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(38-30) Effect of the pH on the adsorption of prometryn on Hungarian soils. Földényi, Rita1, Ertli, Tímea*,1, Décse, Zsuzsa1, 1 University of Veszprém, Veszprém, Hungary ABSTRACT- The concentration of hydrogen ion can influence the movement of pollutants in the soil. Concerning the environmental fate of pesticides the study of the effect of pH on their adsorption is important. Static equilibrium experiments were carried out with prometryn, a slightly soluble s-triazine type herbicide. Typical Hungarian soils were used as adsorbents (chernozem, brown forest and sandy soil). Hydrogen ion concentration was set to the values occurring in the nature (pH 5, 7 and 8) by 0.01 mol/l phosphate buffer. The analysis was carried out by liquid chromatography (RP-HPLC) and UV spectrophotometry. The results measured by HPLC approximately correspond to those of UV referring to good applicability of this method. Adsorbed amounts were calculated from the equilibrium concentration of the compound. Even the calibration of prometryn is pH-dependent which is caused by the structure of the molecule. The isotherms consist of more steps referring to various types of active sites. The pH-dependency is apparent but its degree is significantly influenced by the properties of the soils. The higher the pH the more humic substances are dissolved in the aquatic phase which leads to better solubility of prometryn in water. It contributes to the difference between the isotherms formed at various pH values. The properties of the adsorbent as well as those of the adsorbate are modified by pH resulting in other type of interactions. In acid media higher amounts of prometryn are bounded on the soils than at basic pH values. It was experienced in our adsorption studies of another slightly polar herbicide (isoproturon), too. These results corroborate the significant influence of the pH on the mobility of pesticides in the environment. Key words: herbicide, prometryn, adsorption, soil |
