extraction of which is notable for certain difficulties.

The total amount of dissolved minerals, i.e. salts, in 1 kg of sea water, however, like the water of salt lakes (brine), in some cases, the water of deep aquifers, taken by weight (in grams), is called the salinity of the water. The average salinity of the World Ocean water is 35 g of salts dissolved in 1 kg of sea water, i.e. 0.035 fractions of a kilogram (L.K. Davydov et al. Hydrology. Gidrometeoizdat., L., 1973).

The salinity of the brine of salt lakes can reach 200 and even 400 g/kg (for example, lakes Baskunchak, Elton, the Dead Sea, etc.). The same can be attributed to the brines of deep underground aquifers.

In oceanological and limnological practice, salinity is expressed in thousandths, i.e. ppm (from lat. pro mille - per thousand), and is denoted S ‰, the same as g / kg.

In hydrogeology, the concept of mineralization is more often used. The dimension of the mineralization value is g / l (g / dm 3) or for low-mineralized waters mg / l.

It is possible to convert salinity into mineralization and vice versa using the density value, which can be seen from the detailed problems No. 1 - 36. The values ​​​​of water density at a selected temperature for a given salinity value can be taken from the appropriate reference book, or experimentally measured with high accuracy special device- hydrometer.

The mineralization of sea water is 20.25 g / l, and its density at a temperature of 20 0 C is 1.0125 g / cm 3. Determine the salinity of this water in ‰.

Decision:

one). 1.0125 g/ml = 1.0125 kg/l = 1012.5 g/l, etc. Let us choose a unit convenient for further calculations, for example, the last one. Let's make the first proportion.

1012.5 g of this sea water occupies a volume of 1 liter

X \u003d 1000 1: 1012.5 \u003d 0.9877 l

1 liter of sea water contains 20.25 g of salts

B 0.9877 l - X g of salts

X \u003d 0.9877 l 20.25 g / l \u003d 20.00 g. So many salts are contained in water with a volume of 0.9877 l or a mass of 1 kg.

3). Thus, the salt concentration is exactly 20 g/kg, or the salinity is 20‰.

Answer: The salinity of this water is 20‰.

The mineralization of sea water is 10.05 g / l, and its density at a temperature of 20 0 C is 1.0053 g / cm 3. Determine the salinity of this water in ‰.

Decision:

one). 1.0053 g/ml = 1.0053 kg/l = 1005.3 g/l, etc. Let us choose a unit convenient for further calculations, for example, the last one. Let's make the first proportion.

1005.3 g of this sea water occupies a volume of 1 liter

1000 g, i.e. 1 kg of this water - X l

X \u003d 1000 1: 1005.3 \u003d 0.9947 l

It is this volume of water that "weighs" 1 kg.

2). Let's make the second proportion:

1 liter of sea water contains 10.05 g of salts

B 0.9947 l - X g of salts

X \u003d 0.9947 l 10.05 g / l \u003d 9.997 g. So many salts are contained in water with a volume of 0.9947 l or a mass of 1 kg.

3). Thus, the salt concentration is 9.997 g/kg, or the salinity is 9.997 ‰.

Answer: the salinity of this water is 9.997 ‰.

Task options 1 and 2

Sea water densities are given for arbitrary temperatures

task number	Mineralization, g/l	Density, g/ml	task number	Mineralization, g/l	Density, g/ml
	10,12	1,0061		30,02	1,0262
	11,15	1,0099		31,21	1,0268
	12,45	1,0104		32,34	1,0272
	15,63	1,0211		33,65	1,0279
	18,00	1,0219		34,11	1,0297
	20,22	1,0225		34,57	1,0310
	24,59	1,0231		35,25	1,0337
	28,68	1,0258		37,97	1,0345

The salinity of the brine of the salt lake is 120 ‰, and the density at 20 0 C is 1.0857 g/ml. Determine the mineralization of this brine in g / l.

Decision:

one). 1.0857 g/ml = 1.0857 kg/l = 1085.7 g/l, etc. Let us choose a unit convenient for further calculations, for example, the last one. Let's make the first proportion.

