Modification of the sequential elution technique for the extraction of heavy metals from bryophytes

The sequential elution technique (S.E.T.) has frequently been used to deter mine the distribution of metals at different cellular sites in contaminated lichens and, to a lesser extent, in mosses. Here we evaluate certain aspec ts of the technique in order to improve the reliability of the results obta ined when it is used on bryophytes. Various experiments were carried out us ing the aquatic moss Fontinalis antipyretica Hedw. Results confirmed that t wo consecutive washings are sufficient to ensure total extraction of the ex tracellular metal. In addition, the possibility of using new extractants to remove the metal that is accumulated at extracellular sites was investigat ed. Although NiCl2, (the extractant originally used by the authors of the t echnique [Brown DH, Buck GW. J Briol 1978a;10:199-209; Brown DH, Buck GW. A nn Bot 1978b;42:923-929]) was adequate for metals with low affinity for the binding sites, EDTA and Pb(NO3,)(2) were more efficient for the extraction for metals with a medium-high affinity for extracellular binding sites. Th e optimum concentrations of extractant were found to be 10 or 20 mM for NiC l2, and EDTA, and 50 mM for Pb(NO),. (C) 1999 Elsevier Science B.V. All rig hts reserved.