Agriculture Reference
In-Depth Information
Table 16.1   Potential candidates for phytoremediation approach
Species
Metal contaminants Reference
A. halimus
Cd/Zn/Pb
Lutts et al. 2004
A. portulacoides
Cd/Cu/Zn/Fe/Ti
Luque et al. 1999 ; Rebordea and Caçador
2007 ; Cambrollé et al. 2012a, b
A. canescens
Cd/Cr
Sawalha et al. 2006
A. hortensis spp purpurea Pb/Zn
Kachout et al. 2012
A. hortensis spp rubra
Cu/Ni
Kachout et al. 2012
A. atacamensis Phil
Ar
Vromman et al. 2011
A. conodocarpa
Hg
Lomonte et al. 2010
A. palula
Se
Vickerman et al. 2002
A. spongiosa
Se
Vickerman et al. 2002
 The Importance of  Atriplex  Species in Heavy Metal 
Phytoremediation
The contamination of soil by heavy metals is one of the most serious environmental
problems and has significant implications for human health. The clean up of heavy
metals contaminated soils is one of the most difficult tasks for environmental engi-
neering. In most cases, traditional physiochemical methods are quite expensive and
may lead to soil alterations (Gardea-Torresdey et al. 2005 ). Phytoremediation based
on the use of plants to remove or degrade inorganic and organic pollutants, has
been proposed as a promising, environmentally friendly and relatively cheap. The
success of phytoremediation depends upon the identification of suitable plant spe-
cies those hyperaccumulate heavy metals. The use of deep-rooting xero-halophyte
species is may be of special interest in this context to remediate salty contaminated
area, especially in arid and semi-arid regions. Several species of the genus Atriplex ,
which are naturally salt- and drought-tolerant have been also suggested as poten-
tial candidates for a phytoremediation approach (Table 16.1 ) because of their high
biomass production associated with a deep root system. A. portulacoides was sug-
gested as a suitable species for the phytoremediation owing to the high translocation
rates of Cd and Cu towards the aboveground tissues (Reboreda and Caçador 2007 ).
A. portulacoides can tolerate external Cu levels of up to 15 mmol/l (1,000 mg Cu/l)
without suffering adverse physiological effects (Cambrollé et al. 2012a ). Further-
more, despite the fact that Cu concentrations of between 20 and 100 mg Cu/kg
DW in leaf tissue are generally considered excessive or toxic (Kabata-Pendias and
Pendias 2001 ), growth parameters of this species are unaffected by leaf tissue con-
centrations as high as 80 mg Cu/kg DW. A. portulacoides is able to survive with
external Cu levels of 35 mmol/l and can be found growing in sediments that con-
tain 300-3,000 ppm Cu. Sousa et al. ( 2008 ) stated that compartmentalization and
detoxification mechanisms are crucial to allow A. portulacoides to tolerate high
levels of heavy metals, and found that this species is able to retain a considerable
quantity of metals in the root cell wall. Cambrollé et al. ( 2012b ) reported also that
this salt-marsh shrub may represent a valuable tool in the restoration of Zn-polluted
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