Copper in plant species in a copper gradient in Catalonia (North East Spain) and their potential for phytoremediation

The accumulation of Cu in roots and shoots of 32 plant species growing on s oils with a wide range of Cu concentrations (30-18 500 mug g(-1) total soil Cu) located in Collserola Mountain (Barcelona, Spain) was analysed. High C u availability decreased the species diversity in the Hyparrhenietum hirto- pubescentis, the natural plant association at the study sites. Shoot and ro ot Cu concentrations in relation to extractable soil Cu concentrations were used for the evaluation of the Cu resistance strategy in the different spe cies. Saturation of Cu accumulation in roots was observed in most species. Hyparrhenia hirta was the most efficient shoot excluder, while the linear i ncrease of shoot Cu with the Cu soil concentration exhibited the highest sl ope in Hirschfeldia incana. Most species accumulated more Cu in roots than in shoots. High shoot/root Cu ratios were only found in the highly Cu-resis tant Hirschfeldia incana, in the resistant or moderately resistant Spartium junceum and Reseda sp. (R. lutea and R. phyteuma), and in the much less re sistant Ononis natrix. Only two species, Hirschfeldia incana and Sedum sedi forme were able to support the extreme Cu-toxicity conditions on soils with 5000-16 800 mug g(-1) extractable Cu. Among the grass species tested Hypar rhenia hirta was the most Cu-resistant species (up to 1950 mug g(-1) extrac table soil Cu). The potential usefulness of these pseudometallophytes for p hytoremediation of Cu-contaminated soils is discussed.