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Miscible Displacement, Sorption and Desorption of Atrazine in a Brazilian Oxisol

^a Escola Superior de Agricultura "Luiz de Queiroz"/Universidade de São Paulo, Caixa Postal 09, CEP: 13418-900, Piracicaba, São Paulo, Brazil
^b Institut für Chemie und Dynamik der Geosphäre, ICG-IV, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

View larger version (14K): [in a new window]   Fig. 1. Molecular structure and some physicochemical properties of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine]. * denotes position of the 14C.

View larger version (9K): [in a new window]   Fig. 2. Sorption (circles) and desorption isotherms (diamonds) of atrazine in a Brazilian Rhodic Oxisol collected from no-till or conventional agricultural management systems. Lines are fits of the Freundlich model to the sorption (dashed line) and desorption (full line) isotherms.

View larger version (24K): [in a new window]   Fig. 3. Measured and fitted breakthrough curves of Br- and atrazine in a Brazilian Rhodic Oxisol collected from no-till or conventional agricultural management systems.

View larger version (43K): [in a new window]   Fig. 4. Measured and predicted distribution of the radioactivity in the different fractions in the soil columns, packed with a Brazilian Rhodic Oxisol collected from no-till or conventional agricultural management systems, after leaching experiments with 14C atrazine. 100% of radioactivity corresponds with the total applied radioactivity. (Horizontal lines below the bars represent the standard deviation of the total resident radioactivity in the three replicate soil columns.)

View larger version (17K): [in a new window]   Fig. 5. Relative amounts of radioactivity characterized as atrazine and its metabolites in the leachate from soil columns packed with a Brazilian Rhodic Oxisol collected from no-till or conventional agricultural management systems. 100% of radioactivity corresponds with the total radioactivity in the leachate. (ATZ, atrazine; HA, hydroxyatrazine; DEA, deethylatrazine; DIA, deisopropylatrazine. Vertical lines represent the standard deviation of the percentages in the three replicates.)

View larger version (24K): [in a new window]   Fig. 6. Relative amounts of radioactivity characterized as atrazine and its metabolites in the desorbed and extracted fraction at different depths in the soil columns packed with a Brazilian Rhodic Oxisol collected from no-till or conventional agricultural management systems. 100% radioactivity corresponds with the total radioactivity detected in a certain fraction at a certain depth. Horizontal lines represent the standard deviation in the three replicates.