Environmental Engineering Reference
In-Depth Information
Table 2
Arsenic accumulation in ferns
Name of the fern
translocation factor increased in most ferns to
maintain nutrient requirements and ion balance
(Sridokchan et al.
2005
). Phosphate fertilizer sig-
nifi cantly increased plant biomass and As accu-
mulation in
P. calomelanos
(silverback fern)
when grown in As-contaminated soil. P-fertilizer
and rhizosphere bacteria enhanced
As-phytoextraction, whereas rhizosphere fungi
exerted their effects on phytostabilization
(Jankong et al.
2007
). The toxicity of different
forms of As decreases in the following order:
arsine> inorganic arsenite> organic arsenite>
inorganic arsenate> organic arsenate> free
arsenic (Mandal and Suzuki
2002
). Some algae,
fungi, and bacteria have the ability to transform
arsenite to arsenate. The mechanisms involved in
the microbial transformation and removal of As
from the environment included adsorption and
reduction reaction (Anderson and Cook
2004
).
Arbuscular mycorrhizal fungi (AMF) can play an
important role in phytoremediation. The princi-
ple role of mycorrhizal fungi is obtaining phos-
phorus (P) for their hosts. Hence, enhanced
acquisition of phosphate may also lead to
enhanced acquisition of arsenate (Meharg and
Hartley-Whitakar
2002
). However, the effect
depends on the interactions between AMF and
their host plants. Inoculation of AMF (
Glomus
mosseae
,
Glomus intraradices
, and
Glomus etu-
nicatum
) reduced As accumulation in
P. calo-
melanos
and
Tagetes erecta
and had no effect on
the plants growth. In contrast, the AMF improved
growth and As accumulation in
M. malabathri-
cum
(Jankong and Visoottiviseth
2008
). Effects
of AMF on As accumulation by plants were also
infl uenced by root morphology.
P. calomelanos
and
T. erecta
possess wide-root system with a
fi ne network of roots that enhance phytostabiliza-
tion. AMF also enhanced the growth of
M. mala-
bathricum
because of the plant's root structure
(Jankong and Visoottiviseth
2008
).
The fern has the capability to accumulate
5,000
As (mg kg
−1
)
References
Pteris vittata
22,630
Ma et al. (
2001
)
Pityrogramma
calomelanos
8,350
Francesconi et al.
(
2002
)
P. umbrosa
7,600
Zhao et al. (
2002
)
P. cretica
3,030
Zhao et al. (
2002
)
The site is part of the Southeast Asian tin belt, an
area that has a 100-year history of bedrock and
alluvial mining. Soil and groundwater in the area
were contaminated with up to 0.1 % arsenopyrite
and 100 times of the regulatory arsenic level of
0.01 mg/L in drinking water (Mandal and Suzuki
2002
). People live near or in old tin mine area
were sick, and illness includes chronic As poi-
soning (arsenicosis), skin cancer, and bladder
cancer, resulting from drinking As-contaminated
water (Choprapwon and Porapakkham
2001
).
The high concentrations of toxic inorganic arse-
nic (predominantly arsenate) in an edible fi sh
Channa striata
had human health implications
and warrant wider investigations (Jankong et al.
2007
). The As was weathered from arsenopyrite
by both natural and mining activity, which
leaches out and contaminates local soil and
groundwater (William et al.
1996
). Although tin
mining was prohibited on February 4, 1994, the
release of arsenopyrite from the tin ore has left
extensive damage. The point source of waste
piles (2,500 m
3
, approximately) had to be land-
fi lled secure at Suangchan-Ronna mountain,
Khao Luang Naional Park, in Ron Phibun
District, and the old tin mine had to be reclaimed
and remediated. Monitoring program detects As
contamination in river, water supply, and soil at
least once in 2 years. Constructed wetland and
phytoremediation to remediate the mine tailing
and the As-contaminated site are a promising
option. Two species of ferns (
Pityrogramma cal-
omelanos
and
Pteris vittata
), an herb (
Mimosa
pudica
), and a shrub (
Melastoma malabrathri-
cum
) and about 36 plant species are recom-
mended as potential candidates for
phytoremediation (Visoottiviseth et al.
2002
).
The root uptake of K, P, and S was signifi cantly
reduced when ferns were exposed to As, but the
g As/g dry mass of fronds, assuming the
soil contains 500
ʼ
g As/g with the density of 2 g/
cm
3
. The fern's root system is able to reach 25 cm
depth; a plant this size will have approximately
50 g dry mass of fronds; and 16 plants per m
2
can
be cultivated/harvested each year. The annual
ʼ
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