Transparency of sea water. Study of the physical properties of water temperature determination Characteristics of water by the value of total hardness

Water transparency

Transparency- a value indirectly indicating the amount of suspended particles and other pollutants in ocean water. It is determined by the disappearance depth of a flat white disk with a diameter of 30 cm. The transparency of water is determined by its selective ability to absorb and scatter light rays and depends on surface illumination conditions, changes in the spectral composition and weakening of the light flux. With high transparency, water acquires an intense blue color which is typical for the open ocean. In the presence of a significant amount of suspended particles that strongly scatter light, the water has a blue-green or green color, characteristic of coastal areas and some enclosed seas. At the confluence of large rivers carrying a large number of suspended particles, the color of the water takes on yellow and brown shades. The maximum value of relative transparency (66 m) was noted in the Sargasso Sea (Atlantic Ocean); in the Indian Ocean it is 40-50 m, in the Pacific Ocean 59 m. In general, in the open part of the ocean, transparency decreases from the equator to the poles, but it can also be significant in the polar regions.

Water transparency- an indicator characterizing the ability of water to transmit light. Under laboratory conditions, transparency is taken to be the thickness of the water layer through which a standard font is discernible.

In natural reservoirs, a Secchi disk is used to assess transparency. This is a white metal disk with a diameter of 30 cm. It is lowered to such a depth that it completely disappears from sight, this depth is considered transparency. A similar measurement method was first used in the US Navy in the year. Currently, there are also a number of electronic instruments for measuring the transparency of water.

Transparency is usually determined by the turbidity of the water and its color.

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CLEARANCE OF WATER- the ability of water to transmit light. Usually measured by the Secchi disk. It depends mainly on the concentration of organic and inorganic substances suspended and dissolved in water. May drop sharply as a result anthropogenic pollution and… … Ecological dictionary

The main pollutants present in wastewater from urban wastewater treatment plants are grouped and presented in Scheme 1

Organic matter in wastewater physical condition can be in undissolved, colloidal and dissolved states, depending on the size of their constituent particles (Table 1). As the particle size of pollutants changes, they are sequentially removed at all stages of biological treatment (Scheme 2).

Table 1 Composition of organic substances in raw wastewater by particle size

Scheme 1

Water transparency

The transparency of waste water is due to the presence of undissolved and colloidal impurities in it. The measure of transparency is the height of the water column at which the font can be read through it. certain size and type. Municipal wastewater entering the treatment has a transparency of 1-5 cm. The effect of treatment is most quickly and simply estimated by the transparency of the treated water, which depends on the quality of the treatment, as well as the presence in the water of small flakes of activated sludge that do not settle in two hours. and dispersed bacteria. The grinding of sludge flakes can be the result of the decay of larger, older flakes, the result of their rupture by gases, or under the influence of toxic sewage. Small flakes can stick together again, but, having reached a certain small size, they do not grow further. Transparency is the most prompt, sensitive to violations, indicator of the quality of cleaning. Any, even minor, unfavorable changes in the composition of wastewater and in the technological regime of their treatment lead to the dispersion of sludge flakes, disruption of flocculation, and, consequently, to a drop in the transparency of treated water.

Biological wastewater treatment should provide at least 12 cm of purified water transparency. With complete, satisfactory biological treatment, the transparency is 30 centimeters or more, and with such transparency, all other sanitary indicators of pollution, as a rule, correspond high degree cleaning.

Transparency is determined in shaken (characterizes the presence of suspended and colloidal substances), and in settled (presence of colloidal substances) samples. Transparency in the settled sample characterizes the operation of aerotanks, transparency in the shaken one characterizes the operation of secondary settling tanks.

Examples. If the transparency of purified water in a shaken sample is 19 cm, and in a settled one 28 cm, we can conclude that the aerotanks work satisfactorily (colloidal substances are well removed) and secondary settling tanks (it can be expected that the removal of suspended solids in purified water will not exceed 15 mg/dm3 ),

Scheme 2 Sequential removal of organic particles (depending on their size) at different stages of wastewater treatment

If, according to the results of the analyzes, the transparency in a shaken sample is 10 cm, and in a settled sample it is 30 cm, this means that colloidal substances are well removed from wastewater in aerotanks, but secondary settling tanks do not work satisfactorily and provide low transparency of treated water.

