Bioaccumulation efficiency comparison of heavy metals in Verbascum speciosum, Acantholimon hohenackeri, Acanthophyllum microcephalum, and Euphorbia macroclada, grown around lead and zinc mines

Background and Phytoremediation stands out as one of the effective techniques for stabilizing, extracting, trapping, or detoxifying pollutants utilizing plants. This cost-effective and environmentally friendly approach leads to the revitalization and enhancement of vegetation, along with increased activity and growth of microorganisms. In this study, the species cultivated in the tailings of the lead and zinc mines of Ravanj were identified and assessed. Indigenous plants thriving in mineral tailings were isolated from the root portion. Random sampling of the identified soil and plant species was conducted. The accumulation of heavy metals (lead, zinc, manganese, chromium, copper, nickel, cadmium, and cobalt) in the soil, aerial organs, and roots of plants were quantified. Additionally, the bioconcentration factor of the aerial and root parts and the transfer factor were computed. Among the heavy metals, cadmium, zinc, lead, and manganese displayed the highest accumulations in the leaves of Euphorbia macroclada (3.91±0.17 mg/kg), Verbascum speciosum (751.94±42.67 mg/kg), Acanthophyllum microcephalum (272.11±31.73 mg/kg), and Acanthophyllum microcephalum (594.59±9.76 mg/kg), respectively. Conversely, cobalt, chromium, copper, and nickel exhibited the most significant accumulations in the roots of Acantholimon hohenackeri (3.17±0.55 mg/kg), Acantholimon hohenakeri (20.16±2.28 mg/kg), Euphorbia macroclada (19.51±0.36 mg/kg), and Verbascum speciosum (17.56±0.90 mg/kg), respectively. Euphorbia macroclada demonstrated the highest bioconcentration in aerial parts and roots concerning cadmium metal (0.40). Furthermore, the Acantholimon hohenackeri plant exhibited the highest transfer factor (2.75), primarily associated with lead metal. Based on the findings of this study, the investigated species within the lead and zinc mines of Ravanj could serve as heavy metal-resistant ecotypes, contributing to the reduction of heavy metal mobility and bioavailability, thereby enhancing soil texture quality.