Phytoremedial assessment of flora tolerant to heavy metals in the contaminated soils of an abandoned Pb mine in Central Portugal

Significant accumulation of heavy metals in soils and flora exists around the abandoned Barbadalhos Pb mine in Central Portugal. Soil and plant samples 49 species] were collected from two line transects, LT 1 and LT 2, in the mineralized and non-mineralized area, respectively to gain a comprehensive picture of heavy metals in soils and flora to assess its potential for phytoremediation. Phytosociological inventories of the vegetation were made using the Braun-Blanquet cover-abundance scale. Metal concentrations in soil ranged from (in mg kg^?1): 98–9330 Pb], 110–517 Zn], 7.1–50 Co], 69–123 Cr], 31–193 Cu], 33 400–98 500 Fe], 7.7–51 Ni], 0.95–13 Ag], 2.8–208 As], and 71–2220 Mn] along LT 1; and 24–93 Pb], 30–162 Zn], 3.7–34 Co], 61–196 Cr], 21–46 Cu], 24 100–59 400 Fe], 17–87 Ni], 0.71–1.9 Ag], 4.3–12 As], and 44–1800 Mn] along LT 2. Plant metal content ranged from (in mg kg^?1): 1.11–548 Pb], 7.06–1020 Zn], 0.08–2.09 Co], 0.09–2.03 Cr], 2.63–38.5 Cu], 10.4–4450 Fe], 0.38–8.9 Ni], and 0.03–1.9 Ag] along LT 1; and 0.94–11.58 Pb], 2.83–96.5 Zn], 0.12–1.44 Co], 0.21–1.49 Cr], 1.61–22.7 Cu], 4.6–2050 Fe], 0.51–4.81 Ni], and 0.02–0.31 Ag] along LT 2. Plants with highest uptake of metals were: Cistus salvifolius (548 mg Pb kg^?1), Digitalis purpurea (1017 mg Zn kg^?1 and 4450 mg Fe kg^?1). Mentha suavolens and Ruscus ulmifolius were seen to hyperaccumulate Ag (1.9 and 1 mg Ag kg^?1, respectively). More metals and higher concentrations were traced in plants from LT 1, especially for Pb and Zn.