A change in the transparency of the nadil water can serve as an operational signal about changes in the purification process, even when other methods of physicochemical control do not yet record deviations, since all violations are accompanied by crushing of activated sludge flakes, which is immediately fixed by a reduced transparency of the above interstitial water.

Transparency sea ​​water - an indicator characterizing the ability of water to transmit light rays. Depends on the size, quantity and nature of suspended solids. To characterize the transparency of water, the concept of "relative transparency" is used.

Story

For the first time, the degree of transparency of sea water was able to determine the Italian priest and astronomer named Pietro Angelo Secchi in 1865 using a disk with a diameter of 30 cm, lowered into the water on a winch from the shady side of the ship. This method was later named after him. AT this moment there are and are widely used electronic devices for measuring the transparency of water (transmissometers)

Methods for determining the transparency of water

There are three main methods for measuring water transparency. All of them involve the determination of the optical properties of water, as well as taking into account the parameters of the ultraviolet spectrum.

Areas of use

First of all, water transparency calculations are an integral part of research in hydrology, meteorology and oceanology, the transparency / turbidity index determines the presence of undissolved and colloidal substances of inorganic and organic origin in water, thereby affecting pollution marine environment, and also allows you to judge the accumulation of plankton, the content of turbidity in the water, the formation of silt. In shipping, the transparency of sea water can be a determining factor in the detection of shallow water or objects capable of causing damage to the vessel.

Sources

• Mankovsky V. I. An elementary formula for estimating the light attenuation index in sea water from the visibility depth of a white disk (Russian) // Oceanology. - 1978. - T. 18(4). - S. 750–753.
• Smith, R. C., Baker, K. S. Optical properties of the clearest natural waters (200-800 nm)
• Gieskes, W. W. C., Veth, C., Woehrmann, A., Graefe, M. Secchi disc visibility world record shattered
• Berman, T., Walline, P. D., Schneller, A. Secchi disk depth record: A claim for the eastern Mediterranean
• Guidelines. Determination of temperature, smell, color (color) and transparency in wastewater, including treated wastewater, storm water and melt water. PND F 12.16.1-10

The transparency of Lake B. Miassovo for most of the ice-free period fluctuates within 1 3-5 m and only shortly before freezing rises to 6.5 m. In May, after the ice has melted, and in autumn, starting from the end of August, the lowest water transparency is noted. The minimum transparency in spring and autumn depends on the mass development and death of phytoplankton and the entry of allochthonous suspensions into the water during ice melting and intense precipitation. An important role is played by spring and autumn homothermy, which contributes to the mixing and removal of precipitation into the water column.[ ...]

The transparency of water depends on its color and the presence of suspended matter. . substances.[ ...]

The transparency of water is determined using a glass cylinder with a polished bottom (Snellen cylinder). The cylinder is graduated in height in centimeters, starting from the day. The height of the graduated part is 30 cm.[ ...]

The transparency of water for ultraviolet rays is one of its most important properties, thanks to which the decomposition of chemicals in all areas of the environment is possible. Waves of effective length (approximately 290 nm), entering the atmosphere, quickly lose energy and become almost inactive (450 nm). However, such radiation is sufficient to break a whole series chemical bonds.[ ...]

The transparency of water depends on the amount of suspended and dissolved mineral and organic substances in it, and in summer period- from the development of algae. Closely related to transparency is the color of water, which often reflects the content of dissolved substances in it. The transparency and color of the water are important indicators the state of the oxygen regime of the reservoir and are used to predict fish kills in ponds.[ ...]

The transparency of water determines the amount of sunlight entering the water, and consequently, the intensity of the photosynthesis process in aquatic plants. In muddy water bodies, photosynthetic plants live only near the surface, and in clear water they penetrate to great depths. The transparency of water depends on the amount of mineral particles suspended in it (clay, silt, peat), on the presence of small animals and plant organisms.[ ...]

The transparency of water is one of the indicative signs of the level of development of life in reservoirs and along with thermals. Chemistry and circulation conditions constitute the most important ecological factor.[ ...]

