Table C-2
Summary of Characteristic Times of Sediment Fate and Transport Processes
Process
Characteristic Time
Relationship
Typical Range of Key
Parameter Values
Illustrative Value of
Characteristic Time
1
Diffusion
D
R
H
4
=
eff
f
2
2
diff
p
t
R
f
> 1,000
(Hydrophobic
organics)
D
eff
~ 10
-6
cm
2
/s
1,280 years
Advection
v
R
H
=
f
adv
t
Groundwater velocity,
v
,
widely variable
100 years
Sediment Erosion
U
H
=
ero
t
Bed erosion rate, U,
widely variable
10 years
Bioturbation
D
H
4
=
bio
2
2
bio
p
t
0.3 cm
2
/yr
bio
<30
cm
2
/yr
13 years
Reaction
k
1
=
rxn
fate
t
Reaction rate,
k
rxn
,
widely variable
100 years
*
Assumes a 10 cm thick
surficial layer contaminated with a hydrophobic organic with an effective
retardation factor of 1,000. A groundwater velocity of
1 meter/
yr, a bed erosion rate of 1 cm/
yr, an effective
bioturbation diffusion coefficient of 3 cm
2
/yr and a reaction rate of 0.01 yr
-1
are assumed for purposes of
illustration.
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