Activity concentrations of radionuclides in water
The activity concentrations of 226Ra, 232Th, and 40K were ascertained in water samples. The present study examined the distribution of naturally occurring radionuclides 226Ra, 232Th and 40K, in water. Table 4 with Figure 2, presents the results of activity concentrations of natural radionuclides of 226Ra, 232Th and 40K in water samples taken from 20 different locations such as (Shorja, Azady, Arafa, Horya, Ahmad aqha, Tapa, Rahym awa, Eskan, Musalah, Emam –Qasm, Qadseay Yeak, Hay Askari, Hay Qharnata, Qadseay Dwo, Hay Wasty, Hay Nasr, Zeeawiah, Panja Ali, Roonaky, Preeady), of Kirkuk-Iraq. That were ranged from (140.845 to 89.428) mBq.L-1with an average value of 121.952 mBq.L-1of 226Ra, from (106.894 to 47.398) mBq.L-1with an average value of 81.523 mBq.L-1of 232Th, and from (1550.516 to 379.551) mBq.L-1with an average value of 1091.375 mBq.L-1 40K. From Table 4 the results show that the mean activity concentration values of 226Ra, 232Th and 40K were lower than the world average values suggested by UNSCEAR: 35, 30, 400 Bq.kg−1, respectively) (UNSCEAR, 2000). The data showed that the average value of activity concentration of 40К in the samples (1091.375 mBq.L-1) is higher than the one of 232Th (81.523 mBq.L-1) and 226Ra (121.952 mBq.L-1).
Table 1 shows significant variations between the average activity concentrations of 226Ra, 232Th and 40K in the examined samples, where the average estimations of 226Ra fluctuate between the maximum activity concentration in (Qadseay Dwo) and the minmum activity concentration in (Hay Qharnata), the average estimations of 232Th fluctuate between the maximum activity concentration in (Qadseay Dwo) and the minmum activity concentration in (Roonaky), the average estimations of 40K fluctuate between the maximum activity concentration in (Roonaky) and the minmum activity concentration in (Hay Qharnata) that is agree with (Nisar et al., 2018). As shown the results in this table, the radioactivity in water samples varied from one locaition to another depends on the locality geological conditions. The measured activities of 226Ra in the samples did not exceed the guidance level recommended by (Mohsin & Muttaleb, 2016; WHO, 2011).
Table 4 Radioactivity concentration (mBq.L-1) of 232Th, 226Ra, and 40K
No.
|
Locations
|
Code of Samples
|
Radioactivit concentration (mBq.L-1) of
232Th, 226Ra, and 40K
|
Th (mBq.L-1)
|
Ra (mBq.L-1)
|
K (mBq.L-1)
|
1
|
Shorja
|
SW01
|
105.673
|
140.421
|
482.098
|
2
|
Hay Qharnata
|
SW02
|
66.137
|
89.428
|
379.551
|
3
|
Azady
|
SW03
|
75.868
|
114.424
|
852.900
|
4
|
Arafa
|
SW04
|
104.424
|
118.974
|
1190.301
|
5
|
Horya
|
SW05
|
50.224
|
118.929
|
966.3128
|
6
|
Ahmad aqha
|
SW06
|
91.656
|
128.425
|
1206.432
|
7
|
Tapa
|
SW07
|
54.043
|
124.848
|
1162.982
|
8
|
Rahym awa
|
SW08
|
100.218
|
122.022
|
1236.289
|
9
|
Qadseay Dwo
|
SW09
|
106.894
|
140.845
|
976.782
|
10
|
Musalah
|
SW10
|
53.255
|
138.244
|
1315.591
|
11
|
Emam –Qasm
|
SW11
|
92.404
|
122.287
|
1302.99
|
12
|
Eskan
|
SW12
|
101.814
|
124.741
|
1145.676
|
13
|
Qadseay Yeak
|
SW13
|
88.493
|
128.972
|
1213.166
|
14
|
Hay Askari
|
SW14
|
75.589
|
114.057
|
1144.541
|
15
|
Hay Wasty
|
SW15
|
91.144
|
130.015
|
1204.174
|
16
|
Hay Nasr
|
SW16
|
93.133
|
102.005
|
1084.195
|
17
|
Zeeawiah
|
SW17
|
85.049
|
131.681
|
1122.327
|
18
|
Panja Ali
|
SW18
|
85.058
|
126.267
|
1328.145
|
19
|
Roonaky
|
SW19
|
47.398
|
135.851
|
1550.516
|
20
|
Preeady
|
SW20
|
61.989
|
96.606
|
962.538
|
|
|
Ave.
