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Fitzgerald et al. (
2001
) were also able to quantify the rates of deposition and
resuspension by comparing the new inventory in the sediment core to the residual
inventory. The residual inventory was taken to be the
7
Be activity within the core
during an earlier sampling period (decay-corrected to the more recent sampling date),
whereas the new inventory was calculated as the total inventory (obtained from the
most recent sampling campaign) less the residual inventory. When the new inventory
exceeded the residual inventory, deposition had occurred and vice versa. Moreover,
short-term depositional or erosional rates,
ʨ
, were calculated by Fitzgerald et al.
(
2001
) using the equation:
fl
7
Be
μ
ʨ
=
(3.7)
7
Be
where
fl
7
Be
is the
7
Be flux equal to the new deposit inventory divided by the time
between the sampling intervals and
7
Be
is the mean
7
Be particle activity in sus-
pended sediments. In the study by Fitzgerald et al. (
2001
), the mean
7
Be activity in
suspended particles was determined by the analysis of suspended particles captured
in sediment traps.
Fisher et al. (
2010
) also noted that important insights into scour and fill processes
could be gained by examining the vertical
7
Be activity in channel bar deposits. In
fact, they developed a conceptual model, presented in Fig.
3.11
, that illustrates the
types of vertical patterns that would result from differing sequences of scour and
μ
(a)
(b)
Fig. 3.11
Conceptual model of sediment bar scour and deposition as determined from
7
Be depth
profiles.
a
Submerged bar composed of sediment with no
7
Be activity.
Solid black line
on activity
versus depth plot shows that
7
Be activity is below detection throughout bar.
b
Typical depth-activity
profiles observed for single and multi-phase depositional events. Change in
7
Be activity with depth
is related to time of sediment storage in bar (modified from Fisher et al.
2010
)
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