Glyphosate adsorption on soils of different characteristics.

Adsorption of glyphosate on clays and soils from Paraná State: effect of pH and competitive adsorption of phosphate

“…Glass (1987) studied the adsorption of GPS in three soils (Houston clay loam, Muskingum silt loam, Sassagras sandy loam) and showed that the adsorption of GPS by the soil was related to the clay content and CEC. By the other hand, Morillo et al (2000) showed that adsorption of the other three different soils (Ultic Haploxeralf, Alfic Dystric Eutrochrepts, Podosol) were not related to CEC and clays content, but to the content of iron and aluminum amorphous oxides and OM. Prata et al (2000) also showed that the adsorption of GPS by different soils (Rhodic Kandiudalf, Anionic Acrudox, Typic Humaquept) was related to iron and aluminum oxides content, and OM played a secondary role.…”

“…McConnell and Hossner (1985) using kaolinite, hematite and goethite and Sheals et al (2002) using goethite also showed that the adsorption of GPS were dependent on the pH GPS/clay system. Nomura and Hilton (1977) and Morillo et al (2000) also showed that adsorption of GPS on soils decreased with an increase in pH. It was due to an increase in negative charge of GPS and mineral surfaces with an increase in pH resulting in a decrease in the adsorption.…”

“…However, there is no agreement about the most important factors that control the adsorption of GPS. Several authors also studied the effect of pH on the adsorption of GPS by soils or clays and they agreed that an increase of pH decreased the adsorption of GPS (Nomura and Hilton, 1977;McConnell and Hossner, 1985;Morillo et al, 2000;Sheals et al, 2002). However, Glass (1987) showed that pH had no effect on the adsorption of GPS by ilite.…”

“…In the literature, there are several papers describing that the adsorption of GPS by soils or clays depends on cation exchange capacity (CEC) and clay content (Glass, 1987); iron and aluminum amorphous oxides and organic matter (Morillo et al, 2000); and iron and aluminum oxides (Prata et al, 2000;Gerritse et al, 1996). However, there is no agreement about the most important factors that control the adsorption of GPS.…”

Determinação voltamétrica do herbicida glifosato em águas naturais utilizando eletrodo de cobre

“…O Brasil, desde os anos 70, destaca-se como um dos dez maiores consumidores mundiais de pesticidas, mas o único dado relativo à extensão com que são usados no país refere-se às linhas de comercialização, destacando-se a grande utilização de herbicidas, principalmente nas culturas de soja, milho, cana-de-açúcar, café e arroz [3][4][5] . Na molécula do glifosato -N-fosfonometil glicina -(classe dos ácidos fosfônicos) a presença dos grupos funcionais amino, carboxila e fosfonato (Figura 1) explica a capacidade de ligação a íons metálicos formando quelatos 6 . O grupo fosfonato pode formar complexos bastante estáveis com íons metálicos e os grupos funcionais amino e carboxila podem também coordenar-se fortemente com íons metálicos, principalmente dos metais de transição, em soluções de pH próximo da neutralidade, onde estes grupos encontram-se desprotonados 7 .…”