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Phytotechnologies for Site Remediation
The term “bioavailability” is defined as the fraction of an element in soil which
is available for absorption by humans, animals, or plants. In the processes of
in situ inactivation or chemical stabilization the appropriate soil amendments are
used for immobilization of contaminants in soil (Attanayake et al., 2014; Berti &
Cunningham, 1997; Brown et al., 2003; Defoe et al., 2014; Hettiarachchi et al., 2000).
Contaminant immobilization is achieved through enhanced sorption in soil,
absorption and accumulation in roots, adsorption to roots or precipitation within
the root zone, and physical stabilization of soils (USEPA, 2000). Phytostabilization
assisted with soil amendments can also support re-establishment of vegetation
at contaminated sites lacking native grasses because of high concentrations of
phytotoxic trace elements or poor soil characteristics, i.e., low pH and poor
agrichemical and physical characteristics (Gudichuttu, 2014; Solís-Dominguez
et al., 2012; Tordoff et al., 2000; Wijesekara et al., 2016). Phytostabilization is recommended when other remediation approaches are not feasible due to extended
contaminated area. It is also useful in case of limited funds for another remediation technique. The advantages of phytostabilization are low cost, simple
implementation, and aesthetic aspects (Berti & Cunningham, 2000). The disadvantages are as follows: needs a long period (usually 30–40 years) for restoration
of the certain area, problems connected with disposal of contaminated biomass,
limited development of root system, seasonal and climate dependence.
There are two types of plants suitable for a phytostabilization process.
One group is formed by plants tolerant to high concentrations of contaminants, i.e., trace element excluders. Another group is represented by species
with highly developed root systems that can immobilize contaminated substances through uptake, precipitation, or reduction. In this case rather often
relevant contaminants are concentrated in the roots and only a small portion
of contaminants can move to the aboveground part of the plant.
Careful selection of plant species is the determining factor for the success of
phytostabilization. Plant characteristics and soil properties are both important for proper selection of the most suitable phytoagent. Native species
which can survive in targeted contaminated soil are made a preferred
choice in many phytostabilization processes (Solís-Dominguez et al., 2012).
In addition, the plants appropriate for phytostabilization are grasses and
fast-growing plants which can provide sufficient coverage with developed
root systems to stabilize trace elements. Selected plants should be simple for
further maintenance after establishment.
2.4 Bioenergy Crops and Phytostabilization Options
Bioenergy crops are promising candidates for phytostabilization of soils
contaminated with trace elements due to their good ability to grow in contaminated and marginal soils (Pidlisnyuk et al., 2014). Below the main energy