Accumulation of heavy metals in plants grown on mineralised soils of the Austrian Alps

A held survey of higher terrestrial plants growing on 18 metalliferous site s of the Austrian Alps was conducted to identify species accumulating excep tional large concentrations of Cd, Cu, Ni, Pb and Zn in shoots. Minuartia v erna (Caryophyllaceae) was confirmed and Biscutella laevigata (Brassicaceae ) newly identified as hyperaccumulators of Pb (> 1000 mg kg(-1) Pb in shoot s). Metal concentrations in shoots exceeded those in roots. Cadmium concent rations detected in shoots of Thlaspi rotundifolium ssp. cepaeifolium (up t o 108 mg kg(-1)), Cardaminopsis halleri (up to 80 mg kg(-1)), Biscutella la evigata (up to 78 mg kg(-1)) and Minuartia verna (up to 59 mg kg(-1)) may r epresent hyperaccumulation. In addition, populations of Thlaspi goesingense (up to 12400 mg kg(-1) Ni) and Thlaspi rotundifolium ssp. cepaeifoliium (u p to 1934 mg kg(-1) Pb) were confirmed to be hyperaccumulators. The strateg y of neighboring Thlaspi rotundifolium ssp. cepaeifolium populations to tol erate high Pb and Zn was found to switch from hyperaccumulation at moderate and large, to exclusion at very large metal concentrations in soil. Metal partitioning in soils determined by sequential extraction gives evidence fo r large proportions of potentially mobile fractions. Metals stored in shoot s typically do not exceed the soil metal pool in fractions I (exchangeable) and 2 (readily mobile). There is evidence that hyperaccumulation may be as sociated with depressed translocation of K from roots to shoots. Under natu ral conditions metals accumulated in shoots are annually recycled to the so il, hyperaccumulators do not necessarily rely on metal phases less soluble than fractions 1 and 2. These should be considered in future development of phytoremediators, because after extraction of these phases by harvesting s hoots, further metal removal may be limited by dissolution kinetics of oxid es and silicates. (C) 1999 Elsevier Science Ltd. All rights reserved.