title: Glyphosate behavior at soil and mineral-water interfaces.
abstract: Adsorption isotherms and surface coverage of glyphosate, N-phosphonomethylglycine (PMG), in aqueous suspensions of three Argentine soils with different mineralogical composition were measured as a function of PMG concentration and pH. Zeta potential curves for PMG/soils system were also determined. Montmorillonite and soil sample surface charges were negative and increased as the amount of adsorbed PMG increased, showing that the surface complexes are more negative than those formed during the surface protonation. PMG adsorption on soils were described using Langmuir isotherms and the affinity constants, and the maximum surface coverage was estimated at pH 4 and 7 using a two-term Langmuir isotherm, the mineralogical composition percentages, and maximum surface coverage and Langmuir constants for pure minerals. The influence of organic matter (OM) and iron content of soils on the PMG adsorption was evaluated. The surface coverage of PMG decreased when the OM and iron content decreased for minerals and soils.
authors.affiliation: INQUIMAE and Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria Pabellón II, (C1428EHA) Buenos Aires, Argentina. rpessagno@qi.fcen.uba.ar
authors.forename: Romina C
authors.initials: RC
authors.lastname: Pessagno
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Torres Sánchez
authors.forename: María
authors.initials: M
authors.lastname: dos Santos Afonso
mesh_terms: D000327:Adsorption; D001118:Argentina; D001546:Bentonite; D004784:Environmental Monitoring / Q000379:methods; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D006540:Herbicides / Q000737:chemistry*; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D007501:Iron; D012989:Soil Pollutants / Q000737:chemistry*; D014873:Water Pollutants / Q000737:chemistry; D000097797:Glyphosate
chemical_list: D001546:Bentonite; D005998:Glycine; D006540:Herbicides; D006812:Humic Substances; D007501:Iron; D012989:Soil Pollutants; D014873:Water Pollutants; D000097797:Glyphosate