Fig. 4. Sequentially extracted fractions of Zn and Cu in freshly contaminated and 4 yr contaminated soil before and after the growth of plants (expressed in % of the total extracted amounts). (A) Fractions of Zn extracted in steps F1 through F7. (B) Sum of the fraction of Zn extracted in steps F1 and F2. (C) Fractions of Cu extracted in steps F1 through F7. (D) Sum of the fraction of Cu extracted in steps F1 and F2 and fraction of Cu extracted in step F4. The bars in panels (C) and (D) represent the 95% confidence limits of the means from 4 replicates (duplicate extraction of soil from two pots per treatment).