1085.7 g of this brine have a volume of 1 liter

X \u003d 1000 1: 1085.7 \u003d 0.9211 l

Those. 1000 g of brine have a volume of 0.9211 liters.

2). 120 ‰ \u003d 120 g / kg, therefore, 1 kg of brine contains 120 g of salts, but 1 kg of brine occupies a volume of 0.9947 liters, therefore, you can write 120 g / kg \u003d 120 g / 0.9211 l.

120 g of salts are contained in 0.9211 l of brine

X \u003d 120 1: 0.9211 \u003d 130.28 g / l

Answer: water mineralization is 130.28 g/l.

The salinity of the brine of the salt lake is 260 ‰, and the density at 20 0 C is 1.1972 g/ml. Determine the mineralization of this brine in g / l.

Decision:

one). 1.1972 g/ml = 1.1972 kg/l = 1197.2 g/l, etc. Let us choose a unit convenient for further calculations, for example, the last one. Let's make the first proportion.

1197.2 g of this brine have a volume of 1 liter

1000 g of this brine (brine) - X l

X \u003d 1000 1: 1197.2 \u003d 0.8353 l

Those. 1000 g of brine have a volume of 0.8353 liters.

2). 260 ‰ \u003d 260 g / kg, therefore, 1 kg of brine contains 260 g of salts, but 1 kg of brine occupies a volume of 0.8353 l, therefore, we can write 260 g / kg = 260 g / 0.8353 l.

3). Let's make the second proportion:

260 g of salts are contained in 0.8353 l of brine

X \u003d 260 1: 0.8353 \u003d g / l

Answer: the mineralization of water is 311.27 g/l.

Problem options 19 and 20

The brine densities are given for arbitrary temperatures

Salinity - the total content of solid dissolved substances in 1 kg of sea water, expressed in ppm. average value salinity of the World Ocean is 34.71 ° / oo.

The average salinity of MO is from 32 to 37% o on the surface and from 34 to 35 in the bottom layers. Salinity and temperature determine the density of water. Average density sea ​​water more than 1, the highest is typical for pov. waters in the tropics and adjoining. at great depths, the latter circumstance is associated not so much with salinity as with the temperature of the water, which is very low in the bottom layers. High salinity is observed in surface water ah tropical latitudes, where evaporation significantly predominates over precipitation. Water with the highest salinity (up to 37.9°/oo) is formed in the Atlantic Ocean in the zone of the Azores anticyclone. AT equatorial zone oceans, where heavy rainfall is frequent, the salinity is lower (34-35°/oo). In temperate latitudes it is comparatively equal to 34°/oo. The lowest salinity of ocean waters - up to 29 ° / oo is observed in summer among melting ice in the Arctic Ocean. The salinity of deep and near-bottom waters in the oceans is approximately 34.5°/oo, and its distribution is determined by the circulation of the waters of the World Ocean. In the coastal regions of oceans with significant river runoff (Amazon, St. Lawrence, Niger, Ob, Yenisei, etc.), salinity can be significantly less than the average salinity and equal to only 15-20 ° / oo. Salinity of waters in mediterranean seas there can be both less and more salinity of ocean waters. Thus, the salinity of surface waters in the Black Sea is 16-18°/oo, in the Azov Sea 10-12°/oo, in the Baltic Sea 5-8°/oo. In the Mediterranean and Red Seas, where evaporation greatly exceeds precipitation, the salinity reaches 39 and 42°/oo, respectively. Salinity, together with temperature, determines the density of sea water, which determines the draft of the vessel, the propagation of sound in water, and many others. physical characteristics water.

