Environmental Engineering Reference
In-Depth Information
Plants forming mycorrhizas can grow on
As-contaminated soils (Meharg and Hartley-
Whitaker
2002
; Sharples et al.
1999
,
2000a
,
b
).
High concentrations of As inhibited the growth of
the ericoid mycorrhizal fungus
Hymenoscyphus
ericae
(Sharples et al.
2000a
). Inoculation with
the AM fungus led to a decrease in the As con-
centration in the host plants and an increase in
dry matter yield, especially of the fronds.
Although the As concentrations in the fronds
were lower at the high As application rate, inocu-
lated treatments had higher biomass, giving
larger amounts of As uptake by the fronds of
mycorrhizal plants. The enhanced biomass with
mycorrhizal inoculation was associated with
enhanced P uptake and consequently increased
the quantity of As removed from the soil by the
hyperaccumulator (Koltai and Kapulnik
2010
).
Further, AM fungi acquire P for their host plants,
but this may lead to problems on arsenate-
contaminated substrates if enhanced acquisition of
phosphate is accompanied by enhanced acquisition
of arsenate. Since arsenate can enter plants
through their phosphate transporters (Lee
1982
),
mycorrhizal fungi may enhance uptake of both
phosphate and arsenate by plants.
Arsenic resistance of mycorrhizal plants
might be partly explained by the higher P/As
ratios in mycorrhizal plants. Thus, mycorrhizal
plants obtained more P than non-mycorrhizal
controls, and the higher P/As ratios may be one
of the mechanisms by which AM fungi can
enhance host plant resistance to As, even in the
case of As hyperaccumulators. Many studies
have indicated positive effects of mycorrhizas on
host plants under environmental stresses could be
directly or indirectly attributed to improved plant
P nutrition (Koltai and Kapulnik
2010
). However,
there were signifi cant increases in root P
concentration with mycorrhizal colonization. In
general, the phosphate analogue arsenate is more
toxic to plants than arsenite. On the other hand,
arsenate reductase, which catalyzes the reduction
of arsenate to arsenite, is expressed in leaves only
and not in roots (Dhankher et al.
2002
). Since
more P was stored in the roots with increasing
As application and mycorrhizal colonization
enhanced this trend, we suggest that the higher P
concentration in the roots may contribute to As
resistance in the mycorrhizal plants. Phytotoxicity
of arsenate has been observed under conditions
of low P supply (Wang et al.
2010
), and mycor-
rhizal inoculation has been observed to alleviate
As phytotoxicity by increasing plant P content.
Although tin mining was stopped in the late
1980s, the release of arsenopyrite (FeAsS) from
the tin ore has left extensive As contamination in
many areas of Ron Phibun District. The long-
term use of contaminated water for agriculture or
direct consumption poses a serious risk of chronic
As poisoning among the local population causing
diseases such as skin melanoma, cancer, and high
blood pressure. The environmental problems
originating from As contamination is still
observed. Therefore, to protect animal and human
health, remediation of the As-contaminated sites
has been a priority area of research and develop-
ment. The Ron Phibun wasted soil is a highly
complex, heterogeneous mixture of sulfi de, sili-
cates, and oxide with high total concentrations of
As (Arrykul et al.
1996
). Use of
P. calomelanos
for phytoextraction of As appears to be a feasible
solution (Alkorta et al.
2004
).
5
Lead Contamination in Klity
Creek and Reclamation
Lead (Pb) in Thong Pha Phum District,
Kanchanaburi Province are primary deposit of
lead sulfi de (galena, PbS) in stratabound deposit
and secondary deposit (cerussite, PbCO
3
). The
secondary deposit of lead, which is changed from
lead sulfi de due to oxygen and underground
water, is in topsoil and subsoil. In 1998, torrential
rain caused the mine's tailings facility to rupture,
releasing more than 800 metric tons of Pb into
the Klity Creek watershed, Thong Pha Phum
District, Thailand. The mine and processing
facility were immediately shut down, and the
Public Health Ministry prohibited using water
from the creek and banned fi shing (Nobuntou
et al.
2010
; The Nation
2013
). The Pb tailing was
excavated from Klity Creek in 2.5 km distance
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