INTRODUCTION
For community purposes, water must be in sufficient supply and free from contamination,
pollution and turbidity. Although there is a great interest in the study of
man-made radiation and radioactivity in water but at first the exposed population
to man-made radioactivity at different levels is an importance factor which
depend on man-made radioactive in water for each region in the world (Mokrov,
2004).
Man-made radiation and environmental radioactivity has led to the performance
of extensive surveys in many countries of the world. Such investigations can
be useful for both the assessment of public dose rates and the performance of
epidemiological studies, as well as to keep reference data records, in order
to ascertain possible changes in the environment radioactivity due to nuclear,
industrial and other human activities. Man-made environmental radioactivity
such as 125I arises mainly from reactor activity or from the rainfall
(Seki et al., 1988) and radioactive waste (Mokrov,
2003) and their decay products, which occur at trace levels in water.
Man-made radioactivity and the associated external exposure due to gamma radiation
depend primarily on the geographical conditions. The specific levels of water
radiation are related to the composition of water. There are many types of water
depending upon the physical and chemical composition. The water is classified
as saline, drinking water and alkali etc. In drinking water, the concentration
of salts is decreased to the level at which the crop growth is affected. Drinking
water has not a high content of natural salts and has not pH generally above
7.3 and not over 8.5. Nuclear fission in connection with atomic weapons testing
provides another source of water contamination (Amachi et
al., 2003).
Direct fall out from the atmosphere on the drinking water was primary source
of contamination. The fission product 125I is strongly absorbed and
retained by water, as are radio nuclides, which will be found randomly in drinking
water due to accident. The subject of radioactive contamination gained considerable
public importance because of Chernobyl accident (Mettler
et al., 2007). Man-made radio nuclides more or less contributors to
radiation doses received by human beings. Because of increased public concern
and awareness about radioactive pollution, this study has been carried out to
determine the heat effect on amount of radioactivity from the drinking water
of Chah Nimeh station in Zaboul city which is given its drinking water to Zahedan
city by pipng and Khatam hospital well water in Zahedan irrigating garden.
MATERIALS AND METHODS
The experiment was undertaken in Medical Physics Laboratory. The distance
between Medical Laboratory and point of checking gamma ray (site) was
about 4 km. Drinking water from Chah Nimeh of Zaboul city and Khatam Hospital
well water of Zahedan sampling were done in the month of May-June 2007,
by 2 L plastic glasses which total amount of samples was 20 L. Sampling
from the both of them was performed using the Standard Sampling Methods.
The samples were properly marked, cataloged and brought to medical Physics
Laboratory at Zahedan city, Iran for processing before analysis.
The samples were put in 2 L cylindrical plastic containers (Chemical
resistant) were filled and packed with drinking water samples. The empty
containers were weighed and were filled with drinking water samples and
weighed again. The net weight of the drinking water was noted. The containers
were closed by screw caps and plastic tapes were wrapped over the caps.
Same procedure was applied for the reference material. Before performing
the chemical analysis, temperature of water was measured with a thermo
meter and pH was measured with a pH meter. The drinking water samples
were first kept in the sun for several days.
125I is similar to 129I with its half life less than
man-made radio nuclides 129I. According to Seki
et al. (1988), 125I is found in drop of rain. So, this radio
isotope has been chosen for the experiment in stead of 129I.
The case samples of the drinking water and Khatam Hospital well water
were then heated under 20, 30 and 40°C by electrical oven at the time
15 min, but the control samples of drinking water were not. 125I
had been poured into both of case and control samples of drinking water
before heating it. Its total activity of 125I was 445 Bq. The
case and control samples of Khatam Hospital well water were heated at
5, 10, 15°C temperature. 125I was put into the case samples,
but 125I was not poured into the control samples before heating.
The technique of gamma ray counting was applied for determination of
radioactivity of the samples under investigation. The concentration of
radioactivity in water supply of drinking water has been experimented
by Gamma counting set. The characteristics of the gamma counting component
were as follows: Serial No. GM1 8335 S 307, Counting system model: Automatic
Gamma Manufacturer: KONTRON. Counting of every drinking water sample was
collected for 20 sec. The lowest limits of detection (LLD) were determined
for 125I.
RESULTS AND DISCUSSION
High-resolution technique was employed for the measurement of gamma ray.
Case and control water samples of Zaboul were compared (Table
1):
| • |
Temperature increase radioactivity of drinking water samples |
| • |
The radioactivity of drinking water samples was increased in 30°C
temperature than 20 and 40°C temperature. Because high
temperature cause the activity of atoms and molecules will be raised.
|
| • |
Activity of solid and liquid is less than gas or volatile materials
such as 125I under temperature 20, 30 and 40°C |
| • |
Activity of radio iodine in case drinking water is more than control
drinking water samples under 20, 30 and 40°C temperature |
Case and control water samples of Khatam hospital well of Zahedan were
compared (Table 2):
| • |
Heating case samples causes to increase activity iodine-125 of it
|
| • |
There was not any change in activity iodine-125 of control samples |
| • |
There was more variation in radio iodine-125 between case and control
samples |
Heating case and control samples in two water showed that figures of
low heating 5, 10 and 15°C was more than 20, 30 and 40°C temperature.
