This experiment was conducted in leaching tubes filled with soils classified as Typic Quartzipsament (AQ), Typic Hapludox (LV) and Rhodic Typic (LE). Sewage sludge was periodically added and incorporated to the soils in a total amount corresponding to 156,0 t ha-1 (dry weight basis), for an incubation period of 310 days. The soils were then treated with water and the following salt solutions: 0.9 mol L-1 KCl; 0.9 mol L-1 KNO3; 0.3 mol L-1 K2SO4 and 0.3 mol L-1 Ca(NO3)2. The water and salt solutions were added in amounts corresponding to 4 times the water retention capacity of the soils. The leachate was analyzed for Cd, Cr, Cu, Ni and Zn. In the percolate obtained with the water passage, Ca2+ and Mg2+ quantities were also determined, besides those of the previously mentioned metals. The results showed that the addition of KCl caused the leaching of 5% of the Cd added by sludge to LV and LE soils. For the other salts used and also for water, the heavy metal leachate was below 2%. The soil retention of Cd, Cu, Cr and Ni increased with the increase of the content of iron and aluminum oxide in soils. The movement of the heavy metals was also decreased with the increase of the soil pH and organic matter content, with the movement of some metals increasing with the presence of the salts KCl and K2SO4.
mobility; cadmium; copper; chromium; nickel; zinc