salt lake

salt lake

It is a kind of saltwater lake with high salinity in arid area. The salinity of freshwater lake is less than 1 g / L, that of saline lake is more than 1 g / L, and that of salt lake is more than 35 g / L. Salt lake is the product of Lake development to the old age, it is rich in a variety of salts, is an important mineral resources.

General situation

Salt lake is a kind of salinized water body, which usually refers to the lake with a salinity of 3.5% (higher than the average salinity of seawater), and also includes the dry salt lake (underground brine lake) composed of surface brine, salty deposition and intergranular brine. There are about 200 kinds of salt minerals deposited in the salt lake. Human beings have mined a large amount of halite, alkali, mirabilite, potassium, lithium, magnesium, boron, bromine, saltpeter, gypsum, medical sludge and other basic chemical, agricultural, light industry, metallurgy, construction, medical and other important raw materials from salt lakes.

There are also rubidium, cesium, tungsten, strontium, uranium, calcium chloride, magnesite, zeolite, Lithium Montmorillonite and other resources of industrial significance in the salt lake. There are also a large number of special biological resources, such as halophilic algae, brine shrimp, spirulina, rotifer, etc., which have important economic value and scientific significance, as well as gene resources of drought and salinity tolerance. They have opened up a good prospect for human beings to obtain egg quality, natural food pigments, energy, a variety of industrial scientific materials and purify the environment, and to turn salt lakes into "good fields". At the same time, salt lake is an important tourism resource and medical resource. The heat storage characteristics of salt lake brine have been used in "solar salt pool" power generation.

Salt lakes are also natural environmental information and natural laboratories; they are also "carbon sinks" and "natural bioreactors". Salt lake deposits account for a large proportion of the world's land surface area, with a large number of carbonate deposits, which can delay the greenhouse effect related to human beings to a certain extent.

Four salt lakes

The four salt lakes in China are

Chaka Salt Lake

Located in Chaka Town, Wulan County, Haixi Mongolian and Tibetan Autonomous Prefecture, Qinghai Province, China, the lake is 3059 meters above sea level. The lake water is rich in sodium salt, the salt layer is thick, close to the lake surface, and the lake water has become dry. There is a branch line connecting Qinghai Tibet railway by the lake.

Chaerhan Salt Lake

Located in the south of Qaidam Basin, it straddles Golmud City and Dulan county. It is a salt lake in the west of Qinghai Province, China. It is composed of Dabson lake and salt ponds of South Hobson, North Hobson and senei, with a total area of 5856 square kilometers. It is the largest salt lake in China. Several inland rivers such as Golmud River and Qaidam river flow into the lake.

Yuncheng Salt Lake

Located in Yuncheng City, southwest of Shanxi Province, and at the north foot of Zhongtiao Mountain, it is the largest lake in Shanxi Province and the third largest sodium sulfate inland lake in the world. Geological research shows that Yuncheng Salt Lake was born in the period of Himalayan tectonic movement in Cenozoic tertiary, with a history of about 50 million years. It extends from northeast to southwest, with a length of about 30 kilometers and a width of 3-5 kilometers. The lake is 324.5 meters above sea level, and the deepest is about 6 meters, with a total area of 132 square kilometers.

Balikun Salt Lake

It is a famous salt lake in Xinjiang, located in Balikun Kazakh Autonomous County in the east of Xinjiang. The lake is slightly oval, about 9 km wide from east to west, 13 km long from north to south, covering an area of 117 square kilometers.

Classification of types

According to the main Hydrochemical Composition of lake water, there are carbonate type, sulfate type and chloride type salt lakes.

According to the types of salt minerals, there are not only the most common rock salt lake, mirabilite lake and natural alkali lake, but also gypsum lake, potassium magnesium salt lake, boron lake, lithium lake, and the world's rare nitrate (potassium) salt lake.

There are three main principles for the classification of Salt Lake types: first, according to the occurrence state of salt lake brine. Secondly, according to the main salt deposits of salt lakes; thirdly, according to the chemical composition of brine.

According to the occurrence state of salt lake brine, salt lake can be divided into brine lake, dry salt lake and Shaxia lake.

Brine lakes are characterized by the presence of surface brine in the lake basin throughout the year, while salt deposits are only found in some parts of the shore or lake bottom; the lake water rises and falls throughout the year, but there is always free surface brine in the lake.

The main feature of dry salt lake is that it is dry most of the year, and only in wet season can there be temporary surface brine. The dry salt flat on the bare surface is cracked due to the sun and strong evaporation, and the expansion of salt precipitation of underground brine, and the huge salt shell is formed due to the wind, rain and sun evaporation all the year round. Chaerhan is a huge dry salt lake.

