“Glyphosate and its Interactions with Mineral Oxides and Water”

B. C. BARJA; J. HERSZAGE; M. DOS SANTOS AFONSO

Buenos Aires

Otro; Escuela de Ciencia y Tecnología Ambiental, EdeA, UNSAM; 1998

Centro Atómico Constituyentes, CNEA.

Transport of herbicides in soils cccurs in different ways. Since movement of a herbicide through the soils is generally nediated by water, water solubility, aqueous reactions with dissolved metals and adsorption characteristics are the great importance concerning the rate of transport process for any herbicide. Transport of herbicides in soils cccurs in different ways. Since movement of a herbicide through the soils is generally nediated by water, water solubility, aqueous reactions with dissolved metals and adsorption characteristics are the great importance concerning the rate of transport process for any herbicide. Generally, herbicides are bound to soils by adsorption constituents such as metallic oxides and clays minerals. Glyphosate is rapidly adsorbed and tightly complexed by most soils where it is escentially immobilized. The residence time on the surface will be a function of the composition of the solid phase. Certainly, little is known about its interaction with transition metals naturally occuring in soils natural waters and plants. A deep knowledge of these interactions would allow us to evaluate the fate and mechanism of immobilization of glyphosate in thr environment. The purpose of this work is to elucidate the coordination chemistry of this molecule with iron (III) and iron(hydr)oxide and other related compounds corresponding to moieties of glyphosate: methyl phosphonic acid and sarcosine. Synthesis techniques to obtain the solid coordination compounds were developed. Their chemical compositions were verified by elemental analysis and AAS. By means of spectroscopic techniques (UV Vis, FTIR), structural information was obtained. The transition enthalpy energies were evaluated via DSC. The adsorption isother of glyphosate onto goethite at different pH were obtained and the structure of the surface complexes is under study via ATR-FTIR.