Basic HTML Version
International Journal of Marine Science 2014, Vol.4, No.35
http://ijms.biopublisher.ca
8
(1) The Nile Delta coastal profiles were classified
according to their coastal processing status into
erosion profile (e.g. west of Rosetta), accretion profile
(e.g. east of El-Burullus), erosion-accretion profiles
(e.g. east of Rosetta and east of Ras El-Bar) and
accretion-erosion profiles (e.g. west of El-Burullus
and west of Ras El-Bar).
(2) The average concentrations of
226
Ra,
232
Th and
40
K
in the Nile Delta coastal profiles were 23.78±8.54,
23.95±11.79 and 280.93±68.19 Bq/kg, respectively.
These average values are lower than the worldwide
averages but still within its ranges.
(3) The concentration values of
226
Ra and
232
Th were
found higher in erosion sites between and within the
profiles compared with the accretion sites. On the
other hand, the light radionuclide
40
K concentration
values were behave as reverse as the heavy
radionuclides that it detected at the erosion sites with
lower concentrations than the accretion sites.
(4) The investigation of Radium equivalent index
indicated that all the sediments under investigation are
acceptable to use as building materials. The average of
the outdoor gamma dose rate was 37.25±9.58 nGy/h
and the annual external effective dose 0.05±0.01
mSv/y and these values were in agreement with the
corresponding values at different parts of the world.
(5) The distribution of the detected natural radio-
nuclides and grain size in sediments at surf, breaker
and offshore zones has been discussed.
3 Materials and Methods
3.1 Study area
The area under investigation is the Nile Delta coastal
region which represents a part of the Mediterranean
coast of Egypt (Figure 8). It covers about 280 km
2
of
coastal sediments profiles extended distances seaward
till 500 m bounded by latitudes 26º35
/
- 26º45
/
N and
longitudes 33º42
/
- 33º52
/
E. Generally, the coast of
Nile Delta is highly active dynamical coastal
processing area and it is highly affected by River Nile
discharge. Coastal erosion has been observed and
induced on the Rosetta and Damietta Promontories
after construction of the Aswan High Dam in 1964
due to elimination of alluvial sediments, although
climatic factors may have been important (Frihy and
Figure 7 The concentrations of the parameters under investi-
gation at the offshore zone
Khafagy, 1991). Many artificial coastal protection
structures have been established at the Nile Delta
coast to control the erosion process such as sea walls,
detached breakwaters and groins. The original
erosion/accretion patterns along the Nile Delta
promontories have been reshaped due to the massive
protective structures built after 1990. The behavior of
coastline pre and post construction indicates that
coastal erosion fronting protective structures has
declined in the case of the seawalls at the tips of the
Rosetta and Damietta promontories, or has been
partially replaced by sand accumulation in the case of
detached breakwaters at Baltim (east of Burullus
headland) and at Ras El-Bar (west of the Damietta
promontory) (Frihy et al., 2003).
3.2 Sampling and sample preparation
In order to study the behavior of the different natural
radionuclides and in accordance with the
hydrochemical zoning of the Nile Delta coast,
different sampling points at six profiles lie east and
west of Rosetta promontory, El-Burullus outlet and
Damietta promontory have been selected (Figure 8).
Surface sediments were collected from the coastal
profiles at different distances 100, 200, 300, 400 and
500 m from fixed benchmarks at beach using grab
sampler from rubber boat (Zodiac) at the end of May
2008. Each distance is corresponding to specific depth
according to the sampling site. The samples were
washed and dry for mechanical analysis.