Long-term field study on stabilization of contaminated wastes by growing clonally reproduced Silene vulgaris calamine ecotype

Abstract

Aims: Pseudo-metallophyte Silene vulgaris frequently colonizes polluted areas. We investigated whether plants obtained under in vitro conditions can be used to form long-term communities on zinc-lead tailings rich in cadmium. To this end, we checked the species stabilization capacity and biochemical properties of the area subjected to long-term cultivation of a local S vulgaris ecotype. We focused on evaluation of its ability to accumulate trace metals (TMs) after 10-year cultivation period. Methods: The calamine S. vulgaris ecotype was propagated in vitro and acclimatized to ex vitro conditions in a greenhouse. The plants were then replanted on plots created on the flotation settler heavily polluted with Zn, Pb and Cd. The capacity of trace metal accumulation in plant material was checked based on translocation (TF) and bio-concentration (BCF) factors. Nutrient, TMs content, and enzyme activity of substrate were determined after 1 and 10 years of cultivation and compared with the properties of bare flotation waste. Results: Numerous plants obtained through vegetative in vitro propagation were planted in the field after a short hardening period. Cultivation of plant material obtained this way increased microbial activity, C concentration, and reduced TM contents in the substrate. TF calculated after the first season of S. vulgaris cultivation was similar for all metals and amounted to about 40%. After 10 years, it was the highest for Cd (50%). Independently of the experiment duration, BCF for Zn and Pb was <1, while for Cd it reached about 1.4 after 10 years for both shoots and roots. Conclusions: The calamine S. vulgaris ecotype cloned in tissue culture proved useful material for stabilization of trace metal contaminated post-flotation wastes. Ten years of its cultivation in tailings rich in Zn, Pb and Cd contributed to humus layer formation and increase in microbial activity in the substrate. Thus, the beginning of soil formation was noticed in heavily polluted tailings.