Zhang G
.


Sumber
: http://www.ncbi.nlm.nih.gov/pubmed/12920919 ….
Diunduh

7/5/2012

. The biosynthesis pathway of
phytochelatins

(PC) and its function in heavy metal
tolerance of higher plants were summarized in this paper. The toxic heavy metal
accumulation in soil would deteriorates crop growth and yield components, and
threaten the agro
-
products security. There were significantly differences in the
accumulation and tolerance to heavy metals among plant species and genotypes. The
formation of PC in response to the stress caused by heavy metals was one of the truly
adaptive responses occurred commonly in higher plants. In the heavy metal tolerant
genotypes, there was a much higher accumulation of PC than the non
-
tolerant lines.
Glutathione (GSH) was the substrate for the synthesis of PC, which
chelated

the
metals. The inactive toxic metal ions of metal
--
PC
chelatins

were subsequently
transported from
cytosol

to vacuole before they could poison the enzymes of life
-
supporting metabolic routes, and transiently stored in vacuole to reduce the heavy
metal concentration in
cytosol
, thus, heavy metal detoxification was attained. The
break through of genetic mechanism and bio
-
chemical pathway of PC synthesis
induced by heavy metals would depend on the further study on molecular biology in
this field. The isolation of
Cd
-
sensitive cad1 and cad2 mutants of Arabidopsis thaliana,
that was deficient in PC,
demonstrted

the importance of PC for heavy metal tolerance.
The effect of PC on food security and on
phytoremediation

of soil and water
contaminated by heavy metals was also discussed in this paper.

Gene.

1996 Nov 7;179(1):21
-
30.

Heavy metal detoxification in higher plants
--
a review.

Zenk

MH
.

Sumber
: http://www.ncbi.nlm.nih.gov/pubmed/8955625 ….
Diunduh

7/5/2012

. A set of heavy
-
metal
-
complexing

peptides was isolated from plants and plant
suspension cultures. The structure of these peptides was established as (gamma
-
glutamic

acid
-
cysteine
)n
-
glycine

(n = 2
-
11) [(gamma
-
Glu
-
Cys
)n
-
Gly
]. These peptides
appear upon induction of plants with metals of the transition and main groups (
Ib
-
Va
, Z
= 29
-
83) of the periodic table of elements. These peptides, called
phytochelatins

(PC),
are induced in all autotrophic plants so far analyzed, as well as in select fungi. Some
species of the order
Fabales

and the family
Poaceae

synthesize aberrant PC that
contain, at their C
-
terminal end, either beta
-
alanine
, serine or
glutamic

acid. For this
group of peptides the name
iso
-
PC is proposed. The biosynthesis of PC proceeds by
metal activation of a constitutive enzyme that uses glutathione (GSH) as a substrate;
this enzyme is a gamma
-
glutamylcysteine

dipeptidyl

transpeptidase

which was given
the trivial name PC
synthase
. It catalyzes the following reaction: gamma
-
Glu
-
Cys
-
Gly

+
(gamma
-
Glu
-
Cys
)n
-
Gly
--
>(gamma
-
Glu
-
Cys
)n+1
-
Gly +
Gly
. The plant vacuole is the
transient storage compartment for these peptides. They probably dissociate, and the
metal
-
free peptide is subsequently degraded. Sequestration of heavy metals by PC
confers protection for heavy
-
metal
-
sensitive enzymes. The isolation of a
Cd
(2+)
-
sensitive
cadl

mutant of Arabidopsis thaliana, that is deficient in PC
synthase
,
demonstrates conclusively the importance of PC for heavy metal tolerance. In spite of
the fact that nucleic acid sequences and proteins are found in higher plants that have
distant homology to animal
metallothioneins
, there is absolutely no experimental
evidence that these "plant
metallothioneins
' are involved in the detoxification of heavy
metals. PC
synthase

will be an interesting target for biotechnological modification of
heavy metal tolerance in higher plants.

.

J Trace Elem Med Biol.

2005;18(4):339
-
53.

Molecular mechanisms of heavy metal
hyperaccumulation

and
phytoremediation
.

Yang X
,
Feng

Y
,
He Z
,
Stoffella

PJ
.


Sumber
: http://www.ncbi.nlm.nih.gov/pubmed/16028496 ….
Diunduh

7/5/2012

A relatively small group of
hyperaccumulator

plants is capable of sequestering heavy
metals in their shoot tissues at high concentrations. In recent years, major scientific
progress has been made in understanding the physiological mechanisms of metal
uptake and transport in these plants. However, relatively little is known about the
molecular bases of
hyperaccumulation
. In this paper, current progresses on
understanding cellular/molecular mechanisms of metal tolerance/
hyperaccumulation

by plants are reviewed. The major processes involved in
hyperaccumulation

of trace
metals from the soil to the shoots by
hyperaccumulators

include: (a)
bioactivation

of
metals in the
rhizosphere

through root
-
microbe interaction; (b) enhanced uptake by
metal transporters in the plasma membranes; (c) detoxification of metals by
distributing to the
apoplasts

like binding to cell walls and
chelation

of metals in the
cytoplasm with various
ligands
, such as
phytochelatins
,
metallothioneins
, metal
-
binding proteins; (d) sequestration of metals into the vacuole by
tonoplast
-
located
transporters. The growing application of molecular
-
genetic technologies led to the well
understanding of mechanisms of heavy metal tolerance/accumulation in plants, and
subsequently many transgenic plants with increased resistance and uptake of heavy
metals were developed for the purpose of
phytoremediation
. Once the rate
-
limiting
steps for uptake, translocation, and detoxification of metals in
hyperaccumulating

plants are identified, more informed construction of transgenic plants would result in
improved applicability of the
phytoremediation

technology.

Crit

Rev
Biotechnol
.

2010 Mar;30(1):23
-
30.

Understanding molecular mechanisms for improving
phytoremediation

of heavy metal
-
contaminated soils.

Hong
-
Bo S
,
Li
-
Ye C
,
Cheng
-
Jiang R
,
Hua

L
,
Dong
-
Gang G
,
Wei
-
Xiang L
.

Sumber
: http://www.ncbi.nlm.nih.gov/pubmed/19821782 ….
Diunduh

7/5/2012

Heavy metal pollution of soil is a significant environmental problem with a negative
potential impact on human health and agriculture.
Rhizosphere
, as an important
interface of soil and plants, plays a significant role in
phytoremediation

of
contaminated soil by heavy metals, in which, microbial populations are known to affect
heavy metal mobility and availability to the plant through release of chelating agents,
acidification, phosphate
solubilization

and
redox

changes, and therefore, have
potential to enhance
phytoremediation

processes.
Phytoremediation

strategies with
appropriate heavy metal
-
adapted
rhizobacteria

or
mycorrhizas

have received more and
more attention. In addition, some plants possess a range of potential mechanisms that
may be involved in the detoxification of heavy metals, and they manage to survive
under metal stresses. High tolerance to heavy metal toxicity could rely either on
reduced uptake or increased plant internal sequestration, which is manifested by an
interaction between a genotype and its
environment.A

coordinated network of
molecular processes provides plants with multiple metal
-
detoxifying mechanisms and
repair capabilities. The growing application of molecular genetic technologies has led
to an increased understanding of mechanisms of heavy metal tolerance/accumulation
in plants and, subsequently, many transgenic plants with increased heavy metal
resistance, as well as increased uptake of heavy metals, have been developed for the
purpose of
phytoremediation
. This article reviews advantages, possible mechanisms,
current status and future direction of
phytoremediation

for heavy
-
metal
-
contaminated
soils.

Environ
Sci

Pollut

Res Int. 2003;10(5):335
-
40.

Heavy metals in plants and
phytoremediation
.

Cheng S.

Sumber
: http://www.ncbi.nlm.nih.gov/pubmed/14535650 ….
Diunduh

7/5/2012.

GOAL, SCOPE AND BACKGROUND:

In some cases, soil, water and food are heavily polluted by heavy metals in China. To
use plants to remediate heavy metal pollution would be an effective technique in
pollution control. The accumulation of heavy metals in plants and the role of plants in
removing pollutants should be understood in order to implement
phytoremediation
,
which makes use of plants to extract, transfer and stabilize heavy metals from soil and
water.

METHODS:

The information has been compiled from Chinese publications stemming mostly from
the last decade, to show the research results on heavy metals in plants and the role of
plants in controlling heavy metal pollution, and to provide a general outlook of
phytoremediation

in China. Related references from scientific journals and university
journals are searched and summarized in sections concerning the accumulation of
heavy metals in plants, plants for heavy metal purification and
phytoremediation

techniques.

