Environmental Engineering Reference
In-Depth Information
(a)
Fig. 9.6
Simulated
concentration in leaves for
compounds with varying log
K
OW
and varying partition
coefficient air-water (
K
AW
),
for a concentration in soil
equal to 1 mg kg
−
1
(wet
weight). Concentration in air
is (
a
)0and(
b
) in phase
equilibrium with soil
10
1
0.1
0.01
0.001
1.E-06
0.
0.001
0
1
2
3
4
Kaw
5
6
log Kow
(b)
10
1
0.1
0
1
2
3
4
0.01
log Kow
5
6
Kaw
contaminants the accumulation decreases. The largest accumulation is seen for
non-volatile contaminants, in particular for the polar ones (low
K
OW
). These con-
taminants are readily soluble in soil pore water, taken up by plants with the soil
pore water and translocated to the leaves. From the leaves, the water evaporates, but
the contaminants remain. For non-volatile chemicals (
K
AW
→
0), calculated con-
centrations of polar contaminants in leaves are more than 100 times higher than
in soil.
Sulfolane (tetrahydrothiophene 1,1-dioxide) is an organo-sulfur contaminant
used as solvent that accumulates in leaves. Sulfolane is neutral, polar (log
K
OW
of
-0.77) and non-volatile (
K
AW
of 2.14
10
−
4
). The uptake of sulfolane into wetland
vegetation was measured in field and greenhouse studies (Doucette et al.
2005
). The
measured
RCF
was between 0.3 and 1.4 L kg
−
1
(related to the initial concentra-
tion in solution). High translocation to leaves was found. The
BCF
values for shoots
were up to 160. Another experiment with sulfolane was done for apples (Chard et al.
2006
). The concentration ratio of fruit to soil was 2.8. For leaves, a
BCF
of 652 was
found. As far as the authors are aware, this is the highest
BCF
plant to soil that
was ever measured, and confirms model predictions in which polar, non-volatile
contaminants are best translocated to and accumulated in leaves. Also measured
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