|
81.523
|
121.952
|
1091.375
|
|
|
Mix
|
106.894
|
140.845
|
1550.516
|
|
|
Min.
|
47.398
|
89.428
|
379.551
|
To obtain uranium concentration content in the water samples, the value of 238U concentrations in ppm were calculated using (1 ppm of 238U =12.25 Bq.Kg-1), the concentration contents of 238U is ranged from (1.104 to 1.734) ppm with an average value of 1.506 ppm, the value of 232Th concentration in ppm was calculated using 1ppm (232Th = 4.10 Bq.Kg-1), the concentration of 232Th is ranged from (0.192 to 0.434) ppm with an average value of 0.331 ppm, and the concentration contents of 40K is ranged from (118.799 to 485.311) ppm with an average value of 341.601 ppm, as shown in Table 5.
The values of concentration followed by contents of concentration in 84% for 40K with average in 341.6005 ppm, 10 % for 232Th with average in 0.3309 ppm , and 16% for 226Ra (238U) with average in 1.5061 ppm as shown in Table 5 and Figure 3. From the results found that the higher and lower values of radium, thorium and potasium in the drinking water samples in locations (Eskan) and (Hay Qharnata) have been found to be (0.363) ppm, (0.119) ppm, have been found to be (0.363) ppm, (0.119) ppm in the locations (Qadseay Dwo) and (Eskan) and have been found to be (1.864) ppm, (0.523) ppm, respectively. The results obtained were generally lower than the normal levels (which is lower than the normal rate of uranium concentration in nature that reaches (2-2.8) ppm and reaches (6-10) ppm in thorium (Mohammed, 2003). this considers as a secure situation for human environmental safety in the region so it has no danger on human is life. The aim of the present study is to measure the radioactivity concentration of radium, thoriom and potasium in drinking water in Kirkuk city. The reason for vibration in radon concentration could be a function of geological structure of the area, depth of the water source, also differences in the climate (Ali et al., 2019; Najeba et al., 2015). It was also observed that the concentration of 40K measured markedly exceeds the values of both radium and thorium, as it is the most abundant radioactive element considered.
Table 5 Radioactivity concentration (ppm) of 232Th, 226Ra, and 40K
No.
|
Code of Samples
|
Radioactivity concentration (ppm) of
232Th, 226Ra, and 40K
|
Th(ppm)
|
Ra(ppm)
|
K(ppm)
|
1
|
SW01
|
0.429032
|
1.734199
|
150.8967
|
2
|
SW02
|
0.268516
|
1.104436
|
118.7995
|
3
|
SW03
|
0.308024
|
1.413136
|
266.9577
|
4
|
SW04
|
0.423961
|
1.469329
|
372.5642
|
5
|
SW05
|
0.203909
|
1.468773
|
302.4559
|
6
|
SW06
|
0.372123
|
1.586049
|
377.6132
|
7
|
SW07
|
0.219415
|
1.541873
|
364.0134
|
8
|
SW08
|
0.406885
|
1.506972
|
386.9585
|
9
|
SW09
|
0.43399
|
1.615936
|
305.7328
|
10
|
SW10
|
0.216215
|
1.707313
|
411.7800
|
11
|
SW11
|
0.37516
|
1.510244
|
407.8359
|
12
|
SW12
|
0.413365
|
1.540551
|
358.5966
|
13
|
SW13
|
0.359282
|
1.592804
|
379.7210
|
14
|
SW14
|
0.306891
|
1.408604
|
358.2413
|
15
|
SW15
|
0.370045
|
1.605685
|
376.9065
|
16
|
SW16
|
0.37812
|
1.259762
|
339.3530
|
17
|
SW17
|
0.345299
|
1.62626
|
351.2884
|
18
|
SW18
|
0.345335
|
1.559397
|
415.7094
|
19
|
SW19
|
0.192436
|
1.67776
|
485.3115
|
20
|
SW20
|
0.251675
|
1.193084
|
301.2744
|
Ave.
