The importance of substrate compaction and chemical composition in the phytoextraction of elements by Pinus sylvestris L.

Trees of Scots pine (Pinus sylvestris L.) are known for their effective phytoextraction capabilities. The results obtained in this study point to the significant role of substrate composition and chemical characteristics in the phytoextraction potential of this species. A multi-elemental (53 elements) analysis of pines from unpolluted (soil) and polluted (post-flotation tailings) sites was performed using inductively coupled plasma optical emission spectrometry. The analyzed flotation tailings were characterized by alkaline pH (7.19 ± 0.06) and significantly higher conductivity (277.7 ± 2.9 µS cm-1) than the soil (pH = 5.11 ± 0.09; 81.3 ± 4.9 µS cm-1). The two substrates also differed with respect to the contribution of the clay fraction (0% in the unpolluted and 8% in the polluted substrate). The specimens of P. sylvestris growing on flotation tailings had significantly smaller height (381 ± 58 cm) and total aboveground biomass (4.78 ± 0.66 kg) than the trees growing in soil (699 ± 80 cm and 10.24 ± 2.10 kg). The biomass of the trunk, twigs and branches, and needles of the trees from polluted sites was between 40.0% and 48.7% of the biomass of the same organs of the control trees. Generally, the organs (trunk, twigs and branches, needles) of the P. sylvestris specimens from polluted sites had significantly higher concentrations of Au, Al, Ba, Cd, Co, La, Lu, Ni, Pd, Sc, Zn, and lower concentrations of B, Bi, Ca, Ce, Er, In, K, Mg, Na, Nd, P, Pr, Re, Se, Sr, Te than in the control plants, these metals being accumulated effectively in the whole of the aboveground biomass (BCF>1). Although the concentration of the majority of elements was significantly higher in the flotation tailings, significantly higher concentrations of these elements were observed in the tree organs from unpolluted sites, which points to the important role of substrate characteristics in the phytoextraction efficiency of P. sylvestris.

Phytoextraction of potentially toxic elements by six tree species growing on hazardous mining sludge.

The aim of the study was to compare the phytoextraction abilities of six tree species (Acer platanoides L., Acer pseudoplatanus L., Betula pendula Roth, Quercus robur L., Tilia cordata Miller, Ulmus laevis Pall.), cultivated on mining sludge contaminated with arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), thallium (Tl), and zinc (Zn). All six tree species were able to survive on such an unpromising substrate. However, A. platanoides and T. cordata seedlings grown on the polluted substrate showed significantly lower biomass than control plants (55.5 and 45.6%, respectively). As, Cd, Cu, Pb, and Tl predominantly accumulated in the roots of all the analyzed tree species with the following highest contents: 1616, 268, 2432, 547, and 856 mg kg-1, respectively. Zn was predominantly localized in shoots with the highest content of 5801 and 5732 mg kg-1 for U. laevis and A. platanoides, respectively. A. platanoides was the most effective in Zn phytoextaction, with a bioconcentration factor (BCF) of 8.99 and a translocation factor (TF) of 1.5. Furthermore, with the exception of A. pseudoplatanus, the analyzed tree species showed a BCF > 1 for Tl, with the highest value for A. platanoides (1.41). However, the TF for this metal was lower than 1 in all the analyzed tree species. A. platanoides showed the highest BCF and a low TF and could, therefore, be a promising species for Tl phytostabilization. In the case of the other analyzed tree species, their potential for effective phytoextraction was markedly lower. Further studies on the use of A. platanoides in phytoremediation would be worth conducting.

The role of selected tree species in industrial sewage sludge/flotation tailing management.

The aim of the study was to estimate the ability of ten tree and bush species to tolerate and accumulate Cd, Cu, Pb, Zn, and As species [As(III), As(V), and total organic arsenic] in industrial sewage sludge extremely contaminated with arsenic (almost 27.5 g kg(-1)) in a pot experiment. The premise being that it will then be possible to select the most promising tree/bush species, able to grow in the vicinity of dams where sewage sludge/flotation tailings are used as landfill. Six of the ten tested tree species were able to grow on the sludge. The highest content of total As was observed in Betula pendula roots (30.0 ± 1.3 mg kg(-1) DW), where the dominant As species was the toxic As(V). The highest biomass of Quercus Q1 robur (77.3 § 2.6 g) and Acer platanoides (76.0 § 4.9 g) was observed. A proper planting of selected tree species that are able to thrive on sewage sludge/flotation tailings could be an interesting and promising way to protect dams. By utilizing differences in their root systems and water needs, we will be able to reduce the risk of fatal environmental disasters.