Clear water and bright sunshine call for baits with a matte surface or a dull color. The splendor of the bait, which scares away fish, can be easily and quickly extinguished by holding it over a piece of burning birch bark.[ ...]

Water transparency ranges from 1.5 m in summer to 9.5 m in winter, and it is much higher near deep lakes.[ ...]

The transparency of water depends on the amount and degree of dispersion of substances suspended in water (clay, silt, organic suspensions). It is expressed in centimeters of water column, through which lines 1 l m thick are visible, forming a cross (definition by “cross”) or font No. 1 (according to Snellen or according to “font”).[ ...]

The transparency of water is one of the main criteria for judging the state of the reservoir. It depends on the amount of suspended particles, the content of dissolved substances and the concentration of phyto- and zooplankton. Affects the transparency and color of water. The closer the color of water to blue, the more transparent it is, and the more yellow, the less transparent it is.[ ...]

Water transparency is a measure of self-purification of open water bodies and a criterion for the efficiency of treatment facilities. For.the consumer, it serves as an indicator of the good quality of water.[ ...]

The color of the water in the lake experiences seasonal fluctuations and is not uniform in different parts of the lake, as well as transparency. So, in the open part of the lake. Baikal, with high transparency, the water has a dark blue color, in the area of ​​\u200b\u200bthe Selenginsky shallow water it is grayish-green, and near the river. Selengi - even brown. In Lake Teletskoye, in the open part, the color of the water is green, and near the shores it is yellow-green. The mass development of plankton not only reduces transparency, but also changes the color of the lake, giving it the color of organisms in the water. During flowering, green algae color the lake in green color, blue-greens give it a turquoise color, diatoms yellow, and some bacteria color the lake crimson and red.[ ...]

Less transparent water heats up more near the surface (in the case when there is no intensive mixing of water due to wind or current). More intensive heating has serious consequences. As warm water has a lower density, the heated layer seems to "float" on the surface of cold and therefore heavier water. This effect of stratification of water into almost non-mixing layers is called stratification. water body(usually a reservoir - a pond or a lake).[ ...]

Usually water transparency is correlated with biomass and plankton production. In conditions of different natural areas moderate pops, the lower the transparency, the better, on average, the plankton is developed, i.e. there is a negative correlation. This was pointed out by researchers at the end of the last and the beginning of this century. Further, the study of water transparency makes it possible to delineate the distribution of water masses of various genesis and indirectly judge the distribution of currents in reservoirs with slow water exchange [Butorin, 1969; Rumyantsev, 1972; Bogoslovsky et al., 1972; Vologdin, 1981; Ayers et a.l., 1958].[ ...]

Solid particles and plankton suspended in the water, as well as snow and ice in winter, make it difficult for light to penetrate the water. Only 47% of light rays penetrate through a meter layer of distilled water, and through dark water(for example, swamp lakes) almost no light passes to a depth of more than one meter. Approximately 50 cm ice transmits less than 10% of the light. And if the ice is covered with snow, then only 1% of the light reaches the water. Of the light rays, green and blue penetrate deepest into transparent water.[ ...]

Studies of water transparency of the lake. B. Miassovo were carried out in 1996-1997, the results are presented in fig. 11. Transparency measurements were made on the main measurement vertical using the standard Secchi disk method. The frequency of measurements is monthly.[ ...]

To determine the transparency of water directly in the reservoir, the Secchi method is used: a white enameled disk is lowered on a string into the reservoir; the depth in centimeters is noted at the following moments; a) when the visibility of the disk disappears and b) when the visibility of it appears when it is raised. The average of these two observations determines the transparency of the water in the reservoir.[ ...]

The conditions of illumination in water can be very different and depend, in addition to the strength of illumination, on the reflection, absorption and scattering of light, and many other factors. An essential factor determining the illumination of water is its transparency. The transparency of water in various reservoirs is extremely diverse, ranging from the muddy, coffee-colored rivers of India, China and Central Asia, where an object immersed in water becomes invisible as soon as it is covered with water, and ending with transparent waters Sargasso Sea(transparency 66.5 m), the central part of the Pacific Ocean (59 m) and a number of other places where the white circle - the so-called Secchi disk, becomes invisible to the eye only after diving to a depth of more than 50 m. Naturally, the lighting conditions in different reservoirs located even at the same latitudes at the same depth are very different, not to mention different depths, because, as you know, with depth, the degree of illumination decreases rapidly. So, in the sea off the coast of England, 90% of the light is absorbed already at a depth of 8-9 m.[ ...]