|
0.330984
|
1.506108
|
341.6005
|
Mix.
|
0.43399
|
1.734199
|
485.3115
|
Min.
|
0.192436
|
1.104436
|
118.7995
|
The activity concentrations radionuclide of 226Ra were found to be slightly higher (but not significant) than that of 232Th, which may be attributed to the fact that 226Ra is more soluble than 232Th in water Whereas, the concentrations of 40K was very much higher than 226Ra and 232Th because of its natural abundance that is agree with (Nisar et al., 2018). Potassium is an abundant element in all environmental media including water. However, the isotope 40K is radiologically less important compared to radium isotopes because it is homeostatically controlled in the human bodyand also an essential element (Nisar et al., 2018).
Correlation between 226Ra, 232Th and 40K
The values of ratio of specific activity concentrations of 232Th, 226Ra, 40K for all samples ranged from (0.348 to 0.913) with a mean value 0.673 of 232Th/226Ra, from (3.433 to 11.413) with a mean value 8.933 of 40K/ 226Ra, and from (4.562 to 32.712) with a mean value 14.457 of 40K / 232Th, a low 232Th/ 226Ra ratio (0.348) was recorded, which could be related to the systematic loss of thorium during the fabrication process that is agree with (Saifeldin et al., 2018).
A positive correlation between 226Ra and 232Th in the investigated samples was identified from the observed significant correlation, as showed in Table 6.
Table 6 Ratio of specific activity of 232Th, 226Ra, and 40K
No.
|
Code of Samples
|
Ratio of specific activity of 232Th, 226Ra, and 40K
|
232Th/226Ra
|
40K/ 226Ra
|
40K /232Th
|
1
|
SW01
|
0.752
|
3.433
|
4.562
|
2
|
SW02
|
0.739
|
4.244
|
5.738
|
3
|
SW03
|
0.663
|
7.454
|
11.241
|
4
|
SW04
|
0.877
|
10.004
|
11.398
|
5
|
SW05
|
0.422
|
8.125
|
19.240
|
6
|
SW06
|
0.713
|
9.394
|
13.162
|
7
|
SW07
|
0.433
|
9.315
|
21.519
|
8
|
SW08
|
0.821
|
10.131
|
12.336
|
9
|
SW09
|
0.817
|
7.465
|
9.137
|
10
|
SW10
|
0.385
|
9.516
|
24.703
|
11
|
SW11
|
0.755
|
10.655
|
14.101
|
12
|
SW12
|
0.816
|
9.184
|
11.252
|
13
|
SW13
|
0.686
|
9.406
|
13.709
|
14
|
SW14
|
0.662
|
10.034
|
15.141
|
15
|
SW15
|
0.701
|
9.262
|
13.212
|
16
|
SW16
|
0.913
|
10.628
|
11.641
|
17
|
SW17
|
0.645
|
8.523
|
13.196
|
18
|
SW18
|
0.673
|
10.518
|
15.614
|
19
|
SW19
|
0.348
|
11.413
|
32.712
|
20
|
SW20
|
0.641
|
9.963
|
15.527
|
|
Ave.
|
0.673
|
8.934
|
14.457
|
|
Mix
|
0.913
|
11.413
|
32.712
|
|
Min.
|
0.348
|
3.433
|
4.562
|
Evaluation of radiological hazard parameters
Radium equivalent activity
The activity levels of 238U, 232Th and 40K are not uniformly distributed in water samples. Hence, the water samples would be examined by radium equivalent activity (Raeq). The acceptable maximum value of the radium equivalent activity is 370 Bq.kg-1 (Abdalrahman & Riyadh,. 2019), therefore, The maximum value of Raeq, in water samples must be less than 370 Bq.kg−1 in order to be considered safe for use (ICRP, 1996). From Table 7, radium equivalent activity (Raeq) varied from (223.2445 to 369.9037) mBq.kg−1 with a mean of 339.9506 mBq.kg−1 which is less, lower than the worldwide average. These values are far below the allowable limit (370 Bq.kg–1) recommended by the International Atomic Energy Agency (IAEA) (ICRP, 1996; Altaf & Nasima, 2015).
