The so-called salinity is the weight percentage of all inorganic salts present in 1 kg of water. A more accurate definition is：Convert all carbonates to oxides in 1000 grams of seawater, convert all bromides and iodides to chlorides, and completely oxidize all organic matter. The sum of the solid matter contained in it is g/kg, or ‰To represent.

The average value of salinity in the oceans of the world is 35‰ at a temperature of 25℃. Of course, there are certain differences in the salinity of different waters around the world. This is mainly affected by the temperature and the distance from the land. For example, the Bohai Sea in China is surrounded by land on three sides, and its salinity is 25‰~29‰, the East China Sea and the Yellow Sea are 30‰~32‰, and the South China Sea is 34‰.