RESULTS AND DISCUSSION:

Plants can take up heavy metals by their roots, or even via their stems and leaves, and
accumulate them in their organs. Plants take up elements selectively. Accumulation
and distribution of heavy metals in the plant depends on the plant species, element
species, chemical and
bioavailiability
,
redox
, pH,
cation

exchange capacity, dissolved
oxygen, temperature and secretion of roots. Plants are employed in the
decontamination of heavy metals from polluted water and have demonstrated high
performances in treating mineral tailing water and industrial effluents. The purification
capacity of heavy metals by plants are affected by several factors, such as the
concentration of the heavy metals, species of elements, plant species, exposure
duration, temperature and
pH.

CONCLUSIONS:

Phytoremediation
, which makes use of vegetation to remove, detoxify, or stabilize
persistent pollutants, is a green and environmentally
-
friendly tool for cleaning polluted
soil and water. The advantage of high biomass productive and easy disposal makes
plants most useful to remediate heavy metals on site.

RECOMMENDATIONS AND OUTLOOK:

Based on knowledge of the heavy metal accumulation in plants, it is possible to select
those species of crops and pasturage herbs, which accumulate fewer heavy metals, for
food cultivation and fodder for animals; and to select those
hyperaccumulation

species
for extracting heavy metals from soil and water. Studies on the mechanisms and
application of
hyperaccumulation

are necessary in China for developing
phytoremediation
.

.

Phytoremediation

of Mercury
-
Contaminated Mine Tailings by Induced Plant
-
Mercury
Accumulation

Fabio N.

Moreno

a1
c1
,
Chris W. N.

Anderson

a1
,
Robert B.

Stewart

a1

and

Brett H.

Robinson

Environmental Practice

(2004), 6 : pp 165
-
175

Sumber
:
http://journals.cambridge.org/action/displayAbstract;jsessionid=1E7D249F1167541C9ABFF5DBF479E2F9.jo
urnals?fromPage=online&aid=348969 ….
Diunduh

7/5/2012

In most contaminated soils and mine tailings, mercury (Hg) is not readily available for
plant uptake. A strategy for inducing Hg mobilization in soils to increase accumulation
potential in plants was investigated to enhance Hg
phytoremediation
. Accumulation of
Hg in the nickel
hyperaccumulator

Berkheya

coddii
, the salt
-
tolerant
Atriplex

canescens
, and the
nonaccumulators

Brassica

juncea

and
Lupinus

sp. was studied by
pot trials containing mine tailings treated with either soluble Hg or sulfur
-
containing
ligands
. Accumulation of Hg in shoots of
B.
coddii

and
A.
canescens

after addition of
soluble Hg was lower than 10 mg/kg dry weight. The addition of ammonium
thiosulfate

(NH
4
S
2
O
3
) to tailings mobilized Hg in substrates, as indicated by the
elevated Hg concentrations in
leachates

from the pots of both species. Ammonium
thiosulfate

caused a significant increase in the Hg concentration in shoots of
B.
juncea
.

Conversely, Hg translocation to
Lupinus

sp. shoots was significantly reduced in the
presence of this
ligand
. Mass balance calculations revealed a significant fraction of Hg
was lost from the system. This unaccounted
-
for Hg may indicate Hg volatilization. The
results suggest that there is potential for induced plant Hg accumulation for
phytoremediation

of Hg
-
contaminated sites. Issues of Hg leaching and volatilization,
however, need to be addressed before this technology can be implemented in the
field.

Effect of Selective Pressure and Genetically Engineered Microorganism (GEM) Densities on
Mercury Resistance (
mer
)
Operon

Transfer in Elbe River and Estuarine Sediments

Björg

V.

Pauling

a1
,
Niels

Kroer

a2

and

Irene

Wagner
-
Döbler

Environmental Practice

(2004), 6 : pp 176
-
190

Sumber
:
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=348969&next=true&jid=ENP&
volumeId=6&issueId=02 ….
Diunduh

7/5/2012

Bacterial reduction of mercury ions to elemental mercury by the
mer

operon
-
encoded
microbial resistance mechanism has recently been shown to be a promising approach
in the bio
-
remediation of mercury
-
contaminated wastewater. Mercury resistance is
widespread among environmental bacteria and several isolates have proven to be
adaptable
catalyzers

for mercury reduction in bioreactors. To accomplish high, stable,
and predictable performance, however, the genetically engineered microorganism
(GEM)
Pseudomonas
putida

KT2442::mer73 has been constructed, which constitutively
expresses the mercury resistance
operon

at a high level, is nonpathogenic, and does
not contain plasmids. To assess the safety of this GEM in an open environmental
application, gene transfer was investigated in stream and estuarine microcosms
containing sediments from the Elbe River and Roskilde Fjord, Denmark. In
P.
putida

KT2442::mer73, the
mer
TPAB

genes have been stably integrated into the chromosome
to reduce the chance of horizontal transfer. Consequently gene transfer to an
isogenic

recipient strain,
P.
putida

KT2442::
Tc
, could not be detected, although parameters such
as recipient cell density, cell shock, continuous addition of cells, or application of
mercury selective pressure were adjusted with respect to increasing the probability of
gene exchange. On the basis of these experiments, the strain
P.
putida

KT2442::mer73
can be regarded as safe.

.

Mercury Behavior in a Tropical Environment: The Case of Small
-
Scale Gold Mining in
Poconé
, Brazil

Lazaro

J.

Oliveira

a1
c1
,
Lars D.

Hylander

a2

and

Edinaldo

de Castro e Silva.

Environmental Practice

(2004), 6 : pp 121
-
134

Sumber
:
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=348961&fulltextType=RA&fileI
d=S1466046604000237 ….
Diunduh

7/5/2012

. An estimated 50 tons of mercury (Hg) have been emitted by gold miners in the Bento
Gomes river basin, in the municipality of
Poconé
, Brazil, since the 1980s. Since the mid
-
l990s, the state agency for environmental protection, FEMA (
Fundação

Estadual

do
Meio

Ambiente

de
Mato

Grosso
), has enforced regulations to reduce Hg emissions to
air and water and has also implemented an environmental assessment program. The
objectives of this study were to evaluate efforts to reduce emissions of Hg to air and
water from nine improved amalgamation centers, and to assess the pollution level in
sediment at 25 sites around
Poconé
. In spite of the fact that retorts were used, results
showed large emissions of Hg when burning amalgam, resulting in Hg air
concentrations above the limit for occupational air (50
μ
g/m
3
) at all centers except
one. Keeping washing water in closed systems and dumping residues in specially
prepared sites reduced Hg emissions to watercourses. The average Hg concentration of
fine sediments (<74
μ
m) in the Bento Gomes river basin was 104
ng

Hg/g dry weight,
three to four times higher than the background level; large amounts of Hg
-
contaminated sediments are re
-
suspended during the rainy season. In conclusion,
present emissions to local watercourses have been efficiently reduced, but the use of
retorts in improved amalgamation centers has not adequately reduced Hg emissions to
air, which is why the use of Hg remains an occupational and environmental problem.

.

Bioaccumulation Factors for Mercury in Stream Fish

George R.

Southworth

a1
c1
,
Mark J.

Peterson

a1

and

Mary Anna

Bogle
.

Environmental Practice

(2004), 6 : pp 135
-
143

Sumber
:
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=348961&next=true&jid=ENP&
volumeId=6&issueId=02 ….
Diunduh

7/5/2012

. The bioaccumulation of
methylmercury

in fish is a complex process affected by many
site
-
specific environmental factors. The US Environmental Protection Agency (USEPA)
recently recommended changing the basis for expressing the ambient water quality
criterion for mercury from an aqueous concentration to a measure of the
methylmercury

concentration in fish. This change would make the regulation of
mercury in surface waters a site
-
specific exercise in which fish
-
based bioaccumulation
factors (BAF; the ratio of mercury concentration in fish to the concentration of mercury
in water) are used to calculate aqueous concentration limits for total mercury. These
limits would then be used to allocate mercury loading among various point and
nonpoint sources and guide regulatory actions. In order for this approach to succeed, it
is critical that the site
-
specific BAFs and
methylmercury:total

mercury conversion
factors be independent of aqueous total mercury concentration (
Hg
T
). We investigated
this relationship by measuring aqueous
methylmercury

and
Hg
T
s

and mercury in fish in
ecologically similar warm
-
water streams in the southeastern United States.
Bioaccumulation factors based on
Hg
T

in water were found to decrease with increasing
Hg
T
, primarily as a consequence of the reduction in the ratio of aqueous
methylmercury

to total mercury with increasing
Hg
T
.

Methylmercury
-
based BAFs did
not vary as a function of
Hg
T
.

The implication of this relationship is that site
-
specific
determination of aqueous
Hg
T

limits at contaminated sites may use BAFs that would be
underestimates of the appropriate BAFs to describe mercury bioaccumulation in the
system after mercury inputs have been reduced. In such cases, regulatory limits set
using site
-
specific BAFs might not achieve their intended purpose of reducing mercury
contamination in fish to acceptable concentrations.

