The effects of chemical remediation treatments on the extractability and speciation of cadmium and lead in contaminated soils

Two rural soils contaminated by cadmium (Cd) and lead (Pb) were used to eva luate the effect of different chemical treatments on changes in speciation and extractability of Cd and Pb, and in phytoavailability to wheat. Triplic ates of seven chemical treatments were tested to compare and evaluate the r emediation techniques for contaminated soils using pot experiments. Treatme nts applied were calcium carbonate, a high quantity of phosphate salt, hog composts, iron oxide, manganese oxide, zeolite, and unamended control. Whea t (Triticum aestivum) was planted in the different amended soils for a furt her one month to evaluate the effectiveness of treatments on uptake of Cd a nd Pb by the wheat shoots. Results indicated that addition of calcium carbo nate, manganese oxide, or zeolite reduces the extractability of Cd or Pb in both soils, and significantly reduce the uptake of Cd and Pb by wheat shoo ts. Changes in the extractability and metal sequential fractionations indic ate that the exchangeable (or available) form of Cd and Pb in two soils can be transformed into unavailable forms after these amendments. (C) 2000 Els evier Science Ltd. All rights reserved.