Environmental Engineering Reference
In-Depth Information
Results and Discussion
The results revealed varying concentrations of the metals in the soil, extremely high
concentrations, mg/kg of dry substances (DS), of total As up to 3,000, but also
Pb £ 3,100, Cd £ 16, Cu £ 2,000, total Cr £ 1,200 and Zn £ 870 in close proximity
to the former impregnation barrel. All these values significantly exceed the Swedish
guideline values for contaminated soil; the guideline value for total As is 15 mg/kg
DS. A mean As concentration in the soil in the highly contaminated area around
the former impregnation barrel was calculated to 250 mg/kg DS. Extremely high
concentrations of As in soil has also been reported at an industrial site in Belgium
[18]
.
The dry matter content (75% in soils B and C, and 81% in soil A) indicates that
soil A consists of larger grain sizes with a lower ability to bind water. The organic
matter content was low (1.5%) in all soils. Total concentrations of several metals
were analyzed in all soil samples and the results are presented in Fig.
1
.
Soil C was highly contaminated with As, while soils A and B contained lower
As concentrations. Soil C also had elevated levels of Cr, P and Al compared to soils
A and B. Soil B generally exhibited low concentrations of all elements, although
the As and Al levels were higher compared to soil A. Compared to soils B and C,
soil A had higher concentrations of Fe, Mn, Cu, Ni, Pb and Zn.
The arsenic speciation showed that the soil samples had high levels of arsenate/
As(V), see Fig.
2
. This was expected, since the soil was unsaturated and therefore
in an oxidizing environment; arsenate is formed under oxidizing conditions
[6]
.
The arsenate/arsenite relation was around 80 in soil C, 70 in soil B and 20 in soil
A, and similar relations were observed in a previous study
[19]
. The concentrations
of DMA and MMA were low, which was expected because of the low organic
content of the soils
[12]
.
120000
2500
100000
2000
80000
1500
1000
60000
Soil A
500
Soil B
40000
Soil C
0
As Be
Cd
Co
Cr Hg
Li Mn Mo
Ni
PPbSrV Zn
20000
0
Fe
Al
Cu
As
Be
Cd
Co
Cr
Hg
Li
Mn
Mo
Ni
P bSrV
Fig. 1
Total metal and phosphorus concentrations in mixed soil samples A-C
