Study of the behaviour of azinphos-methyl in a clay mineral by batch and column leaching

Research efforts dealing with the processes affecting the transport of pesticides in soils are needed in order to prevent further damage of surface and groundwater reserves. Although organic matter has been recognised as the most important contributor to the adsorption of non-ionic organic pesticides in soils, in some cases clay minerals may have an important role in the retention of these compounds. The present study was designed to improve the knowledge of the behaviour of azinphos-methyl in soils. Coefficients from adsorption isotherms and HPLC analysis of soil column leachates were used in this work for predicting pesticide mobility in soils. The studied clay mineral was a Spanish bentonite with a predominant montmorillonite fraction. The results showed that azinphos-methyl was adsorbed on the clay mineral and demonstrated the catalytic effect of bentonite on the hydrolysis of the pesticide. (C) 2000 Elsevier Science B.V. All rights reserved.