Thermal Desorption for Mercury Removal from Sediments Sampled from the
Adriatic Sea

Daniele

Benotti

a1
c1
,
Massimo

Delfini

a1
,
Mauro

Ferrini

a1
,
Floriana

La
Marca

a1
,
Paolo

Massacci

a1
,
Luigi

Piga

a1

and

Paolo

Colosimo

Environmental Practice

(2004), 6 : pp 144
-
156

Sumber
:
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=348963&next=true&jid=ENP&
volumeId=6&issueId=02 ….
Diunduh

7/5/2012

. Overall sampling of the sediments in the Adriatic Sea at the mouth of the
Isonzo

(
Soça
) River in Italy has permitted updating of the extent and level of mercury
contamination. The
lsonzo

River transports mercury
-
bearing residues from the
ldrija

mine (Slovenia); that area is contaminated due to the mining of cinnabar (
HgS
). The
mercury mine started operations in the 15th century and was finally shut down in the
1980s because of the decreased demand for mercury. An attempt was made to remove
mercury from the contaminated sediments by thermal desorption, with the aim of
ascertaining whether low temperature and short residence time could be suitable
parameters for sediment cleanup if future needs should so require. To date, no studies
have been done on the health of the Italian population living in the Gulf of Trieste
area; hence there is no known correlation between the anomalous mercury content of
the sediments and symptoms attributable to the ingestion of even small quantities of
mercury. Desorption times of about 20 to 30 minutes, at temperatures ranging from
325
°

C to 350
°

C, yielded residues with a mercury content below the limit imposed by
Italian regulations for contaminated soils and sediments (5
ppm
). The air and the
mercury vapors driven off during roasting were treated before being released to the
atmosphere.

.

Phytoremediation

of Mercury
-
Contaminated Mine Tailings by Induced Plant
-
Mercury
Accumulation

Fabio N.

Moreno

a1
c1
,
Chris W. N.

Anderson

a1
,
Robert B.

Stewart

a1

and

Brett H.

Robinson

Environmental Practice

(2004), 6 : pp 165
-
175

Sumber
:
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=348969&fulltextType=RA&fileI
d=S1466046604000274 ….
Diunduh

7/5/2012

In most contaminated soils and mine tailings, mercury (Hg) is not readily available for
plant uptake. A strategy for inducing Hg mobilization in soils to increase accumulation
potential in plants was investigated to enhance Hg
phytoremediation
. Accumulation of
Hg in the nickel
hyperaccumulator

Berkheya

coddii
, the salt
-
tolerant
Atriplex

canescens
, and the
nonaccumulators

Brassica

juncea

and
Lupinus

sp. was studied by
pot trials containing mine tailings treated with either soluble Hg or sulfur
-
containing
ligands
. Accumulation of Hg in shoots of
B.
coddii

and
A.
canescens

after addition of
soluble Hg was lower than 10 mg/kg dry weight. The addition of ammonium
thiosulfate

(NH
4
S
2
O
3
) to tailings mobilized Hg in substrates, as indicated by the
elevated Hg concentrations in
leachates

from the pots of both species. Ammonium
thiosulfate

caused a significant increase in the Hg concentration in shoots of
B.
juncea
.

Conversely, Hg translocation to
Lupinus

sp. shoots was significantly reduced in the
presence of this
ligand
. Mass balance calculations revealed a significant fraction of Hg
was lost from the system. This unaccounted
-
for Hg may indicate Hg volatilization. The
results suggest that there is potential for induced plant Hg accumulation for
phytoremediation

of Hg
-
contaminated sites. Issues of Hg leaching and volatilization,
however, need to be addressed before this technology can be implemented in the
field.

Phytoremediation

of mercury using
Eichhornia

crassipes

(Mart.)
Solms


Upma

Narang
,
Renu

Bhardwaj
, S.K.
Garg
, A.K.
Thukral

International Journal of Environment and Waste Management 2011
-

Vol. 8, No.1/2

pp.

92


105.



Sumber
: http://www.inderscience.com/search/index.php?action=record&rec_id=40967 ….
Diunduh

8/5/2012

Roots of
Eichhornia

crassipes

were found to accumulate maximum content
of mercury (92.21
μ
g
g
−1

dry wt) in the roots of plants treated with 1000
μ
g
l
−1

concentration of mercuric acetate on 14th day of treatment. The
bioconcentration

factor (BCF) was found to be highest for lowest mercury
concentrations (1
μ
g l
−1
) in the medium. The uptake of mercury follows dual
pattern of ion uptake. Type
-
1 mechanism operates at mercury
concentrations up to 100
μ
g l
−1
, which is carrier
-
mediated and follows
Michaelis

Menten

kinetics. Type
-
2 mechanism occurs at concentrations up
to 1000
μ
g l
−1
.

. International Journal of Chemical Engineering

Volume 2011 (2011), 31 pages

A Review on Heavy Metals (As,
Pb
, and Hg) Uptake by Plants through
Phytoremediation

Bieby

Voijant

Tangahu
,
Siti

Rozaimah

Sheikh Abdullah, Hassan
Basri
,
Mushrifah

Idris
,
Nurina

Anuar
, and Muhammad
Mukhlisin

Sumber
: http://www.hindawi.com/journals/ijce/2011/939161/abs/ ….
Diunduh

8/5/2012

. Heavy metals are among the most important sorts of contaminant in the
environment. Several methods already used to clean up the environment from these
kinds of contaminants, but most of them are costly and difficult to get optimum
results. Currently,
phytoremediation

is an effective and affordable technological
solution used to extract or remove inactive metals and metal pollutants from
contaminated soil and water. This technology is environmental friendly and potentially
cost effective. This paper aims to compile some information about heavy metals of
arsenic, lead, and mercury (As,
Pb
, and Hg) sources, effects and their treatment. It also
reviews deeply about
phytoremediation

technology, including the heavy metal uptake
mechanisms and several research studies associated about the topics. Additionally, it
describes several sources and the effects of As,
Pb
, and Hg on the environment, the
advantages of this kind of technology for reducing them, and also heavy metal uptake
mechanisms in
phytoremediation

technology as well as the factors affecting the uptake
mechanisms. Some recommended plants which are commonly used in
phytoremediation

and their capability to reduce the contaminant are also reported.


Phytofiltration

of mercury
-
contaminated water:
Volatilisation

and plant
-
accumulation
aspects

Fabio N. Moreno, Christopher W.N. Anderson, Robert B. Stewart, Brett H. Robinson.

Environmental and Experimental Botany

Volume 62, Issue 1
, January 2008, Pages 78

85


Sumber
: http://www.sciencedirect.com/science/article/pii/S009884720700113X ….
Diunduh

8/5/2012

.
Phytofiltration

may be a cost
-
effective approach for treating Hg
-
contaminated
wastewater. We investigated the removal of Hg from solutions by Indian mustard
[
Brassica

juncea

(L.)
Czern
.] grown in hydroponic conditions with solutions containing
Hg concentrations from 0 to 10

mg/L. Plants were enclosed in gastight
volatilisation

chambers to assess the effect of Hg concentrations on plant transpiration,
accumulation and
volatilisation
. We also determined the speciation and site of origin
of
volatilised

Hg. Solution Hg concentrations of 5 and 10

mg/L detrimentally affected
transpiration. Roots concentrated Hg 100

270 times (on a dry weight basis) above
initial solution concentrations. The plants
translocated

little Hg to the shoots, which
accounted for just 0.7

2% of the total Hg in the plants.
Volatilisation

from planted
vessels increased linearly as a function of Hg concentrations in solutions. Most Hg
volatilisation

occurred from the roots.
Volatilised

Hg was predominantly in the Hg(0)
vapour

form.
Volatilisation

was dependant on root uptake and absorption of Hg from
the ambient solution. Production of Hg(0)
vapour

in the solutions may result from the
activity of root
-
associated algae and Hg
-
resistant bacteria.
Phytofiltration

effectively
removed up to 95% of Hg from the contaminated solutions by both
volatilisation

and
plant accumulation. However, Hg(0)
vapours

released from living roots may have
unforeseen environmental effects.

.

Mercury
volatilisation

and
phytoextraction

from base
-
metal mine tailings

Fabio N. Moreno, Chris W.N. Anderson, Robert B. Stewart

, Brett H. Robinson.

