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International Journal of Marine Science 2014, Vol.4, No.35
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3
currents than the eastern side profile ones. The
sediments resulted from erosion at the western side
transferred eastward to deposit at the eastern profiles
with the dominant currents carrying the light
radionuclides
40
K and left the heavy radionuclides
226
Ra and
232
Th at the erosion sites. The worldwide
average concentrations of
238
U,
232
Th reported by
UNSCEAR (2000) are 35, 30 Bq/kg, respectively.
Comparably, the detected activities of
226
Ra ranged
between 10.42 Bq/kg and 40.3 Bq/kg, while activities
for
232
Th have been found between 9.21 Bq/kg to 53.1
Bq/kg. However, the worldwide averages were close
to the resulted ranges.
Table 2 illustrates the variations between the average
concentrations of radionuclides under investigation
detected at erosion sites compared with the other
accretion ones at Nile Delta coastal profiles. The
erosion profile (W_R) shows relatively higher
226
Ra
and
232
Th concentration values with profile averages
31.17 and 30.44 Bq/kg, respectively, compared with
the accretion profile (E_B) with averages 18.13 and
18.8 Bq/kg, respectively. On the other hand,
40
K
detected as relatively higher in the accretion profile
(E_B) with average as 298.34 Bq/kg than the erosion
one (W_R) with average as 240.48 Bq/kg. Regarding
the profiles have the two situations (erosion and
accretion), comparison has been set between the first
two sites (100-200 m) and the last two sites (400-500
m) to be away from the intersection point around 300
m. It is recognized that the heavy radionuclide
232
Th
was detected in erosion sites as the greater
concentrations than at the accretion sites as shown in
Table 2. Also,
226
Ra acting as heavy radionuclide has
the same behavior like
232
Th. It was found in relatively
higher concentrations at erosion sites than the
accretion ones at the same profile except at E_R. On
the other hand, the light radionuclide
40
K has reverse
behavior than the heavy radionuclides (
226
Ra and
232
Th). Generally, it detected at erosion sites with
lower concentrations than at accretion sites except at
E_R and W_B.
Figure 1 The depths of the profiles under investigation compared with the available data
B
A
C
D
E
F