Page 7 - IJMS-2014v4n34

International Journal of Marine Science 2014, Vol.4, No.35
http://ijms.biopublisher.ca
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size and heavy mineral distributions regarding its
contents of the natural radioactive elements of the Nile
Delta coastal sediments has been investigated by
El-Gamal and Saleh (2012).
The present work aims to assess radioactivity
distribution in erosion and accretion sites in Nile Delta
Profiles and to indicate this variation in surf, breaker
and off shore zones in Nile Delta coastal area and its
surrounding environment. The data obtained will be
used as reference information to assess any change in
radioactivity background levels due to coastal
processes such as erosion and accretion or any
influences on the radiation environment. These results
can guide us to a better understanding of
oceanographic and coastal processes and phenomena
in order to protect and for management of the marine
environment.
1 Results and Discussions
The present study revealed that the sediment samples
collected from Nile Delta coastal profiles contain
primordial terrestrial radioactive elements at
remarkably natural levels. Based on HPGe Detector
Gamma spectrometric measurements, it could be
inferred that elements such as Uranium (238U),
Thorium (232Th) and Potassium (40K) are the major
causative factors for the radioactivity thus confirming
to the previous observations (Ibrahim et al., 1993;
El-Gamal et al., 2004; Saleh et al., 2004; Hussein,
2011; El-Gamal and Saleh, 2012). The study indicated
that the distribution of the sediment grain size and the
natural radioactive nuclides under investigation are
dependent on the geological and chemical characters
of the coastal sediments and controlled by coastal
processing (erosion or accretion) and the protection
structure established on the coast.
It is well known that, at the erosion sites, parts of the
sediments are removed and transported with the main
sea current to deposit at the next sites parallel to the
shoreline or transported seaward to the next position
at the same profile. The depths of the profiles under
investigation were compared with the previous depth
records of the same profiles to indicate the actual
situation of them are either erosion or accretion.
Figure 1A shows that West of Rosetta profile was
recognized as erosion profile at its sampling sites.
Figures 1B and F represent East of Rosetta and East of
Ras El-Bar profiles beginning as erosion at distances
from 100-300 m and continue as accretion sites at the
400-500 m distances. On the other hand, Figure 1D
shows East of El-Burullus profile was recognized as
accretion profile. Figures 1C and E show that West of
El-Burullus and West of Ras El-Bar profiles were
started as accretion sites at distances from 100-300 m
and continue as erosion sites at the 400-500 m
distances.
Results of the activity concentrations of primordial
radionuclides 226 Ra, 232 Th and 40K (values reported as
Bq/kg) and the ratio 226Ra/232 Th as well as the
calculated radiation hazards indices of the sediment
samples are given in Table 1. Out of the 275 km
stretch of the coastal line featured in our present study
in Nile Delta and coastal profiles extending to 500 m
distance, the average activity of 226 Ra was 23.79±8.54
Bq/kg and it found to be the highest value
(40.3±6.77Bq/kg) at 400 m distance west of Ras
El-Bar, while the lowest activity (10.42±7.92Bq/kg)
was recorded at 200 m distance east of Rosetta.
Likewise, the average activity of 232Th was
23.95±11.79 Bq/kg and its highest activity
(53.1±10.26 Bq/kg) was recorded at 500 m distance
from west of Ras El-Bar, the lowest activity of 232Th
(9.21±6.18Bq kg−1 ) was recorded at 500 m distance of
east El-Burullus. The average 40K activity was
280.93±68.19 Bq/kg and its highest activity
(399.04±41.85Bq/kg) was recorded at 400 m distance
of east El-Burullus, while the lowest activity
(160.55±37.48Bq/kg) was recorded at 200 m distance
of west Rosetta.
The distributions of the detected radionuclides activity
concentrations are presented in Figures 2a, 2b and 2c
for 226 Ra, 232 Th and 40K, respectively. Figure 2a shows
that generally the eastern profiles have relatively
lower 226 Ra (originally from the heavy nuclide 238 U)
activities than the western profiles. Moreover, at 400
and 500 m distances of the western side profiles at
Rosetta and Ras El-Bar observed as higher
concentrations than the nearest distances (100-300 m)
to shore line. The behavior of the heavy radionuclide
232 Th is like 226Ra as shown in Figure 2b. Reverse
behavior has been observed for the light radionuclide
40K with distribution shown in Figure 2c. This is may
be due to that the western profile sediments are
subjected more to causes of erosion such as wave and