Sequential extraction method of Tessier was used in this study [23].The extraction was carried out in
50 ml polypropylene centrifuge tubes with an initial mass of 0.5 g samples. The five heavy metal forms
were divided in the following fractions: exchangeable form (EX), carbonate-bound form (CB), Fe/Mn
oxide-bound form (OX), organic matter/sulfide-bound form (OM), residual form (RS).Sequential
extraction scheme for Pb and Cd in contaminated soils as described in Table.3. After each successive
extraction, separation was accomplished by centrifugation at 8000 r/min for 10 min