In the seasonal fluctuations in the transparency of lake waters, winter and autumn maxima and spring and summer minimums are outlined. Sometimes the summer minimum shifts to the autumn months. In some lakes, the lowest transparency is due to a large amount of sediment delivered by tributaries during floods and rain floods, in others - the massive development of zoo- and phytoplankton ("blooming" of water), in others - the accumulation of organic substances.[ ...]

The amount of coagulant introduced into the water (mg / l, mg-eq / l, g / m3 or g-eq / m3) is called the coagulant dose. The minimum concentration of coagulant that corresponds to the best clarification or discoloration of water is called the optimal dose. It is determined empirically and depends on the salt composition, hardness, alkalinity of water, etc. The optimal dose of coagulant is considered to be its minimum amount, which during trial coagulation gives large flakes and maximum water transparency after 15-20 minutes. For aluminum sulfate, this concentration usually ranges from 0.2 to 1.0 meq / l (20-100 mg / l) During the flood, the dose of coagulant is increased by approximately 50% - At water temperatures below 4 ° C, the dose of aluminum coagulant is increased almost twice.[ ...]

With the content of suspended solids in the source water up to 1000 mg/l and color up to 150 degrees, clarifiers provide water transparency of at least 80-100 cm on the cross and color not higher than 20 degrees of the platinum-cobalt scale. In this regard, in some cases, clarifiers are used without: filters. Clarifiers are designed round (diameter no more than 12-14 m) or rectangular (the area does not exceed 100-150 m2). Usually clarifiers work without flocculation chambers.[ ...]

Biological processes are an important factor determining the transparency of water in stagnant water bodies. Water transparency is closely related to biomass and plankton production. The better developed plankton, the less water transparency. Thus, the transparency of water can characterize the level of development of life in a reservoir. Transparency has great importance as an indicator of the distribution of light (radiant energy) in the water column, on which photosynthesis and the oxygen regime of the aquatic environment primarily depend.[ ...]

Most of our planet is covered with water. Water environment is a special habitat, since life in it depends on the physical properties of water, primarily on its density, on the amount of oxygen and carbon dioxide dissolved in it, on the transparency of water, which determines the amount of light at a given depth. In addition, the speed of its flow, salinity are important for the inhabitants of the water.[ ...]

For thousands of years, people have tried to get clean water. Several centuries ago, the main efforts of people were aimed at obtaining clear water. Thus, for example, water treatment in the early US water systems was mainly to remove sludge, and in many cases the reason for the creation of the first public water systems was simply the desire to eliminate dirty channels along streets and roads. Thus, almost until the beginning of the XX century. the danger of contamination through water was not the main argument in favor of establishing public water supply systems. Prior to 1870, there were no water filtration plants in the United States. In the 70s of the XIX century, sand filters were built coarse cleaning on the river Poughkeepsie and R. Hudson, pcs. New York, and in 1893 the same filters were built in Lawrence, pc. By 1897, more than 100 fine sand filters were built, and by 1925 - 587 fine sand filters and 47 coarse sand filters, providing treatment of 19.4 million m3 of water.[ ...]

Primary phytoplankton production correlates with water transparency (Vinberg, 1960; Romanenko, 1973; Baranov, 1979, 1980, 1981; Bouillon, 1979, 1983; Voltenvveider, 1958; Rodhe, 1966; Ahlgren, 1970]. Correlation coefficients d) between transparency , phytoplankton biomass and chlorophyll a content are quite reliable and amount to r = -0.48-0.57 for water bodies of the BSSR [Ikonnikov, 1979]; Estonia - r = -0.43-0.60 [Milius, Kieask, 1982], Poland - r - -0.56, ponds of the state of Alabama r = -0.79 [Almaran, Boyd, 1978]. The average values ​​of the content of chlorophyll "a" and the transparency of water on a white disk for deep lakes are given in Table. 64.[ ...]

