Sea water has an unpleasant bitter-salty taste, which is why it is impossible to drink it. However, it is not the same in all seas. Many are interested in what the salinity of water depends on, and experts find many explanations for this.
The water in all the seas on the planet has a different composition. Salinity, which is measured in ppm, depends on the geographical location of water bodies. According to experts, the further north the sea is, the higher this figure. Consequently, the seas and oceans of the southern part of the planet are less salty.
However, there are exceptions to any rule - the water in the oceans is much saltier than in the seas, and regardless of the region. Researchers do not give explanations for such a geographical division. Perhaps the answer lies at the very beginning of the development of life on our planet?
It is known that the salinity of water is influenced by:
- sodium chlorides;
- magnesium chlorides;
- other salts.
Probably certain areas earth's crust are rich in deposits of such substances, in contrast to neighboring regions. Although such an explanation is rather fragile: if you take into account the factor of sea currents, the salinity level should have leveled off sooner or later.
Causes of high salinity
Scientists put forward several theories that explain this phenomenon. Some argue that the increased amount of salt is the result of the evaporation of the water of the flowing rivers. Others are supporters of the theory that explains the high salinity by washing out stones and rocks. And some associate this composition of water with active volcanoes.
To many, the hypothesis that claims that an increased amount of salt in the sea appears with the water of the rivers flowing into it may seem strange. Nevertheless, any river moisture contains salt. Of course, it is much less than, say, in any ocean.
Therefore, when a river enters the sea, its composition is desalinated. But after the evaporation of river water, salt remains in the reservoir. Of course, the amount of river impurities is small, but given that the process lasts millions of years, a lot of them have accumulated in sea water. They settle at the bottom, forming huge rocks and boulders there for thousands of years. But the sea current is very strong - it can destroy any stones. This process is quite long and constant. By the way, it is he who is the culprit of the bitter taste of sea water.
Explanations that indicate what the salinity of sea water depends on include the presence of underwater volcanoes. Periodically they throw out a large number of various substances including salts.
Volcanoes were very active during the formation of the Earth. They released acids into the atmosphere. It is assumed that due to frequent acid rain, the water in the seas and oceans was initially acidic. However, when interacting with magnesium, calcium or potassium, salts were obtained. It was in this way that the water acquired its usual salinity.
There are other assumptions, which include:
- Salt-bearing winds.
- Soils that, passing water through themselves, enrich it with salts and throw it into the ocean.
- Salt-forming minerals that, while under the ocean floor, penetrate through hydrothermal vents.
Which sea is the saltiest
Sea water is perhaps the most abundant substance on earth. Many people associate a full and healthy vacation with warm waves and sunny beaches. As mentioned above, all reservoirs have their own mineral composition. But which of the seas is the most salty?
Scientists have come to a consensus that this is the Red Sea. The composition of one liter of its water includes 41 g of salts. Compared to other reservoirs, this is a very high figure. For example, in the Mediterranean Sea it is 39 g, much less salt in the Black Sea -18 g, and in the Baltic even less - only 5 g. But in the water of the oceans it is 34 grams.
Why is the sea salty: Video
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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 of the temperate zone, which receive 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 more salt 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. The temperature of ocean water at the surface depends on the influx of 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 faults in the oceanic 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 of deep-water depressions, the temperature is about 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 the salinity in tropical regions reach highest values for the open part of the ocean (up to 37 - 38 ° / oo), and in equatorial latitudes the 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.
I had a chance to ride to the seas in my life. Indeed, everyone is different! Somewhere you can safely swim and even dive - and even your eyes practically do not sting. And somewhere you can’t even plunge headlong, otherwise the salt will turn your hair into straw, and your eyes will be red until the next day. But what is the reason for this difference in salinity between different seas?
What determines the salinity of sea water
For a while, I thought it was just self-deception. Indeed, why should there be any differences between the seas!
But long hours on the Internet and reading books told me: the salinity of the water is really different for each sea. And it depends on the following things:
The ratio of all these parameters determines how salty the sea will be.
Which sea is the most salty and why
The most- The Dead Sea is the saltiest- where for every liter of water there are about 200 grams of salt.
Such a high concentration of salts leads to its consequences. Simply in the sea living organisms cannot live- do not withstand the salinity of water. That is why the sea got its name.
The reasons for this accumulation of salt are commonplace. Here only one river flows- Jordan. And no river flows from the Dead Sea. In addition, next to dead sea very hot.
It turns out that salt simply has nowhere to go from the sea. Water evaporates, salt does not disappear - and a concentrated salt solution is obtained.
But there is another plus - because of such salinity It is almost impossible to drown in the Dead Sea. The water itself will push you to the surface.
Education
What is the salinity of water? Salinity of the waters of the oceans
March 29, 2017Our 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 that consist of cations (positively charged ions) of metals and anions (negatively charged ions) of acidic 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. Warm currents affect the salt content in positive side, cold, on the contrary, reduce it.
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Salinity of the oceans
What is the salinity of sea water? We already know that it is far from the same in different parts of the planet. Its performance depends on geographical latitudes, climatic features of the area, the proximity of river objects, 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 saline ocean is the Northern Arctic Ocean(32%o). The Indian Ocean is the highest. It covers the area of the Red Sea and the Persian Gulf, as well as the southern tropical zone, 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 warm and cold currents balance each other. 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. So, in the area of the 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 salinity indian ocean. The most salty is the Dead Sea, in which the concentration of substances ranges from 300 to 350% o.
Properties and significance of sea water
Salt water is 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.