impurities in water. Clarity of sea water Odors of natural origin

Transparency 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 height of observations increases, 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 belt is associated with the almost complete absence of suspended particles and the weak development of plankton. in the Weddell Sea and 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.

The transparency of water in hydrology and oceanology is the ratio of the intensity of light passing through a layer of water to the intensity of light entering the water. Water transparency is a value that indirectly indicates the amount of suspended particles and colloids in water.

The transparency of water is determined by its selective ability to absorb and scatter light rays and depends on the surface illumination conditions, changes in the spectral composition and attenuation of the light flux, as well as the concentration and nature of living and inanimate suspension. With high transparency, water acquires an intense Blue colour 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 shallow seas. At the confluence major rivers, bearing a large number of suspended particles, the color of the water takes on yellow and brown shades. River runoff, saturated with humic and fulvic acids, can cause the dark brown color of sea water.

The transparency (or light transmission) of natural waters is due to their color and turbidity, i.e. the content in them of various colored and suspended organic and mineral substances.

Determination of water transparency is a mandatory component of monitoring programs water bodies. Transparency is the property of water to let light rays through. Reducing the light flux reduces the efficiency of photosynthesis and, consequently, the biological productivity of watercourses.

Even the purest, free of impurities, waters are not absolutely transparent and completely absorb light in a sufficiently thick layer. However natural waters are never completely pure - they always contain dissolved and suspended substances. Maximum transparency is observed in winter period. With the passage of the spring flood, transparency noticeably decreases. The minimum transparency values ​​are usually observed in summer, during the period of mass development ("blooming") of phytoplankton.

For Belarusian lakes with a natural hydrochemical regime, the transparency values ​​(according to the Secchi disk) vary from several tens of centimeters

up to 2-3 meters. In places where wastewater enters, especially during unauthorized discharges, transparency can be reduced to several centimeters.

Water, depending on the degree of transparency, is conventionally divided into clear, slightly turbid, medium turbidity, turbid, very turbid (Table 1.4). The measure of transparency is the height of the cable of the Secchi disk lowered into the water. certain sizes.

Table 1.4

Characteristics of waters in terms of transparency

Conclusion: Lakes - reservoirs occupying a natural depression on earth's surface. There are a number of classifications of reservoirs with stagnant water, the main indicators of pollution of which are the degree of saprobity and trophic status. To classify lakes as one or another water body in terms of saprobity and trophicity, their physical indicators and species composition macrozoobenthos.

Transparency of water according to the Secchi disk, according to the cross, according to the font. Turbidity of water. The smell of water. Water color.

There are suspended solids in the water, which reduce its transparency. There are several methods for determining the transparency of water.

1. According to the disk of Secchi. To measure the transparency of river water, a Secchi disk with a diameter of 30 cm is used, which is lowered on a rope into the water, attaching a weight to it so that the disk goes vertically down. Instead of a Secchi disk, you can use a plate, lid, bowl, placed in a grid. The disk is lowered until it is visible. The depth to which you lowered the disk will be an indicator of the transparency of the water.
2. By the cross. Find the maximum height of the water column, through which the pattern of a black cross is visible on a white background with a line thickness of 1 mm, and four black circles with a diameter of 1 mm. The height of the cylinder in which the determination is carried out must be at least 350 cm. At the bottom of it is a porcelain plate with a cross. Bottom part cylinder should be illuminated by a 300 W lamp.
3. By font. A standard font is placed under a cylinder 60 cm high and 3-3.5 cm in diameter at a distance of 4 cm from the bottom, the test sample is poured into the cylinder so that the font can be read, and the maximum height of the water column is determined. The method for quantitative determination of transparency is based on determining the height of the water column, at which it is still possible to visually distinguish (read) a black font 3.5 mm high and a line width of 0.35 mm on a white background or see an adjustment mark (for example, a black cross on white paper) . The method used is unified and complies with ISO 7027.

Water has increased turbidity due to the content of coarsely dispersed inorganic and organic impurities. The turbidity of water is determined by the gravimetric method, and by a photoelectric colorimeter. The weight method is that 500-1000 ml muddy water filtered through a dense filter with a diameter of 9-11 cm. The filter is preliminarily dried and weighed on an analytical balance. After filtering, the filter with sediment is dried at a temperature of 105-110 degrees for 1.5-2 hours, cooled and weighed again. The amount of suspended solids in the test water is calculated from the difference between the masses of the filter before and after filtration.

In Russia, the turbidity of water is determined photometrically by comparing samples of the studied water with standard suspensions. The measurement result is expressed in mg / dm 3 using the main standard suspension of kaolin (turbidity for kaolin) or in MU/dm 3 (turbidity units per dm 3) when using formazin stock standard suspension. The last unit of measurement is also called the Turbidity Unit. according to Formazin(EMF) or in Western terminology FTU (formazine Turbidity Unit). 1FTU=1EMF=1EM/dm 3 .

AT recent times The photometric method for measuring turbidity by formazin has been established as the main one all over the world, which is reflected in the ISO 7027 standard (Water quality - Determination of turbidity). According to this standard, the unit of measure for turbidity is FNU (formazine Nephelometric Unit). Agency for Protection Environment USA (U.S. EPA) and World Organization The World Health Organization (WHO) uses the Nephelometric Turbidity Unit (NTU) for turbidity.

The relationship between the basic turbidity units is as follows:

1 FTU(EMF)=1 FNU=1 NTU

WHO does not standardize turbidity according to indications of health effects, however, from the point of view of appearance recommends that turbidity be no higher than 5 NTU (nephelometric turbidity unit) and, for decontamination purposes, no more than 1 NTU.

Odors in the water may be associated with vital activity aquatic organisms or appear when they die - these are natural smells. The smell of water in a reservoir can also be caused by sewage effluents entering it, industrial effluents are artificial odors. First, a qualitative assessment of the smell is given according to the relevant features:

• marsh,
• earthy,
• fish,
• putrefactive,
• aromatic,
• oil, etc.

The strength of the smell is evaluated on a 5-point scale. The flask with a ground stopper is filled 2/3 with water and immediately closed, shaken vigorously, opened and the intensity and nature of the odor are immediately noted.

A qualitative assessment of the color is made by comparing the sample with distilled water. To do this, separately investigated and distilled water is poured into glasses made of colorless glass, against the background white sheet in daylight, they are viewed from above and from the side, the chromaticity is evaluated as the observed color, in the absence of color, the water is considered colorless.

Transparency of 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 sewage, including treated sewage, storm and melt. PND F 12.16.1-10