This study aims to evaluate the pesticide concentrations in the soil profile under cultivation of onion in the municipality of Ituporanga in Santa Catarina. Samples of soil were collected, at depths of 0-20, 40-60 and 80-100 cm in three areas. In these the maize, onion, potatoes, beans, and beets are used in crop rotation. Three sets of samples were collected in the period 2006 and 2007. In the first year single samples were collected and in the other year, a composite sample. For each sample, the concentrations of herbicide 2,4-D, alachlor, atrazine, diuron, of fungicides: azoxystrobin, metalaxyl, metconazole, tebuconazole and of insecticides: lambda-cyhalothrin were determined. The results show that the active ingredients were detected in three depths. The fungicides were detected more frequently in the surface layer. Those, in turn, were detected more frequently in the deeper layer. The concentrations varied among the areas and depths, occurring in discontinuous form. The behavior of the distribution of concentrations was similar for all pesticides. It is supposed that the existence of preferential paths in the soil profile is the responsible factor for the irregular occurrence of high concentrations in depth.
leaching; pesticides residues in soil; groundwater degradation potential
