Biomedical Engineering Reference
In-Depth Information
(a)
(b)
FIGURE 10.17
Chironomus plumosus larva (a) and after adult fly has emerged (b).
that the volumetric flow rates moved by the larvae was between 54.6 and
61.7 mm
3
/
s.
An early modeling of the effect of tube-dwelling animals was presented by
Aller (1980). He defined a microenvironment in marine sediments as a single,
tube-dwelling animal together with its surrounding sediment represented by a
finite hollow cylinder. Ignoring advection, the transport of solutes within the
bioturbated zone was then modeled within a microenvironment given by the
diffusion-reaction equation:
r
∂C
∂r
+
R
=
D
s
∂
2
C
∂x
2
∂C
∂t
+
D
s
r
∂
∂r
(10.35)
where
x
is depth in sediment relative to the sediment-water interface,
r
is the
radial distance from the center of the tube/burrow, and
t
is time. Furthermore,
the parameters
C
,
D
s
, and
R
are concentration of the dissolved solute, solute
diffusion coecient in bulk sediment, and reaction function, respectively.
Equation (10.36) was solved subject to the initial and boundary conditions,
such as constant concentration within the burrow by bioirrigation, or conti-
nuity of solute flux between the bioturbated and underlying sediment zones.
The effect of sediment permeability was taken into account by correcting the
diffusion coecient via tortuosity.
Boudreau and Marinellli (1994) introduced modifications to the cylinder
model allowing for periodic bioirrigation because the majority of infaunal
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