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International Journal of Marine Science 2014, Vol.4, No.35
http://ijms.biopublisher.ca
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Research Article Open Access
Assessment of Natural Radioactivity Distribution in Surface Sediments at
Erosion and Accretion Sites of Nile Delta Coastal Profiles, Egypt
Ayman A. El-Gamal
Department of Marine Geology, Coastal Research Institute (CoRI), National Water Research Center, (NWRC), 15 St., Elpharanaa, Elshalalat 21514,
Alexandria, Egypt
Corresponding email
International Journal of Marine Science, 2014, Vol.4, No.35 doi: 10.5376/ijms.2014.04.0035
Received: 16 May, 2014
Accepted: 30 May, 2014
Published: 17 Jun., 2014
Copyright
©
2014 El-Gamal, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:
El-Gamal A.A., 2014, Assessment of Natural Radioactivity Distribution in Surface Sediments at Erosion and Accretion Sites of Nile Delta Coastal Profiles,
Egypt, International Journal of Marine Science, Vol.4, No.35 (doi: 10.5376/ijms.2014.04.0035)
Abstract
The Nile Delta coast is highly active dynamical coastal processing area. The investigation of gamma emitters of the
surface sediments collected from Nile Delta coastal profiles revealed that the distribution of the detected natural radioactive materials
is dependent mainly on the coastal processes. 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. The concentrations of the heavy radionuclides
226
Ra and
232
Th were found higher in erosion sites compared
with the accretion ones. On the other hand, the light radionuclide
40
K was behave as reverse as the heavy radionuclides that its
concentration values detected at the erosion sites were lower than at the accretion ones. Radium equivalent index calculation
indicated that all the sediments under investigation can use safely as building materials. The average of the outdoor gamma dose rate
was 37.25±9.58 nGy/h and the annual external effective dose was 0.05±0.01 mSv/y and these values were in agreement with the
corresponding values at different parts of the world. The distribution of the detected natural radionuclides and grain size in the coastal
sediments at surf, breaker and offshore zones and their correlations has been discussed.
Keywords
Natural radioactivity; Coastal erosion; Nile Delta; Radium equivalent index; Gamma dose; Grain size
Introduction
Coastal processes are the set of mechanisms that
operate along a coastline, bringing about various
combinations of erosion and deposition. Sediment
transport is one of the important coastal processes
(Dean and Dalrymple, 2002). Erosion of the beach
face has resulted in high concentration of dense heavy
minerals, while the lower-density minerals were
transported either to the offshore or alongshore (Frihy,
et al., 1995). Heavy mineral-rich beach sands,
concentrated by wave and wind action, have been
found to contain significant gamma radioactivity, due
primarily to trace amounts of uranium and thorium
found in monazite and zircon minerals (Donoghue and
Greenfield, 1991; El-Gamal and Saleh, 2012).
In marine ecosystems, radionuclides will disperse with
currents, accumulate in biota, and be adsorbed by
particles and sediments depending on local conditions
and radionuclide properties (Jørgensen and Fath,
2011). Sediments can act as a sink for less mobile
discharged radionuclides (Skipperud et al., 2000).
Therefore, the use of radionuclides for studying the
coastal environments can answer important scientific
questions, which may be useful for coastal
management (Cochran et al., 2006). The distribution
of natural radionuclides at coasts can use as indicator
for beach and nearshore sand transport phenomena
(Greenfield et al., 1989) which indicate coastal
processing such as erosion and accretion.
The assessment of gamma radiation doses from
natural sources is of particular importance because
natural radiation is the largest contributor of external
dose to the world population (UNSCEAR, 2000;
Narayana et al., 2007). The primordial and radiogenic
radionuclides (e.g.
238
U and
232
Th series and
40
K) are
the most dominant radioactivity sources at the Nile
Delta coast (El-Gamal et al., 2004). The higher U and
Th series member's concentrations have been recorded
in the black sand at Rosetta (Rashid) as one of the
high background areas compared with the other
stations along the Egyptian Mediterranean coast
(Saleh et al., 2004). The relationship between grain