Progresses in Research on Surface Acid-Base Properties of Variable Charge Soils and Their Models
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National Key Research and Development Program of China(No. 2016YFD0800404)and the National Key Basic Research Program (No. 2014CB441002)

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    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 (Ds), point of zero charge (pHpzc), , and equilibrium constants of protonation and proton abstraction (pKa). 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. pHpzc is mainly obtained through macro-titration, but needs to be continuously optimized thorough experiments to reduce the impacts of meaningless factors, while Dsand pKa 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- pKa to n-site/n- pKa. 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

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CHENG Pengfei, WANG Ying, LI Fangbai, QIN Haoli, PENG Yemian, LIU Tongxu. Progresses in Research on Surface Acid-Base Properties of Variable Charge Soils and Their Models[J]. Acta Pedologica Sinica,2019,56(3):516-527.

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History
  • Received:June 07,2018
  • Revised:August 17,2018
  • Adopted:November 12,2018
  • Online: April 10,2019
  • Published: