Mechanism Of Crystallization On Saturated Chao Soil Surface

On the basis of referring to a lot of liytrature search of both domestic and abroad, it is found that there are many researchers have studied the mechanism of crystallization, and through the theoretical analysis and experiment research, they have made quite a number of achievements in the field of the principle of water and salt movement in the soil. However, there exists an amount of space on the study of soil surface variation. Based on the past researches, a series of experiments were conducted with Chao soil which distributs widely in Jiangsu Province Coastal region, analyzed and summarized the mechanism of crystallization on saturated Chao soil surface deeply by using these measuring methods, "water absorption paper method", "direct method" and "sampling method".Through the simulation column experiments, the main contents and findings of this dissertation are listed as follows.1. From the view of microcosmic and macroscopic, using the visualization method by microscope, the whole process of surface crystallization was observed, and divided into two phases, named horizontal growth and vertical growth. In the first phase, crystallized salt would occur and cover the entire soil surface; nevertheless the crystallized salt in the second one will accumulate and grow vertically in the form of branching.2. Considering all of the varies factors, the rule of crystallization on saturated Chao soil surface was analyzed out. The surface salt concentration was measured by the water absorption paper method, and the results showed:while the condition that the surface salt concentration reached to saturate was satisfied, crystallized salt would appear and accumulate on the soil surface. Using the direct method, the crystallized salt mass at different time was obtained, with the longer elapsed time; we got the higher value, which is in line with the experimental phenomenon. In addition, the vertical profile of salt concentration in the top 0.01m-soil layer was gained in details through the sampling method, comparing three sets of results, it is indicated that the salt concentration near the surface attained saturated.3. Based upon the research of Terasaki (2009), through a great deal of experiments, it is proposed a new technique to measure the surface salt concentration-water absorption paper method, and the measurement value showed a good agreement with the phenomenon, which confirmed the measurement accuracy, was satisfactory. This method has already been adopted by others.4. Comparing all of the results and phenomenon, it was included that, there existed a close connection between evaporation and surface crystallization; both of them were interrelate, interdependent and mutual-constraining. Evaporation can accelerate the accumulation of salts; conversely, through reducing the surface vapor pressure, accumulated salts on the soil surface also can affect the evaporation rate.