ABSTRACTThermodynamic parameters (δF, δH, and δS) governing the adsorption of zinc were determined in soils that differed in physical and chemical properties. The adsorption of zinc in these soils conformed to the linear form of the Langmuir equation. The adsorption maximum, a constant related to bonding energy and differential buffering capacity of soils for zinc, was calculated from the experimental data. The sequential desorption of sorbed zinc by indifferent electrolytes, complexing agents, and acids provided a measure of different chemical pools of zinc in these soils. Higher values of entrophy change in Faridkot sandy loam and Laungowal loam than in the other two soils suggest the possibility of specific adsorption of zinc in these two soils. The adsorption maxima of Zn were related to the clay contents of these soils. Similarly, the differential buffering capacity of zinc in these soils also shows a relationship with their clay contents. A supply parameter combining the quantity, intensity, and buffering capacity of zinc was calculated from the experimental data, and it provides a relative measure of the Zn-supplying capacity of soils. A highly significant relationship between the supply parameter and the uptake of zinc by wheat was noted. The cumulative desorption of Zn was inversely related to the differential buffering capacity of these soils.
Thermodynamic parameters (δF, δH, and δS) governing the adsorption of zinc were determined in soils that differed in physical and chemical properties. The adsorption of zinc in these soils conformed to the linear form of the Langmuir equation. The adsorption maximum, a constant related to bonding energy and differential buffering capacity of soils for zinc, was calculated from the experimental data. The sequential desorption of sorbed zinc by indifferent electrolytes, complexing agents, and acids provided a measure of different chemical pools of zinc in these soils. Higher values of entrophy change in Faridkot sandy loam and Laungowal loam than in the other two soils suggest the possibility of specific adsorption of zinc in these two soils. The adsorption maxima of Zn were related to the clay contents of these soils. Similarly, the differential buffering capacity of zinc in these soils also shows a relationship with their clay contents. A supply parameter combining the quantity, intensity, and buffering capacity of zinc was calculated from the experimental data, and it provides a relative measure of the Zn-supplying capacity of soils. A highly significant relationship between the supply parameter and the uptake of zinc by wheat was noted. The cumulative desorption of Zn was inversely related to the differential buffering capacity of these soils.
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