SOIL SORPTION OF HEAVY-METALS AS INFLUENCED BY SEWAGE-SLUDGE ADDITION

In this paper it was evaluated how the sorption process of heavy metals (Zn, Cu and pb) by soil is influenced by the presence of sewage sludge. Results obtained both from sorption experiments and analytical characterization of a sewage sludge estract, showed that compounds of an organic nature deriving from the sludge adsorb on the soil at first,offering new adsorbing sites to heavy metals, increasing the soil sorption ability. However this sorption capacity is inversely related to the amount of metal sorbed, as evidentiated by the Kd graphs, so that only ''low metal'' sludges will be able to provide new sorbing sites in addition to the ones supplied by the soil.