This study shows that the water samples in the kirkuk region do not have a biological danger that is agree with, it is clear that the values of in all samples were much less than the safe value 370 Bq.kg-1 (Samat et al., 2012) which is equivalent to an external dose of 1.5mSvy−1. Therefore, the water samples are within an acceptable safe limit (Nisar et al., 2018).
The Calculated values of the (Hex) of water samples are presented in Table 7. The total absorbed dose rate were varied from (96.1 to 321.2) nGy h−1 with an average of 188.2 ± 59.4 nGy.h−1 of radium. The obtained mean value is over 3.14 times than the reported population-weighted mean value of 60 nGy h−1 for regular area given by (UNSCEAR, 2000). The mean value of absorbed dose for water samples is 9.62 nGy h−1 and it is lower than the global average value of 55 nGy.h-1. This difference in absorbed dose rate with the reported values of UNSCEAR could be attributed to differences in geology formation of area under study and geochemical structure of the sampling sites (Eric et al., 2016).
The calculated values of the external hazard (Hex) of water samples are presented in Table 7 that were ranged from 0.575 to 0.973 with a mean value of 0.871. Also, the internal hazard (Hin), its values ranged from 0.562 to 0.995 with a mean value of 0.881. All the samples had an internal hazard values below the recommended limit of 1.0 which implies that these samples are suitable to drinking by populations.
The mean value of the index of radiation risk Heks is 0.05 which shows that in the surrounding of Skopje there is no significant radiation risk for the population. The values of the external danger index obtained in this study, regardless of the location, did not exceed the security limits, pointing out the insignificant danger for radiation which arises from water radionuclides which are naturally present.
The estimated Dout (nGy.h-1) values varied from 98.143 to 169.870 with the mean value was calculated to be 152.191 nGy.h−1 within the typical range of worldwide average values (18 - 93) nGy.h−1 reported in (UNSCEAR, 2000). And the estimated Din (nGy.h-1) values varied from 185.388 to 321.403 with the mean value was calculated to be 289.181 nGyh−1, in the water samples, respectively. The maximum value of the gamma index is neer around unity (1.177) as showed in the table 7 like reported by (ICRP, 1996). (Abdalrahman & Riyadh, 2019), also alpha index The internal alpha index Iα is rising because of the radon inhalation as shown in the Table 7 (Abdalrahman & Riyadh, 2019).
Table 7 Evaluation of radiological hazard parameters of the water samples
No.
|
Code of Samples
|
|
Outdoor hazard index
|
Indoor hazard index
|
Raeq mBq.L-1
|
Hex
|
Dout (nGy.h-1)
|
Iγ
|
Hin
|
Din
(nGy.h-1)
|
Iα
|
1
|
SW01
|
343.5966
|
0.8877
|
150.5272
|
1.1571
|
0.8596
|
283.9955
|
0.7021
|
2
|
SW02
|
223.2445
|
0.5759
|
98.14307
|
0.7552
|
0.5625
|
185.3885
|
0.4471
|
3
|
SW03
|
305.1676
|
0.7795
|
135.3253
|
1.0450
|
0.7961
|
256.9569
|
0.5721
|
4
|
SW04
|
366.210
|
0.9722
|
169.1816
|
1.3154
|
0.8909
|
319.5466
|
0.5948
|
5
|
SW05
|
294.6986
|
0.7162
|
126.1212
|
0.9696
|
0.8439
|
241.9661
|
0.5946
|
6
|
SW06
|
368.199
|
0.9518
|
166.2519
|
1.2885
|
0.9453
|
315.4872
|
0.6421
|
7
|
SW07
|
322.1253
|
0.7878
|
139.3712
|
1.0740
|
0.9168
|
267.346
|
0.6242
|
8
|
SW08
|
369.9037
|
0.9737
|
169.8703
|
1.3199
|
0.9169
|
321.4032
|
0.6101
|
9
|
SW09
|
369.2146
|
0.9694
|
167.3533
|
1.2962
|
0.9107
|
316.1034
|
0.6542
|
10
|
SW10
|
352.2444
|
0.8527
|
151.3738
|
1.1656
|
0.9821
|
291.0123
|
