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Evaluation of Soil Surface Charge Using the Back‐Titration Technique
Author(s) -
Ge Ying,
Hendershot William
Publication year - 2004
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2004.8200
Subject(s) - surface charge , titration , adsorption , chemistry , cation exchange capacity , soil water , charge density , dissolution , phase (matter) , analytical chemistry (journal) , ion exchange , ion , soil science , inorganic chemistry , chromatography , geology , physics , organic chemistry , quantum mechanics
Variable surface charge ( Q v ) is one of the most important soil properties controlling ion adsorption on the soil solid phase. In this study, the back‐titration technique was used to determine the Q v of soils with a wide range of properties. The procedure defines the Q v as the OH − consumption by surface reactions corrected for dissolution of the solid phase and other solution reactions (e.g., metal hydrolysis). The Q v , varying from 0 to 80 cmol c kg −1 , was dependent on the pH of the soil suspension and the amount of soil organic matter. We used the non‐ideal competitive adsorption (NICA)–Donnan model to simulate the surface charge, assuming a bimodal distribution of H + affinity on the soil solid phase. With the charge data and Microsoft Excel, the NICA‐Donnan model parameters were optimized. The model provided an excellent fit to the experimental data. When the pH was below 8, the surface charge was dominantly distributed to the Type 1 sites; the Type 2 sites started to contribute to the total surface charge at pH > 8. Multiple linear regressions showed that the charge maxima ( Q max ) of the two sites were related to soil cation‐exchange capacity (CEC) and organic C (Org. C); these significant statistical relationships may be used to estimate the surface charge of soils using values of commonly measured soil parameters.