Environmental Pollution

Volume 136, Issue 2
, July 2005, Pages 341

352


Sumber
: http://www.sciencedirect.com/science/article/pii/S0269749105000035 ….
Diunduh

8/5/2012

. Experiments were carried out in plant growth chambers and in the field to investigate
plant
-
mercury accumulation and
volatilisation

in the presence of
thiosulphate

(S
2
O
3
)
-
containing solutions.
Brassica

juncea

(Indian mustard) plants grown in Hg
-
contaminated
Tui

mine tailings (New Zealand) were enclosed in gastight
volatilisation

chambers to investigate the effect of ammonium
thiosulphate

([NH
4
]
2
S
2
O
3
) on the
plant
-
Hg
volatilisation

process. Application of (NH
4
)
2
S
2
O
3

to substrates increased up to
6 times the Hg concentration in shoots and roots of
B.
juncea

relative to controls.
Volatilisation

rates were significantly higher in plants irrigated only with water (control)
when compared to plants treated with (NH
4
)
2
S
2
O
3
.
Volatilisation

from barren pots
(without plants) indicated that Hg in tailings is subject to biological and photochemical
reactions. Addition of sodium
thiosulphate

(Na
2
S
2
O
3
) at 5 g/kg of substrate to
B.
juncea

plants grown at the
Tui

mine site confirmed the plant growth chambers studies
showing the effectiveness of
thio
-
solutions at enhancing shoot Hg concentrations.
Mercury extraction from the field plots yielded a maximum value of 25 g/ha. Mass
balance studies revealed that
volatilisation

is a dominant pathway for Hg removal from
the
Tui

mine site. A preliminary assessment of the risks of
volatilisation

indicated that
enhanced Hg emissions by plants would not harm the local population and the
regional environment.

Kennedy, C. D. and
Gonsalves
, F. A. N. 1987.

J. exp. Bot. 38: 800

817.

The action of divalent zinc, cadmium, mercury, copper and lead on the trans
-
root potential
and H
+

efflux of excised roots.


Sumber
: http://jxb.oxfordjournals.org/content/38/5/800.abstract?sid=90319c95
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The action of Zn
2+
, Cd
2+
, Hg
2+
, Cu
2+

and Pb
2+

ions on the trans
-
root potential and H
+

efflux of young excised maize roots has been studied. Micro
-
electrode implantations
into root epidermal cells confirmed the root outer membranes as the major
contributor in the trans
-
root potential changes. The effects of these ions on H
+

efflux
were studied over a period of time in a continuous flow cell apparatus, adequate
controls allowing for transient interference due to divalent
cations

at the pH probe.

The addition of Zn
2+
, 5 to 100
μ
mol dm
−3
, to the solution bathing the roots reduces H
+

efflux and depolarizes the trans
-
root potential. However, in the presence of Mg
2+
, 0∙1
or 1∙0
mmol

dm
−3
, not only is this depolarization inhibited, but
hyperpolarization

is
observed instead. Cd
2+

affects trans
-
root potential and H
+

efflux at a much slower rate
than Zn
2+
, suggesting a lower membrane permeability. Without Mg
2+
, Cd
2+

hyperpolarizes the trans
-
root potential, but this is better sustained in its presence.
Hyperpolarization

did not occur with Hg
2+
, Cu
2+

or Pb
2+

whether or not Mg
2+

was
present Hg
2+

and to a lesser extent Cu
2+

are potent depolarizers of the trans
-
root
potential and strongly inhibit H
+

efflux.

The maximum rates of depolarization observed in the absence of Mg
2+

increase in the
order
Cd

≈ PCMBS

.
lt
; Zn ≈ Cu < Hg. This is similar to the relative maximum rates of
H
+

inhibition,
Pb


Cd


.
lt
; Zn < Cu < Hg, suggesting considerable differences in mode
of action and/or membrane permeability. The lower membrane permeability of the
sulphydryl

reagent PCMBS apparently prevents ready access to the site(s) of action
available to Hg
2+
.

The reductions in trans
-
root potential and H
+

gradients induced by this range of
cations

would be detrimental to the acquisition of nutrients using these gradients as an energy
source. In contrast, Zn
2+,

, in the presence of adequate Mg
2+
, could be beneficial to
nutrient uptake by maintaining a higher membrane potential than would occur in its
absence.


.

Cellular damage induced by cadmium and mercury in
Medicago

sativa

Cristina Ortega
-
Villasante
,
Rubén
Rellán
-
Álvarez

,
Francisca F. Del Campo
,
Ramón O.
Carpena
-
Ruiz

and
Luis E.
Hernández


J. Exp. Bot. (August 2005) 56 (418): 2239
-
2251.

Sumber
: http://jxb.oxfordjournals.org/content/56/418/2239.abstract?sid=90319c95
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. Alfalfa (
Medicago

sativa
) plantlets were exposed to
Cd

or Hg to study the kinetics of
diverse stress indexes. In the so
-
called beaker
-
size hydroponic system, plantlets were
grown in 30
μ
M of
Cd

or Hg for 7 d. Oxidative stress took place and increased over
time, a linear response being observed with
Cd

but not with Hg. To improve the
sensitivity of the stress assays used, a micro
-
assay system, in which seedlings were
exposed for 24 h, was developed.
Phytotoxicity

of metals, quantified as growth
inhibition, was observed well before there was any change in the non
-
protein
thiol

tissue concentration. When measured with conventional techniques, oxidative stress
indexes did not show significant variation. To trace early and small plant responses to
Cd

and Hg, a microscopic analysis with novel fluorescent dyes, which had not yet been
exploited to any significant extent for use in plants, was conducted. These fluorescent
probes, which allowed minute cellular responses to 0, 3, 10, and 30
μ
M of both metals
to be visualized in the roots of the alfalfa seedlings, were: (
i
) 2′,7′
-
dichlorofluorescin
diacetate

that labels peroxides; (ii)
monochlorobimane

that stains reduced
glutathione/
homoglutathione

(GSH/
hGSH
); and (iii)
propidium

iodide that marks nuclei
of dead cells. Oxidative stress and cell death increased after exposure for 6

24 h to
Cd

and Hg, but
labelling

of GSH/
hGSH

decreased acutely. This diminution might be the
result of direct interaction of GSH/
hGSH

with both
Cd

and Hg, as inferred from an
in
vitro

conjugation assay. Therefore, both
Cd

and Hg not only compromised severely the
cellular
redox

homeostasis, but also caused cell necrosis. In plants treated with 1
mM

L
-
buthionine

sulphoximine
, a potent inhibitor of GSH/
hGSH

synthesis, only the
oxidative stress symptoms appeared, indicating that the depletion of the GSH/
hGSH

pool was not sufficient to promote cell death, and that other
phytotoxic

mechanisms
might be involved.

.

Silver ions disrupt K
+

homeostasis and cellular integrity in intact barley (
Hordeum

vulgare

L.) roots

Devrim

Coskun
,
Dev T.
Britto
,
Yuel
-
Kai Jean
,
Lasse

M. Schulze
,
Alexander Becker

and
Herbert J.
Kronzucker

J. Exp. Bot. (2012) 63 (1): 151
-
162.

Sumber
: http://jxb.oxfordjournals.org/content/63/1/151.abstract?sid=90319c95
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. The heavy metals silver, gold, and mercury can strongly inhibit
aquaporin
-
mediated
water flow across plant cell membranes, but critical examinations of their side effects
are rare. Here, the short
-
lived radiotracer
42
K is used to demonstrate that these metals,
especially silver, profoundly change potassium homeostasis in roots of intact barley
(
Hordeum

vulgare

L.) plants, by altering unidirectional K
+

fluxes. Doses as low as 5 
μ
M
AgNO
3

rapidly reduced K
+

influx to 5% that of controls, and brought about pronounced
and immediate increases in K
+

efflux, while higher doses of Au
3+

and Hg
2+

were
required to produce similar responses. Reduced influx and enhanced efflux of K
+

resulted in a net loss of >40% of root tissue K
+

during a 15 min application of 500 
μ
M
AgNO
3
, comprising the entire
cytosolic

potassium pool and about a third of the
vacuolar pool. Silver also brought about major losses of UV
-
absorbing compounds,
total electrolytes, and NH
4
+
. Co
-
application, with silver, of the channel blockers Cs
+
,
TEA
+
, or Ca
2+
, did not affect the enhanced efflux, ruling out the involvement of
outwardly rectifying ion channels. Taken together with an examination of
propidium

iodide staining under
confocal

microscopy, the results indicate that silver ions affect K
+

homeostasis by directly inhibiting K
+

influx at lower concentrations, and indirectly
inhibiting K
+

influx and enhancing K
+

efflux, via membrane destruction, at higher
concentrations. Ni
2+
, Cd
2+
, and Pb
2+
, three heavy metals not generally known to affect
aquaporins
, did not enhance K
+

efflux or cause
propidium

iodide incorporation. The
study reveals strong and previously unknown effects of major
aquaporin

inhibitors and
recommends caution in their application.

.