0.6912
|
11
|
SW11
|
367.6046
|
0.9582
|
167.8858
|
1.3039
|
0.9322
|
318.3876
|
0.6114
|
12
|
SW12
|
368.4107
|
0.9684
|
168.3667
|
1.3067
|
0.9128
|
318.4112
|
0.6237
|
13
|
SW13
|
366.3367
|
0.9424
|
164.8123
|
1.2767
|
0.9497
|
313.0498
|
0.6448
|
14
|
SW14
|
326.8202
|
0.8381
|
147.0562
|
1.1396
|
0.8547
|
279.6436
|
0.5703
|
15
|
SW15
|
369.7868
|
0.9536
|
166.5724
|
1.2904
|
0.9535
|
316.2061
|
0.6501
|
16
|
SW16
|
322.4832
|
0.8606
|
149.9318
|
1.1670
|
0.7771
|
283.0265
|
0.5101
|
17
|
SW17
|
359.772
|
0.9176
|
160.1548
|
1.2382
|
0.9454
|
304.4866
|
0.6584
|
18
|
SW18
|
367.887
|
0.9458
|
166.1854
|
1.2888
|
0.9589
|
315.981
|
0.6313
|
19
|
SW19
|
361.0547
|
0.8725
|
156.3476
|
1.2066
|
0.9956
|
301.162
|
0.6792
|
20
|
SW20
|
274.251
|
0.7005
|
123.0036
|
0.9528
|
0.7225
|
234.0685
|
0.4830
|
The annual effective dose (3.25 to 12.60) μSv.y−1 caused criterion limit of 1 mSv.y-1. Hence, yet pose no significant threat to the ecosystem, public health (Hossain et al., 2019).
Mean value of annual effective dose rate of 0.55 mSv. h-1 is slightly higher than the world mean value which is 0.48 mSv.h-1 recommended by UNSCEAR (Fatimh & El-Taher, 2019). But the obtained value is less than the recommended limit established by ICRP which is 1 mSv. h-1 (Kakhaber et al., 2019). Based on measured activity concentrations of 222Rn, the calculated values of annual effective dose AEDE total were calculated as shown in Table 8. The AEDE from radon ranged between minimum and maximum values 208.329 and 120.3627 μSv.y−1 with an average value of 186.648 μSv.y−1.The recommended upper limit of 1 mSv.y−1 is not exceeded in all samples. This means that these rock samples are safety for human health (Nisar et al., 2018).
From the Table 8 the values of ELCR are ranged from 0.421 to 0.729 with an average value of 0.653. The results obtained show that the AEDE and ELCR in all water samples appeared lower than the world average values. The value of risk factor in the public is 0.05 per Sievert as recommended by ICRP for stochastic effects (Abdalrahman & Riyadh, 2019).The excess lifetime cancer risk (ELCR) have been calculated, its values were higher than the world’s average value of (0.29x 10−3). Also from Table 8 the values of AGDE is ranged from (67.964 to 118.415) μSv.y−1 with a mean value of 106.291 μSv.y−1 these values is a lower than the world average values 300 μSv.y−1.
Table 8 The annual effective dose and the excess lifetime cancer risk on the public health
Code of
Samples
|
Dose (nGy.h-1)
|
AEDE x10-3
(mSv.y-1)
|
ELCR x10-3
|
AGDE
(μSν.y-1 )
|
SW01
|
150.5272
|
184.6066
|
646.123
|
102.993
|
SW02
|
98.14307
|
120.3627
|
421.2693
|
67.964
|
SW03
|
135.3253
|
165.9629
|
580.8703
|
93.509
|
SW04
|
169.1816
|
207.4843
|
726.1952
|
117.876
|
SW05
|
126.1212
|
154.675
|
541.3625
|
88.849
|
SW06
|
166.2519
|
203.8913
|
713.6196
|
115.775
|
SW07
|
139.3712
|
170.9248
|
598.2368
|
97.856
|
SW08
|
169.8703
|
208.329
|
729.1514
|
118.154
|
SW09
|
167.3533
|
205.2421
|
718.3472
|
115.838
|
SW10
|
151.3738
|
185.6448
|
649.7570
|
106.875
|
SW11
|
167.8858
|
205.8951
|
720.6329
|
117.254
|
SW12
|
168.3667
|
206.4849
|
722.6973
|
117.774
|
SW13
|
164.8123
|
202.1258
|
707.4403
|
114.358
|
SW14
|
147.0562
|
180.3497
|
631.2241
|
102.784
|
SW15
|
166.5724
|
204.2844
|
714.9955
|
116.839
|
SW16
|
149.9318
|
183.8764
|
643.5674
|
104.929
|
SW17
|
160.1548
|
196.4139
|
687.4485
|
111.811
|
SW18
|
166.1854
|
203.8098
|
713.3343
|
116.745
|
SW19
|
156.3476
|
191.7447
|
671.1066
|
114.765
|
SW20
|
123.0036
|
150.8516
|
527.9806
|
85.863
|
Ave.
