Edafologia

EDAFOLOGIA, Vol. 10 (1), pp. 33-52, 2003

BIODISPONIBILIDAD DE METALES EN SUELOS DE MINA: CAMBIOS INDUCIDOS POR EL CRECIMIENTO DE alyssum serpyllifolium ssp. Lusitanicum
P. S. KIDD y C. MONTERROSO Departamento de Edafoloxía e Química Agrícola, Facultade de Bioloxía, Universidade de Santiago de Compostela, 15782. edcarmel@lugo.usc.es.

Abstract. The efficiency of Alyssum serpyllifolium ssp.lusitanicum (Brassicaceae), a Ni-hyperaccumulator that grows in the Tras-os-Montes region of NE Portugal on serpentine soil, for use in phytoextraction of polymetallic contaminated soils was evaluated. Here we assess changes in the bioavailability of Co, Cr, Cu, Mn, Ni, Pb and Zn, and the ability of A. serpyllifolium to access different soil metal pools. Alyssum serpyllifolium was grown on twomine-spoil soils (MS1 and MS2). The MS1 soil is contaminated with Cr (283 µg g-1) and has slightly elevated background concentrations (25-100 µg g-1) of the metals Ni, Zn and Pb, while the MS2 soil is moderately contaminated with Cr (263 µg g-1), Cu (264 µg g-1), Pb (1433 µg g-1) and Zn (377 µg g-1). Mine-soils were limed to about pHH2O 6.0 with calcium carbonate (MS1/Ca and MS2/Ca) or limed andamended with NPK fertilisers (MS1/NPK and MS2/NPK). Mine-soils that were not amended were lethal to A. serpyllifolium, plants died within 2-3 days. Biomass was reduced on MS2/Ca due to phytotoxic effects of Cu, and plants did not grow on MS2/NPK soil. In contrast, amendment with NPK fertilisers increased plant biomass by about 10-fold on MS1/NPK. However, in the same soil root dry weight was reduced byabout 7-fold compared with MS1/Ca. Alyssum serpyllifolium accumulated Mn, Ni and Zn in its aerial parts (shoot[metal]/root[metal] > 1) and both metal content and transportation were generally greater in MS2 than MS1. However, metal yields were significantly increased in plants grown on MS1/NPK, due to the increment in biomass. After plant growth, concentrations of EDTA-, NH4Cland Mehlich 3(M3)-extractable metals were generally lower. However, concentrations of extractable Mn and Zn were frequently greater after growth. Concentrations of M3-extractable Cr, Ni, Pb and Zn were often significantly increased in rhizosphere soils. In addition, sequential (BCR) extractions suggested that A. serpyllifolium could potentially mobilise metals from soil pools normally considered to be nonplant-available, and provided that these metals are then absorbed by the plant this would increase total metal extraction. These results suggest that A. serpyllifolium could be suitable for phytoextraction uses in polymetallic-contaminated soils, and especially where the contaminants are Mn, Ni and Zn. However, its small biomass production, even on NPK fertilised mine-spoil soils, continues to be a majorlimiting factor for its use in phytoextraction. Keywords: Alyssum serpyllifolium, metal bioavailability, mine-soils, phytoextraction, sequential extractions. Resumen. Se evalúa la eficiencia de Serpyllifolium ssp. Lusitanicum (Brassicaceae), un hiperacumulador de Ni que crece en los suelos serpentiníticos de la región de Tras Os Montes (NE Portugal), para su uso en fitoextracción de metales ensuelos de mina. Para ello se hizo un ensayo de invernadero con Alyssum serpyllifolium y dos suelos de mina (SM1 y SM2). Se estudió la capacidad de esta espe-

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KIDD y MONTERROSO

cie para acceder a diferentes fracciones metálicas del suelo, así como los cambios que inducía sobre la biodisponibilidad de Co, Cr, Cu, Mn, Ni, Pb y Zn. El suelo SM1 estaba contaminado con Cr (283 µg g-1) y teníaconcentraciones ligeramente elevadas (25-100 µg g-1) de Ni, Zn y Pb; el suelo SM2 estaba moderadamente contaminado en Cr (263 µg g-1), Cu (264 µg g-1), Pb (1433 µg g-1) y Zn (377 µg g-1). Los suelos fueron encalados hasta pH 6.0 con carbonato cálcico (SM1/Ca y SM2/Ca) o encalados y fertilizados con NPK (SM1/ NPK y SM2/ NPK). Los suelos sin enmienda fueron letales para A. serpyllifolium, las...