Plasma membrane of
Beta
vulgaris

storage root shows high water channel activity
regulated by
cytoplasmic

pH and a dual range of calcium concentrations

Karina
Alleva

,
Christa M.
Niemietz
,
Moira
Sutka

,
Christophe
Maurel

,
Mario
Parisi

,
Stephen D.
Tyerman

, and
Gabriela
Amodeo

J. Exp. Bot. (February 2006) 57 (3): 609
-
621.

Sumber
: http://jxb.oxfordjournals.org/content/57/3/609.abstract?sid=90319c95
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. Plasma membrane vesicles isolated by two
-
phase partitioning from the storage root
of
Beta
vulgaris

show atypically high water permeability that is equivalent only to
those reported for active
aquaporins

in
tonoplast

or animal red cells (
P
f
=542
μ
m s
−1
).
The values were determined from the shrinking kinetics measured by stopped
-
flow
light scattering. This high
P
f

was only partially inhibited by mercury (HgCl
2
) but showed
low activation energy (
E
a
) consistent with water permeation through water channels.
To study short
-
term regulation of water transport that could be the result of channel
gating, the effects of pH, divalent
cations
, and protection against
dephosphorylation

were tested. The high
P
f

observed at pH 8.3 was dramatically reduced by medium
acidification. Moreover, intra
-
vesicular acidification (corresponding to the
cytoplasmic

face of the membrane) shut down the
aquaporins
. De
-
phosphorylation

was discounted
as a regulatory mechanism in this preparation. On the other hand, among divalent
cations
, only calcium showed a clear effect on
aquaporin

activity, with two distinct
ranges of sensitivity to free Ca
2+

concentration (
pCa

8 and
pCa

4). Since the normal
cytoplasmic

free Ca
2+

sits between these ranges it allows for the possibility of changes
in Ca
2+

to finely up
-

or down
-
regulate water channel activity. The calcium effect is
predominantly on the
cytoplasmic

face, and inhibition corresponds to an increase in
the activation energy for water transport. In conclusion, these findings establish both
cytoplasmic

pH and Ca
2+

as important regulatory factors involved in
aquaporin

gating.

Radial hydraulic conductivity along developing onion roots

David E. Barrowclough

,
Carol A. Peterson

,

and
Ernst
Steudle

J. Exp. Bot. (2000) 51 (344): 547
-
557.

Sumber
: http://jxb.oxfordjournals.org/content/51/344/547.abstract?sid=90319c95
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Although most studies have shown that water uptake varies along the length of a
developing root, there is no consistent correlation of this pattern with root anatomy. In
the present study, water movement into three zones of onion roots was measured by a
series of mini‐
potometers
. Uptake was least in the youngest zone (mean hydraulic
conductivity,
Lp
r
=1.5
×

10
−7
±
0.34
×
10
−7
 m MPa
−1
s
−1
;
±
SE,
n
=10 roots) in which the
endodermis had developed only
Casparian

bands and the
exodermis

was immature.
Uptake was significantly greater in the middle zone (
Lp
r
=2.4
×

10
−7
±
0.43
×
10
−7
 m MPa
−1

s
−1
;
±
SE,
n
=10 roots) which had a mature
exodermis

with both
Casparian

bands and
suberin

lamellae, and continued at this level in the oldest zone in which the
endodermis had also developed
suberin

lamellae (
Lp
r
=2.8
×
10
−7
±
0.30
×

10
−7
 m MPa
−1

s
−1
;
±
SE,
n
=10 roots). Measurements of the hydraulic conductivities of individual cells
(
Lp
) in the outer cortex using a cell pressure probe indicated that this parameter was
uniform in all three zones tested (
Lp
=1.3
×
10
−6
±
0.01
×
10
−6
 m MPa
−1

s
−1
;
±
SE,
n
=60 cells).
Lp

of the youngest zone was lowered by mercuric chloride treatment, indicating the
involvement of mercury‐sensitive water channels (
aquaporins
). Water flow in the older
two root zones measured by mini‐
potometers

was also inhibited by mercuric chloride,
despite the demonstrated impermeability of their
exodermal

layers to this substance.
Thus, water channels in the epidermis and/or
exodermis

of the older regions were
especially significant for water flow. The results of this and previous studies are
discussed in terms of two models. The first, which describes maize root with an
immature
exodermis
, is the ‘uniform resistance model’ where hydraulic resistances are
evenly distributed across the root cylinder. The second, which describes the onion root
with a mature
exodermis
, is the ‘non‐uniform resistance model’ where resistances can
be variable and are concentrated in a certain layer(s) on the radial path.

Plant responses to
abiotic

stresses: heavy metal‐induced oxidative stress and protection
by
mycorrhization

Andres
Schützendübel

and
Andrea
Polle

J. Exp. Bot. (2002) 53 (372): 1351
-
1365.

Sumber
: http://jxb.oxfordjournals.org/content/53/372/1351.abstract?sid=90319c95
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. The aim of this review is to assess the mode of action and role of antioxidants as protection from
heavy metal stress in roots,
mycorrhizal

fungi and
mycorrhizae
. Based on their chemical and physical
properties three different molecular mechanisms of heavy metal toxicity can be distinguished: (a)
production of reactive oxygen species by
autoxidation

and Fenton reaction; this reaction is typical for
transition metals such as iron or copper, (b) blocking of essential functional groups in
biomolecules
,
this reaction has mainly been reported for non‐
redox
‐reactive heavy metals such as cadmium and
mercury, (c) displacement of essential metal ions from
biomolecules
; the latter reaction occurs with
different kinds of heavy metals. Transition metals cause oxidative injury in plant tissue, but a
literature survey did not provide evidence that this stress could be alleviated by increased levels of
antioxidative

systems. The reason may be that transition metals initiate hydroxyl radical production,
which can not be controlled by antioxidants. Exposure of plants to non‐
redox

reactive metals also
resulted in oxidative stress as indicated by lipid
peroxidation
, H
2
O
2

accumulation, and an oxidative
burst. Cadmium and some other metals caused a transient depletion of GSH and an inhibition of
antioxidative

enzymes, especially of glutathione
reductase
. Assessment of
antioxidative

capacities by
metabolic
modelling

suggested that the reported diminution of antioxidants was sufficient to cause
H
2
O
2

accumulation. The depletion of GSH is apparently a critical step in cadmium sensitivity since
plants with improved capacities for GSH synthesis displayed higher
Cd

tolerance. Available data
suggest that cadmium, when not detoxified rapidly enough, may trigger, via the disturbance of the
redox

control of the cell, a sequence of reactions leading to growth inhibition, stimulation of
secondary metabolism,
lignification
, and finally cell death. This view is in contrast to the idea that
cadmium results in unspecific necrosis. Plants in certain
mycorrhizal

associations are less sensitive to
cadmium stress than non‐
mycorrhizal

plants. Data about
antioxidative

systems in
mycorrhizal

fungi in
pure culture and in symbiosis are scarce. The present results indicate that
mycorrhization

stimulated
the
phenolic

defence

system in the
Paxillus

Pinus

mycorrhizal

symbiosis. Cadmium‐induced changes
in
mycorrhizal

roots were absent or smaller than those in non‐
mycorrhizal

roots. These observations
suggest that although changes in
rhizospheric

conditions were perceived by the root part of the
symbiosis, the typical
Cd
‐induced stress responses of
phenolics

were buffered. It is not known
whether
mycorrhization

protected roots from
Cd
‐induced injury by preventing access of cadmium to
sensitive extra‐ or intracellular sites, or by excreted or intrinsic metal‐
chelators
, or by other
defence

systems. It is possible that
mycorrhizal

fungi provide protection via GSH since higher concentrations
of this
thiol

were found in pure cultures of the fungi than in bare roots. The development of
stress‐tolerant plant‐
mycorrhizal

associations may be a promising new strategy for
phytoremediation

and soil amelioration measures.

Relationships of root conductivity and
aquaporin

gene expression in
Pisum

sativum
:

diurnal patterns and the response to HgCl
2

and ABA

Philip C.
Beaudette
,
Michael
Chlup
,
Janet Yee

and
R. J. Neil Emery
.

J. Exp. Bot. (2007) 58 (6): 1291
-
1300.

Sumber
: http://jxb.oxfordjournals.org/content/58/6/1291.abstract?sid=90319c95
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Experiments were undertaken to test how
aquaporins

(AQPs) facilitate the uptake of
water by roots of
Pisum

sativum
. Changes in
PsPIP2
-
1

gene expression and root
hydraulic conductivity (
Lp
r
) were measured in response to the time of day as well as
treatment of the roots with a compound that reduced
Lp
r

[i.e. mercuric chloride
(HgCl
2
)] and one that was intended to increase
Lp
r

[
abscisic

acid (ABA)].

. There was a diurnal rhythm in
PsPIP2
-
1

expression in lateral roots that
was strongly correlated with diurnal changes in
Lp
r
.

Taproots also
displayed a rhythm in
PsPIP2
-
1

expression, but this was offset from that of
Lp
r
. This suggested that changes in
Lp
r

were mediated by changes in
PsPIP2
-
1

mRNA transcript abundance. Reduction of
Lp
r

by HgCl
2

treatment
was accompanied by an increase in
PsPIP2
-
1

expression, implying that
PsPIP2
-
1

expression may have increased to compensate for AQPs blocked
by mercury.