|
152.1918
|
186.648
|
653.268
|
106.291
|
Mix.
|
169.8703
|
208.329
|
729.1514
|
118.154
|
Min.
|
98.14307
|
120.363
|
421.2693
|
67.964
|
Resulting in the minimum detectable activity (MDA) in Radionuclide
The activity concentrations of radium, thorium and potasium in the water samples are given in the Table 1. A less than sign (<) was used to indicate the below MDA values of the detector. The minimum detectable activity for each radionuclide was 1.97 mBq.L-1 for 226Ra, 0.91 mBq.L-1 for 232Th and 0.38 mBq.L-1 for 40K, as shown in both Tables ( 9,10).
Table 9 The (Ave., Mix., and Min.) detectable activity (MDA) in radionuclide
Case of
radionuclides
|
226Ra
|
232Th
|
40K
|
MDA (mBq.L-1)
|
1.97
|
0.91
|
0.38
|
Ave. Concentration (mBq.L-1)
|
121.952
|
81.523
|
1091.375
|
Mix Concentration
(mBq.L-1)
|
140.421
|
106.894
|
1550.516
|
Min. Concentration (mBq.L-1)
|
89.428
|
47.398
|
379.551
|
Table 10 The detectable activity (MDA) in radionuclide
Radionuclide
|
Energy (keV)
|
MDA (Bq.L-1)
|
212Bi
|
727.33
|
0.49284
|
212Pb
|
238.63
|
0.15709
|
228Ac
|
911.20
|
3.10816
|
|
968.97
|
2.46953
|
208Tl
|
510.77
|
0.18143
|
|
583.19
|
0.44443
|
|
860.56
|
0.23338
|
|
2614.53
|
0.21398
|
214Bi
|
609.31
|
1.07910
|
|
1120.28
|
1.16107
|
|
1764.49
|
1.11676
|
214Pb
|
295.22
|
3.35913
|
|
351.93
|
3.13970
|
40K
|
1460.83
|
38.1853
|
Results of pH and Electrical Conductivity
A lower pH indicates acidity while a higher pH indicates alkalinity because PH is the measure of the acidity or alkalinity of a solution. A pH value of 7 is considered normal. This study measured the pH of 20 drinking water samples, Table 1 presented the pH, and concuctivity of the drinking water, the results indicate that the pH of different drinking water samples ranged from 4.67 (highly acidic) in SW04 to 8.49 (highly basic) in SW13 with an average (6.77/ considered normal) at the 22.5˚C that is agree with presented study (Kenya et al., 2014) which tended toward an normal behavior. The pH has effects on enamel, the low pH and high acid concentrations lead to adverse side effects such as enamel erosion. a low or high pH for an a long period of time may cause harmful side effects. cause enamel erosion (Richard et al., 2000). A nother experimental was achieved on the 20 of drinking water samples to know the electrical conductivity, the results indicate that the conductivity varied from (0.18 mS.cm-1) in SW02 to (0.37 mS.cm-1) in SW13 with an average of conductivity of the samples was (0.27) at the 22.5 ˚C, as showed in Table 1.
Effective doses due to ingestion
According to an UNSCEAR report in 2000, the ingestion of drinking water was estimated (UNSCEAR, 2000) report to be 100, 75, and 50 l y_1 for infants, children, and adults, respectively. Assuming the proportion of these groups in the population to be 0.05, 0.3 and 0.65, the estimated weight of consumption was determined as 60 l y_1 (UNSCEAR, 2000; Nisar et al., 2018).
