Time-dependent zinc desorption in soils

Time dependent zinc (Zn) desorption in eight benchmark soils of India was studied in relation to various pH values and ionic strengths. Soil samples were equilibrated in solutions containing 10 μg Zn g -1 soil at pH 5.5,6.5, and 7.5 for 48 h at 25±2°C, and adsorbed Zn extracted with calcium chloride...

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Bibliographic Details
Published in:Communications in soil science and plant analysis 2000-09, Vol.31 (15-16), p.2547-2563
Main Authors: Rupa, T. R., Tomar, K. P., Reddy, D. Damodar, Rao, A. Subba
Format: Article
Language:English
Subjects:
Agronomy. Soil science and plant productions
Biological and medical sciences
Chemical, physicochemical, biochemical and biological properties
Fundamental and applied biological sciences. Psychology
Mineral components. Ionic and exchange properties
Physics, chemistry, biochemistry and biology of agricultural and forest soils
Soil science
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Summary:Time dependent zinc (Zn) desorption in eight benchmark soils of India was studied in relation to various pH values and ionic strengths. Soil samples were equilibrated in solutions containing 10 μg Zn g -1 soil at pH 5.5,6.5, and 7.5 for 48 h at 25±2°C, and adsorbed Zn extracted with calcium chloride (CaCl 2 ) for various periods of time. Desorption of Zn decreased with increasing pH, and the desorption rate decreased abruptly at pH 7.5. In contrast, an increase in the equilibration period and ionic strength of the background electrolyte increased Zn desorption. Four rival kinetic models were fitted and evaluated for their suitability for describing the Zn desorption process. Reaction rate constant (ß) calculated from the Elovich model for the different soils ranged from 9.99 to 25 (mg Zn kg -1 ) -1 . The different kinetic models tested indicated that Zn desorption in soils was a diffusion controlled process. The desorption was rapid in the first 4 h, followed by slower phase in the rest of the time at all the pH values indicating a biphasic desorption, characteristic of a diffusion controlled process. The ß value for the Elovich equation showed a strong association with soil clay content and cation exchange capacity (CEC). Further, the best prediction of Zn desorption reaction rate constant could be made using multiple-regression equation with soil clay content and CEC as variables.
ISSN:0010-3624
1532-2416
DOI:10.1080/00103620009370608