Comparison of EDTA, HCl and sequential extraction procedures, for selected metals (Cu, Mn, Pb, Zn), in soils, riverine and marine sediments

Knowledge of the total concentration of metals in soils and sediments is frequently insufficient to ascertain environmental risk. Simple and sequential extractions are useful tools for estimating the mobility of metals. Many chemical extraction procedures have been proposed in the literature. This study compares the efficiency of three chemical extractions (two single procedures, using EDTA or HCl as reactant, and a sequential chemical extraction) on soils, riverine, estuarine and marine sediments. In the case of riverine sediments and soils, similar results are observed with 0.05 mol.L− 1 EDTA or 0.2 mol.L− 1 HCl extractions, whereas 0.2 mol.L− 1 HCl is inefficient for marine or estuarine samples. Comparison of the results obtained for the various samples, suggests that it is necessary to use a unique procedure for all the samples. The use of 0.05 mol.L− 1 EDTA rather than 0.2 mol.L− 1 HCl, as reactant for the single extractions is recommended. The applied sequential extraction procedure is more aggressive than EDTA (except to evaluate Pb mobility for some samples). Assuming that the metal enrichments are mainly of anthropogenic origin and that these metals are of higher mobility, compared to native metals, it is concluded that, for estimation of metal mobility, EDTA leaching is better adapted for Pb, whereas the sequential extraction procedure is better suited for Zn and Cu.

► 0.05 M EDTA, rather than HCl should be used for single extractions.
► EDTA leaching is the best suited method to estimate the Pb lability.
► The applied sequential extraction is more adapted to estimate Zn or Cu lability.
► Elements present in the residual fraction are supposed to be unavailable.