Kinetics of Zinc Ageing in Typic Torriorthent and Typic Haplocalcid Soils

Document Type : Original Article

Abstract

THIS STUDY aimed at investigating the kinetics of Zn-ageing in .... two arid soils of Egypt. It also introduced the curve-analysis models, beside of the commonly used adsorption-isotherm models for describing Zn-retention data of these soils. To reach these goals, samples of Typic Torriorthent and Typic Haplocalcidsoils, with or without Fe and/or Zn salts, were incubated under the laboratory conditions for 28 days. AB-DTPA-Zn was determined in soils during different time periods through out the experiment. Cumulative Zn-retention data were calculated and fitted using different kinetic models. Another sorption experiment was conducted by shaking soil portions with a series of standard Zn solutions and the obtained supernatants were analyzed for Zn. The retention data were calculated and fitted using curve analysis models and adsorption isotherm models. The results show that application of Fe singly or in combination with Zn increased AB-DTPA-Zn significantly. This occurred up to 24hr after application and decreased afterwards. Parabololic diffusion seemed to be the rate limiting step in the Typic Torriorthent soil up to 336hr afterwards simple Elovich function was the best fitting model while the first order model was the best fitting model in the Typic Haplocalcid soil. Curve-analysis suggests that Zn retained in Typic Torriorthent soil probably occurred due to specific and non-specific adsorption on heterogeneous sites; whereas Zn retained in Typic Haplocalcid soil probably occurred due to adsorption followed by precipitation reactions. Finally, curve analysis models could successfully explain Zn-sorption isotherms acting together in soil, while further calculations are needed for explaining the consecutive Zn-sorption isotherms.

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History

  • Receive Date: 31 July 2013
  • Revise Date: 27 August 2013
  • Accept Date: 28 August 2013

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