The results of investigation for temperature effect on drinking water
samples from Chah Nimeh of Zaboul and Khata hospital well water of Zahedan
in the Sistan and Blouchestan province of Iran showed that the effect
of temperature on radio iodine in drinking water. The investigated radionuclide
in this study was 125I. The measured activity in case samples
was different from control samples. The activity measured at one location
was averaged out and the mean values are only tabulated. Three temperatures
has been used on drinking water with radio iodine-125: 20, 30 and 40°C.
All the case samples under 20, 30 and 40°C possess effect on gamma
radioactivity. During affection of temperature, I125 produces
15±0.17 Bq L-1 in drinking water, with the emission
of beta and gamma radiation. The average value of I125 concentration
in the drinking water as a control was 5.6±0.03 Bq L-1.
| Table 1: |
Radioactivity concentration of Zaboul city drinking water
in different temperature |
|
| Table 2: |
Radioactivity concentration of Zahedan city water in different
temperature |
|
The average value and range of measured concentration of 125I for
drinking water was different in various temperatures. For 125I the
average value and range of measured specific activity for drinking water in
temperature 20°C; was 6±0.08 Bq L-1. The ratio of 125I
in 20°C and 125I as the control drinking water is generally greater
than one and that is also true for the present case. The average activity value
of 125I in temperature 30°C was about two times higher than that
of 125I in control drinking water sample. The activity concentration
of 125I in drinking water in 30°C is order of magnitude higher
than that of 125I in 20°C and 125I for the drinking
water. This is also in accordance with the well-known fact that 125I
under 30°C in the drinking water is of the order of percentage whereas 125I
in 20°C and 125I in 40°C are in activity level. The average
values of activity concentration of 125I in all the samples found
in drinking water of Zaboul city was not the same as each other. The activity
concentration of 125I in most samples of drinking water was below
the lowest limit of detection (LLD). The reasons of less existence of 125I
in the drinking water of Zaboul to Zahedan in control samples are that the radio
iodine might have reduced the amount of 125I from it. The less values
of fall out may be due to drinking water material. Temperature may be other
reason for the reduced values in the radio iodine of interest (Ames
and McGarrah, 1980). The variations in the activity levels have been observed
to be lying within the activity values measured all over the world. According
to Mokrov et al. (2000), the average value of
activity concentration for radio nuclides in different conditions
are known for water. The measured value of activity concentration of 125I
for the drinking water under investigation in 30°C was within the world
average range. The ranges of activity concentrations for radio nuclides water
given in the Mokrov (2003) are reported. The measured
values of the activity concentration for the samples of Zaboul were lying within
averages, when different temperature and adding radioiodine are not considered.
As far as the mutual comparison of the case samples of drinking water and control
samples of the drinking water under investigation is concerned, there is drastic
change in the activity concentrations in both types of drinking water. However,
a slight increasing trend was observed in the measured activity of radio iodine
125 between 20 and 40°C. It is well known that a given temperature effect
radio iodine. Since, temperature effect is an essential raw material used for
the manufacturing of different type′s radio iodine deposit, therefore,
when this temperature is processed into radio iodine drink water sample, most
of the radio iodine and some of the material accompanies the drinking water
(Ashworth and Shaw, 2006). It has also been estimated
earlier that 30°C temperature applied to the samples in recommended amounts
could raise radioactivity level in drinking water. The use of given temperature
in large extent have affected radio nuclides concentration, especially 125I
containing 30°C are the one of the cause of presence of high activity of
radio iodine in drinking water (Spomer et al., 2008;
Dickstein et al., 2008). For case samples under
low temperature 5, 10 and 15°C (Table 1, 2)
was more than 20, 30 and 40°C temperature. The causes of this situation
were related to components of both waters. Heating could produce conditions
in which affect on case and control sample in activity but there was a big difference
in activity between case and control sample. The method of experiments was alike,
only different ions or molecules could be considered. According to Mokrov
(2003), construction of 125I in samples would be changed and
there would be a new matter. However, heating could provide situation for ions
or molecules in the water to vary the component of water (Mokrov
et al., 2000; Bors and Martens, 1992).
In this study, the use of different temperature helps the polluted drinking
water with radio iodine is converted to benefit drinking water. The drinking
water should pass through many experiments with the extensive use of radio
iodine. The slightly increasing trend at the beginning may be an indication
of the large change of activity in the future due to the applications
of temperature.
ACKNOWLEDGMENTS
The authors are thankful to Dr. Dabiri for admitting of doing manuscript
experiments and Mr. Mohhamad Reza Miracky for kind doing experiments.
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