Environmental Engineering Reference
In-Depth Information
during 1999-2000. The lead sludge was landfi lled
in tailing pond. The eight ponds, which were not
in the standard of secure landfi ll, were far from
the creek 5-10 m, with slope 10-20
o
. To protect
the leachage of Pb into the creek and decrease the
contact of lead sulfi de ores with oxygen, the ways
that the Pollution Control Department (PCD)
suggested are to maintain the tailing pond by
covering with geomembrane HDPE and 30 cm
of top soil before growing covering plants such
as
Wedelia trilobata
(L.) Hitchc. The tailing
ponds were surrounded with pass channel and
vetiver grasses. Some rock check dam was con-
structed in the creek to precipitate small particle
of Pb tailing (Water Quality Management Bureau,
PCD, 2009). However, environmental monitor-
ing illustrated that the Pb concentration in the
surface sediment was as high as 869.4 mg/kg,
whereas in agricultural soil ranged between 137
and 613 mg/kg of Pb and was inversely propor-
tion to the distance from the point source.
Moreover, Pb was transported from the point
source to downhill areas. Vegetables (mint, bitter
gourd, Chinese watercress, basil, and turmeric),
tuber crops (cassava and curcumin), and meat
(fi sh and shellfi sh) had Pb concentrations above
the recommended standard (Pusapukdepob et al.
2007
). Karen villagers, an indigenous commu-
nity, were leading a simple life interconnected
with the surrounding nature until the mine
released Pb-contaminated wastewater into the
creek. The villagers suffered due to Pb poisoning
and contamination in the creek (Assavarak
2012
).
Health risk assessment of the villagers have been
reported in low intelligence quotient (IQ) score,
and their blood Pb or tooth Pb levels were higher
than normal limit (Pusapukdepob et al.
2007
). In
January 2013, a Thai court ordered the govern-
ment to clean up the creek and compensate the
villagers (The Nation
2013
). Klity Creek is in the
Thung Yai Naresuan Wildlife Sanctuary; therefore,
this Pb-contaminated area needs to be remediated.
A total of 48 plant species belonging to 14
families were collected from a closed open-pit Bo
Ngam lead mine area, Thong Pha Phum District,
which Pb concentrations in surface soil ranged
from 325 to 142,400 mg/kg. Three species
(
Microstegium ciliatum
,
Polygala umbonata
, and
Spermacoce mauritiana
) showed extremely high
Pb concentrations in their shoots (12,200-
28,370 mg/kg) and roots (14,580-128,830 mg/
kg) (Rotkittikhun et al.
2006
). Most plants had the
highest Pb content during the wet season (May to
September) and the lowest during the dry season
(October to April). There were a total of 17 plant
species that had Pb accumulation in shoots
>1,000 g/kg, though only six species (
Ageratum
conyzoides
,
Buddleja asiatica
,
Chromolaena odo-
rata
,
Conyza sumatrensis
,
Mimosa pudica
, and
Sonchus arvensis
) showed a translocation factor
>1 (Homyog et al.
2008
). The Siam weed,
Chromolaena odorata
, belongs to Asteraceae is a
hyperaccumulator by means of fi eld surveys on
Pb soil around Bo Ngam Pb mine and hydroponic
studies, which grows rapidly and has substantial
biomass. This perennial herb with great ecologi-
cal amplitude possesses great potential for use in
the remediation of Pb-contaminated soil (Tanhan
et al.
2007
). Greenhouse and fi eld trial experi-
ments were performed to evaluate the use of
C. odorata
with various soil amendments for
phytoextraction of Pb-contaminated mine soils,
which contain low amount of nutrients. Inorganic
fertilizer (Osmocote) enhanced Pb accumulation;
cow manure decreased available Pb concentration
and resulted in the highest Pb concentration in
roots; ethylenediaminetetraacetic acid (EDTA)
increased Pb accumulation in shoots and roots
(Tanhan et al.
2011
).
S. arvensis
, a pioneer peren-
nial plant, is a good candidate for Pb phytoreme-
diation. In pot study,
S. arvensis
grown in Pb mine
soils amended with organic fertilizer and EDTA
has the highest Pb shoot accumulation (1,397 mg/
kg), and the plants accumulated Pb in the shoot up
to 3,664 mg/kg when grown in a fi eld experiment
in the mine area (Surat et al.
2008
). The use of
EDTA in the fi eld should be concerned with their
leaching problems (Tanhan et al.
2011
).
A fi eld survey at Bo Ngam Pb mine found 11
fern species including
P. vittata
which accumu-
lated Pb in the range of 23-295 mg/kg in the
aboveground parts. When
P. vittata
was grown at
mine soils for 6 months, the fern tolerated higher
soil Pb (94,584-101,405 mg/kg) and accumulated
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