Adsorption-desorption of atrazine on four soils of Hyderabad |
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| Authors: | Saroja Raman M Krishna P Chandrasekhar Rao |
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| Institution: | 1. A.P. Agricultural University, Rajendranagar, 500030, (A.P.), Hyderabad, India
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| Abstract: | The adsorption-desorption equilibrium of atrazine (2-chloro, 4-ethylamino, 6-isopropyl amino-1, 3, 5 triazine) was studied by the batch equilibration method at 27 ± 1 °C on four soils of Hyderabad. Adsorption isotherms conformed to the Freundlich equation (A = KC1/n ). K increased in the same order as the organic C content of the soils. Desorption studies were conducted by repeated replacement of 5 mL of the supernatant equilibrium solutions after adsorption, with 0.01 M CaCl2. Desorption isotherms showed considerable hysteresis which was more prominent when the desorption was carried out with higher adsorbed concentration of atrazine. Desorption from the lowest level of adsorbed atrazine (3 to 5 μg g?1 soil) was close to the adsorption isotherm. The cumulative desorption after four desorption steps covering five days was significantly different at the 1% level, for different initial adsorbed concentrations of atrazine. Desorption was significantly higher at the lowest adsorbed level of atrazine. The soils differed significantly at 6% level for desorption and the amount desorbed decreased in the inverse order of organic C. Desorption isotherms also conformed to Freundlich equation but K andn values were both higher than that for adsorption and increased with increase in initially adsorbed concentration of atrazine. Desorption thus confirmed the irreversible nature of the adsorption of atrazine on these soils. The quantitative factors and reasons for desorption are discussed. |
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