Sorption of the herbicide terbumeton and its metabolites onto soils. Influence of copper(II)

The intensive use of terbumeton (N-(1,1-dimethyl)-N'-ethyl-6-methoxy-1,3,5-triazine-2,4-diamine) has resulted in its widespread presence, together with its main metabolites, in surface- and groundwater. To estimate the fate of these compounds, their adsorption and desorption properties were studied in vineyard soils. The values of the organic carbon normalized adsorption coefficient (K-OC) for terbumeton (34.6 and 39.2 L g(-1)) were significantly higher than those of its metabolites (between 6.8 and 21.1 L g(-1)). Terbumeton exhibited a higher adsorption capacity and a lower desorption potential as compared with the metabolites. An important hysteresis was observed in all cases. The Freundlich isotherms exhibited a linear shape, which was interpreted as non-specific interaction. The influence of copper(II), a ubiquitous metal cation in vineyard soils, on pesticide sorption was also studied. Copper significantly decreased the amount of adsorbed terbumeton when present in a high concentration (2 x 10(-4) M).