Biological productivity of MO waters

The ocean is home to over 150,000 animal species and over 15,000 plant species; especially many unicellular organisms in particular unicellular algae(they make up to 80% of the total phytomass). The ocean accounts for about 40% primary production and no more than 0.5% of the total biomass of our planet. According to the habitat conditions, marine organisms are divided into: plankton1, benthos2 and nekton3. 1 - numerous species of unicellular algae, protozoa, worms, coelenterates and mollusks. 2 - different. Animals and plants living either on the surface of the seabed or in the bottom soil. 3 - unites all marine animals actively moving in the water or along its surface (fish, mammals, etc.) The nekton biomass is ~ 23 times less than the total plankton mass; the role of nekton benthos and plankton both in terms of biomass and productivity is ambiguous. Two areas of life are distinguished in MO - pelagial (surface of water and water column) and benthal (bottom). In the pelagial, the upper 50-meter water column is most populated, but even here its distribution is uneven. It is much more abundant towards the shore. In Bentali, life is also mainly concentrated in shallow coastal depths. The estuarine regions of the ocean are characterized by an increased number of primary production, and upwelling zones are regions where deep waters rise to the surface. ( Bay of Biscay, districts of the Benguela Canary Peruvian currents, the area of ​​​​monsoon circulations of the Indus Ocean, the area of ​​\u200b\u200bthe origin of the trade winds. Areas of stable subsidence of waters - areas of convergence are poor in life.

Features of the nature of Iceland

Iceland - A vast island (103k km2) in the northern part of the mid-Atlantic ridge with the appearance of Neogene and Quaternary volcanic activity. Iceland at present Time is one of the largest centers of active volcanism on Earth. The originality of the nature of I. lies precisely in the combination of intense volcanoes. Activities (volk.Gekla 1491m) with cold wet maritime climate and modern glaciation. Cold winds, rains and fogs dominate here, geysers gush. The relief of the island is predominantly mountainous, highest point Volk. Khvannadalskhnukor 2119m. Less than 1/5 of the lowlands (mainly in the west and southwest). A significant part of the island is occupied by basalt plateaus with heights of 400-600m and steeply dropping off to the sea. With many fjords. AT ice ages the island was completely covered with powerful glaciation. The island position of I. in the center of the winter baric depression determines strong impact on its climate of cyclonic circulation and the constant instability of the weather, which is intensified due to the convergence of the waters of the warm North Atlantic and the cold East Greenland current near its shores, therefore over the south. and southwestern regions islands are frequent strong winds, rain, fog at avg. January t0 from +1 to -1. Significantly colder in northern regions islands cf. t Jan. From -5 to -15. Weather summer months are more stable t from +7 ... +12. The annual amount of precipitation in the west and south reaches 1-3 mm, respectively, the duration of the growing season does not exceed 3 months. Numerous Indian rivers are fed by glaciers. I. is located in the subarctic mountain tundra zone with a wide distribution of moss-lichen and shrub formations that develop on waterlogged, dark-colored volcanic tundra soils.

We remember: How are the waters of the planet divided by salinity? Why travelers and sailors take in sea ​​travel fresh water?

Keywords:sea ​​water, salinity, water temperature, ppm.

1. Salinity of waters. In all seas and oceans, water has a bitter-salty taste. It is impossible to drink such water. Therefore, sailors leaving on ships to sail take with them a supply of fresh water. Salt water can be desalinated in special plants that are available on ships.

Mostly table salt, which we eat, is dissolved in sea water, but there are other salts (Fig. 92).

* Magnesium salts impart a bitter taste to water. Aluminum, copper, silver, and gold have been found in ocean water, but in very small quantities. For example, 2000 tons of water contains 1 g of gold.

Why is the ocean water salty? Some scientists believe that the primary ocean was fresh, because it was formed by river waters and rains that fell abundantly on Earth millions of years ago. Rivers have brought and continue to bring salt into the ocean. They accumulate and lead to the salinity of ocean water.

Other scientists suggest that the ocean immediately became salty during its formation, because it was replenished with salty water from the bowels of the Earth. Future research may provide an answer to this question.

Rice. 92. The amount of substances dissolved in ocean water.

** The amount of salts dissolved in ocean water is enough to cover the surface of the land with a layer 240 m thick.

It is assumed that all naturally occurring substances are dissolved in sea water. Most of them are contained in water in very small quantities: in thousandths of a gram per ton of water. Other substances are found in relatively large quantities- in grams per kilogram of sea water. They determine its salinity .

Salinity Sea water is the amount of salts dissolved in water.