An indirect method for determining the transparency of water (optical density) is widely used. Optical density is determined by optoelectric devices - colorimeters and nephelometers, using calibration graphs. A number of photocolorimeters for general industrial purposes (FEK-56, FEK-60, FAN-569, LMF, etc.) are produced, which are used at water treatment plants. However, this type of instrumental control over the content of suspended solids in water is associated with large labor and time costs for the collection and delivery of water samples.[ ...]

Comparison of the zooplankton biomass per unit area with transparency shows that in the water bodies of the tundra, northern and middle taiga, with an increase in the transparency value, the zooplankton biomass per unit area decreases. In lakes of the northern taiga, zooplankton biomass from 7.5 g/m1 with water transparency less than 1 m to 1.4 g/m3; with a water transparency of more than 8 m, in the lakes of the middle tzygi, respectively, from 5.78 g/m2 to 2.81 g/m2.[ ...]

Primary lakes, which arose when natural basins were filled with water, are gradually populated by plants and animals. Young lakes have clean clear water, their bottom is covered mainly with sand, overgrowing is insignificant. Such lakes are called oligotrophic (from Greek words oligos - "small", and trophe - "food"), i.e. malnourished. Gradually, these lakes are saturated with organic matter. dying aquatic organisms sink to the bottom, forming silty bottom sediments, and serve as food for animals living on the bottom. accumulate in water organic matter secreted by animals and plants and remaining after their death. An increase in the amount of nutrients in the reservoir stimulates further development life in a pond.[ ...]

The upper pool of the Uglich hydroelectric power station turned out to be polluted. Despite the high water transparency of 130 cm, filter-feeding invertebrates had a very low density, there was no zebra mussel.[ ...]

To prepare masonry mortar High Quality 1 The hardness of the water is of great importance. In order to determine the hardness or softness of water at home, heating it dissolves a small amount of crushed soap in it, after cooling the solution remains transparent - the water is soft, in; With some water, the solution becomes covered with a film when cooled. Except in hard water, soap suds do not whip.[ ...]

Average values ​​of ichthyomass in the lakes of the middle taiga zone and in the lakes of the zone mixed forests decrease with increasing transparency (Table 66).[ ...]

Characteristic of rhodanide compounds is a very slight effect on the organoleptic properties of water. Even at concentrations greater than 100 mg/l, none of the testers indicated any noticeable change in the odor of the water; there was no change in color, and water transparency. The ability of thiocyanates to add flavor to water is somewhat more pronounced.[ ...]

The Ukhta River: an average depth of 5 m, a channel with a large number of riffles, on which communities of the genus Sparganium develop. The transparency of the water is up to 4 m, the bottom is silted sands, pebbles, silted pebbles. The temperature in July-August reaches 18°C. Colva River: depth up to 7 m, water transparency up to 0.7 m, sandy bottom, temperature in July-August does not exceed 12°C.[ ...]

The photoelectronic installation for filter washing control (AOB-7 index) operates on the principle of attenuation of the light flux in a layer of water containing suspended solids. The absorption of light is fixed by a photocell connected to an indicating electrical measuring device of the MRSchPr type. The use of a simple phototurbidimetric technique for measuring water transparency is acceptable in this case, since the filters are always washed with purified water with a low, almost constant, water color. The primary sensor consists of a flow cell, a hermetically sealed chamber for a photocell, a chamber with an electric light bulb, and an electromagnet with hair brushes that periodically clean the cell window. Secondary device indicating the type of MRSchPr or EPV. Their positional regulators are used to stop washing filters when the specified water transparency is reached.[ ...]

In general, it is impossible to put an end to the definition of the concept of a small river. Some works are based on the study of the level of development of aquatic organisms. So, Yu.M. Lebedev (2001, p. 154) wrote: “ small river- a watercourse with water transparency to the bottom, the absence of true phytoplankton and adult fish, except for slow-growing local populations of roach, perch, minnow (trout for mountain rivers and grayling for Siberian), and the predominance of animal scrapers in the benthos.”[ ...]

