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10 Phytostabilization as Soil Remediation Strategy 189

back into the environment in autumn, (5) contaminants may be collected in woody
tissues used as fuel, and (6) time taken to remediate sites far exceeds that of other
technologies.
Plant species selection is a critical management decision for phytoremediation.
Grasses are thought to be excellent candidates, because their fibrous rooting
systems can stabilize soil and provide a large surface area for root–soil contact
(Kulakow et al. 2000). The application of indigenous plant species for phyto-
remediation is often favored as it requires less management and acclimatizes
successfully in native climate conditions and seasonal cycle. However, some exotic
plant species may perform better in remediation of specific metals and can be safely
used where the possibility of invasive behavior has been eliminated (USEPA 2000).
Some important criteria in selecting plant species for phytoremediation are as
follows:
• The levels of tolerance with respect to metal known to exist at the site
• The level of adequate accumulation, translocation, and uptake potential of
metals
• High growth rate and biomass yield
• Tolerance to water logging and extreme drought conditions
• Availability, habitat preference (e.g., terrestrial, aquatic, semiaquatic)
• Tolerance to high pH and salinity
• Root characteristic and depth of the root zone

However, phytoremediation is energy efficient for remediating sites, and it can
be used in combination with other remedial strategies as a finishing step to the
remedial process.

10.3.2 Argentina’s Phytostabilization Experiences

It is essential to use native plants for phytoremediation because these plants are
often better in terms of survival, growth, and reproduction under environmental
stress than plants introduced from other environments (Yoon et al. 2006). It is
important to acknowledge the behavior that each species has into the region it
belongs to (Brown et al. 2006). One way of contributing with the native
phytogenetic resources conservation is to identify the tolerance to heavy metals
of different species (Carpena and Bernal 2007). In order to achieve phyto-
remediation in the Argentinean pampas region, it is essential to assess the tolerance
of species native to this area. In this respect, Sesbania virgata (Cav.) Poir., also
known as Acacia Negra, a medium perennial shrub belonging to the legume family
Fabaceae, is a native species from the Argentinean pampas region. Previous studies
with Sesbania species in different areas have shown good results for
phytoremediation of multicontaminated soils, accumulating significantly higher
amounts of heavy metals in roots than in shoots (Ye et al. 2001; Chan et al. 2003;
Tandy et al. 2006). Different species of Sesbania have been used for revegetation of