J. DIEZ LÁZARO, P. KIDD, C. MONTERROSO

Dpto. de Edafoloxía e Química Agrícola, Facultade de Biología, Universidade de Santiago de Compostela, 15782 Santiago. edcarmel@lugo.usc.es

Abstract. Phytoremediation techniques are now considered to be promising alternatives to conventional techniques for the remediation of metal contaminated soils. Further biogeochemical surveys and plant screenings are necessary in order to identificate new species for such applications. The influence of soil forming rocks on heavy metal contents, fractionation and bioavailability in soils, as well as on heavy metal accumulation in plant, was studied in this paper. Rocks, soils and plants from six sites with several litologies (serpentinites, peridotites, granulites, migmatites, and schists) of the Trás-os-Montes region (NE Portugal) were sampled. Total contents of Mn, Cr, Ni, Co, Cu, Zn, and Pb were analyzed. Additionally, both metal fractionation and metal bioavailability were determined in soil samples. Metal accumulation in plants was compared with the Ni hyperaccumulator Alyssum serpyllifolium Desf subsp. Lusitanicum, an endemic species from the region. Ultrabasic rocks, specially serpentinite, showed the highest concentration of Ni, Cr y Co, basic rocks (granulites) showed the highest concentration of Cu, Zn, and Mn, and acid rocks (schist) showed the highest concentration of Pb. Total content of these metals in soil samples was related with metals in parent rock, but this was not true for metal bioavailability. Heavy metal uptake and accumulation in plant depended on the plant species and edaphic conditions at its provenance. Three species (C. ladanifer, L. stoechas, y T. mastichina) showed an ability to bioaccumulate the metals Cr, Mn and Zn in their aboveground parts, so that they could have potential for phytoremediation technologies such as phytoextraction.

Key words. Biogeochemistry of heavy metal, bioavailability, phytoremediation, serpentinitic soils