The amount of incident solar radiation absorbed earth's surface, is a function of the absorptive capacity of that surface, i.e., depends on whether it is covered by soil, rock, water, snow, ice, vegetation, or something else. Loose cultivated soils absorb much more radiation than ice or rocks with a highly reflective surface. The transparency of water increases the thickness of the absorbing layer, and thus a given water column absorbs more energy than the same thickness of opaque land.[ ...]

Natural E.e. takes place on a millennium scale, it is currently suppressed by anthropogenic EE associated with human activity. EUTROPHICATION (E.) - a change in the state of the aquatic ecosystem as a result of an increase in the concentration of nutrients in the water, usually phosphates and nitrates. With E.v. in plankton in very large quantities cyanobacteria and algae develop, the transparency of water sharply decreases, and the decomposition of dead phytoplankton consumes oxygen in the bottom zone. It drastically impoverishes species composition ecosystems, almost all fish species are dying, plant species adapted to life in conditions are disappearing clean water(salvinia, amphibian buckwheat), and duckweed and hornwort grow en masse. E. is the scourge of many lakes and reservoirs located in densely populated areas.[ ...]

Photo-synthetic release of oxygen occurs when carbon dioxide is taken up by aquatic vegetation (attached, floating plants and phytoplankton). The process of photosynthesis proceeds the more intensively, the higher the water temperature, the more biogenic (nutrient) substances (compounds of phosphorus, nitrogen, etc.) in the water. Photosynthesis is possible only in the presence of sunlight, since in it, along with chemicals light photons are involved (photosynthesis occurs even in non-solar weather and stops at night). The production and release of oxygen occurs in the surface layer of the reservoir, the depth of which depends on the transparency of the water (for each reservoir and season it can be different - from a few centimeters to several tens of meters).[ ...]

This happened with the problem of the color of the sea: in 1921, the origin of the color of the sea was explained simultaneously by Shuleikin (in Moscow) and C. Raman (in Calcutta). The area of ​​work of both authors was reflected in the interpretation of the issue: Raman, who dealt with the crystal clear waters of the Bay of Bengal, gave a theory of the color of the sea, based on the concept of purely molecular scattering of light in water. Therefore, his theory is inapplicable to seas that exhibit strong scattering of light in water.[ ...]

Vaamochka belongs to the firth type of lakes, its depth does not exceed 2-3 m, water transparency is low. Pekulneiskoye is of the fiord type, in the central part of the depth varies from 10 to 20 m, and in the hall. Kakanauts fluctuate within 20-30 m. The lakes Vaamochka and Pekulneyskoye are connected to each other by channels, and through a common mouth, usually washed out in winter, with the Bering Sea. Compared to lake Vaamochka, the role of Pekulneisky in regulating the flow is much higher, since its area exceeds the area of ​​\u200b\u200bthe lake. Vamochka more than four times, and the catchment area is more than half total area basin system. In this regard, from the beginning of the spring flood to the opening of the mouth, the current in the channels is directed from the lake. Vaamochka to Pekulneyskoye, and after the opening of the mouth, Pekulneyskoye Lake is more affected by sea ​​tides.[ ...]

In general, the requirements of environmental safety management water resources are based on the implementation of water use plans developed taking into account the specified factors and processes that describe the state of aquatic ecosystems. The defining indicators of the state of aquatic ecosystems are: water purity class, saprobity index, index species diversity, as well as the gross production of phytoplankton (Otsenka sostoyaniya..., 1992). Parameters related to water quality also include indicators such as water transparency, pH value, content of nitrate ions and phosphate ions in water, electrical conductivity, biochemical oxygen demand, etc.[ ...]

The need of ponds for fertilizer is determined by biological, organoleptic and chemical methods. biological method consists in determining the intensity of photosynthesis in algae by observing the growth of algae in flasks into which different quantities fertilizers and take into account the development of algae in them. More simply, the need for fertilizers can be determined by the transparency of the water. Fertilizers are applied when the water transparency is more than 0.5 m. The most accurate method is the chemical analysis of water for the content of nitrogen and phosphorus and bringing them to a certain norm.[ ...]

