Environmental Engineering Reference
In-Depth Information
Table 1
Metal resou
rce in Thailand
Metal reserved
under patent permit (dmt)
Metal reserved
in potential resource (dmt)
Metal remaining in
potential resource (%)
Metal
Gold
26
172
84.88
Zinc
3,796,190
5,796,190
34.51
Silver
96
526
81.75
Iron
41,068,954
191,068,954
78.51
Antimony
1,246
50,001,246
99.99
Copper
0
1,000,000
100.00
Lead
0
800,000
100.00
Source: Department of Primary Industries and Mines (DPIM) in 2008
Data at the end of 2005
dmt
dry metric tons
Integrated biogeotechnologies for reclamation
of mine waste are shown in Fig.
7
(Benzaazoua
et al.
2008
). In recent times, application of phyto-
technologies for restoration of contaminated sites
is gaining considerable signifi cance. Establishment
of vegetation is not only aiming to return the area
to its original appearance but also to prevent the
leakage of toxic metals (Bradshaw
1997
). Dealing
with mine waste requires integrated package of
practices. A careful selection of plants that do not
transport the metals to the harvestable parts like
shoots is desirable as these would lockup the
metals in the root or the rhizosphere (= phytosta-
bilization). Apart from the physical stabilization
that protects against erosion, the roots have a
benefi cial effect on mine tailings through decreasing
acidity and oxygen concentration, and they prevent
rainwater from percolating to the tailings.
Numerous approaches are being followed to
establish viable plant covers directly on mine
tailings (Bell
2001
). However, since the impound-
ments offer a very harsh environment to the
plants, with high levels of heavy metals, low
levels of macronutrients, and poor substrate
structure, these attempts usually have failed, and
the process is rather very slow in establishment of
plant cover. Natural succession is possible even
on such areas, but a time span of at least
50-100 years is needed before a viable vegeta-
tion cover is developed (Bradshaw
1997
).
Establishment of plants can take place through
natural spreading if the restored site is small and
surrounded by natural vegetation, a low-cost
method that would enhance natural appearance
(Prach and Pyšek
2001
). However, when the sites
are large and heavily polluted, like mine waste
deposits, natural succession will take a consider-
ably longer time (Bradshaw
2000
). To get a faster
and more homogenous establishment of vegetation,
planting and sowing are often practiced, which
should be performed repeatedly to give satisfac-
tory vegetation (Bradshaw
2000
). Important for
a sustainable reclamation of a soil ecosystem
and healthy vegetation is also to establish a func-
tioning microfl ora. If the covering material is
low in nitrogen, colonization of nitrogen-fi xating
bacteria is valuable, but as the nitrifi cation process
generates acidity, favoring of these bacteria might
be disadvantageous for the reclamation of already
acid mine tailings. The use of paper mill sludge,
an organic material with low nitrogen levels, has
shown to be a well-functioning cover material if
used in combination with initial fertilizers and
establishment of leguminous plants.
4
Mitigation Strategies
for Arsenic Contamination
in Ron Phibun
Thailand's well-known hot spots for As contami-
nation are located in the northwest part of the
town in Ron Phibun District, Nakhon Si
Thammarat Province, in the southern part of
Thailand. It lies between 8° 04
′
and 8° 14
′
N lati-
tudes and between 99° 46
E longitudes
(JICA
2000
). The second site is Nakhon Si
Thammarat Province in the Ongpra Subdistrict,
′
and 99° 54
′
Search WWH ::
Custom Search