Rice. 93. Salinity of the surface waters of the oceans

Salinity is expressed in p r o m i l l yae, i.e., in thousandths of a number, and is denoted by - ° / oo. The average salinity of the waters of the World Ocean is 35°/oo. This means that every kilogram of sea water contains 35 grams of salt (Fig. 92). The salinity of fresh river or lake waters is less than 1°/oo.

The Atlantic Ocean has the most salty surface waters, the Arctic Ocean has the least saline ones (see Table 2 in Appendix 1).

The salinity of the oceans is not the same everywhere. In the open part of the oceans, salinity reaches its highest values ​​in tropical latitudes (up to 37 - 38 ° / oo), and in the polar regions, the salinity of surface oceanic waters decreases to 32 ° / oo (Fig. 93).

The salinity of water in the marginal seas usually differs little from the salinity of the adjacent parts of the ocean. Water inland seas differs from the water of the open part of the oceans in salinity: it rises in the seas of the hot zone with a dry climate. For example, the salinity of the water in the Red Sea is almost 42°/oo. This is the saltiest sea in the world ocean.

In the seas temperate zone, which take in a large amount of river water, salinity is below average, for example, in the Black Sea - from 17 ° / oo to 22 ° / oo, in the Azov - from 10 ° / oo to 12 ° / oo.

* The salinity of sea water depends on atmospheric precipitation and evaporation, as well as currents, inflow of river water, ice formation and melting. When seawater evaporates, salinity increases, and when precipitation falls, it decreases. Warm currents usually carry saltier water than cold ones. AT coastal strip sea ​​waters are desalinated by rivers. When sea water freezes, salinity increases; when people melt, on the contrary, it decreases.

The salinity of sea water varies from the equator to the poles, from the open part of the ocean to the coast, with increasing depth. Salinity changes cover only the upper water column (up to a depth of 1500 - 2000 m). Deeper, salinity remains constant and is approximately equal to the average ocean.

2. Water temperature. Temperature ocean water at the surface depends on the incoming solar heat. Those parts of the World Ocean that are located in tropical latitudes have a temperature of + 28 0 С - +25 0 С, and in some seas, for example, in the Red Sea, the temperature sometimes reaches +35 0 С. This is the warmest sea of ​​the World Ocean. In the polar regions, the temperature drops to -1.8 0 C (Fig. 94). At a temperature of 0 0 C, fresh water of rivers and lakes turns into ice. Sea water does not freeze. Freezing is prevented by dissolved substances. And the higher the salinity of sea water, the lower its freezing point.

Fig.94. The temperature of the surface waters of the oceans

With strong cooling, sea water, like fresh water, freezes. Sea ice is forming. They constantly cover most of the Arctic Ocean, surround Antarctica, appear in the shallow seas of temperate latitudes in winter, where they melt in summer.

*Up to a depth of 200 m, the water temperature varies depending on the season: in summer the water is warmer, in winter it becomes colder. Below 200 m, the temperature changes due to the influx of warmer or colder waters by currents, and in the bottom layers it can increase due to the inflow of hot waters from oceanic faults. earth's crust. In one of these springs at the bottom of the Pacific Ocean, the temperature reaches 400 0 C.

The temperature of the ocean waters also changes with depth. On average, for every 1,000 m of depth, the temperature drops by 2 0 C. At the bottom deep sea trenches temperature around 0 0 C.

1. What is called the salinity of sea water, how is it expressed? 2. What determines the salinity of sea water and how is it distributed in the oceans? What explains this distribution? 3. How does the temperature of the waters of the World Ocean change with latitude and depth? 4*. Why does salinity reach the highest values ​​for the open part of the ocean in tropical regions (up to 37 - 38 ° / oo), and in equatorial latitudes salinity is much lower?

Practical work.

Determine the salinity if 25 g of salts are dissolved in 1 liter of sea water.

2*. Calculate how much salt can be obtained from 1 ton of Red Sea water.

Connoisseur Contest . On earth there is a sea in which a person can be on the surface of the water like a float (Fig. 95). What is the name of this sea and where is it located. Why does the water in this sea have such properties?

Rice. 95 "Sea" in which those who cannot swim can swim.

Our planet is covered by water by 70%, of which more than 96% is occupied by oceans. It means that most of the water on Earth is salty. What is the salinity of water? How is it determined and what does it depend on? Can this water be used on the farm? Let's try to answer these questions.

