Sorption Behavior of Deltamethrin in Mediterranean Soils

Water is a vital factor of production, but its diminishing quality may threaten economic growth and social development of a country or a region. One of the most significant irrigated agricultural areas in Morocco is the Loukkos perimeter. The use of pesticides has made this region one of the first agricultural areas of the country in terms of the quantity of its production. The environment, including groundwater, and human health could suffer from the excessive and hazardous use of these chemicals. In this area, Deltamethrin is one of the most widely used insecticides on a variety of crops, including citrus and sugar beet. Excessive use of this insecticide presents a real risk to the deterioration of the groundwater quality, especially in the case of sandy soils. The aim of the present study was to investigate the adsorption and desorption processes of Deltamethrin in two contrasting agricultural soils (sandy and clayey soils) from Loukkos plain, using Batch equilibration method. The study is part of a large program to update information on pesticides for safer use and development of guidance and regulation for their application. The isotherms for adsorption and desorption were described using the Freundlich model. The adsorption coefficients, which were used to evaluate this phenomenon, were calculated using linear regressions. The results showed that adsorption and desorption processes of Deltamethrin on soils were well described by the Freundlich model. The Freundlich's adsorption coefficient (Kd) values for Deltamethrin in the clayey and sandy soils were 3.914 and 1.503 mL.g-1, respectively. Hence, the properties and the composition of the soils have great impacts on the sorption mechanisms of Deltamethrin. The results also showed that the irreversibility of the adsorption process is more important when the adsorption capacities of the soils and their clay content are high. Our study revealed a high risk of the presence of Deltamethrin in the Loukkos groundwater, particularly in sandy soils, which have low retention capacity due to their low clay and organic matter contents.