What is the salinity of water? Salinity of the waters of the World Ocean

Our planet is covered by water by 70%, of which more than 96% are occupied by the oceans. This means that most of the water on the Earth is salty. What is the salinity of water? How is it determined and depends on what? Is it possible to use such water 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. Usually it is called sea water and is found in oceans, seas and some lakes. The rest is fresh, its amount on Earth is less than 4%. Before you figure out 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 acid bases. Lomonosov defined them as "fragile bodies that can dissolve in water." In sea water, a lot of substances are dissolved. It contains sulfates, nitrates, phosphates, cations of sodium, magnesium, rubidium, potassium, etc. Together, these substances are defined as salts.

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

What determines the salinity of water?

In different parts of the hydrosphere and even in different seasons the salinity of water is not the same. It varies under the influence of several factors:

• evaporation;
• Ice formation;
• precipitation;
• Melting of ice;
• River runoff;
• Flow.

When water evaporates from the surface of the oceans, the salts remain and do not weathered. As a result, their concentration increases. The freezing process has a similar effect. Glaciers contain the largest reserve 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 content of salts. In addition to them, the source of fresh water is atmospheric precipitation and rivers flowing into the ocean. The level of salts also depends on the depth and nature of the currents.

Their greatest concentration on the surface. The closer to the bottom, the less salinity. Warm currents affect the content of salts in a positive way, cold, on the contrary, reduce it.

Salinity of the World Ocean

What is the salinity of the sea water? We already know that it is far from the same in different parts of the world. Its indicators depend on geographical latitudes, climatic features of the terrain, proximity of river objects, etc.

The average salinity of the waters of the World Ocean is 35 ppm. A smaller concentration of substances is characterized by cold areas near the Arctic and Antarctic. Although in winter, when the ice is formed, the amount of salts increases.

For the same reason, the least saline ocean is the Arctic Ocean (32% o). The highest content is the Indian Ocean. It covers the area of the Red Sea and the Persian Gulf, as well as the southern tropical belt, where salinity is up to 36 ppm.

The Pacific and Atlantic Oceans have approximately equal concentrations of substances. Their salinity decreases in the equatorial zone and rises in the subtropical and tropical regions. Some warm and cold currents counterbalance each other. For example, not the salt stream of the Gulf Stream and the salted Labrador in the Atlantic Ocean.

Salinity of lakes and seas

Most of the lakes on the planet are fresh, since they are mostly fed by rainfall. This does not mean that there is no salt in them at all, it's just that their content is extremely small. If the amount of dissolved substances exceeds one ppm, the lake is considered salty or mineral. The Caspian Sea has a record value of 13%. The largest fresh lake is Lake Baikal.

The concentration of salts depends on how the water leaves the lake. Fresh water bodies are flowing, and more saline are closed and subject to evaporation. The determining factor is also the rocks on which the lakes were formed. So, in the area of the Canadian shield rocks are poorly soluble in water, so the water there is "clean".

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

Properties and importance of sea water

Salt water is not suitable for economic activities. 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 the level of its salinity. Proceeding from this, organisms are divided into freshwater and marine.

So, many animals and plants living in the oceans can not live in the fresh water of rivers and lakes. Exclusively marine are edible mussels, crabs, jellyfish, dolphins, whales, sharks and other animals.

For drinking, a person uses fresh water. Salt is also used for medicinal purposes. In small quantities, water with sea salt is used to restore the body. The therapeutic effect produces bathing and taking baths in sea water.