Reclamation of polluted soils: potential for phytoremediation of crop-related Brassica species

Soils polluted by heavy metals can be reclaimed using a number of expensive tactics that either remove the contaminants or stabilize them within the soil. The value of metal accumulating plants for environmental remediation has recently come to be appreciated and promising results have been obtained. This paper reports a study on the behavior of Brassica napus, Brassica juncea, Raphanus sativus and Brassica carinata grown on a substrate contaminated by several heavy metals caused by the use of contaminated irrigation water. Data on carbon dioxide assimilation, biomass growth and the bioconcentration and translocation factor of each metal in each species were measured. The polluted substrate caused only a small variation in photosynthesis, however transpiration was more affected by the experimental substrate and in all three species of the genus Brassica the presence of metals in the substrate resulted in higher transpiration levels. Two bioconcentration factors were calculated respectively for the roots (BCF) and the shoots (BCF’); the BCF was >1 for all the species for Cd, Cu, Ni and Zn without significant differences among species. All the values of BCF’ were lower than 0.5; among the metals, all Brassica species demonstrated a similar performance for Cd and Zn, while for other elements the bioconcentration factor was very low.