Dendroremediation of soil contaminated by mining sludge: A three-year study on the potential of Tilia cordata and Quercus robur in remediation of multi-element pollution

The vast amounts of mining and metallurgical wastes containing unimaginable quantities of toxic metal(loid)s require searching for managed ways. The study aimed to long-term assess the growth, elements accumulation (As, Cd, Hg, In, Mn, Mo, Pb, Sb, Sn, Ti, Tl, Zn) and proline content in 2-year-old Tilia cordata Mill. and Quercus robur L. seedlings growing under 1 and 3% extremely polluted mining sludge (MS) after 1, 2 and 3 years. Both species were able to grow efficiently without significant differences resulting from the impact of MS. The overall rise was higher for T. cordata than for Q. robur. The accumulation ability for As, Hg, In, Mn, Mo, Pb, Ti, and Zn in the whole plant was significantly higher for T. cordata, while Cd, Sb, Sn and Tl did not differ considerably between species. The highest content was found for As, Mn and Zn (68.7, 158, and 157 mg per plant, respectively) for T. cordata after 3 years of growth. The calculated Bioconcentration Factors were the highest for Cu (1.23), In (6.86), and Zn (38.4) for Q. robur, as well as for As (1.55), Hg (3.24), Mn (32.8), Mo (1.64) and Ti (18.0) for T. cordata after 3 years. The highest Translocation Factors were observed for In (1.35) and Sn (1.25) after 3 years, as well as for Mn (2.72, 3.38, and 3.03 after 1, 2, and 3 years) for Q. robur seedlings. The proline content was higher for Q. robur, regardless of which organ was examined, and the differences increased with the time of the experiment and the amount of MS addition (possibly more sensitive to stress). Young T. cordata seedlings show much greater potential than Q. robur. This is the first time that a demonstration of the high potential of long-living trees in multi-element MS remediation has been described.