ABA usually increased
Lp
r
, but changes in
PsPIP2
-
1

were variable
and the direction of the response was strongly dependent on the
dose of ABA that was applied.

Overall, the coincident rhythms in
Lp
r

and PIP2 expression and
response to AQP blockage are consistent with the hypothesis that
Lp
r

changes are mediated, at least in part, by changes in
PsPIP2
-
1

expression.

Inconsistencies with ABA data may have been due to more
complex interactions of ABA with AQP channels.

.

Environmental relevance of heavy metal
-
substituted chlorophylls using the example of
water plants

Hendrik

Küpper
,
Frithjof

Küpper

and
Martin Spiller

J. Exp. Bot. (1996) 47 (2): 259
-
266.

Sumber
: http://jxb.oxfordjournals.org/content/47/2/259.abstract?sid=8b94415c
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. Following experiments which studied the substitution of the central ion of isolated
chlorophylls by heavy metal ions
in vitro
,
in vivo

experiments with submersed water
plants were carried out. It was discovered that the substitution of the central atom of
chlorophyll, magnesium, by heavy metals (mercury, copper, cadmium, nickel, zinc,
lead)
in vivo

is an important damage mechanism in stressed plants. This substitution
prevents photosynthetic light
-
harvesting in the affected chlorophyll molecules,
resulting in a breakdown of photosynthesis. The reaction varies with light intensity. In
low light irradiance all the central atoms of the chlorophylls are accessible to heavy
metals, with heavy metal chlorophylls being formed, some of which are much more
stable towards irradiance than Mg
-
chlorophyll. Consequently, plants remain green
even when they are dead. In high light, however, almost all chlorophyll decays,
showing that under such conditions most of the chlorophylls are inaccessible to heavy
metal ions.

.

Water channels in
Chara

corallina

Kerstin
Schütz

and Stephen D.
Tyerman

J. Exp. Bot. (1997) 48 (8): 1511
-
1518.

Sumber
: http://jxb.oxfordjournals.org/content/48/8/1511.abstract?sid=8b94415c
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. Water relations parameters
of
Chara

corallina

inter
-
nodes were measured
using the single cell pressure probe.

The effect of
mercurials
, which are
recognized as non
-
specific water channel
inhibitors, was examined.

. HgCl
2

concentrations greater than 5
mmol

m
−3

were found to inhibit hydraulic
conductivity {
Lp
) close to 90%, whereas
pCMPS

was found to have no effect on
Lp
. The
activation energy of water flow was increased significantly from 21.0 kJ mol
−1

to 45.6 kJ
mol
−1
, following the application of HgCl
2
.

These results are in accordance with evidence for Hg
2+
sensitive water channels in the
plasma membrane of
charophytes

(
Henzler

and
Steudle
, 1995;
Tazawa

et al., 1996).
The metabolic effects must, however, be considered in view of the rapid inhibition of
respiration and the depolarization of the membrane potential with HgCl
2

concentrations lower than those found to affect
Lp
. It was possible to measure
simultaneously water relations and membrane
PD
, in order to examine the
contribution of potassium channels to
Lp
. Cells were induced into a K
+

permeable
state.

The K
+

channels, assumed to be open, were subsequently blocked by various blockers.
No significant difference in
Lp

was found for any of these treatments. Finally, the
permeability of
C.
corallina

membranes to ethanol was examined.


HgCl
2

was found to cause a decrease in reflection coefficient, coinciding with a
decrease in
Lp
, but there was no change in the ethanol permeability coefficient. This
has been interpreted in terms of both the frictional model and composite model of
non
-
electrolyte membrane transport.


Phytoremediation

of mercury
-
contaminated mine wastes : a thesis presented in partial
fulfilment

of the
requirements for the degree of Doctor of Philosophy in Soil Science, Massey University,
Palmerston

North

Morena
,
Fábio

Netto


http://hdl.handle.net/10179/1746


Date: 2004.

Mercury (Hg) is a toxic heavy metal that is concentrated in organisms. Injudicious use of Hg and its
compounds have resulted in widespread soil contamination.

This study investigates the potential use of plants for the remediation of Hg
-
contaminated mine wastes.
Plants can remove soil Hg via
phytoextraction

and
phytovolatilisation
. I investigated both of these strategies
by focusing on a methodology for Hg analyses in plants and soils with a view to the determination of
volatile Hg emitted from plants. Secondly, I determined the feasibility of Hg
phytoextraction

and
phytovolatilisation

from contaminated mine wastes. An accurate method for the analysis of Hg in air, plant
and various soil fractions was a key component of this study. I developed a hydride
-
generation atomic
absorption spectroscopy method for total Hg analyses in digest and liquid matrices of the aforementioned
samples. Quality assurance was ensured by comparing results with those of an external certified laboratory.
The maximum discrepancy was 15 %. To measure plant Hg
-
volatilisation
, a method that captures Hg
-
vapour

in solution for subsequent analyses was developed. Initially this system was used to trap Hg
vapours

released from the root system of
Brassica

juncea

plants grown in hydroponic solutions. A subsequent study
improved the Hg trapping system, allowing the capture of volatile Hg from both roots and shoots. Mercury
recoveries from the whole plant system (traps + plant + solutions) averaged 90 % using this experimental
apparatus. In most contaminated substrates, plant Hg uptake is insignificant, possibly due to the low
bioavailability of Hg. This represents an obstacle for effective remediation using
phytoextraction
.
Geochemical studies were carried out in Hg
-
contaminated substrates to examine the potential of chemical
agents to induce Hg solubility and subsequent plant uptake. These studies
utilised

Hg
-
contaminated mine
tailings collected from three locations: the
Tui

base
-
metal mine, in the North Island of New Zealand, the
Gold Mountain mine, in North
-
Central China and, the Serra
Pelada

artisanal mine site, in Northern Brazil.
The results demonstrated that Hg solubility in all tested substrates is increased in the presence of
sulphur
-
containing chemical
ligands
. The effectiveness of these
ligands

was influenced by site
-
specific geochemistry.
Plants species were able to accumulate up to 60 mg/kg of Hg in shoot tissues upon addition of
sulphur
-
containing
ligands

to
Tui

and Gold Mountain substrates. The degree of plant
-
Hg accumulation was shown to
be dependant on plant species and on the
thioligand
-
induced soluble Hg fraction. Shoot Hg transport was
inhibited for Gold Mountain substrate amended with 1.25g/kg of
humic

acid. The maximum Hg extraction
yield for B.
juncea

plants growing in
Tui

field sites averaged 25 g per hectare following application of sodium
thiosulphate
.
Volatilisation

of Hg
vapour

from barren substrates occurred as a result of biotic
(microorganisms) and
abiotic

(chemical and photochemical reduction) processes. The presence of B.
juncea

plants in substrates enhanced the
volatilisation

process up to 23 fold.

Phytovolatilisation

was the dominant pathway responsible for between 75 to 99.5 % of the total Hg
removed from substrates. It was concluded that Hg removal from contaminated mine wastes can be
accomplished by both
thioligand
-
induced
phytoextraction

and
phytovolatilisation
. There are risks of
groundwater contamination by Hg species
mobilised

after application of
thioligands

to substrates.
Estimated Hg (0) emissions from plant
-
based operations at contaminated sites ranged between 1.5 to 3.6 kg
of Hg/ha per year. Due to extensive atmospheric dilution, Hg emissions from small
-
scale
phytoremediation

operations would not cause serious harm to the local population or the regional environment.
Phytoremediation

combined with gold
-
phytoextraction

can help to mitigate Hg
-
pollution in artisanal mine
sites in the developing world.

.

Accumulation of Mercury in Selected Plant Species Grown in Soils Contaminated With
Different Mercury Compounds

Yi Su ,
Fengxiang

Han, and
Safwan

Shiyab

The 11th International Conference on Environmental Remediation and Radioactive Waste Management
(ICEM2007) . September 2

6, 2007 , Bruges, Belgium

Sumber
:
http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=ASMECP002007043390001001000001&i
dtype=cvips&gifs=yes&ref=no….
Diunduh

8/5/2012

The

objective of our research is to screen and search for

suitable plant species for
phytoremediation

of mercury
-
contaminated soil. Currently our

effort is specifically focused on mercury removal from
the U.S.

