Environmental Engineering Reference
In-Depth Information
Table 1
Total As, As species, Fe, Mn and Al concentrations in the water phase after anaerobic,
aerobic (undisturbed) or aerobic (stirred) treatment of contaminated soil
Stirred beaker-aerobic
Anaerobic
Undisturbed-aerobic
Conc./Rel
Conc./K
d
(µg/L)
(%)
(L/kg)
(µg/L)
(%)
(L/kg)
(µg/L)
(%)
(L/kg)
Total As
21
33
12
Leached As
a
0.0084
0.013
0.0048
K
d
value
b
71,400
45,500
125,000
As(III)
1.4
6
1.3
3
1.4
10
Arsenite
As(V)
20
89
38
94
13
89
Arsenate
DMA
1.1
5
0.6
2
<0.1
<0.5
MMA
<0.1
<0.5
0.4
<1
<0.1
<0.5
∑Species 23 40 15
Fe 73 − 39 − 52 −
Mn 82 − 96 − 110 −
a
Ratio between the As content in the water phase and in the soil (soil C; 1,500 mgAs/kg DS).
b
As concentration in soil C (1,500 mg/kg DS) was used for the calculation of K
d
.
Table 2
Total As, Fe and Al concentrations and K
d
values from the leaching tests
As in leachate
after 6 h
(µg/L)
As in leachate
after 18 h
(µg/L)
K
d
value
after 6 h
(L/kg)
K
d
value
after 18 h
(L/kg)
As in soil
[mg/kg
a
]
Fe in soil
(mg/kg
a
)
Al in soil
(mg/kg
a
)
Soil A
41
1.7
1.5
24,000
27,000
100,000
8,500
Soil B
71
31
38
2,300
1,900
25,000
19,000
Soil C
1,500
34
28
45,000
54,000
68,000
21,000
a
Of dry substances.
low leachability and lead to a classification of the soils as inert waste, which
is incorrect because the As concentration in soil C is higher than the limit for
hazardous waste (>1,000 mg/kg DS). The high K
d
values in soils A and C may be
explained by the binding of As to iron hydr/oxides
[12]
(Table
2
). In addition,
As(V) was the dominant form in the soils analysed, which was expected because
As(V) adsorbs more strongly than As(III) to soil particles
[1, 12]
. Other studies also
demonstrated equally high K
d
values as those presented here
[12]
. In the present
study, the K
d
value was approximately three times higher in the batch test compared
to the leaching test, which is supported by previous studies
[15]
.
Groundwater
Table
3
shows As concentrations in groundwater from one sampling point on
different sampling occasions and with different sample treatment. Groundwater
samples revealed high concentrations of As, up to 42 mg/L but it varied greatly due
