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International Journal of Marine Science 2014, Vol.4, No.35
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6
profile one. The calculated gamma dose average value
is lower than other sites in Turkey but is close to the
present work ranges especially the upper limits. The
detected range was comparable with gamma dose
measured at Balacali (54.1 nGy/h), Yeniyayla (55.8
nGy/h) and Karatas (49.5 nGy/h) (Degerlier, 2012).
UNSCEAR (1993 and 2000) mentioned that the
sources of radiation could vary from place to place but
the dose rate generally falls between 80 and 150
nGy/hr world over which is higher than the average
value of the present work.
An estimation of the annual external effective dose
(AEED) rates depicts a measure of the effective dose
equivalent to be received by the public due to
sediments radioactivity, as computed from the activity
concentrations of
232
Th,
238
U and
40
K in bulk sand
samples from Nile Delta, as listed in Table 1. AEED in
Nile Delta coastal area is varied from 0.03 to 0.07
mSv/y with an average of 0.05±0.01 mSv/y. It is
obvious that the average AEED values at Nile Delta
are considerably lower than the world average (0.07
mSv/y) (UNSCEAR, 1993) but still close to the higher
limit of its range. The values of measured AEED is in
agreement with the values from Northern Jordan, for
instance, which was reported as 0.06 mSv/y (Ibrahim
and Mohammad, 2009) while it is lower than Preta
Beach of Brazil that reported as 0.15 m Sv/y (Freitas
and Alencar, 2004) and from Orissa (2.0 mSv/y)
(Mohanty et al., 2004).
According to depths the sampling locations within the
profiles are classified and divided into three zones;
surf zone (0-2 m), breaker zone (2-4 m) and offshore
zone (>4 m). Figures 4-6 are represent the distribution
of the grain size analysis of the sediment samples and
the detected natural radionuclides (
226
Ra,
232
Th and
40
K) in the three zones. Correlation analysis was
performed between mean grain size (mm) with the
radionuclides concentrations of
226
Ra,
232
Th and
40
K
(Bq/kg) at surf, breaker and offshore zones. The
correlation coefficients are presented in Figure 4. High
correlation was found between the mean grain size
with
226
Ra (r = 0.999) and
232
Th (r = 0.955)
concentration values at surf zone. This is my be due to
the surf zone is the most dynamic part of the beach
and it is characterized by Surf zone currents which can
transport sediment onshore, longshore and offshore
and build the (sand) bars and troughs that occupy the
surf zone (Short, 1999). This sediment transport
mechanism play important rule for sorting the
sediment grains and also the sediments holding the
radioactive materials. No correlation was found
between mean grain size and the light natural
radioactive nuclide
40
K (r = 0.082). In breaker and
offshore zone, negative weak correlations between
mean grain size and the concentration of
226
Ra (r =
-2.61 and -0.323) and
232
Th (r = -0.39 and -0.33),
respectively were found.
Figure 4 The correlation coefficients between mean grain size
(mm) with the concentrations of
40
K,
226
Ra and
232
Th (Bq/kg) at
surf zone (depth <2 m), breaker zone (depth 2-4 m) and
offshore zone (>4 m)
Figure 5 The concentrations of the parameters under investi-
gation at the surf zone