Effect Of Salinization On Physical And Hydrodynamics Characteristics

This study showed the basic physical and chemical properties and hydrodynamics characteristic of the saline soil with the profile and simulation tests, also to explore the effect factors and the laws of salts leaching of saline soil. The main conclusions are as follows:The topsoil congregative type of the saline soil profile of lakeshore in the arid and semi-arid region inland was the majority. 50 cm deep from the surface, there was a heaby clay loam layer of 4cm, and its physical and chemical properties obviously different from the other layers. The soil particle composition and organic matter content were well-distributed except this clay loam layer. Higher soil bulk density, higher initial water content, higher salts content, higher pH value of the surface layer, and higher soil bulk density, higher initial water content, lower salts content, lower pH value of the bottom layer. Each index correlated strongly. Soil bulk density was very significantly positively correlated with soil initial water content, pH value was significantly positively correlated with soil particle composition, significantly negatively correlated with clay content, organic matter content was significantly correlated with soil particle composition, especially very significantly positively correlated with clay content.Hydraulic saturated conductivity of saline soil profile was between 0.14cm/h and 4.76cm/h, which was low permeable intensity. It was low in the surface layer and bottom layer, but high in the middle layers. Hydraulic saturated conductivity of saline soil profile was significantly negatively correlated with the soil initial water content and soil bulk density. The van Genuchten model and Mualem model simulated the soil water characteristic curve of every layers in the saline soil profile well. The water holding capacity was best of the surface layer but worst of the bottom layer.The constant waterhead experiment of salinesoil showed that hydraulic saturated conductivity of saline soil changed periodicity with water supply process. It decreased gradually, then became stable and then fluctuated. It fluctuated gently with the increase of the initial water content. Hydraulic saturated conductivity of saline soil decreased with the increase of the initial water content, and the correlation was significant liner negative correlaton. With the increase of the initial water content of the saline soil, pH value decreased but conductivity increased of the leaching liquid. With the increased of the hydraulic saturated conductivity, pH value increased but conductivity decreased o f the leaching liquid, and both were logarithmic related to hydraulic saturated conductivity. In long-term flooded conditions, hydraulic saturated conductivity of saline soil reduced smoothly, and effect of salts leaching became worse.The study with interior control simulation experiment of different salinization types and degrees showed that the physical and chemical properties of soil were different but also related. Effects of salinization on pH value of the soil were different. With the ration of [HCO₃^-+CO₃2^-] / [SO₄^2-+Cl^-] increased, pH value of the soil increased and alkalinity stronger; for solonchak, pH value of the soil changed smoothly with the increased of the ratio of [Cl^-]/[SO₄^2-]. Effects of salinization on conductivity of the soil were similar. Conductivity increased with the salts content increased gradually, and this trend was more obvious in the soil layers of high salts content; conductivity of alkaline soil was lower than that of solonchak. Hydraulic saturated conductivity of saline soil was very low, and it decreased with the increase of salts content. The relationship of hydraulic saturated conductivity and salts content was power when salts content was in the rage of 0.5﹣12.0 g/kg, exponentiation when salts content was in the rage of 0.5﹣7.0 g/kg. Soil water holding capacity were similar of five types of salinization with salts content. It increased with the increase of salts content.There were three main reasons to the poor salts leaching of saline soil. Firstly, high salts content, high sand content, low organic matter content, high soil bulk density and high soil initial water content in surface soil layer resulted in a tight structure and low porosity, which holding back the migration of water and salts; Secondly, the low hydraulic saturated conductivity of saline soil, especially in the surface and bottom layer, decreased the salts leaching; Thirdly, high soil water absorbing capacity, high soil water holding capacity and low soil water drainage capacity influenced the salts leaching.