perhaps now even the children know that the chemical formula of water - H2O.However, it is a theory, but actually in the water dissolved substances a huge amount of both organic and inorganic origin.Pure water as well known, has no taste or smell, but anyone can verify that in most cases it is not.In drinking water, for example, contains a certain amount of mineral salts, which gives it a salty flavor.In varying degrees, it contains all the things with which it comes into contact.The exact composition of the water depending on where it fence because in different places, it is in contact with different substances.Here and there, the chemists will find in the liquid heavy metal, somewhere - a variety of organic substances.
How is it?
Water is the universal solvent.Distilled water is considered the most pure substance in the chemical sense, but after a while it loses its original state.Here's why: the water is a good solvent so that over time it fall molecules of various substances from the air.In nature, it occurs also due to various vital organisms living in aqueous environment.
Gaza
water pouring water into a glass, you can see the bubbles of gas, which will be located on the vessel walls.Along with salts and other substances in the water dissolves itself and gases.This primarily nitrogen from the air as well as oxygen, carbon dioxide, and in some cases even methane and hydrogen sulfide.And the cold water dissolves gases better than warm, so the lower the temperature, the higher the concentration of the gases.And vice versa - with increasing temperature, the solubility decreases.
sources of dissolved gases
But where do all of these substances are taken in water?Nitrogen is usually dissolved in the interaction with the atmosphere, methane - as a result of contact with rock and decomposition of bottom sludge, and the hydrogen sulfide formed as a product of decomposition of organic residues.Typically, hydrogen sulfide contained in deep water layers and does not rise to the surface.With its high concentration of life is impossible, for example, in the Black Sea at a depth of more than 150-200 meters from the high water saturation serovodorom almost no living organisms, except for some bacteria.
Oxygen is also always contained in the water.It is a versatile oxidizing agent, thus partially decompose hydrogen sulfide, reducing its concentration.But where does the oxygen in the water?About him we will talk special.
Oxygen
Almost all living organisms need oxygen.People breathe vohduhom, which is a mixture of gases, a large part of which is exactly it.
aquatic organisms also need this stuff, so that the concentration of oxygen in the water - it is a very important indicator.Usually it is up to 14 mg / l, in the case of natural waters, and sometimes even more.In the same fluid that flows from the tap, it contains much less oxygen, and it is easy to explain.Tap water intake after passing through several stages of purification, and dissolved oxygen - extremely unstable compound.As a result, the gas exchange with the air among a large part of it just disappears.Since oxygen is taken in from the water, if not from the air?
In fact, this is not entirely true, from the air, he is also taken, but the proportion of dissolved as a result of contact with the atmosphere, is very small.In order to interaction of oxygen with the water it has been sufficiently effective, requires special conditions: low temperature, high pressure and relatively low salinity.They are not always respected, and life is unlikely to exist in its present form if the only way to the formation of gas in aqueous media was the interaction with the atmosphere.Fortunately, there are two sources of the origin of the oxygen in the water.First, the dissolved gas molecules in large quantities contained in the snow and rain waters, and secondly - and this is the main source - as a result of photosynthesis carried out by aquatic vegetation and phytoplankton.
way, despite the fact that the water molecule contains oxygen and remove it therefrom organisms certainly not.Therefore, they remain satisfied with it diluted shares.
The significance of algae
Few people in everyday life reflects what we breathe and why the composition of the air just the way it is.Almost everyone knows that most living organisms, air-breathing, adapted specifically to such a mixture.But when it comes to ground-air environment, the question does not arise.And where the oxygen in the water?How on earth, there are many plants that are using a process called photosynthesis, consuming light and carbon dioxide, release O2.
If to be more exact, in recent decades, for whatever reasons, mankind has destroyed a large part of the forests.But the question of the global crisis yet, although the world's population is constantly increasing and the consumption of oxygen
enormous.And of great importance in this regard are the algae that live in the oceans, most of it at their expense saturate water with oxygen.Some of the types of people and marine animals eat, but their number is sufficient to effectively fotosintezirovaniya.That oxygen is taken from water, which means that due to gas exchange with the atmosphere, and air.It photosynthesis of algae - its main source.By the way, due to the processes occurring in plants, it has accumulated a primary oxygen in the atmosphere, and now there is only maintaining its constant composition.
role of dissolved oxygen (DO)
Although the respiratory system aquatic life is arranged differently than the residents of the ground-air environment, they need all the same substances.First of all, we are talking about oxygen, which plays an important role in the life of the vast majority of organisms.And if we remove it from the atmosphere, where its share is more or less stable at around 21%, the inhabitants of the rivers, seas and oceans are heavily dependent on how much oxygen in the water found in their habitats.Besides fish and plants need oxygen.However, its products are generally higher than the level of consumption, so this should not cause concern.
normal values
Due to its significant role in the normal functioning of ecosystems, the level of the Republic of Kazakhstan is often subjected to the control of the biology and ecology.After all, everything in nature is connected, a violation of the gas balance in a body of water can cause problems in neighboring ones, if they are connected.Typically, measurements are carried out before noon, at this time the gas concentration in the surface water becomes a maximum of up to 14 mg / l.This rate is subject to significant daily and seasonal fluctuations, but it should not fall below 4 mg / l.
decrease in concentration of 2 mg / l and less cause mass death of the inhabitants of the hydrosphere.In fact - from suffocation.The gradual decline may indicate water pollution and also may eventually result in the death of aquatic inhabitants.
RK in artificial ecosystems
important is a good aeration, for example, in the aquarium.It is therefore necessary not only to install special pumps pump air into the water and saturating it with oxygen, but also, for example, if necessary planted at the bottom of various algae.Of course, those who have similar interests, first and foremost interested in the aesthetics of the ecosystem, but we should not forget about its stability and a certain longevity.
If we are talking about fisheries, production of pearls and other specific industries of this type, in addition to various measures aimed at preserving a sufficient concentration of dissolved oxygen in the water, you need to regularly measure this indicator using special tests.When they fence it is essential that there was no contact with air, it can distort the results of the analysis.
