Metal associations in soils before and after EDTA extractive decontamination: implications for the effectiveness of further cleanup procedures

The distribution of Pb, Ni and Zn in two contaminated soils was determined before and after treating the soils with an EDTA solution. After the EDTA e xtraction, the proportion of Pb accumulated in the acid-extractable fractio n considerably increased, which was related to the greater degree of metal extraction from the other fractions. EDTA was also able to extract certain amounts of Pb, Zn and Ni from the silicate matrix, which implied that these extractable amounts were not so strongly fixed to the residual fraction as previously supposed. As a consequence, after EDTA application, metal conte nt (especially Pb) remained more weakly adsorbed to soil components (more e asily leachable), potentially favouring the application of phytoremediation technologies. The extraction recoveries (for only one application) were ge nerally low for the three metals (33-37% for Pb, 5-11% for Ni and 14-19% fo r Zn), although this fact is an advantage as plants would not be able to as similate very high mobilised contents of metals. (C) 2001 Elsevier Science Ltd. All rights reserved.