Metals are very common contaminants in the
soil. High-yielding biomass crops offer good potential for
the phytoremediation of soils contaminated with heavy
metals. Biomass fuel crops grown on contaminated land
have several advantages as site remediation combined with
bioenergy production. In this context, two energy crops,
Sorghum bicolor
and
Carthamus tinctorius
, were grown
hydroponically to assess their potential use in phytoremediation
of nickel (Ni), lead (Pb) and zinc (Zn) and biomass
production. The experiment was carried out in a growth
chamber using half-strength Hoagland’s solution spiked
separately with five concentrations for Ni, Pb and Zn (between
5 and 100 mg L
-1). Shoot and root biomass were
determined and analyzed for their metals contents. Results
showed that the tested plants were able to uptake Ni, Pb
and Zn. Furthermore, roots accumulated more metals than
shoots. Ni seems to be more toxic than Zn and Pb. In fact,
both species were unable to grow at Ni concentration above
10 mg L
-1. Metal toxicity ranked as follows:
Ni > Zn > Pb. High toxicity symptoms and biomass reduction
were observed at concentrations of Pb and Zn
above 25 mg L
-1 for both species.
S. bicolor was more
efficient than
C. tinctorius in metal uptake due to the high
biomass production and the relatively high shoot
concentration of metal.
S. bicolor could be successfully
used in phytoremediation applications in marginal soils
with moderately heavy metal contamination. However,
results obtained through the hydroponic experiment need to
be confirmed by field experiments.
