SILPHIUM PERFOLIATUM A PROMISING ENERGY CROP FOR PHYTOREMEDIATION OF HEAVY METAL CONTAMINATED SOILS.

Comparative studies have been carried out to determine the quantities and depositions of heavy metals, macro, and microelements in the vegetative organs of Silphium perfoliatum, the efficiency for phytoremediation and the quality of the biomass as a renewable energy source for the combustion process. The field experiment was conducted on an agricultural field contaminated by the Non-Ferrous Metals Plant near Plovdiv, Bulgaria. Silphium perfoliatum is tolerant to heavy metals and can be grown on highly contaminated soils (1671.6 mg/kg Zn, 1694.8 mg/kg Pb, and 54.8 mg/kg Cd). Pb, Zn, Hg, Cu, Fe, Mn, Ca and Mg accumulated in leaves, Cd and P - in roots, and K in stems. Cup plant can be classified as a exluder plant with bioconcentration factor < 1 and can also be used in phytoremediation of contaminated soils. Silphium perfoliatum can be a significant source of good-quality raw material in producing solid biofuels. The biomass studied is of high quality (high in C and H and low in ash, N, Cl, and S) and has high energy potential. Biomass of Silphium perfoliatum from highly contaminated soils could be used as a source of energy. [ABSTRACT FROM AUTHOR]