What is the salinity of water?

Most of the water on the planet has salinity. It is usually called sea ​​water and found in the oceans, seas and some lakes. The rest is fresh, its amount on Earth is less than 4%. Before you understand what the salinity of water is, you need to understand what salt is.

Salts are complex substances, which consist of cations (positively charged ions) of metals and anions (negatively charged ions) of acid bases. Lomonosov defined them as "fragile bodies that can dissolve in water." Many substances are dissolved in sea water. It contains sulfates, nitrates, phosphates, sodium, magnesium, rubidium, potassium cations, etc. Together, these substances are defined as salts.

So what is the salinity of water? This is the content of dissolved substances in it. It is measured in thousandths - ppm, which are indicated by a special symbol -% o. Ppm is the number of grams in one kilogram of water.

What determines the salinity of water?

AT different parts hydrosphere and even different times salinity varies throughout the year. It changes under the influence of several factors:

• evaporation;
• ice formation;
• precipitation;
• melting ice;
• river flow;
• currents.

When water evaporates from the surface of the oceans, the salts remain and do not erode. As a result, their concentration increases. Freezing has a similar effect. Glaciers contain the largest supply of fresh water on the planet. During their formation, the salinity of the waters of the World Ocean increases.

The melting of glaciers is characterized by the opposite effect, reducing the salt content. In addition to them, the source of fresh water is precipitation and rivers flowing into the ocean. The salt level also depends on the depth and nature of the currents.

Their highest concentration is on the surface. The closer to the bottom, the less salinity. affect the salt content in positive side, cold, on the contrary, reduce it.

Salinity of the oceans

What is the salinity of sea water? We already know that it is far from the same in various points planets. Its performance depends on geographical latitudes, climatic features terrain, proximity to river facilities, etc.

The average salinity of the waters of the World Ocean is 35 ppm. Cold regions near the Arctic and Antarctic are characterized by a lower concentration of substances. Although in winter time when ice forms, the amount of salt increases.

For the same reason, the least salty ocean is the North Arctic Ocean(32%o). by the most high content celebrated Indian Ocean. It covers the area of ​​the Red Sea and the Persian Gulf, as well as the southern tropical belt, where the salinity is up to 36 ppm.

Quiet and Atlantic Oceans have approximately the same concentration of substances. Their salinity decreases in the equatorial zone and increases in subtropical and tropical regions. Some are warm and balance each other out. For example, the non-salty Gulf Stream and the salty Labrador in the Atlantic Ocean.

Salinity of lakes and seas

Most of the lakes on the planet are fresh, as they are fed mainly by precipitation. This does not mean that there are no salts in them at all, just that their content is extremely small. If the amount of dissolved substances exceeds one ppm, then the lake is considered salty or mineral. The Caspian Sea has a record value (13% o). The largest fresh lake is Baikal.

Salt concentration depends on how the water leaves the lake. Fresh water bodies are flowing, while more saline ones are closed and subject to evaporation. The determining factor is also the rocks on which the lakes formed. Yes, in the area Canadian shield rocks poorly soluble in water, therefore, the reservoirs there are “clean”.

The seas are connected to the oceans through straits. Their salinity is somewhat different and affects the average ocean waters. Thus, the concentration of substances in the Mediterranean Sea is 39% o and is reflected in the Atlantic. The Red Sea with an indicator of 41% o greatly raises the average. The most saline is the Dead Sea, in which the concentration of substances ranges from 300 to 350% o.

Properties and significance of sea water

Not suitable for economic activity. It is not suitable for drinking, as well as watering plants. However, many organisms have long adapted to life in it. Moreover, they are very sensitive to changes in its salinity. Based on this, organisms are divided into freshwater and marine.

So, many animals and plants that live in the oceans cannot live in the fresh water of rivers and lakes. Edible mussels, crabs, jellyfish, dolphins, whales, sharks and other animals are exclusively marine.

People use fresh water for drinking. Salt is used for medicinal purposes. Small amounts of water sea ​​salt used to restore the body. Therapeutic effect bathing and taking baths in sea water.