Abstract
A total of twenty five (25) drinking water samples from two categories
of water resources, i.e., underground water (spring and well waters) and
surface water from Erbil-governorate(Kurdistan region-Iraq) were collected
systematically and analyzed for radon 222Rn activity concentration.
The measurement has been carried out by using RAD7 as an active
method for alpha analyses ,which is an electronic radon detector connected
to
a RAD-H2O accessory from (Durridge Co. USA) and a permeable cup
provided with CR-39 alpha nuclear track detector (Tastrak from Track
Analysis Systems Ltd, from the UK) as a passive method . Sodium iodide
NaI (Tl) as an active method for gamma spectrometry was used for radium
(
226Ra) activity concentration measurement for the same water samples.
These detectors were first characterized for back ground count, as well as
their detection limits. From the results, it was found that these detectors
are
well characterized for alpha and gamma energies detection and has a low
detection limits.
The obtained Results shows that the range of radon (222Rn) concentration
values vary from (0.081±0.002 to 14.742±0.262) Bq/l and from (0.069±0.01
to13.062±0.15) Bq/l using passive and active methods respectively. The
obtained values of radon concentration in drinking water samples from
both
methods in this study are below the maximum contamination level (MCL)
11.1 Bq/l as recommended by US-EPA, except sample no. (12), from
Barsaleen region, but the total average was lower than the recommended
levels.
The results of radium concentration in water samples obtained by using
NaI (Tl) gamma spectrometry were ranged from (6.258±2.365 to
645.468±24.021) mBq/l. The higher and lower values recorded at (S12) VI
Barsaleen and (S10) Bekhal and were found to be (645.468±24.021) mBq/l
and (6.258±2.365) mBq/l respectively. Only the two (2) drinkable well water
samples include (S12) and (S3), radium values are higher than the
maximum
contamination levels 555mBq/l as suggested by US-EPA, while other
samples
“most of them from surface water” were lower than 555mBq/l. But the
total
averages were lower than the recommended levels.
The two methods (active and passive for alpha detection) show a linear
correlation for radon activity concentration detection and a good linearity
with NaI (Tl) scintillation for radium detection in all samples under the
study.
The results of the calculated annual effective dose due to ingestion for
adult, children and infants were ranged from (0.278±0.120 to
61.978±0.735)
µSv/y, (0.343±0.148 to 76.282±0.902) µSv/y and (0.899±0.389 to
200.240±2.368) µSv/y respectively. The maximum value was found in (S12)
from Barsaleen region which was (61.978±0.735, 76.282±0.902and
200.240±2.368) µSv/y respectively, while the minimum value found in (S20)
from Koya which was (0.278±0.120, 0.343±0.148 and 0.899±0.389) µSv/y
for adult, children and infant respectively. While the results measured for
annual effect dose due to inhalation was vary from (0.151±0.005 to
32.916±0.616) µSv/y. The maximum value found in (S12) from Barsaleen
region which was (32.916±0.616) and the minimum reported in Koya (S20)
which was (0.151±0.005) µSv/y respectively. The results of total annual
effective dose were ranged from (0.00043±0.0001 to 0.09489±0.0007)
mSv/y,
(0.00049±0.0001 to 0.10920±0.0009) mSv/y and (0.001±0.0004 to
0.233±0.0024) mSv/y for adult, children and infants respectively. The
results
of this study indicate that 4% and 32% of the total annual effective doses of
radon in drinking water samples which intake by children and infants
respectively, were higher than the maximum contaminate levels of
0.1mSv/y
proposed by WHO for intake of radionuclide in drinking water. As well as,
VII
the 222Rn and 226Ra concentrations in ground water “well and sprig
water”
samples are higher than that of surface water.
Finally, the physico-chemical properties of water samples such as
temperature
(T), pH and electrical conductivity (EC) are studied. The values were ranged
from (10 to30) Cº, (6.3 to 7.8) and (177 to 940) µS/cm with an average of
(20) Cº, (7.076), and (423) µS/cm respectively. It was found that there is no
correlation between the physico-chemical properties and radon activity
concentrations in water samples especially for pH and EC.