Identification of nickel hyperaccumulator plants in the Valozoro (Madagascar) nickel deposit using BCF and TF indices

Heavy metal pollution, particularly nickel (Ni), poses significant threats to ecosystems and public health in industrial areas. This study investigated the Valozoro mining site in Madagascar to identify native Ni-hyperaccumulator plants suitable for phytoextraction. Sixteen herbaceous species were analyzed for Ni concentrations in roots and aerial parts, and their Bioconcentration Factor (BCF) and Translocation Factor (TF) were calculated. Three promising species were identified. Two were confirmed as hyperaccumulators: Senecio cochlearifolius (1252 mg/kg Ni, BCF=4.93, TF=2.03) and Helichrysum phylicaelofolium (1154 mg/kg Ni, BCF=4.54, TF=3.23). While Helichrysum aff. gymnocephalum remained below the 1,000 mg/kg hyperaccumulation threshold, its BCF and TF values (>1) indicate significant phytoremediation potential. H. phylicaelofolium is especially notable for its high translocation capacity. However, since the Helichrysum genus is widely used in Madagascar for traditional medicine, its high Ni accumulation raises urgent public health concerns. Use of these plants in herbal remedies could lead to heavy metal toxicity in local populations. Therefore, while H. phylicaelofolium, S. cochlearifolius, and H. aff. gymnocephalum are excellent candidates for soil decontamination, their integration into phytoremediation programs must include strict management and community awareness to prevent accidental medicinal use of contaminated biomass.