It is believed that the average salinity surface water Atlantic Ocean largest compared to other oceans. However, off the coast of Africa at point B, it is significantly lower than at point A. Explain why this is due, indicating two reasons. The salinity of the surface waters of the world's oceans depends on the amount of precipitation and evaporation, on the inflow river waters. Point b is located in the equatorial climate zone, where more precipitation falls during the year than in the tropical climate zone where point a is located. At point b, evaporation from the surface is less, since at equatorial belt high cloudiness, which reduces evaporation from the surface. At point a, evaporation is greater, since in the tropical zone the absence of clouds and descending air currents increase evaporation. Point b is in the Gulf of Guinea, where major rivers Africa. Comment.
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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 salinity 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 Arctic Ocean (32% o). by the most high content noted 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.
The Pacific and Atlantic oceans have approximately equal concentrations 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 salty 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. In small quantities, water with sea salt is used to restore the body. Therapeutic effect bathing and taking baths in sea water.
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 ‰.
Solution:
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 ‰.
Solution:
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.
Solution:
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.
Solution:
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
The water in the sea and in the river is very different. First of all, it has a salty taste in the sea or ocean. This is due to various factors, and what exactly affects the average salinity of the world's oceans will be discussed further.
salinity sign
Scientists have come up with a special designation for salinity. It is called ppm, and is very similar to%, but differs by an additional zero behind - ‰. Ppm shows what the volume of a substance dissolved in one liter of water is equal to. If we have a component and its quantity is 2 grams per liter of water, then we have a value of 2 ‰.
Why is water bitter?
Have you noticed how the water in the sea tastes?
It's not just salty, it's also bitter. This is due to its heterogeneity. It contains 44 different natural elements. But the main ones are salts. We are used to cooking - it gives an ordinary flavor, as in any food. And here's another magnesium salt, very bitter and if there is more of it, then the water will seem nasty.
There is so much salt in the ocean that if you dry it all and sprinkle it on land, you get a layer at least 150 meters high.
Factors affecting the level of taste in ocean water
Consider what determines the average salinity of the world's oceans:
- Evaporation. The more intense the water leaves its location, the more particulate matter stays in the ocean. Salts do not evaporate.
- Are there glaciers in the ocean, and how intense is their melting. Cold natural conditions can affect the level of salts in the water in different ways. If the process of ice formation occurs, then all the fresh water goes into the snow, and the minerals remain, increasing their concentration. Conversely, the more glaciers melt, the more they dilute the water.
- Rainfall per year. The more fresh rain waters the ocean, the less salinity.
- Quantity Wastewater . All rivers are fresh, and naturally, the more rivers flow into world waters, the lower the concentration of substances.
Rice. 1. Map of the oceans and the value of salinity depending on latitude
Places with the lowest and highest ppm
In the world's oceans, the value of ppm is very different. Most high results noticeable in the North Atlantic Ocean (between 20° and 30°) and reach a level of 37 ‰. And if you measure the water in the Gulf of Panama, then here the indicator will be 28‰. Part of the ocean the smallest value lies between two continents and receives so many tropical showers that the concentration solid elements low. In the Atlantic, it's the other way around. Latitudes 20°-30° are located close to the equator, which means that there is little precipitation, and evaporation is large.
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The average salinity value throughout the water area is 35‰.
Rice. 2. Red Sea: view from space
Sea with highest value ppm - Red (42‰). It has a unique geographical location, because not a single river flows into it, and the arid climate leads to abundant evaporation.
The Baltic Sea is the freshest. The ppm indicator is 1 ‰. The location in the North of Europe suggests that, firstly, most of the European rivers, and secondly, there is a very rainy climate, and there are few hot days.
The salinity of the waters in the ocean is also affected by currents. The largest is the Gulf Stream. It carries water with a value of 35‰ from the south to the North Arctic Ocean, where the salinity is only 10-11‰. And another current - Labrador has reverse action. fresh water Arctic it carries into hot climate Central America.
The main feature that distinguishes water oceans from the waters of the land, is their high salinity. The number of grams of substances dissolved in 1 liter of water is called salinity.
Sea water is a solution 44 chemical elements, but salts play a primary role in it. Salt gives the water a salty taste, and magnesium - bitter. Salinity is expressed in ppm (%o). This is a thousandth of a number. In a liter of ocean water, an average of 35 grams is dissolved various substances, so the salinity will be 35%.
The amount of salts dissolved in will be approximately 49.2 10 tons. In order to visualize how large this mass is, we can make the following comparison. If all sea salt dry spread over the surface of the entire land, then it will be covered with a layer 150 m thick.
The salinity of the ocean waters is not the same everywhere. Salinity is influenced by the following processes:
- evaporation of water. In this process, salts with water do not evaporate;
- ice formation;
- fallout, lowering salinity;
- . The salinity of the ocean waters near the continents is much less than in the center of the ocean, since the waters desalinate it;
- melting ice.
Processes such as evaporation and ice formation contribute to an increase in salinity, while precipitation, river runoff, and melting ice lower it. main role salinity is affected by evaporation and precipitation. Therefore, the salinity of the surface layers of the ocean, as well as temperature, depends on latitude-related.
