الفهرس 
Sources of RadioactivityOnly 14 pages are availabe for public view
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Abstract
Burullus is chosen as the study area with an aim of
establishing a useful radiometric data base for this lake. This
study examines the distribution of radon concentration and
radioactivity levels in the Burullus Lake. The radioactivity in
water may ultimately find its way to humans through the food
chain by direct or indirect contact with the marine
environment. Fish is an important daily diet item for the
people of Egypt. Through this analysis, we investigated the
radioactive contaminants to support the possibility of
redistribution of radionuclides into the lake. In addition, we
get information about contamination patterns, and to ensure
that their accumulation does not rise to high levels, calling for
an urgent attention on ecological safety.
The results of physico-chemical parameters of the lake
affect the influx of the drainage water. The pH values of the
water were found in the alkaline side. Water transparency is
low, because Burullus Lake is shallow basin. Salinity of the
lake is a brackish water. On the other hand, it was observed
that the levels of heavy metals in water were decreased in
order of: Fe> Pb> Ni> Zn> Cu> Cd and for heavy metals in
sediment were decreased in order of: Fe> Zn> Pb> Ni> Cu>
Cd. It concludes that the only element that changes from water
to sediment in sequence is zinc. Because, in the aquatic
environment, partitions of zinc in sediments or suspended solids sorption onto hydrous iron and manganese oxides, clay
minerals, and organic material. Pollutants introduced in the
lake through agricultural, domestic or industrial wastes
discharge. The source of heavy metals in Burullus Lake water
and sediment is mostly from agricultural drainage water.
The results of radioactivity in water and sediment
show that the uranium primordial series is in disequilibrium
where: Activity Pb-210> Activity U-238>Activity Ra-226.
This disequilibrium is probably due to the difference in
geochemical properties between the three radionuclides,
whereas uranium has greater mobility than radium in the
environment. There is excess 210Pb concentration in water and
sediment could be due to the contamination of atmosphere.
Furthermore, the highest values of 238U may due to the effect
the drainage water of agricultural activity into the lake.
Whereas, there is hyperactive agricultural activities contains
amounts of phosphate fertilizer. The phosphate fertilizer
contain uranium could be dissolved and enter into the lake.
The isotopes of radioactivity in water and sediment of
Burullus Lake have a slight change from season to another.
The values of the activity of 232Th and 226Ra are nearly having
the same concentrations in water of the lake. Moreover, the
concentration of 40K is high at El Bughaz channel; whereas;
the salt water. The distribution of 137Cs shows more
contamination in the shore line of the lake. Because of the
high solubility of 137Cs and high values of TOM contents, it
can be assumed that its excess was released into Lake
Environment from the surrounding soil through the water current. The 137Cs and 134Cs might have been deposited in
sediment of Burullus Lake, presumably a result atmospheric
contamination of nuclear weapon tests and nuclear accidents.
137Cs and 134Cs do not exist in sediment naturally and it is a
product of fallout radioactivity. The spatial variation of 134Cs
activity is relatively small and average activity ratios of
134Cs/137Cs are less than the reference value during two
seasons.
The calculated value of absorbed dose in sediment of
Burullus Lake was agreement with the range reported by
UNSCEAR (2000) (18-93 nGyh-1) and less than the average
value of the world wide (59 nGyh-1). The average value of the
annual effective dose of studied lake is less than the average
recommended value (0.5mSvy-1) reported by UNSCEAR
(2000). Hex and Iγ are lower than the recommended values Raeq
< 370 in order to keep the external dose <1.5 mGy/y, and the
value of Iγ 0.66 Bq kg-1. Moreover, the sediment–water
distribution coefficient (Kd) is widely used to describe the
partitioning of radionuclides between aqueous and solid
phases. The sediment partition coefficient for 137Cs is higher
than 238U, 226Ra, 232Th, 40K and 210Pb as sequence 137Cs> 40K>
232Th> 232U> 226Ra> 210Pb. This means that 137Cs is more
mobile and has higher solubility compared to the other
radionuclides. It is obvious that the values of 238U and 137Cs
only of this study are within the range reported by IAEA
(1982). The results of radioactivity in plants show that there
are five of the most dominant and abundant plants in all parts
of the lake. Plant samples from Burullus Lake have the values
of 238U, 232Th, 40K, and 137Cs are 68.87, 6.19, 608.86 and 1.08
Bq/kg , respectively. On the other hand, there are two types of
fish species; The Nile tilapia and Catfish were collected during
the same period of study. The activity concentration of 2238U,
232Th, 40K, and 137Cs are 35.30, 2.10, 289.81 and 0.63 Bq kg-1.
The activity ratios of 238U/226Ra and 210Pb/226R in fish samples
of Burullus Lake (exceed unity) are reflecting a state of
radioactive disequilibrium between uranium and its daughter.
