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20 M. Barbafieri et al.

while phytostabilization aims to reduce the mobility/bioavailability of heavy metals
in the soil and the re-vegetation of the site, often in combination with adding
adsorbents and other chemicals to the soil (Kucharski et al. 2005; Mench et al.
2003). Normally technologies should be defined in detail regarding their application
protocol, efficiency, and cost–benefit calculations. In the case of phytoextraction
and phytostabilization, however, it is not possible to establish fixed schemes and
procedures based on exact data from technology evaluations. This is limited by the
nature of the technology itself which has to deal with soil complexity in relation to
heavy metal biogeochemistry, plant behavior in relation to agronomic practice and
climate conditions, variations in plant varieties within one species regarding uptake,
phytotoxicity of heavy metals, etc. The authors of this chapter gained experience on
this issue during the past 15 years, developing a realistic and balanced view on the
applicability of phytoextraction and phytostabilization of heavy metals in soils. This
includes awareness of the intrinsic methodic limitations and site-specificity, thus
contributing to avoiding phytoremediation to become a “hype” which after unavoid-
able failures would possible have backfired to the approach itself. Many studies have
been conducted in this field in the last two decades. Numerous plant species have
been identified and tested for their traits regarding the uptake and accumulation of
different heavy metals. Mechanisms of metal uptake at the whole plant level and at
cellular levels have been investigated (Clemens 2006). Progress has been made in
the mechanistic and practical application aspects of phytoremediation. They are
briefly reviewed and reported in this chapter.

2.1.1 The Importance of a Feasibility Test

As the technology is based on site-specific variables (soil characteristics, contaminant
levels, vegetation type, etc.), many variables during the implementation of a
phytoremediation process make fulfilling the objectives not always easy to attain.
In order to avoid that this could happen or, better, in order to minimize the likelihood
that the process proves to be not corresponding with our goals at the end, it is
imperative, before starting any real-life phytoremediation project, to perform checks,
which together are defined as a “feasibility test” (Nowolsieska-Sas et al. 2005).
In practice, a feasibility test simulates in a controlled environment the chemical,
physical, and biological processes at stake and the conditions which are assumed to
prevail in the field during phytoextraction or phytostabilization implementation.
A feasibility study or test is therefore an essential step to imitate as closely as
possible the real situation. The test is basically carried out by sampling the soil
matrix to be treated in a way as representative as possible for the whole site; the test
will therefore be carried out on real samples taken from the site. The test includes
all the analyses to characterize the soil and the contaminant behavior. After that, the
test proceeds with the selection of the most appropriate plant, based on the soil
analyses and on available literature experiences and references. This selection can
include specific lysimeter or pot experiments. The results obtained from the