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10 Phytostabilization as Soil Remediation Strategy 193

Fig. 10.5 Effects of heavy metals stress on biomass of Sesbania virgata. Data are means 1 S.D.
Means followed by the same letter (a–e) were not significantly different at p < 0.05

active tissues of the shoot parts (Zhang et al. 2010). These results are in agreement
with those of Sinha and Gupta (2005), who demonstrated that the accumulation of
heavy metals varies from one part to another within the plant tissues.
In general, plants grown in treatments with low levels of heavy metals had the
highest biomass performance (p < 0.001, Fig. 10.5) compared to treatments with
high levels. In particular, the maximum decrease in S. virgata biomass was noticed
in the mixture of Cu and Zn at high levels (87.4 %), having, also, a delay in their
development. These results suggest that the type of interactions between the
constituent metals in the mixture is a synergistic or additive response. In conclu-
sion, the results suggest that the uptake of one metal is affected by the presence of
other metals. In addition, S. virgata plants have the capacity to tolerate and stabilize
high concentrations of Cu, Zn, and Cr in soils. It is assumed that roots may play an
important role in metal retention by preventing an excessive and toxic accumulation
in shoots. The co-presence of metals resulted in a greater reduction in S. virgata
biomass than the presence of a single metal. In particular, when Cu and Zn were
present at high levels this reduction was higher, thus suggesting a synergistic or
additive response. Based on this experiment, and in view of their uptake capacity
and tolerance, we propose that S. virgata plants can be used for phytostabilization
of metals in contaminated soils.

10.4 Recycling Heavy Metals

According to the Environmental Protection Agency, hazardous wasted reuse,
recycling, and reclamation (recycling metals) can avoid environmental hazards, pro-
tect natural resources, and reduce the nation’s reliance on raw materials and energy.