Determination of radiological implications received by the
consumers from ingestion of fish containing concentrations of
radionuclides depicts whether the fish diet is free from
radiological risks. The concentrations of radium equivalent
activity (Raeq), the internal hazard index (Hin), the total of
daily intake of radioactivity (Dint) and the total committed dose
from annual intakes (Deff) are 26.22 Bq kg-1 , 0.084 , 0.46
Bq/Kg/d and 18.33 μSv/year. The estimated values of
committed effective doses of
226Ra, 232Th and 40K and total
dose are lower than the values reported by UNSCEAR
(2000a). In addition, the transfer of radionuclides from water
into aquatic biota is characterized by the transfer coefficient,
the bioaccumulation factor BF. In this study, the value of BF
of 238U, 232Th, 40K and 137Cs 26.72, 4.32, 78.32 and17.57 l/kg.
The concentrations of 222Rn in water of Burullus Lake
are found in surface water higher than bottom water
concentrations could be due to agricultural activities. The principal factor of producing a high 210Pb concentration in
water over this lake was the significant radon-222 exhaled into
the atmosphere from land and rainfall scavenged the 210Pb
from the atmosphere into the water. 210Pb in water is mainly
derived from the decay of radon in the air and the resulting
deposition of this nuclide with rain for 210Pb concentrations in
surface water seem to exceed to those in water from deep
wells. Most of the radionuclides that transport to the surface
water can be attach to sediments on the bottom. Furthermore,
there is a relation between 226Ra and 210Pb of gamma
measurements and radon measurement in surface and bottom
water during two seasons. The results of modeling approach to
examine the applicability of naturally-occurring radon-222 as
environmental tracer for the investigation of water discharge
into the lake. The method has a good agreement with
discharge rates obtained from Mechanical and Electrical
Department, Ministry of Agriculture. It could be shown that
the radon method generally allows reliable quantitative
estimation of water discharge rates into small lakes even with
just a few water samples. Thus, the use of radon-222 as
naturally-occurring tracer allows the easy, fast, and
inexpensive assessment of discharge water/surface water
interaction and the prediction of the future development of the
respective water resources. Furthermore, it clear that there are
difference between the data of this study and data of
Mechanical and Electrical Department, Ministry of
Agriculture. This may be due many reasons (1) The
measurements of radon in this modeling approach is more accurate with RAD7, because this device is more convenient
in field for direct measure (2) this modeling approach assessed
quantitatively discharge rate of the groundwater into a lake by
using radon-222 (3) Radon-222 is a violated gas with short
half-live the transport samples from field to laboratory
measurements affect on the measurements (4) the volumetric
of discharge of water is include of the volumetric of
groundwater enter into the lake. If taking into account these
reasons, we may be improvement the data.
The concentration of 222Rn in air and fish unit Bq/m3
has been measured from tracks density of SSNTD detector. It
is obvious that the concentration of radon in air, radon in fish,
areal exhalation rate, mass exhalation rate, effective radium,
activity of radon and uranium content are high at the north side
of the lake beside El Bughaz channel and at El Brinbal canal.
It is clear that the inlets of the lake El Bughaz channel and El
Brinbal canal have a higher effect on the distribution of radon
in fish. The concentration of radon could be affected by the
atmospheric contaminations especially in open area. In
addition, the value of daily intake of 222Rn is 0.102 Bq/Kg/d
and the value of committed effective dose due to 222Rn is 8.20
μSv/y. The average value of committed effective dose is lower
than the value reported by UNSCEAR (2000) 1 mSv/y.
It is obvious that there is a good correlation between
40K and salinity whereas potassium is highly soluble in water
with increase salinity. Otherwise, Pb-210 is related to salinity
with positive correlation. On the other hand, the pH shows a
weak positive correlation with 238U and 226Ra and 137Cs, while it shows a negative correlation with 40K and 210Pb during
summer. Radionuclide isotopes solubility is related to
parameters such as pH, redox potential, temperature, salinity
and organic complexing. Moreover, there is no correlation
between heavy metals and radionuclides isotopes. A positive
correlation between the organic matter content and 238U and
232Th in sediment samples has been found. In addition, there is
a positive correlation between Ra, Th and Cs activity
concentration and calcium carbonate has been found during
winter. Otherwise, a negative correlation between calcium
carbonate and U and K concentration has been found during
winter. On the other hand, there is a positive correlation
between Fe and 226Ra, 40K, 137Cs and 210Pb in sediment during
summer. 137Cs has a positive correlation with TOM and a
negative correlation with pH. There is a negative correlation
between radon in water and pH. Otherwise, there is a positive
correlation between radon in water and salinity. On the other
hand, there is a positive correlation between radon in surface
and 210Pb and 226Ra. In this connection, the relation between
radon in water and pH converted to a positive correlation.
Furthermore, there is no relation between heavy metals and
radon. There is rapprochement between the estimated values
from predict radionuclides of Burullus Lake by discharge
water of the drains into the lake and the measured values.