The objectives of this study were to determine the influence of different soil tillage methods on the loss of heavy metals by erosion, and to evaluate the level of contamination in sediments and water from the main stream in Caetés watershed, Paty do Alferes County, Rio de Janeiro. The experiment was conducted from December 1996 to March 1997, and cucumber (Cucumis sativus L.) was the cultivated crop. Four Wichmeier plots were installed, with an area of 22 x 4 m. The following treatments were used: (a) tillage with machinery and operation down hill and burning of the grassland (MAQ); (b) tillage with machinery and operation down and without burning of grassland between lines of crop (MANQ); (c) tillage with animal traction and following the natural contour of the hill, strip cropping grass each 7 m (AA); and minimum tillage (CM). Heavy metal concentrations were also determined in the samples of sediments and water from the main Caetés watershed stream. The highest losses of heavy metals by erosion were in the MAQ treatment. The bottom stream sediments showed an increase in the total concentration of Cd, Ni, Pb, Zn and Mn, according to the sampling position, upstream and downstream, showed Cd, Mn and Pb concentration above the maximum limits established for tap water. The results obtained allowed to conclude that the intensive use of agrochemicals associated with the high soil losses by erosion can determine serious risks of contamination of the water from the main stream in Caetés watershed, which is used by animals and for irrigation.
erosion; agrochemicals; Cd; Ni; Pb; Zn; Mn