The amount and proportion of dissolved salts in natural water are different, but there are certain rules and characteristics. For example, in seawater and brine, most of the ions are Cl- and Na+; in the gypsum water, most of the ions are Ca2+, S "one; the purpose of classifying natural water is to judge the characteristics of the salts contained in the water. Commonly used in the classification method proposed by O·A Alejin, according to the principle of distinguishing between cation and anion and the principle of distinguishing between ions, the anions (in mmol/L) which are the majority in natural water are divided into three categories (see Figure 1). -10) bicarbonate brine (HCO3 + CO2-3, symbol C>, sulfuric acid brine (SO4-", symbol S> and chloride water (Cl-CD, symbol Cl). The cation (in mmol/L) is pressed Ca2+, Mgz+, and N a+ are divided into three groups, and the type of sleep is determined according to the content relationship between them.
(1) Type I. The water is characterized by a ratio of HCO3 > Ca2 ten + Mg2, which contains a large amount of Na+ and K+, and is alkaline soft water.
(1) Type II. It is characterized by a ratio of HCO3 < Ca2+ ten Mg2 ten < HCO3 + SU4, and most of the rivers, lakes and some medium-salt groundwater with low salinity belong to this type.
(2) Type III. The water is characterized by a ratio of HC to ten s with a Na+, typically seawater and high salinity groundwater.
(3) Type IV. Water is characterized by a ratio of HC03 =0, which is acidic water, which is rare in natural water.
To indicate the characteristics of the water chemistry classification, use the induction description. Such as CcaII (bicarbonate, calcium group, type III), s19 (sulfate, sodium group, type III),
According to the Alejin classification, there are 13 types of surface waters in China, among which five kinds of waters, such as calcium bicarbonate, sodium bicarbonate, calcium sulfate, sodium sulfate and sodium chloride, are of the main type. The surface water has the widest distribution area of ​​bicarbonate water, accounting for 78l of the total water area of ​​the country. The Loess Plateau such as Shaanxi-Gansu-Ningxia, the salt-soil area of ​​the Haihe Plain, the non-lithi-coastal coastal waters and the local salt lake are affected. Most of the rivers are sodium chloride or sulphate water, and the distribution area accounts for 17 latitude and 1% of the national water body area. There are three types of water, including bicarbonate, chloride and sulfate, which account for about 4% of the national area. The dominant cation of surface water in China is calcium, accounting for 67%, followed by sodium (potassium plus sodium), accounting for 3100, and a small amount of magnesium, accounting for about 2%.
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