| There is about 10ha of land which is spoiled every minute all around the world, within which about 3ha is due to salinization. In China, about 2.5×105 hm2 land was spoiled each year, and about 3.63×108 hm2 of land which is used for grazing,forest and agriculture are suffering salinization. The net economic loss caused by salinization is 129 million every year in China, and 66 billion yuan are invested for the restoration of the salinized soil.97.5% of the of the earth's surface is covered with salt water, only a small part can be drunk directly. Water and land are two basic resources for social development. Therefore, to prevent the continuing salinization of water and soil, long-term restoration work is need.Zuli River Basin is suffering severe water and soil salinization, which greatly restrict the development of the region. The average salt concentration of Zuli River for many years is 7264mg/L, which is the maximum value in the nation, and is 73 times as high as the world average level (100mg/l). In the present study, the reason of the water and soil salinization was analyzed, and we also conducted study about purifying of the brackish water using the freezing method. The study aimed to help control the water and soil salinization in this area by taking advantage of the natural conditions, purify the brackish water, thus improve the clean water supply.The main study contents and results are as follows:(1) The main study contents includes:collecting information of climate, hydrology, geomorphology, geological structure and culture in Zuli River Basin; investigating the situation of water and soil salinization; selecting representative samples (water and soil) sites in the basin; analyzing the changing rules of water and soil; finding out the reason of water and soil salination based on the climate, geology, topography and other natural factors and human factors in Zuli River Basin. The water and soil salinization is a process of coupling of water, soil and salt. The rock is rich in salt, so the soil that originate from the rock contains a lot of salt.Under the situation of higher evaporation and lower rainfall, the salt of soil can be concentrated in the surface soil, leading to soil salinization. Because the water has higher salt concentration in the basin, long-term irrigation with the water also lead to soil salinization. Zuli river basin is located in arid areas, lower rainfall, most of which is in the form of heavy rain, would cause serious soil erosion. The surface soil can be washed into the water, thus cause the water salinization in the basin.(2) In the present study, the advantages and disadvantages of desalination methods were analyzed. The freezing process was affected by many factors. In the study, the relationship between the factors and desalination rate in the process of freezing was analyzed. The results showed that with the decrease of freezing temperature and increase of the concentration, the desalination rate reduced. The seed ice had no effect on the desalination rate, but it could generate extra ice crystals, resulting in no super-cooling. The influence of initial temperature on the quality of ice was not notable. With the increase of the surface area of the freezing containers, the desalination rate decreased.(3) Because of both the human and other factors, salt can be entrapped into ice crystals in the freezing process, resulting in low quality of ice crystals. It was found out that the salt was trapped in ice in the form of brine pockets. To further purify the ice crystals, the method of crushing ice and centrifugation was introduced. The result showed that the method can further improved the quality of ice by breaking the "ice-salt pocket" and releasing the brine. On the other hand, when the concentration of ice crystals was higher, the desalination rate was higher.
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