Geoscience Reference
In-Depth Information
Table 17.2 Toxic
a
metal concentrations (lg/L) in groundwater under an abandoned zinc mine,
South Korea (Lee et al.
2005
)
Species
Mine area
Downgradient area
Comparison area
50-4,680
b
(1,204)
c
nd
d
-1,240 (217)
nd-30 (30)
e
Al
Cr
nd
nd
nd
Mn
63-8,286 (1,662)
nd-97 (29)
nd-48 (27)
Fe
160-2,280 (661)
nd-950 (192)
nd-220 (111)
Cu
nd
nd-84 (32)
nd-30 (23)
Zn
50-2,395(1,130)
4-11,280 (490)
7-2,533 (271)
Cd
nd-17 (11)
nd
nd
Pb
nd-9 (8)
nd-90 (90)
nd
a
Hard, soft, and borderline metals regulated by Korean drinking water standards are all termed as
toxic metals in this study
b
Range of values
c
Arithmetic mean (censored values are replaced by 0.55 times the lower detection limits for
calculation)
d
Not detected (below detection limit, less than 1 lg/L)
e
Single value
surface to groundwater, below a car battery salvage unit located on an alluvial
sandy soil in Denmark. At this site, increased concentrations of cadmium, zinc,
and nickel were detected in the soil and in groundwater at a depth of 3 m. The
migration of these metals can be associated with the low soil pH values, ranging
between 2.8 and 3.9, likely caused by acid release from the car batteries.
Groundwater contamination by toxic metals around an abandoned zinc mine in
South Korea was reported by Lee et al. (
2005
). High concentrations of Al, Mn, Fe,
and Zn were observed in groundwater, especially in the mine area (Table
17.2
).
Relative metal abundance in groundwater at the mine area shows the trend:
Mn [ Al [ Zn [ Fe [ Cd [ Pb. In the downgradient area, the relative abun-
dance sequence was Zn [ Al [ Fe [ Cu [ Mn. It was found that toxic metal
content decreases with distance from the mine. This behavior confirmed the zinc
mine as the point source for groundwater contamination.
17.3.3 Metalloids
Metalloids such as arsenic and selenium may enrich groundwater, emanating from
industrial
pollution
and
from
the
natural
geological environment
altered
by
anthropogenic activities.
In groundwater, arsenic is found mostly in the inorganic forms arsenite (As
+3
)
and arsenate (As
+5
). Under oxic conditions and at thermodynamic equilibrium,
aqueous As is dominated by arsenate oxyanions, while under reducing conditions,
the uncharged arsenite species is predominant. The main form of arsenic in
groundwater is controlled by the pH. In a reducing environment, dissolved As-S
species may precipitate as As sulfide, while in the presence of high amounts of