Shaxia lake is a kind of Salt Lake characterized by no surface brine in the whole year. The water level of the intercrystalline brine is much deeper than that of the dry salt lake, and the water level is relatively stable because the brine seldom exchanges with the outside world. Only precipitation infiltration or salt autolysis can cause slight fluctuation of the water level. Another intuitive feature of Shaxia lake is that the top of its salt deposits is often covered with thick or thin floating soil and quicksand, and there is no surface runoff supply throughout the year.

According to the main salt sedimentary minerals, salt lakes can be divided into stone Salt Lake, mirabilite Salt Lake, alkali lake, borate salt lake and potassium magnesium salt lake.

According to the chemical composition of salt lake brine, it is the most widely used in China, which can be divided into carbonate type, sulfate type (including sodium sulfate subtype and magnesium sulfate subtype) and chloride type. The classification of brine chemical composition indicates the characteristics of lake water physicochemical action and water salt balance system.

Main components

The evaporation of salt lake water is greater than or at least equal to the precipitation and the recharge of surface groundwater. The concentration of Cl ⁻, so ₄⁻, HCO ₃⁻, Co ₃⁻, Na ＋, K ＋, Mg ＋, CA ＋ in the lake is very high, and the salt content is more than 24.7 ‰. The evaporation of Qaidam Basin in China is 2400-2600 mm, which is 30-50 times of the annual precipitation. The precipitated salts can be divided into new sedimentary salt, old sedimentary salt and solid salt according to their origin and morphology. Solid salt constitutes a salt mine area and is an important mineral resource.

Formation conditions

The formation of salt lakes requires certain natural conditions, the most important of which are as follows:

A dry or semi-arid climate. Under the arid or semi-arid climate conditions, the evaporation of the lake often exceeds the supply of the lake, the lake water is continuously concentrated, and the salt content is increasing day by day, which makes the various elements in the water reach the saturated or supersaturated state, and forms various kinds of salt deposits in the lakeshore and lake bottom. For example, the Qaidam Basin, which is 2600-3200 meters above sea level, is a typical inland desert basin. It is deeply inland, surrounded by continuous mountains, and under the influence of the westerly circulation in the middle latitude all the year round, the water vapor transport and precipitation are very scarce, and the air is dry. The annual precipitation of Chaka Salt pool in the northeast margin of the basin is about 210 mm, and that of Chaerhan Salt Lake in the center of the basin is only about 30 mm. The evaporation is far greater than the precipitation. This climate is obviously very favorable for the formation of salt lakes, so many salt lakes are distributed in the basin. If the climate is extremely dry, there is no rain all the year round, or there is little precipitation, it is also not conducive to the formation of salt lakes. For example, in the Taklimakan Desert and Gurbantunggut Desert of Xinjiang, it is difficult for these areas to form salt lakes because of the continuous sand dunes, no runoff on the surface, and scattered salt.

Closed terrain and a certain amount of salt and water supply. The closed topography makes the runoff in the basin flow to the lake, and the lake water does not leak out. The salt is continuously transported from the basin to the lake through the runoff. Under the strong evaporation, the lake water becomes more and more salty and salty. As time goes by, the salt lake is formed.

In the Salt Lake area, you can often see a ring of silver white salt belt around the lake, just like a beautiful collar on the salt lake. This natural phenomenon is a strong evidence for the migration of salt from the flowing domain to the salt lake. Because in the process of the migration of various salts dissolved in the water from the basin to the salt lake, the water gradually evaporates and the concentration increases. Once it reaches the saturated or supersaturated state, it will produce precipitation. However, due to the different solubility of various salts, there is a certain precipitation sequence. From the upstream of the material source to the salt lake, there is an obvious zonal distribution of various salt deposits. For example, in some salt lake areas at the northern foot of Kunlun Mountain, the area near the mountain is boron salt zone, the area near the lake is mirabilite zone, and the lake deposits salt and carnallite.

Salt lakes can be formed not only in the mainland, but also in the Gulf. The vast ocean has an average salt content of 35 grams per liter of water. If the bay is isolated from the ocean due to the gradual development and expansion of sand bars along the coast, and the climate is dry and hot, the salinity of the water body will continue to increase under the action of strong evaporation, and eventually salt lakes will be formed, resulting in various salt deposits. This kind of Salt Lake evolved from the bay is called Haicheng salt lake. The salt lakes in modern China belong to the Continental Salt Lakes. Salt lake is a peculiar landscape created by drought.

Distribution law

From the formation conditions of the salt lake, we can see

Chinese PinYin : Yan Hu