【摘要】 可变电荷土壤表面酸碱性质是指土壤与质子的结合能力,主要包括表面质子反应活性位点密度Ds、电荷零点pH_pzc以及质子化、去质子平衡常数pK_a。表面酸碱性质对于评估土壤酸碱缓冲能力、揭露酸化机制有重要意义,也是探究阳离子和阴离子在土壤固液间的分配,控制微量元素移动性和生物有效性的重要土壤性质之一。本文综述了通过表面络合模型获取表面酸碱性质参数的方法以及研究复杂土壤体系的两种方法。电荷零点pH_pzc主要通过宏观滴定实验获得,但需要不断优化实验操作来减少无意义因素的影响。而表面质子反应活性位点密度D_s和质子化、去质子化平衡常数pK_a,则通常分别通过Gran函数和直线外推法计算等方法得到。目前,土壤活性成分金属氧化物、黏土矿物及腐殖质表面酸碱性质已通过表面络合模型得到广泛研究,研究方法和相关数据已逐渐趋于完善。而随着表面络合模型的发展,土壤混合体系表面酸碱性质的研究也在不断加深。组分添加法通过各组分表面性质的加和来预测质子在土壤和溶液中分配和形态,目前已从矿物聚合模型扩展到矿物-有机物聚合模型,因为有机物和矿物组分之间的相互作用对于研究相当重要。而广义复合法假设土壤表面性质均一,依据实验吸附数据和表面积拟合获得表面酸碱性质,现在已发展为n-site/n-p Ka,并建立了一种通过土壤化学性质预测表面酸碱性质广义回归方程。最后,文章探讨了表面络合模型相关研究应该解决的科学问题,以及土壤表面酸碱性质研究在未来的趋势。更多还原

【Abstract】 Surface acid-base properties of variable charge soils refer to ability of the soil to bind protons, mainly involving density of surface proton reaction active sites（D_s）, point of zero charge(pH_pzc), and equilibrium constants of protonation and proton abstraction（pK_a）. Surface acid-base properties are important indices of great significance to evaluation of acid-base buffering capacity of soils and exposition of mechanisms of soil acidification. Meanwhile, they are also one of the soil properties that are important to exploration of distribution of cations and anions in the soil solid-liquid interface and control of mobility and bioavailability of soil micro-elements. This paper presented a review of approaches to acquisition of the parameters of surface acid-base properties using the surface complexation model（SCM）, and the two methods of studying complex soil systems. pH_pzc is mainly obtained through macro-titration, but needs to be continuously optimized thorough experiments to reduce the impacts of meaningless factors, while D_s and pK_a are usually worked out separately with Gran function and linear extrapolation. At present, extensive researches have been done on surface acid-base properties of soil active component metal oxides, clay minerals and humus with research methods and relevant data approaching perfection. Charge Distribution Multisite Complexation Model（CD-MUSIC） and Non-ideal Competitive Adsorption-Donnan（NICA–Donnan） have been established to describe ion adsorption on minerals and organic matter, separately. With the development of SCM, the research on surface acid-base properties of the complex soil systems or natural soil systems is going on in depth. The component addition（CA） and generalized composite（GC） approaches are recommended for use to simulate the properties of soils. CA is used to predict distribution and morphology of protons in soils and soil solutions by adding up surface properties of various components, and its use has extended from the mineral polymerization model to the mineral-organic polymerization model, because the interaction between the organic and mineral components is very important to the research on natural systems. An LCD model, combining the CD–MUSIC and NICA–Donnan models into a mechanistic framework, is introduced for description of sorption of organic matter to the surface of minerals, and ions binding the two. Furthermore, GC assumes that the surface properties of the soil are uniform and can be obtained by fitting the experimental adsorption data and the surface area. Quality of the fitting depends on how detailed the surface information is, and the GC has developed from 1-site/1-pK_a to n-site/n-pK_a. Besides, a generalized regression equation is recommended for prediction of acid-base properties merely based on basic chemical properties. Finally, the paper further explores scientific issues that need to be solved for researches related to surface complexation models and future trends of the research on acid-base properties of soils.更多还原