Fractionation of various elements in CRMs and in polluted soils

An optimised BCR three steps sequential extraction procedure (BCR SEP) and several single extractions with KCl, NH4Cl, Na4P2O7 and 0.5 mol L-1 HCl were used for the fractionation of Al, Cu, Fe, Mn, Pb and Zn in CRMs and in samples from a mining area with sulphidic deposits. A good interlaboratory comparability was obtained for Cu, Pb and Zn in CRM 483, CRM 701, SRM 2710 and SRM 2711 by BCR SEP. The reliability of the results obtained is also very satisfactory. Some differences were found between our results and the indicative data for Al and Fe fractionation. However, serious discrepancies were found for Mn, not only for individual steps of the fractionation, but for the data obtained overall (sum of 1-3 steps), and for the total concentration as well. Our results could be utilized as a contribution to the existing indicative values for CRM 483, SRM 2710 and SRM 2711 for interlaboratory study. Moreover, data for the fractionation of elements mentioned above for CRM 701 are first presented here. A high correlation between 0.5 mol L-1 of HCl-extractable amounts of the elements studied, and the sum of the three steps of BCR SEP in acid sulphatic weathering products and naturally acidified soils was established, which allows us to suggest this rapid and cost-effective single extraction procedure as a valuable tool in contamination assessment.