Use of High-Yielding Bioenergy Plant Castor Bean (Ricinus communis L.) as a Potential Phytoremediator for Copper-Contaminated Soils

Abstract

Copper (Cu) contamination in the environment has been increased during the years with agricultural and industrial activities. Biotechnological approaches are needed for bioremediation in these areas. The aims of this study were i) to evaluate the phytoremediation capacity of the high-yielding bioenergy plant castor bean (Ricinus communis L.) in vineyard soils (Inceptisol and Mollisol) contaminated with Cu and a Cu mining waste; ii) to characterize the castor bean as a Cu phytoremediation plant; and iii) to evaluate the nutrient uptake by castor bean. Castor bean plants cultivated in soil with toxic levels of Cu for 57 d exhibited high phytomass production, a high tolerance index of roots' fresh mass and shoots' dry mass, a high level of Cu phytoaccumulation in the roots and also, a robust capacity for Cu phytostabilization. Furthermore, castor bean plants did not significantly deplete soil nutrients (such as N, P, and Mg) during cultivation. Plants cultivated in Inceptisol, Mollisol and Cu mining waste exhibited a strong potential for Cu phytoaccumulation, with values of 5 900, 3 052 and 2 805 g ha−1, respectively. In addition, the castor bean's elevated phytomass production and strong growth in Cu-contaminated soils indicated a high level of Cu phytoaccumulation and a potential application in biofuels. These findings indicate that the castor bean is a efficient hyperaccumulator of Cu and a potential candidate plant for the phytoremediation of Cu-contaminated soil.