Geology Reference
In-Depth Information
Table 5 Properties of a ''model world'' for modelling the behaviour of organic
chemicals
28
Area (m
2
)
Volume (m
3
)
Depth (m)
Advective residence Time (h)
10
11
10
14
Air
1000
100
10
10
2
10
11
Water
20
1000
9
10
10
1.8
10
10
Soil
0.2
10
10
5
10
8
Sediment
0.05
50,000
Organic carbon or
lipid mass fraction
Density,
kg m
3
Volume fractions
2
10
11
Aerosol
2000
5
10
6
Particles in water
0.2
1500
10
6
Fish
0.5
1000
Soil pore air
0.2
Soil pore water
0.3
Soil solids
0.5
0.02
2400
Sediment pore water
0.8
Sediment solids
0.2
0.04
2400
which relate to the fundamental physico-chemical properties of the
organic chemical under consideration. Important in this context is the
Henry's Law constant, which describes the equilibrium partitioning
between air and water that is defined as
C
W
¼
p
s
p
H
¼
K
aw
¼
S
aq
where p is the vapour pressure in air
C
W,
the concentration in water,
S
aq
, the equilibrium aqueous solubility, and
p
s
, the saturation vapour pressure for the pure substance.
Partition between compartments within the aqueous environment is
typically described through the octanol-water partition coefficient, K
ow
,
or the organic carbon-water partitioning coefficient, K
oc
(see Chapter 5).
This approach assumes that partitioning from water into fish or sus-
pended solids within the water is determined by the availability of organic
matter whose properties as a solvent can be described by a parallel with
octanol for which partitioning data are widely available
Concentration in octanol
Concentration in water at equilibrium
K
ow
¼