In addition, for exposure to radon from ingestion, annual effective doses from 226Ra, 232Th and 40K and 222Rn were separately calculated for infants, children and adults. Annual effective dose due to intake of 232Th ranged from 0.3507 to 0.7910 μSv.y_1 with an average of 0.6032 μSv.y_1 for infants (0–1 y), ranged from 0.0663 to 0.1496 μSv.y_1 with an average of 0.1141μSv.y_1 for children (2–7 y) and ranged from 0.0203 to 0.0459 μSv.y_1 with an average of 0.0350μSv.y_1 for adults (>17 y), respectively. Similarly, Annual effective dose due to intake of 226Ra ranged from 42.03 to 65.99 μSv. y_1 with an average of 57.312 μSv.y_1 for infants (0–1 y), ranged from 5.54 to 8.70 μSv.y_1 with an average of 7.557 μSv.y_1 for children (2–7 y) and ranged from 2.5039 to 3.9317 μSv.y_1 with an average of 3.4146μSv.y_1 for adults (>17 y), respectively, also the annual effective dose due to intake of 40K ranged from 0.0235 to 0.0961 μSv.y_1 with an average of 0.0676 μSv.y_1 for infants (0–1 y), ranged from 0.0079 to 0.0325 μSv.y_1 with an average of 0.0229 μSv.y_1 for children (2–7 y) and ranged from 0.0026 to 0.0107 μSv.y_1 with an average of 0.0075 μSv.y_1 for adults (>17 y), respectively. The age-dependent annual effective doses due to ingestion of 226Ra, 222Rn 232Th and 40K were found to be below the WHO permissible limit of 0.1 mSv.y_1 for all ages (WHO, 2011) the most radiotoxic radionuclide is radium because 20% of ingested radium is absorbed into the bloodstream and then distributed to bones and soft tissues. Tables (11, 12) with the Figure 4, and Figure 5, shows that average annual effective dose due to the intake of 226Ra is higher for infants than children and adults (infants> children> adults). This study shows that infants are more vulnerable and comparatively at risk due to the intensive growth of bone.
Table 11 Effective doses due to ingestion
Code
of
Sam.
|
Ingestion of 232Th (μSv.y_1)
|
Ingestion of 226Ra (μSv.y_1)
|
Ingestion of 40K (μSv.y_1)
|
Infants (0–1 y)
|
Children (2–7 y)
|
Adults (>17 y)
|
Infants (0–1 y)
|
Children (2–7 y)
|
Adults (>17 y)
|
Infants
(0–1 y)
|
Children (2–7 y)
|
Adults
(>17 y)
|
SW01
|
0.7819
|
0.1479
|
0.0454
|
65.99
|
8.7
|
3.9317
|
0.0298
|
0.0101
|
0.0033
|
SW02
|
0.4894
|
0.0925
|
0.0284
|
42.03
|
5.54
|
2.5039
|
0.0235
|
0.0079
|
0.0026
|
SW03
|
0.5614
|
0.1062
|
0.0326
|
53.77
|
7.09
|
3.2038
|
0.0528
|
0.0179
|
0.0058
|
SW04
|
0.7727
|
0.1461
|
0.0449
|
55.91
|
7.37
|
3.3312
|
0.0737
|
0.0249
|
0.0082
|
SW05
|
0.3716
|
0.0703
|
0.0215
|
55.89
|
7.37
|
3.3300
|
0.0599
|
0.0202
|
0.0066
|
SW06
|
0.6782
|
0.1283
|
0.0394
|
60.35
|
7.96
|
3.595
|
0.0747
|
0.0253
|
0.0083
|
SW07
|
0.3999
|
0.0756
|
0.0232
|
58.67
|
7.74
|
3.4957
|
0.0721
|
0.0244
|
0.0080
|
SW08
|
0.7416
|
0.1403
|
0.0431
|
57.35
|
7.56
|
3.4166
|
0.0766
|
0.0259
|
0.0085
|
SW09
|
0.7910
|
0.1496
|
0.0459
|
61.49
|
8.11
|
3.6636
|
0.0605
|
0.0205
|
0.0067
|
SW10
|
0.3940
|
0.0745
|
0.0229
|
64.97
|
8.57
|
3.8708
|
0.0815
|
0.0276
|
0.0091
|
SW11
|
0.6837
|
0.1293
|
0.0397
|
57.47
|
7.58
|
3.4240
|
0.0807
|
0.0273
|
0.0089
|
SW12
|
0.7534
|
0.1425
