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142 T. Vamerali et al.

spp.) (Laureysens et al. 2004a, b) and willow (Salix spp.) (Rosselli et al. 2003;
Dickinson and Pulford 2005) may provide an efficient and cost-effective decon-
tamination method. Herbaceous species produce a denser vegetation cover which is
effective against erosion and may create an aerobic environment in the rhizosphere,
increasing soil aggregation and binding contaminants through the release of organic
matter (Pulford and Watson 2003; Robinson et al. 2006). Roots can also efficiently
act in phytostabilisation by sequestering metals, especially those with limited
mobility such as Pb and Cu (Marmiroli et al. 2005; Yoon et al. 2006) and favouring
precipitation with root exudates (Heim et al. 1999; Yang et al. 2005). Various
means have been successfully tested in the last 10 years to improve phytoextraction
efficiency in biomass species, but mainly in agricultural or forest soils. Assisted
phytoextraction with low toxic organic chelators, like NTA (nitrilotriacetic acid)
and EDDS (ethylene-diamine-disuccinic acid), positively increase metal uptake in
Ethiopian mustard (Brassica carinata A. Braun) (Quartacci et al. 2007). Exogenous
applications of growth regulators may also result in higher growth and metal uptake
in alfalfa (Medicago sativa L.) and sunflower (Helianthus annuus L.) (Lopez et al.
2005; Liphadzi et al. 2006), whereas mycorrhization facilitates metal acquisition in
maize (Zae mays L.) (Shen et al. 2006; Wang et al. 2007). However, investigations
are often conducted in the laboratory or in microcosms, thus making transferral of
results to the open field ineffective. Only few experiments have been carried out
in situ and limited information is available on particular substrates, such as
sediments and industrial wastes. In this framework, a summary of results on the
phytoremediation of pluri-metal-contaminated pyrite cinders is presented here,
focusing on plant responses to several agronomic practices at pot and field level.
As a single green technology may fail in this context, the traditional concept of
phytoremediation should be reviewed in the light of a multidisciplinary approach.

8.2 What the Literature States on Phytoremediation of Pyrite

Among metal-polluted media, great concern focuses on industrial waste or
sediments, the unusual composition of which may further limit plant establishment
and growth. Among these, we considered pyrite waste, which remains after sulphur

extraction from pyrite ore roasting at extremely high temperatures (~800 C). The
waste presents itself as red cinders, mainly composed of fine particles of pyrite
(FeS 2 ) and other minerals and devoid of organic matter (Vidal et al. 1999). Oxida-
tion of metal sulphides from pyrite residues can release soluble metals and increase
soil acidity (Clemente et al. 2006), with consequent hazardous metal movements.
Phytomanagement of pyrite waste is an interesting and inexpensive option to
reduce wind erosion and metal leaching, but little information is available in the
literature on this issue, particularly at field scale. In recent years, some authors have
found that cultivation of soybean (Glycine max (L.) Merr.), sorghum (Sorghum
bicolor L.), maize and sunflower is possible at various rates of pyrite dilution, but
only at pot level (Fellet et al. 2007). In the open field, the establishment and