Environmental Engineering Reference
In-Depth Information
Experimental and Methods
The study site is situated less than 1 km from the centre of a city on the west coast
of Sweden. Activities at the site include welding, engine and wood treatment
and assembly. The CCA fluid Boliden K33 was used at the site from 1943 to 1979.
As an example, 4,800 kg of Boliden K33 was purchased in 1978. The impregnation
equipment, in the form of a barrel, was not kept in a protected area. After impregna-
tion, the wood was dried in open areas close by. Sawdust formed during treatment
of the dried wood was probably combusted in the area. In an environmental inves-
tigation carried out in 1998, the contaminants were judged highly hazardous and
the dispersal potential was regarded as high. Due to the current use of the land area
for industrial activities, the site was classified as risk class 2, which corresponds to
“great risk” and not “high risk” as indicated by class 1
[17]
.
The property is flat with mostly hardened surfaces (asphalt) and has a total area
of 80,000 m
2
. The contaminated area around the former impregnation barrel is
1,800 m
2
. The groundwater flow is generally towards the north where a stream is
located. The groundwater surface is assumed to be at the same level as the water
surface of the stream. The soil to the north of the former impregnation barrel consists
of muddy sand and to the south of filling material comprising rocky gravely sand
over lake sand on top of clay.
Samples
Soil samples were collected by means of an auger sample in September 2007, at 11
locations in the area of the former impregnation barrel. At each location, four to
five samples were taken at different depths to a maximum of 2-3 m. The soil
samples were analyzed for concentrations of total As and other metals. From the
total of 52 soil samples collected in the area around the former impregnation barrel,
15 were selected on the basis of the As concentration levels, and new samples were
mixed and classified as A-C with the following degrees of contamination:
•
Soil A: 15-40 mg As/kg of dry substances (DS).
•
Soil B: 40-400 mg As/kg DS
•
Soil C: 400-3,000 mg As/kg DS
Five samples from each category were mixed in a mortar without crushing the
material. Particle fractions >10 mm in diameter were removed by hand; however
there were very few particles of that size. The mixed samples were then stored
(+4°C) in diffusion-tight plastic bags designed for soil samples. The concentration
of total As, As (III), As(V), DMA, MMA, other elements, water content and loss of
ignition were then analyzed.
A set of batch tests was carried out aimed at studying the effects of mixing
and aerobic/anaerobic conditions on the leachability of the different As species.
