Environmental Engineering Reference
In-Depth Information
phytoremediation potential of flora that are toler-
ant to heavy metal in the contaminated soils of
an abandoned Pb mine in Central Portugal and
found several plants exhibiting high uptake of
metals, including
Cistus salvifolius
(Pb 548 mg/
kg),
Digitalis purpurea
(Zn 1017 mg/kg and Fe
4450 mg/kg),
Mentha suavolens
(Ag 1.9 mg/kg)
and
Ruscus ulmifolius
(Ag 1 mg/kg). Ruiz et al.
(
2011
) reported development of a transplastomic
approach showing expression of mouse metallo-
thionein gene (
mt1
) in a plant chloroplast result-
ed in high accumulation of mercury within plant
cells. Recently,
Wolffia globosa
was found to be a
strong Cd accumulator and has great potential for
Cd phytoremediation (Xie et al.
2013
).
soils in China. Their study revealed that alfalfa
was effective in both monoculture and intercrop-
ping for removing PAEs from contaminated soils.
Saiyood et al. (
2013
) found that an evergreen
mangrove tree,
Bruguiera gymnorhiza gymno-
rhiza,
is tolerant to bisphenol A (BPA) and has
the capability to remove BPA. Souza et al. (
2013
)
showed that
Myriophyllum aquaticum
can reduce
oxygen demand (COD), biochemical oxygen de-
mand (BOD), and total phosphorus (TP) in 15
days, and ammoniacal nitrogen (AN) as well as
total Kjeldahl nitrogen (TKN) in 30 days, indi-
cating potential as a candidate for phytoremedia-
tion of polluted water.
5.6
Genetic Engineering in Phytore-
mediation
5.5.2
For Other Pollutants
Besides heavy metals, plants are also screened
for the phytoremediation of other pollutants such
as PCB, benzo[a]pyrene (B[a] P) and tetracy-
cline (TC). Ficko et al. (
2011
) investigated the
effects of plant age, contaminant characteristics
and species-specific properties on PCB uptake
and accumulation patterns in plant tissues of the
three perennial weed species (L. (
ox-eye daisy
),
L. (
curly dock
), and L. (
Canada goldenrod
)) and
correlated that shoot contaminant concentrations
and total biomass are dependent on plant age and
life cycle (vegetative and reproductive stages).
Sun et al. (
2011
) showed that the French
marigold (
Tagetes patula
) might be useful for
phytoremediation of B[a] P and B[a] P-Cd con-
taminated sites. The presence of veterinary and
human antibiotics in soil and surface water is also
an emerging environmental concern. Datta et al.
(
2013
) evaluated the potential of vetiver grass
(
Chrysopogon zizanioides
L.) for removing TC
from aqueous media and provide a base for the
development of a cost-effective, in situ phytore-
mediation technique to remove antibiotics con-
sisting of TC groups from wastewater. Ma et al.
(
2013
) reported the use of legume (alfalfa,
Medi-
cago sativa
L.) grass (perennial ryegrass,
Lolium
perenne
L. and tall fescue,
Festuca arundinacea
)
for removing phthalic acid esters (PAEs) by in-
tercropping in e-waste contaminated agricultural
Phytoremediation, although having potential for
cleaning up the environment, alone cannot suc-
cessfully detoxify or interconvert the metals,
PCBs and other contaminants to more benign
forms. But biotechnological approaches, espe-
cially the application of genetic engineering,
may prove to be a potential technique through
which the gene from other organisms can be inte-
grated to enhance phytoremediation capabilities
in plants.
In case of mercury pollution the plants have
been genetically engineered both via nuclear ge-
nome and chloroplast genome (Ruiz and Daniel
2009
). The cloning of
merA
(mercuric ion reduc-
tase) and
merB
(organomercurial lyase) genes
from bacteria for the remediation of Hg (Bizly
et al.
2003
; Che et al.
2003
; Heaton et al.
2003
;
Lyyra et al.
2007
) is a well-understood protocol.
The chloroplast has been the main target for mer-
cury poisoning (Bernier and Carpentier
1995
;
Sinha et al.
1996
; Sabat
1996
). The protection
of essential metabolic reactions occurring within
plastids has been working area for expressing
merA
and
merB
genes within plant chloroplasts
(Ruiz et al.
2003
).
For iron phytoremediation, the
FRO2
gene,
which encodes ferric chelate reductase was found
to restore ferric chelate reductase activity in an
Arabidopsis
mutant deficient in this enzyme
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