Glyphosate behavior at soil and mineralewater interfaces

ROMINA C. PESSAGNO; TORRES SÁNCHEZ, ROSA M.; DOS SANTOS AFONSO, M

ENVIRONMENTAL POLLUTION

Thomson Scientific

Año: 2008 vol. 153 p. 53 - 59

0269-7491

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/soilssystem 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 soilswere 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 pureminerals. 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.