UN Resolution introduced the annual World Water Day, which is celebrated in different countries on March 22.On this day event, whose purpose is the preservation and development of water resources, which are in the rivers, lakes, canals, storage, seas and oceans, in underground sources in the form of soil moisture, polar ice and mountain or vapors in the atmosphere.All resources include surface and underground sources and may be used or used for human needs.The total volume of (liquid, gaseous or solid) on Earth is 1.39 billion cubic meters, and only less than 3% of the total resources are related to freshwater reserves.
In the oceans and seas is the largest amount of water (approximately 98%) of all surface water sources.Chemicals it varies depending on the location and time of year.Sea water contains dissolved ions much more than any kind of fresh.Also, in sharp contrast ratio of substances dissolved in it.For example, in the seas and oceans contained approximately 2.8 times more bicarbonate than in rivers but the molar proportion of them in relation to all the dissolved ions is much lower (0.14%) than in river sources (48%).This is due to the different residence times of solutes.Ions of sodium and chlorine are dissolved, while calcium is precipitated as carbonate.On the content in a kilogram of sea water are the most common ions:
- chlorine (0.546 moles);
- sodium (0.469 mol);
- magnesium (0.0528 moles);
- sulfate (0.0282 mol);
- calcium (0.0103 moles);
- potassium (0.0102 moles).
One of the most important indicators, which is characterized by sea water - is salty.It is measured in per mille (‰) and can be different for all the seas and oceans.The average value of salinity of 35 ‰, that is, 1 liter in solution is 35 g salt, mainly sodium chloride.At an average salinity of water the following elemental composition:
- oxygen 85.84%;
- hydrogen 10.82%;
- chlorine 1.94%;
- magnesium 1.1292%;
- sodium 1.08%;
- 0.091% sulfur;
- calcium 0.04%;
- potassium 0.04%;
- bromine 0.0067%;
- carbon 0.0028%.
sea water on the surface at 25 ° C has an average density of 1.025 g / cm3 - is more than the net whose density at 25 ° C is equal to 1.003 g / cm3.Density - a physical quantity having a direct dependency on the concentration of salts and inverse temperature.The more dissolved salts, the greater density.The lower the temperature of sea water, the greater the density.The temperature at the highest density of marine 3,52S minus plus 3,98S pure.But these values are not only vary from source to source, but also depends on the depth at which they are measured.At greater depths the density can reach values of 1.050 g / cm3 or higher.Changing the qualitative and quantitative composition as well traced by the pH, which ranges 7,5-8,4 (Wednesday weakly alkaline), and due to the nature of the dissolved ions and their concentration.At higher surface pH than at depth.Neutral and slightly acid can be freshened Wednesday sites.The highest pH value (lowest concentration of hydrogen ions) is always observed at the sea surface.
freezing point of seawater decreases with increasing salinity (concentration of dissolved salts).At an average salinity it freezes at a temperature minus 2C.In 2010 it was recorded in the history of the lowest temperature in the stream under the Antarctic glacier when measured minus 2,6S.There are other characteristics that indicate the difference between the sources and their variability depending on other parameters.For example, the speed of sound at 0C.It goes through the marine environment 1 second 1450 m, and in the net - 1407 m. The sea water at 25 ° C has a dynamic viscosity of 9.02 millipuaza.For a clean environment, the same characteristics at the same temperature equals 8.09 millipuaza.
Sea water is not used for drinking due to the high concentration of mineral salts.With its use need to drink a lot more clean fluid to bring all received her salt from the body.Therefore drink only fresh water, which dissolves not more than 0.001 g / cm3 salts.Because of its scarcity building installation and use special techniques to reduce the salt concentration.They include freezing, distillation, electrolysis, ion exchange, reverse osmosis, separation (hydrodynamic separation).For example, in Kazakhstan, Aktau (formerly known as Shevchenko) was built in 1972 and has worked for almost 30 years, the world's only nuclear power plant for desalination.
