【作者】 罗从双；

【导师】 韩文峰； 谌文武；

【作者基本信息】 兰州大学 ， 地质工程， 2010， 博士

【摘要】 世界范围内每分钟有lOha的土地遭到破坏,其中有3ha是由于盐化造成的。全国每年因盐化废弃的土地约25万hm2,农林牧用地受盐化危害的土地面积有3630万hm2。中国土地盐化造成的净经济损失年平均为129亿元,盐化土地综合治理共需投资约660亿元。地球的面积是14亿km2,97.5%的面积是盐水,只有一少部分是可以直接应用的。水资源和土地资源是社会发展的两种基本资源,是国家的基础,经济的根基。所以,防止水、土的进一步盐化,治理改良现有的水、土盐化是势在必行的一项长期工程。祖厉河流域水、土盐化问题,已经严重制约着本地区的发展,影响人们的正常生产和生活。祖厉河多年平均含盐为7264mg/L,居全国之冠,是世界平均值(100mg/L)的73倍。祖厉河流域冬季多年温度为0℃--11.9℃范围内,平均日最低气温≤0℃的天数150-200天,有着丰富的冷能资源,可为冷冻法淡化本地区的咸水提供能源。本文研究分析祖厉河流域的水、土的盐化成因及咸水的冷冻淡化研究,可为本地区水、土盐化防治提供依据,利用本地区的自然条件淡化盐水资源,丰富本地区供水需求。论文的主要研究内容及成果如下：(1)搜集祖厉河流域的气候、水文、地形地貌、地质构造、人文等基础资料,开展流域内水、上的盐化调查,选取流域内具有代表性地点进行取样(水样,上样)分析,通过实验研究水、土的盐分变化规律。从气候、地质、地形地貌等自然因素和人为因素的角度探讨祖厉河流域水、土盐化的成因。祖厉河流域内水、上盐化是水、上、盐的耦合过程。流域内母岩富含盐分,风化形成的上体中必然含有大量的盐分,在长期的蒸发量大于降水量的条件下,使土体的盐分富集到土壤表层,引起土壤的盐化；流域内的水体含盐量高,耕地长期灌溉这种咸水,导致土壤次生盐化。流域地处干旱区,降雨少而且多以暴雨形式出现,致使流域内水土流失特别严重,表面盐化的土壤被侵蚀冲刷汇流到水中,土壤的盐分溶解汇集到水中,造成流域内的水不断盐化。流域内人类活动是造成水土次生盐化的主要因素。(2)分析咸水淡化方法的优劣性,冷冻法净化咸水受多种因素的影响,本文主要分析冷冻过程中各种影响因素与脱盐的关系,通过研究,随着冷冻温度的降低和咸水矿化度的增加,脱盐率呈下降趋势；种冰对脱盐率没有明显影响,而种冰能促使水样结晶,抑制水样的过冷现象；水样初始温度对脱盐效果影响不大；随着冷冻容器表面积的增加,脱盐率呈下降趋势。(3)在冷冻法净化苦咸水过程中,由于人为原因或是各种影响因素的作用都会导致冰晶中含有一定量的盐分,导致冰晶质量不高,甚至达不到淡化目的。通过研究,冰晶中的盐分都是以盐泡的形式存在冰晶当中,为了进一步净化冰晶,本文采用碎冰离心的方式对冰晶做进一步处理。经研究发现,碎冰离心打破了冰晶中盐泡的屏障,通过离心脱水的方式使夹在冰晶中的盐分被很好地分离出来,从根本上达到脱盐的目的。采用碎冰离心可以弥补冷冻过程中自然因素和人为因素导致高浓度水样脱盐效果差的不足,而且此种方法对冰晶的脱盐效果是随着冰晶浓度的增高而增高。更多还原

【Abstract】 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.更多还原