As a result of these factors, the upper layer of the ocean is usually well mixed. It is called so - mixed. Its thickness depends on the season, wind strength and geographical area. For example, in summer, in calm weather, the thickness of the mixed layer in the Black Sea is only 20–30 m. pacific ocean near the equator, a mixed layer about 700 m thick was discovered (by an expedition aboard the research vessel "Dmitry Mendeleev"). From the surface to a depth of 700 m there was a layer of warm and transparent water with a temperature of about 27 ° C. This region of the Pacific Ocean is similar in its hydrophysical properties to the Sargasso Sea in Atlantic Ocean. In winter, the mixed layer on the Black Sea is 3-4 times thicker than the summer one, its depth reaches 100-120 m. big difference due to intense mixing winter time: how stronger wind, the more unrest on the surface and goes stronger mixing. Such a jump layer is also called seasonal, since the depth of the layer depends on the season of the year.[ ...]

For hydrobiology, it is important that the size classification of streams reflect the ecosystem components. From this point of view, foreign studies are extremely interesting, demonstrating that in watercourses of a low order, a transit character prevails, and in more major rivers- accumulative. This approach to classification, although attractive, is not very operational. It has been established that in the upper parts of the river network, among the benthic animals, scrapers predominate, and below they are replaced by gatherers. It is also known that if the transparency of water exceeds maximum depth rivers, then periphyton algae develop in such streams, and the true plankton is poorly represented. With increasing depths, the ecosystem acquires a planktonic character. Apparently, the latter criterion can be chosen as the boundary between small and larger watercourses. Unfortunately, it is necessary but not sufficient. For example, Zeya upstream according to its hydrooptical characteristics, it can be classified as small, and its tributary in this section of the Arga is not transparent to the bottom due to the high coloration of the water. Therefore, the criterion must be supplemented. As you know, fish live in streams, the depth of which exceeds a certain minimum. For trout ego 0.1 m, for grayling - 0.5, for barbel - 1 m.

The transparency of sea water is the ratio of the radiation flux that has passed through the water without changing direction, a path equal to unity, to the radiation flux that has entered the water in the form of a parallel beam. The transparency of sea water is closely related to the transmittance T of sea water, which is understood as the ratio of the radiation flux transmitted by a certain layer of water I z to the radiation flux incident on this layer I 0 , i.e. T \u003d \u003d e - with z. Transmittance is the opposite of light attenuation, and transmittance is a measure of how much light travels a given length of path in seawater. Then the transparency of sea water will be Θ=e - c, which means that it is related to the light attenuation index c.

Along with the indicated physical definition of transparency, the concept is used conditional (or relative) n transparency, which is understood as the depth of the cessation of visibility of a white disk with a diameter of 30 cm (disc of Secchi).

The depth of disappearance of the white disc or relative transparency is related to the physical concept of transparency, since both characteristics depend on the light attenuation coefficient.

The physical nature of the disappearance of the disk at a certain depth is that when the light flux penetrates into the water column, it is weakened due to scattering and absorption. At the same time, with increasing depth, there is an increase in the flow of scattered light to the sides (due to higher-order scattering). At a certain depth, the flow scattered to the sides is equal to the flow of direct light. Consequently, if the disk is lowered below this depth, then the flow scattered to the sides will be greater than the main flow going down, and the disk will cease to be visible.

According to the calculations of academician V.V. Shuleikin, the depth at which the energies of the main stream and the stream scattered to the sides are equalized, corresponding to the depth of the disappearance of the disk, is equal to two natural lengths of light attenuation for all seas. In other words, the product of the scattering index and transparency is a constant value equal to 2, i.e. k λ × z = 2, where z - depth of disappearance of the white disk. This ratio makes it possible to link the conditional characteristic of sea water - relative transparency with a physical characteristic - the scattering index k λ . Since the scattering index is an integral part of the attenuation index, it is also possible to relate the relative transparency to the attenuation index, and, consequently, to the physical characteristics of transparency. But since there is no direct proportionality between the absorption and scattering indices, then in each sea the relationship between the attenuation index and transparency will be different.

Relative transparency depends on the height from which observations are made, the state of the sea surface, and lighting conditions.

