Supported by the National Natural Science Foundation of China (Nos.42077016 and 4187703) and the Local Innovative and Research Teams Project of the Guangdong Pearl River Talents Program of China (No. 2017BT01Z176)
Compared with the constant charge soils that distribute in temperate regions, the variable charge soils in tropical and subtropical zones are unique soils, with highly variable particle surface charges. Investigations on the surface chemical characteristics of variable charge soils have received considerable attentions. The potentiometric acid-base titration method is the most straightforward approach to qualitatively and quantitatively identify the surface chemical characteristics of variable charge soils. In this paper, the characteristics of variable charge soils are briefly described and the concept and difference of point of zero charge (PZC) is described and classified according to (i) the conditions for surface charge measurement, (ii) the modes of expression for PZC, and (iii) measurement methods for surface charge of soil colloidal particles. On this basis, the influence of the acid-base potentiometric titration setup conditions on the observed PZC, including co-existing ions, ionic strength of the solution, pre-equilibrium time, titration ranges, reaction atmosphere and titration method, is summarized and discussed. Furthermore, the research progresses on the application of potentiometric titration combined with surface complexation model (SCM, including diffuse layer model, basic stern model, triple layer model and distribution multi-site complexity and so on) to analyze the acid-base buffering capacity of variable charge soils were further summarized. Moreover, how related factors such as clay mineral composition, metal oxides, organic matter and other factors, affect the acid-base buffering capacity of variable charge soils are discussed. We believe that future studies on the variable charge soils could be carried out with the hope to:(1) establish a typical acid-base potentiometric titration method for all types of soils; and (2) verify if the combination of various surface complexation models could accurately quantify the acid-base buffer capacity of variable charge soils. It is hoped that this review can help soil science beginners to understand the basic concepts of variable charge soils, invite more researchers to pay more attentions to variable charge soils, and further encourage sustainable utilization of soil resources.
温晓翠,李九玉,宋洁,陶亮.电位滴定法研究可变电荷土壤表面酸碱性质的进展[J].土壤学报,2022,59(4):910-923. DOI:10.11766/trxb202010090558 WEN Xiaocui, LI Jiuyu, SONG Jie, TAO Liang. Research Progress on the Acid-base Properties of Variable Charge Soils Using Potentiometric Titration[J]. Acta Pedologica Sinica,2022,59(4):910-923.复制