engleski

Sorption and leaching potential of organophosphorus insecticide dimethoate in Croatian agricultural soils

Dimethoate is an organophosphorus insecticide widely used in Croatia and the rest of the European Union, with polar structure and high water solubility that make it prone to leaching. This study investigated how physico- chemical soil properties affected dimethoate sorption and mobility. For that purpose, five soil samples were collected in three Croatian regions (two coastal and one mountain region) and analyzed. Dimethoate sorption process was studied using the batch procedure while its mobility and leaching potential was investigated by column experiment. The results showed that the sorption efficiency of dimethoate can be adequately described by Freundlich model ; all isotherms were of L-type with various degrees of non-linearity, suggesting that soils had different distribution of sorption sites energies. Energy distribution was wider for soils richer in organic matter (OM). KF values indicated relatively low sorption efficiency for all soils, but the increase of KF values was proportional to OM content. In order to determine the mechanisms involved in soil dimethoate sorption and mobility, breakthrough curves (BTCs) were fitted by two mathematical models, namely: one-site equilibrium (ELM) and two-site nonequilibrium sorption model (NELM). Parameters obtained by fitting showed trends that correlated well with OM, humic acid content and CEC. The correlations were quantified using Kendall-Tau statistical test and enabled us to form a model for prediction of leaching potential. A simplified model for dimethoate sorption/transport was also proposed.

column leaching experiments ; dimethoate ; nonequilibrium transport ; sorption ; soil ; two-site model

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