Metallophytes and thallium hyperaccumulation at the former Raibl lead/zinc mining site (Julian Alps, Italy)

Abstract

An ecological survey of metallophytes belonging to the Thlaspietum cepaeifolii plant community was carried out at the former Raibl lead and zinc mining site (Julian Alps, Italy). The aims of this work were to evaluate metal hyperaccumulation and to determine whether it was restricted to a single element or, instead, involved multiple elements. The concentrations of Cd, Pb, Tl and Zn were measured in specimens of Alyssum wulfenianum, Biscutella laevigata subsp. laevigata, Minuartia verna and Thlaspi rotundifolium subsp. cepaeifolium collected from native and mining soils, mine tailings and stream banks. Cadmium hyperaccumulation was not demonstrated, whereas in the case of Pb and Zn contradictory results were obtained. Thallium hyperaccumulation was strongly confirmed in B. laevigata subsp. laevigata (up to 32,661 mg kg⁻¹ of Tl in shoots and bioconcentration factor > 1). Surprisingly, this was also discovered in A. wulfenianum and M. verna (up to 1934 and 3632 mg kg⁻¹ of Tl in shoots, respectively, and bioconcentration factor >1). Multiple metal hyperaccumulation was verified in B. laevigata subsp. laevigata (Pb and Tl), M. verna and T. rotundifolium subsp. cepaeifolium (Pb, Tl, and Zn) although it could not be confirmed in any of these species when coefficients calculated on shoot concentration of the elements were considered.

Keywords:

• Metallophytes
• hyperaccumulators
• Thallium
• Raibl
• mining site

Acknowledgments

This research was part of the project “Persistent green capping on polluted or metalliferous sites: functional role and reservoir of biodiversity” supported by the Italian Ministry of University and Research (PRIN 2008, N° 2008JZ27T7). The authors are indebted to Rufus Chaney (USDA-ARS, Beltsville, MD, USA) for his valuable comments on the manuscript and to Antonino Danelutto for indicating the locations of A. wulfenianum and T. rotundifolium subsp. cepaeifolium populations in the Rio del Lago valley. Technical assistance by Diego Chiabà and contributions made by Sabina Moroldo are gratefully acknowledged.