Fig. 3. Total extracted amount of Zn, Pb, Fe, and Mn of all five steps in mmol kg^–1, percentage of Zn, Pb, Fe, and Mn extracted by sequential chemical extractions in samples P3–0.16, P3–0.7, and P3–3.0; F1 (NH₄NO₃), F2 (NH₄OAc), F3 (NH₂OH*HCl), F4 (NH₄–EDTA), and F5 (HF/HNO₃/HClO₄).