Agriculture Reference
In-Depth Information
baseline. Based on visual field accuracy assessment and laboratory analysis to more
quantitatively verify our results, we were able to confirm that the red dust map attained for
the chosen study area has reached a good level of accuracy (i.e. an Overall Accuracy of 86%).
The attained promising results highlight the usefulness of hyperspectral remote sensing
data for mapping hazardous industrial pollutant, such as the red dust deposition on soils,
providing their exact position.
3. Solidification/stabilization technologies for soil remediation: use of fly ash
and red mud
Over the last few years a great deal of research has been carried out in order to develop
remediation methods for reducing environmental risks due to polluting metal and several
soil remediation technologies are based on physico-chemical processes of
solidification\stabilization (S\S). In general, solidification refers to the physical
encapsulation of the contaminant in a solid matrix while stabilization includes chemical
reaction to reduce contaminant mobility (Mulligan et al., 2001). The S\S process could be
applied both in laboratory and in situ showing good results against the risk with the
remarkable benefit of immobilizing heavy metal inside natural minerals, such as clays and
zeolite or soil-compatible materials. Among these, fly ash and red muds are widely used
(Apak et al., 1998; Castaldi et al., 2010; Ciccu et al., 2003; Coruh & Nur Ergun, 2010;
Dermatas & Meng, 2003; Garau et al., 2011; Glenister & Thornber, 1985; Gray et al., 2006;
Lombi et al., 2002a; McPharlin et al., 1994; Summers et al., 1996).
In particular, many authors show that amendment of contaminated soil with red mud
results in a durable reduction in metal mobility and also in a smaller risk of metal re-
mobilization if soil pH were to decrease (Gray et al., 2006; Lombi et al., 2002a). Detailed
experiments on the evaluation of the interaction mechanisms between red mud and heavy
metals also indicate that only low toxic elements concentration absorbed by red muds are in
the water-soluble and exchangeable form while the greatest concentration of metals
absorbed are tightly bound and would not be expected to be released readily under natural
conditions (Santona et al., 2006).
Application of red mud can also lead to a reduction in heavy metal uptake by plants (Friesl
et al., 2003; Lombi et al., 2002b; Muller & Pluquet, 1998).
Other methods for reducing environmental risks lean towards toxic element immobilization
using fly ash or zeolite synthesized from fly ash.
The addition of fly ash during S/S treatment of heavy metal contaminated soil is mainly
responsible for their effective immobilization by absorbing the waste species on their
surfaces or determining precipitation mechanisms (Dermatas & Meng, 2003; Singh & Pant,
2006; Vandecasteele et al., 2002). Precipitation of heavy metals results from the presence of
calcium hydroxide, while adsorption may be due to the presence of silica and alumina
available in fly ash.
Synthetic zeolite can be added to polluted soils (Querol et al., 2006; Lin et al., 1998; Rayalu et
al., 2006) or crystallized directly in those contaminated (Belviso et al. 2010b; 2010c; Terzano
et al., 2006) in order to solve environmental problems.
Zeolites are hydrated aluminosilicate minerals with a three-dimensional open structure
making them very useful for solving the mobility of toxic elements in a number of
environmental applications (Babel and Kurniawan, 2003; Ćurković et al., 1997; de'Gennaro
et al., 2003; Inglezakis et al., 2002, 2003; Kesraoui-Ouki et al.
,
1994; Kocaoba et al., 2007;
