Environmental Engineering Reference
In-Depth Information
roots. For neutral organic chemicals (
phenylureas
and
o-methylcarbamoyloximes
),
the relation between log
K
OW
and sorption to roots was:
7,
r
2
log(
RCF
−
0.82)
=
0.77 log
K
ow
−
1.52 (
n
=
=
0.96).
(9.5)
The dependency on the log
K
OW
was explained by lipophilic sorption of the con-
taminants to plant lipids. The value of 0.82 was interpreted as water content of
the roots. A similar result was obtained for cut pieces of bean roots and stems for
N-methyl-arylcarbamates
(Trapp and Pussemier
1991
):
12,
r
2
log(
RCF
−
0.85)
=
0.557 log
K
ow
−
1.34 (
n
=
=
0.92).
(9.6)
This equation gives lower root concentration factors for lipophilic contaminants
(Fig.
9.3
). Both
RCF
-regressions describe partitioning to water. But roots typi-
cally grow in soil. The sorption of organic contaminants to soil is related to the
organic carbon content,
OC
. Many regressions for the organic carbon normalised
sorption to soil,
K
OC
(L kg
dw
-1
), were established, for example for neutral organic
contaminants (EC
2003
)
81,
r
2
log
K
OC
=
0.81 log
K
OW
+
0.1 (
n
=
=
0.89)
(9.7)
Bulk soil consists of solids, water and air. For the concentration ratio between
bulk soil and soil pore water,
K
SW
(L kg
-1
) follows
C
Soil
C
W
=
OC
×
K
OC
×
ρ
S
,
dry
+
θ
×
ρ
W
ρ
S
,
wet
1
K
SW
K
SW
=
=
(9.8)
where
OC
is the fraction of organic carbon in soil (kg kg
-1
),
θ
is the water content
of soil (L kg
-1
),
ρ
W
is the density of water (1 kg L
-1
),
ρ
S,dry
is the soil dry density
(kg
dw
L
-1
) and
ρ
S,wet
is the soil wet density (kg
ww
L
−
1
). Division of
RCF
with
K
SW
gives the equilibrium concentration of the ratio of roots to soil.
100
10
1
Fig. 9.3
Measured data and
root concentration factor
(
RCF)
-regression lines of
Briggs et al. (
1982
)andTrapp
and Pussemier (
1991
),
compared to the
concentration ratio bulk soil
to water (
K
SW
)
0.1
-1
0
1
2
3
4
5
log Kow
Briggs meas
Briggs regr
T&P regr
Ksw
T&P meas
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