Living at the edge of life: metallophytes from the most toxic arsenic-thallium tailings in the world (Allchar, North Macedonia)

Abstract

Background and aims: The abandoned Allchar Mine in the Republic of North Macedonia is a globally unique deposit with historical tailings from processing ore containing extremely toxic metal(loid)s concentrations, with up to 76.1 g kg−1 and 6.5 g kg−1 of As and Tl, respectively. Methods: Five pseudo-metallophyte species which naturally colonise the Allchar tailings were sampled: Alyssum kavadarcensis, Knautia caroli-rechingeri, Minuartia verna, Plantago lanceolata, and Silene vulgaris. Rhizosphere soils, roots and leaves were collected for each individual. The samples were subjected to elemental analysis to determine macro and micro-elemental concentrations. Results: The results show that the studied species exhibit different strategies in relation to the dominant elements in the substrate, with exclusion being the most common among them. Hyperaccumulation of Tl was found in M. verna and P. lanceolata (with 1770 and 1030 mg kg−1 as the mean concentration, respectively), whereas As was found in concentrations above the threshold for hyperaccumulation and leaf-to-root ratio > 1 in M. verna, S. vulgaris, and A. kavadarcensis (up to 1340, 2870 and 1330 mg kg−1, respectively). Conclusions: The studied plants have great potential for use in phytoremediation of mine wastes contaminated with As and Tl.