Department of Energy (DOE) sites, where mercury contamination is a

major concern. In order
to cost effectively implement mercury remediation

efforts, it is necessary now to obtain an improved
understanding

of biological means of removing mercury and mercury compounds

Phytoremediation

is a technology that uses various plants to degrade, extract,

contain, or immobilize
contaminants from soil and water. In particular,

phytoextraction

is the uptake of contaminants by
plant roots and

translocation within the plants to shoots or leaves. Contaminants are

generally
removed by harvesting the plants. We have investigated
phytoextraction

of mercury from
contaminated soil by using some of the

known metal
-
accumulating plants since no natural plant
species with mercury

hyperaccumulating

properties has yet been identified. Different natural plant
species

have been studied for mercury uptake, accumulation, toxicity and overall

mercury removal
efficiency. Various mercury compounds, such as
HgS
, HgCl
2
,

and Hg(NO
3
)
2
, were used as contaminant
sources. Different types of

soil were examined and chosen for
phytoremediation

experiments. We
have

applied microscopy and diffuse reflectance spectrometry as well as conventional

analytical
chemistry to monitor the
phytoremediation

processes of mercury uptake,

translocation and
accumulation, and the physiological impact of mercury contaminants

on selected plant species. Our
results indicate that certain plant

species, such as beard grass (
Polypogon

monospeliensis
),
accumulated a very

limited amount of mercury in the shoots (<65 mg/kg), even

though root mercury
accumulation is significant (maximum 2298 mg/kg). Consequently,

this plant species may not be
suitable for mercury
phytoremediation
.

Other plant species, such as Indian mustard (
Brassica

juncea
),
a

well
-
studied metal accumulator, exhibited severe
chlorosis

symptoms during some experiments.

Among all the plant species studied, Chinese brake fern (
Pteris

vittata
) accumulated significant
amount of mercury in both roots and

shoots and hence may be considered as a potential candidate

for mercury
phytoextraction
. During one experiment, Chinese brake ferns accumulated

540 mg/kg
and 1469 mg/kg in shoots after 18 days

of growing in soils treated with 500 parts
-
per
-
million (
ppm
)
and

1000
ppm

HgCl
2

powder, respectively; no visual stress symptoms were

observed. We also studied
mercury
phytoremediation

using aged soils that

contained
HgS
, HgCl
2
, or Hg(NO
3
)
2
. We have found
that up

to hundreds of
ppm

mercury can be accumulated in the

roots of Indian mustard plants grown
with soil contaminated by

mercury sulfide;
HgS

is assumed to be the most stable

and also the
predominant mercury form in floodplain soils. We

have also started to investigate different mercury
uptake mechanisms, such

as root uptake of soil contaminant and foliar mercury accumulation

from
ambient air. We have observed mercury translocation from roots

to shoot for Chinese fern and two
Indian mustard varieties.

Mercury Detoxification with Transgenic Plants and Other Biotechnological Breakthroughs
for
Phytoremediation

Clayton L.
Rugh

In Vitro Cellular & Developmental Biology. Plant

Vol. 37, No. 3 (May
-

Jun., 2001), pp. 321
-
325

Sumber
:
http://www.jstor.org/discover/10.2307/4293468?uid=3738224&uid=2129&uid=2&uid=70&uid=4&sid=561
50158803….
Diunduh

8/5/2012

.
Phytoremediation
, or the use of plants for removal and detoxification of
environmental pollutants, has garnered great attention in recent years. This
heightened interest is both scientifically, due the fascinating processes utilized by
plants for tolerance and removal of harmful compounds, and commercially, as plants
represent a more environmentally compatible and less expensive method of site
remediation compared to standard approaches. The majority of
phytoremediation

studies have been with naturally occurring plant species after empirical discovery of
their exceptional abilities for such applications. This has led to a growing body of
literature and wider acceptance for plants in many aspects of environmental
rehabilitation. However, this has occurred with little understanding of their basic
biological mechanisms of action or investigation of alternative strategies for enhancing
the capabilities of these extraordinary plants. Better understanding of plant physiology,
biochemistry and molecular biology in response to specific contaminants is critical for
optimization and advancement of
phytoremediation
. By applying the tools of
biotechnology, the potential for plants as an aggressive method of environmental
decontamination may be realized. This paper will serve as an introduction to the first
Symposium assembled exclusively to review the use of molecular genetic and
biotechnological methods for improvement of plants for
phytoremediation
. After a
brief review of the other invited speakers' works (with more extensive papers
following), the pioneering work using bacterial genes expressed in plants for removal
of mercurial compounds will be surveyed.

.

Journal of Soil Contamination .
Volume 7
,
Issue 4
, 1998.
pages 497
-
509

Phytoremediation

of Mercury
-

and
Methylmercury
-
Polluted Soils Using Genetically
Engineered Plants

Andrew C. P.
Heaton
a
,
Clayton L.
Rugh
b
,
Nian
-
jie

Wang
b

&
Richard B.
Meagher
b

Sumber
: http://www.tandfonline.com/doi/abs/10.1080/10588339891334384….
Diunduh

8/5/2012

Inorganic mercury in contaminated soils and sediments is relatively immobile, though
biological and chemical processes can transform it to more toxic and
bioavailable

methylmercury
.
Methylmercury

is
neurotoxic

to vertebrates and is biomagnified in
animal tissues as it is passed from prey to predator. Traditional remediation strategies
for mercury contaminated soils are expensive and site
-
destructive. As an alternative
we propose the use of transgenic aquatic, salt marsh, and upland plants to remove
available inorganic mercury and
methylmercury

from contaminated soils and
sediments. Plants engineered with a modified bacterial mercuric
reductase

gene,
merA
, are capable of converting Hg(II) taken up by roots to the much less toxic Hg(0),
which is volatilized from the plant. Plants engineered to express the bacterial
organo
-
mercurial
lyase

gene,
merB
, are capable of converting
methylmercury

taken up by
plant roots into
sulfhydryl
-
bound Hg(II). Plants expressing both genes are capable of
converting ionic mercury and
methylmercury

to volatile Hg(0) which is released into an
enormous global atmospheric Hg(0) pool. To assess the
phytoremediation

capability of
plants containing the
merA

gene, a variety of assays were carried out with the model
plants Arabidopsis thaliana, and tobacco (
Nicotiana

tabacum
).

.

Mercury in Plants from Fields Surrounding a Contaminated Channel of
Ria

de
Aveiro
,
Portugal

E.
Pereira
a
,
C.
Vale
b
,
C. F.
Tavares
a
,
M.
Válega
a

&
A. C. Duarte

Soil and Sediment Contamination: An International Journal .
Vol. 14
,
Issue 6
, 2005.
p. 571
-
577
.

Sumber
: http://www.tandfonline.com/doi/abs/10.1080/15320380500263774….
Diunduh

8/5/2012

. Samples of plants and soil were collected in March and June 1995 at 12 sites in fields
surrounding the
Estarreja

Channel (
Ria

de
Aveiro
), where the mercury
-
rich effluent of a
chlor
-
alkali plant has been discharged since the 1950s. Mercury concentrations in soil
ranged from 0.64 to 182
μ
g
g
−1
. The highest values were attributed to soil
contaminated with sediments dredged from the
Estarreja

Channel. Plant roots
contained between 0.03 and 3.2
μ
g
g
−1

of total mercury, and there is evidence that
root systems uptake mercury from the soil. The linear relationship between mercury
concentrations in the roots of
Holcus

lanatus

and in soil over a wide range of mercury
concentrations suggests that mercury uptake depends on the element's concentration
in the soil. The ratio
root:soil

concentrations for the analyzed plants varied between
0.003 and 0.199, indicating varying mercury uptake by the root systems. Levels of
mercury in the aerial parts of plants showed no clear relationship with the values
found in soil or in roots, presumably being influenced mostly by the atmospheric
deposition of airborne particles or absorption of atmospheric mercury.

Bioaccessibility

of Mercury in Soils

Mark O.
Barnett
a

&
Ralph R.
Turner
a

Soil and Sediment Contamination: An International Journal .
Vol. 10
,
Issue 3
, 2001

p. 301
-
316


Sumber
: http://www.tandfonline.com/doi/abs/10.1080/20015891109275….
Diunduh

8/5/2012

. The initial risk assessment for the East Fork Poplar Creek (EFPC) floodplain in Oak
Ridge, Tennessee, a superfund site heavily contaminated with mercury, was based on a
reference dose for mercuric chloride. Mercuric chloride, however, is a soluble mercury
compound not expected to be present in the floodplain, which is frequently saturated
with water. Previous investigations had suggested mercury in the EFPC floodplain was
less soluble and therefore potentially less
bioavailable

than mercuric chloride, possibly
making the results of the risk assessment unduly conservative. A
bioaccessibility

study,
designed to measure the amount of mercury available for absorption in a child's
digestive tract (the most critical risk pathway endpoint), was performed on 20 soils
from the EFPC floodplain. The average
bioac
-
cessible

mercury for the 20 soils was
5.3%, compared with 100% of the mercuric chloride subjected to the same conditions.
The alteration of the procedure to more closely mimic conditions in the digestive tract
did not significantly change the results. Therefore, the use of a reference dose for
mercuric chloride at EFPC, and potentially at other mercury
-
contaminated sites,
without incorporating a corresponding bioavailability adjustment factor may
overestimate the risk posed by the site.