As the observation altitude increases, the relative transparency increases due to the decrease in the influence of the light flux reflected from the sea surface, which interferes with observations.

During waves, there is an increase in the reflected flow and a weakening of the flow penetrating into the depths of the sea, which leads to a decrease in relative transparency. This was noticed in antiquity by pearl seekers who dived on the bottom of the sea with olive oil in his mouth. The oil released by them from their mouths floated to the surface of the sea, smoothed out small waves and improved the illumination of the bottom.

In the absence of clouds, the relative transparency decreases, as observations are difficult. sun glare. Powerful cumulus clouds significantly reduce the light flux incident on the sea surface, which also reduces relative transparency. The most favorable lighting conditions are created in the presence of cirrus clouds.

The greatest number of optical observations relates to measurements of relative transparency with a white disk.

Relative transparency varies greatly depending on the content of suspended particles in sea water. In coastal waters rich in plankton, the relative transparency does not exceed a few meters, while in the open ocean it reaches tens of meters.

The clearest waters are found in subtropical zone World Ocean. In the Sargasso Sea, relative transparency is 66.5 m, and this sea is considered the standard of transparency. Such high transparency in the subtropical zone is associated with the almost complete absence of suspended particles and the weak development of plankton. In the Weddell Sea and in the Pacific Ocean near the islands of Tonga, an even higher transparency was measured - 67 m. In temperate and high latitudes, the relative transparency reaches 10-20 m.

In the seas, transparency varies considerably. So, in the Mediterranean Sea it reaches 60 m, in the Japanese - 30 m, Black - 28 m, Baltic - 11-13 m. In the bays and especially near the mouths of the rivers, the transparency ranges from several centimeters to several tens of centimeters.

When considering the issue of the color of the sea, two concepts are distinguished: the color of the sea and the color of sea water.

Under the color of the sea refers to the apparent color of its surface. The color of the sea in a strong way depends on the optical properties of the water itself and on external factors . Therefore, it varies depending on external conditions (illumination of the sea with direct sunlight and diffused light, on the angle of view, waves, the presence of impurities in the water, and other reasons).

Own color of sea water is a consequence of selective absorption and scattering, i.e. it depends on the optical properties of water and the thickness of the considered water layer, but does not depend on external factors. Taking into account the selective attenuation of light in the sea, it can be calculated that even for clear ocean water at a depth of 25 m, sunlight will be deprived of the entire red part of the spectrum, then with increasing depth the yellow part will disappear and the color of the water will appear greenish, only the blue part will remain at a depth of 100 m and the color of the water will be blue. Therefore, it is possible to talk about the color of water when the water column is considered. In this case, depending on the water column, the color of the water will be different, although its optical properties do not change.

The color of sea water is assessed using the water color scale (Forel-Uhle scale), which consists of a set of test tubes with color solutions. Determination of the color of water consists in the visual selection of a test tube, the color of the solution of which is closest to the color of water. The color of the water is indicated by the number of the corresponding test tube on the color scale.

An observer standing on the shore or watching from a ship sees not the color of the water, but the color of the sea. In this case, the color of the sea is determined by the ratio of the magnitudes and the spectral composition of the two main light fluxes that enter the eye of the observer. The first of them is the flow of the light flux reflected by the surface of the sea, falling from the Sun and the firmament, the second is the light flux of diffuse light coming from the depths of the sea. So as the reflected stream is white, as it increases, the color of the sea becomes less saturated (whitish). When the observer looks vertically down at the surface, he sees a stream of diffuse light, and the reflected stream is small - the color of the sea is saturated. When moving the gaze to the horizon, the color of the sea becomes less saturated (whitish), approaching the color of the sky, due to the increase in the reflected flow.

In the oceans there are huge expanses of dark blue water (the color of the ocean desert), indicating the absence of foreign impurities in the water and its exceptional transparency. As you approach the coast, there is a gradual transition to bluish-green, and in the immediate vicinity of the coast - to green and yellow-green tones (the color of biological productivity). Near the mouth of the Yellow River, which flows into the Yellow Sea, a yellow and even brown tint of water prevails, due to the removal of a huge amount of yellow loess by the river.