土壤表面电化学特征及其化学表现的研究

The project aims at a direct comparison of surface electrochemical characteristics and their chemical manifestations between variable charge soils and constant charge soils. The research consists of surface charge properties of representative soils, chemical kinetics between soil colloid and ions, chemical equilibria between soil colloids and ions, interactions between soils and protons (soil acidity), and interactions between soils and electrons (redox processes)..Two types of soils were used for the study. A Ali-Haplic Acrisol, a.Ferrali-Haplic Acrisol, a Rhodic Ferralsol, and a Hyper-Rhodic Ferralsol,collected from the subtropical zone of China, belong to the variable charge soils. A Haplic Luvisol, a Dystric Cambisol, a Dystric Luvisol and a Phaeozems, collected from the transitional zone and the temperate zone,respectively, belong to the constant charge soils. Variable charge soils are characterized by the high content of iron and aluminum oxides. The clay mineralogical composition is dominated by 1:1 –type minerals, such as kaolinite. These two factors make the surface charge properties of variable charge soils distinctly different from those of constant charge.soils of temperate regions, which chiefly contain 2:1-type clay minerals..Owing to the differences in clay mineralogical composition and.particularly in the kind, form, and amount of iron and aluminum oxides,.the quantities of surface charges as well as the changing pattern of these.charges with the change in pH are remarkably different. A fundamental.difference is that the quantities of surface charge of variable charge soils.are remarkably variable and that this characteristic feature has a profound.influence on many other properties of the soil, such as the ability to.adsorb anions. The surface charge density of the colloid fraction of.variable charge soils is lower than that of constant charge soils..Adsorption of ions is a direct consequence of the carrying of surface.charge for soils. Owing to the characteristics of variable charge soils in chemical and mineralogical compositions, these soils possess distinct amphoteric properties. Therefore, they can adsorb cations as well as anions. Generally, the interaction force between most cation commonly found in soils and the surface of soil particles during adsorption is.electrostatic in nature. However, owing to the characteristics of variable.charge soils, a specific force may also be involved in the adsorption of.some cations. The adsorption of such anions as chloride, nitrate, and perchlorate ions by variable charge soils is controlled chiefly by electrostatic force, in the adsorption some specific force may also be involved, at least for chloride ions. Such adsorption is related to both the nature of the anions and the properties of the soils.In the electrostatic adsorption of cations by variable charge soils there are a variety of characteristics that are different from constant charge soils. In particular, both the quantity and strength of adsorption vary with environmental conditions. Negative adsorption may also occur.Such a phenomenon can never occur in constant charge soils. These.features are determined by the particular nature of the surface of variable charge soils.The effect of ionic strength on adsorption and desorption of Cu2+ions in variable charge soils and constant charge soils are remarkably different. The adsorption of Cu2+ ions in constant charge soils decreases with the increase in ionic strength. The effect of ionic strength on the adsorption of Cu2+ ions in variable charge soils is smaller than that in constant charge soils. If the content of iron oxide in variable charge soils is sufficiently high, the adsorption of Cu2+ ions increases with the increase in ionic strength. The Cu2+ ions adsorbed by constant charge soils can be desorbed by electrolyte solution, but cannot be desorbed by de-ionized water. However, a part of the Cu2+ ions adsorbed by variable charge soils can be desorbed b

研究可变电荷土壤与恒电荷土壤的电化学特征及其化学表现，直接对它们的表面化学性质进行比较，建立起较全面的土壤化学体系。通过对土壤的表面电荷性质、土壤与离子间的反应平衡、土壤与离子间的动态反应、土壤与质子间的反应、土壤与电子间的反应等研究，更有效地为土壤管理、合理施肥、防治土壤污染、提高土壤肥力与土壤质量及其持续利用服务。

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