Screening and Thermal Desorption for Remediation of a Sediment Polluted by the Mercury
of a
Chlor
-
Alkaly

Plant

Andrea
Manni
, Paolo
Massacci
, Luigi
Piga

& Silvia
Serranti

Soil and Sediment Contamination: An International Journal. Vol. 13, Issue 4, 2004

p. 391
-
404

Sumber
: http://www.tandfonline.com/doi/abs/10.1080/10588330490466003….
Diunduh

8/5/2012

Thermal desorption tests were performed on samples taken from a mercury polluted
sediment (133 mg/kg) in the vicinity of a
chlor
-
alkali plant that has been operating
over a long period using mercury cathodes.

After characterization of
the sediment, by means
of TGA/DTA, SEM, XRD
and chemical analysis,
the material was
screened into various
size
-
fractions. Chemical
analysis showed that
only the finest size
-
fractions had a mercury
content above the
regulatory limit (5
mg/kg) established for
areas destined for
industrial installations.



Thermal desorption tests were applied on the finest size
-
sediment fractions at
furnace temperatures between 300
°
C and 400
°
C and solids residence times between
3 minutes and 120 minutes.

After 3 minutes at 400
°
C, the treated sediment residue had a mercury content below
the regulatory limit.

The short solid residence time and the low desorption temperature required to meet
the treatment standards would permit the use of a continuous thermal desorption
treatment process in a
rotatory

dryer, providing that the values of residence times
obtained by the lab
-
scale plant are suitable for a larger scale plant.


Mercury translocation in and evaporation from soil. III. quantification of evaporation of
mercury from
podzolized

soil profiles treated with Hg
Cl

K.
Schlüter
,
H. M.
Seip

&
J.
Alstad
.
Journal of Soil Contamination .
Vol. 5
,
Issue 2
, 1996
.
pages 121
-
139.

Sumber
: http://www.tandfonline.com/doi/abs/10.1080/15320389609383518….
Diunduh

8/5/2012

Mercury evaporation from undisturbed iron‐humus
podzol

lysimeters

was measured
over 3 months after treatment with HgCl
2

spiked with radioactive
203
Hg.

The relative evaporation rate
from HgCl
2

treated soils followed
the sum of two exponential
functions. Because evaporation
asymptotically approaches zero
with time, the integral of the fit
curve represents the evaporative
loss in percent of atmospheric
deposition. For the soil
investigated, about 5% of
atmospheric Hg deposition was
reemitted into the atmosphere.


It is hypothesized that mercury
evaporation can decrease the
leaching of mercury in and from
soil significantly; this effect is
probably increasing with
decreasing rain acidity or soil
acidity.

Mercury deposited as soluble
salt remains susceptible to
reemission to air for 300 d after
incorporation into the soil
matrix.

Indications are found that Hg evaporation from soils in geological background areas
predominantly derives from recent atmospheric Hg deposition and not from geological
sources.

Mercury translocation in and evaporation from soil. I. soil
lysimeter

experiments with
203
Hg‐radiolabeled compounds

K.
Schlüter
, J.
Alstad

& H. M.
Seip


Journal of Soil Contamination . Vol. 4, Issue 4, 1995 .
pages 327
-
353


Sumber
: http://www.tandfonline.com/doi/abs/10.1080/15320389509383504 ….
Diunduh

8/5/2012

Due to a considerable increase of anthropogenic mercury emissions, the mercury load
of many soils has risen significantly, for instance in northern Europe. Understanding
the fate of mercury in soils is a prerequisite for assessing the effects of
ecotoxicological

concern.

. This paper presents a method for
obtaining qualitative and quantitative
information about mercury
translocation in and evaporation from
soil. Soil
lysimeters

were treated with
203
Hg‐labeled HgCl
2

and CH
3
HgCl and
irrigated with artificial rain.

It was demonstrated that the leaching of
Hg can be detected by measuring the
relative y‐activity throughout the soil
profile by means of Na(TI)I detectors.
Furthermore, the set‐up was designed
to allow detection of Hg volatilization
from soil by using traps of iodized
charcoal, followed by a potassium
peroxodisulfate

solution and measuring
the
γ‐
activity. The amount of radioactive
Hg in soil
leachate

was measured by a
Na(
Tl
)I well‐type detector after
upconcentration
.

The determination of
monomethyl

203
Hg was been performed by extraction
procedures that isolate the methyl mercury compounds.

The amount of
203
Hg retained in the soil profile and the real depth of leaching were
determined by stratifying the soil profile at the end of the experiment and measuring
the y‐activity.

With control of all pathways of Hg, the experimental design allows performance of a
mass balance analysis.

Mercury translocation in and evaporation from soil. I. soil
lysimeter

experiments with
203
Hg‐radiolabeled compounds

K.
Schlüter
, J.
Alstad

& H. M.
Seip

.

Journal of Soil Contamination .
Vol. 4
, Issue 4, 1995 .
pages 327
-
353

Sumber
:
http://www.tandfonline.com/doi/abs/10.1080/15320389509383504?prevSearch=mercury&searchHistoryK
ey= ….
Diunduh

8/5/2012

Due to a considerable increase of anthropogenic mercury emissions, the mercury load
of many soils has risen significantly, for instance in northern Europe. Understanding
the fate of mercury in soils is a prerequisite for assessing the effects of
ecotoxicological

concern.

This paper presents a method for
obtaining qualitative and quantitative
information about mercury translocation
in and evaporation from soil. Soil
lysimeters

were treated with
203
Hg‐labeled HgCl
2

and CH
3
HgCl and
irrigated with artificial rain. It was
demonstrated that the leaching of Hg can
be detected by measuring the relative
y‐activity throughout the soil profile by
means of Na(TI)I detectors. Furthermore,
the set‐up was designed to allow
detection of Hg volatilization from soil by
using traps of iodized charcoal, followed
by a potassium
peroxodisulfate

solution
and measuring the
γ‐
activity. The amount
of radioactive Hg in soil
leachate

was
measured by a Na(
Tl
)I well‐type detector
after
upconcentration
. The
determination of
monomethyl

203
Hg was
been performed by extraction
procedures that isolate the methyl
mercury compounds.

The amount of
203
Hg retained in the soil profile and the real depth of leaching were
determined by stratifying the soil profile at the end of the experiment and measuring
the y‐activity. With control of all pathways of Hg, the experimental design allows
performance of a mass balance analysis.

ADSORPTION/DESORPTION AND FATE OF MERCURY (II) BY TYPICAL BLACK SOIL AND RED
SOIL IN CHINA

Jia

Liu,
Jiulan

Dai,
Renqing

Wang,
Fasheng

Li,
Xiaoming

Du &
Wenxing

Wang

Soil and Sediment Contamination: An International Journal. Vol. 19, Issue 5, 2010 .
pages
587
-
601.

Sumber
:
http://www.tandfonline.com/doi/abs/10.1080/15320383.2010.499925?prevSearch=mercury&searchHistor
yKey= ….
Diunduh

8/5/2012

Rapid industrial development in the old northeastern industrial region of China
resulted in Hg pollution.

A series of batch experiments
were conducted to assess the
adsorption/ desorption and
transfer of Hg (II) within typical
black soil in this region and
typical red soil in south China as
a comparison: both are typical
soils in China.


It was found that both soils had
high affinity for Hg (II) and the
absorbed amount was more than
95% of the added.


Hg (II) adsorption isotherms
were well fitted with the
Langmuir and
Freundlich

equations. The affinity of Hg (II)
for black soil was three times
higher than that of red soil.

Results demonstrated that soil organic matter had an important role in Hg (II)
adsorption. Fifty
-
three and twenty
-
eight percent of the maximum sorption amount for
Hg (II) was contributed by organic matter for black soil and red soil, respectively.
Kinetic studies showed that Hg adsorption on both soils was characterized by a
biphasic pattern, with a fast step followed by a slow step. Black soil completed 90% of
total Hg (II) adsorption in 34 min and reached equilibrium in 321 min, compared to 91
min and 630 min on red soil, respectively.

The influence of pH and chloride on the retention of cadmium, lead, mercury, and zinc by
soils

David G.
Lumsdon
, Leslie J. Evans & Kim A. Bolton

.

Journal of Soil Contamination.
Vol. 4
, Issue 2, 1995.
pages 137
-
150


Sumber
: http://www.tandfonline.com/doi/abs/10.1080/15320389509383488 ….
Diunduh

8/5/2012

The extent of contamination of soils by toxic heavy metals not only depends on the
rate of loading of the metal but also on the nature of the adsorbing surfaces, the
degree of alkalinity or acidity of the soil and the presence of aqueous
complexant

ligands
.

This work reports on the role of pH on the retention of
Cd
, Hg,
Pb

and Zn
by two soils and on the influence of the chloride,
Cl
‐, ion on the chemical
speciation and retention of the four metals. Batch adsorption
experiments were conducted from pH 3 to 7 in the presence of either 0.1
M