Sorption of Imidacloprid on Soil Clay Mineral and Organic Components

Abstract

Soil clay mineral and organic components have been shown to be responsible for sorption of many pesticides. This study assessed the influence of the different components of the clay fraction of five soils and model sorbents (montmorillonite, Fe oxide, and humic acid) and their binary and ternary associations on sorption of the insecticide imidacloprid (1‐[(6‐chloro‐3‐pyridinyl)‐methyl]‐N‐nitro‐2‐imidazoli‐dinimine). Sorption was very high on a clay fraction containing a high content of low‐laminar‐charge montmorillonite and relatively high organic C content. When organic matter of the soil clays was reduced by H2O2, sorption decreased; however, the sorption coefficient based on organic C (Koc) increased. The increase in Koc was greater on clays whose surface areas substantially increased after H2O2 treatment. This indicates a contribution of the surfaces of mineral components of the soil clay to sorption of imidacloprid. Imidacloprid sorbed on both montmorillonite and humic acid, whereas sorption on Fe oxide was very low. The sorption distribution coefficient, Kd, on montmorillonite increased from 15 to 180 when pH was decreased from 3.5 to 1.0, suggesting protonation of the ‐NH group of the imidazol ring. Sorption on binary and ternary associations of these model sorbents indicated that organic matter is the single most important component affecting sorption of imidacloprid, although there is some contribution of the mineral surfaces.

Lixiviação de clomazone + ametryn, diuron + hexazinone e isoxaflutole em dois tipos de solo

“…Houve maior controle do bioindicador na lâmina de 80 mm no solo de textura argilosa até 20 cm de profundidade; entretanto, no solo de textura mé-dia observou-se maior concentração do herbicida nas camadas abaixo de 20 cm, comparado ao solo de textura argilosa (Figura 1). Os dados obtidos demonstram que solos com maiores teores de matéria orgânica e argila apresentam menor tendência geral de lixiviação dos herbicidas, representando, assim, menor risco de contaminação dos lençóis freáticos (Cox et al, 1998). Resíduos de clomazone foram detectados um ano após a aplicação em diferentes tipos de solo, e em solos com textura arenosa ocorre mais facilmente a dessorção deste herbicida, o que pode propiciar a lixiviação (Cumming et al, 2002).…”

Persistência e lixiviação de ametryn e trifloxysulfuron-sodium em solo cultivado com cana-de-açúcar

“…SP 801816 contribuem para a maior disponibilidade dos herbicidas na solução do solo, sendo sua ação mais pronunciada sobre a espécie indicadora C. sativus, conforme verificado no bioensaio. Embora existam inúmeros interferentes nas características de sorção de herbicidas à matéria orgânica, Cox et al (1998) ressaltam que a interação herbicida-matéria orgânica é mais estável do que aquela resultante da ligação com componentes minerais do solo e que, nesses solos, existe, em geral, menor tendência de lixiviação de herbicidas, representando menor risco de contaminação de águas subterrâneas.…”

Factors Affecting Performance of Soil Termiticides

“…Pesticide concentration affects adsorption (Kamble & Saran, 2005), but not to an extent that prevents comparison of relative mobility of different pesticides. For polar solutes, surfaces other than organic carbon can become important sorbents particularly when soils are low in organic matter (Cheung et al, 1979;Cox et al, 1998;Means et al, 1982). Another useful measure of potential pesticide mobility is the octanol -water partition coefficient (K ow ).…”