|
0.0437
|
58.62
|
7.73
|
3.4927
|
0.0710
|
0.0240
|
0.0079
|
SW13
|
0.6548
|
0.1238
|
0.0380
|
60.61
|
7.99
|
3.6112
|
0.0752
|
0.0254
|
0.0084
|
SW14
|
0.5593
|
0.1058
|
0.0325
|
53.60
|
7.07
|
3.1935
|
0.0709
|
0.0240
|
0.0078
|
SW15
|
0.6744
|
0.1276
|
0.0391
|
61.10
|
8.06
|
3.6404
|
0.0746
|
0.0252
|
0.0083
|
SW16
|
0.6891
|
0.1303
|
0.0400
|
47.94
|
6.32
|
2.8561
|
0.0672
|
0.0227
|
0.0075
|
SW17
|
0.6293
|
0.1191
|
0.0365
|
61.89
|
8.16
|
3.6870
|
0.0695
|
0.0235
|
0.0077
|
SW18
|
0.6294
|
0.1190
|
0.0364
|
59.34
|
7.82
|
3.5354
|
0.0823
|
0.0278
|
0.0092
|
SW19
|
0.3507
|
0.0663
|
0.0203
|
63.85
|
8.42
|
3.8038
|
0.0961
|
0.0325
|
0.0107
|
SW20
|
0.4587
|
0.0867
|
0.0266
|
45.40
|
5.98
|
2.7049
|
0.0596
|
0.0202
|
0.0066
|
Ave.
|
0.6032
|
0.1141
|
0.0350
|
57.32
|
7.56
|
3.4146
|
0.0676
|
0.0229
|
0.0075
|
Max.
|
0.7910
|
0.1496
|
0.0459
|
65.99
|
8.70
|
3.9317
|
0.0961
|
0.0325
|
0.0107
|
Min.
|
0.3507
|
0.0663
|
0.0203
|
42.03
|
5.54
|
2.5039
|
0.0235
|
0.0079
|
0.0026
|
The values of specific activity and the calculated doses obtained in this study, did not exceed the safety limits, therefore, there is the insignificant danger for radiation which arises from the radionuclides in the water samples When choosing the methods of possible decontamination, one must pay attention to the half-life of the radioactive isotopes. These results can be used as reference values for current assessment of doses due to natural radioactivity in the surrounding of the city of Kirkuk.
From the radioactivity analysis all values of the samples under the test are below of permissible values 370 Bq.kg-1of radium content, recommended by Organization for Economic Cooperation and Development (OECD). Hence the area under investigation is safe as for as health hazards of radium and safe in radiological risks due to radium exposure from the water. But for this study the results of the specific activity of 226Ra, 232Th, 40K (from this study have been found to be lower than) measured to be lower than the recommended reference limits by (UNSCEAR, 2000), 32 Bq.kg-1 and 45 Bq.kg-1, 412 Bq.kg-1) (Ali et al., 2019; UNSCEAR, 2000).
On the other hand, relatively increased levels of 40K were found in variation of radioactivity. It can be seen that the radium, thorium and potasium in the water samples changed from location to other. This variation in the concentration of radionuclides content in each water sample may be due to different degrees of agitation and change in meteorological parameters (Najeba et al., 2019).
Table 12 Effective doses due to ingestion by radionuclides
Parents
|
Case of radionuclides
|
Infants (0–1y)
(μSv.y_1)
|
Children (2–7 y)
(μSv.y_1)
|
Adults (>17y) (μSv.y_1)
|
226Ra
|
Minimum
|
42.032
|
5.541
|
2.504
|
|
Maximum
|
65.993
|
8.706
|
3.931
|
|
Average
|
57.312
|
7.557
|
3.414
|
232Th
|
Minimum
|
0.351
|
0.066
|
0.020
|
|
Maximum
|
0.791
|
0.149
|
0.046
|
|
Average
|
0.603
|
0.114
|
0.035
|
40K
|
Minimum
|
0.0235
|
0.008
|
0.003
|
|
Maximum
|
0.096
|
0.032
|
0.011
|
|
Average
|
0.067
|
0.023
|
0.007
|
|
Av. Cumulative
|
18.58
|
2.466
|
1.108
|