[4]
The analysis of soil sample The soil samples are collected at the same time with the measurement of gamma radiation dose rate and radon concentration in air. The analysis results of soil samples are shown in the table 4(totally 91 soil samples). Table 4 The analysis results of soil samples 238U (Bq/kg)
226Ra (Bq/kg)
232Th (Bq/kg)
40K (Bq/kg)
137Cs (Bq/kg)
α (Bq/kg)
β (Bq/kg)
Ir
IRa
Xinchang and Jijicao rock
mean
28.8
26.9
33.7
597.5
7.8
1023.9
678.5
0.3
0.2
range
8.44～51
10.7～48.2
14～76.1
250～1058
0.07～37.7
323～4455
254～1495
0.1～0.5
0.1～0.4
Soil in Jiuquan[[] X.Y. Ren, S.M. Bai, Q. Sun,etc.: Investigation of Natural Radionuclide Contents in Soil in Gansu Province, Natural Environmental Radioactivity Level in China (The Chinese National Environmental Protection Agency, China 1995). ]
mean
80.0
25.4
35.7
429.2
range
20.1～200.0
14.4～46.1
16.4～70.3
115.5～711.8
Soil in Beishan[[] China Institute For Radiation Protection: The Summary Report of Radioactive Background Investigation in Beishan Preselected Region (Taiyuan, China 2006) ]
mean
34.1
34.3
38.8
652.1
19.8
1255.5
861.4
range
19.3～76.4
20.2～76.8
16.2～64.9
496～861
4.58～49.7
641～3157
640～1130
From the analysis results of soil sample, the content of 238U,226Ra,232Th,40K are generally within normal environmental background in Jiuquan and Beishan. The external and internal exposure index of soil samples are all small which can meet the relevant requirements of the Limit of Radionuclides in Building Materials(GB6566-2001)，and the use of soil is unrestricted. The artificial radionuclide 137Cs with certain content is detected in all soil samples, and the total α and total β of some samples are slightly high due to there are activities of nuclear research and nuclear waste disposal near the study area.
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[5]
The analysis of plant sample A total of 67 plant samples were collected in the environmental investigation, there were 15 kinds of plant, mainly including Nitraria Tangutorum, Zygophyllum, Ephedra, Branchy Tamarisk, Ammodendron and Achnatherum Splendens, etc. The analysis results of plant samples are shown in table 5. Table 5 The analysis results of plant samples Location
238U (Bq/kg)
226Ra (Bq/kg)
232Th (Bq/kg)
40K (Bq/kg)
137Cs (Bq/kg)
α (Bq/kg)
β (Bq/kg)
Xinchang and jijicao rock
mean
0.9
1.0
1.2
162.9
0.2
89.3
359.2
range
0.15～3.64
0.07～5
0.14～6.52
44.9～558
0.01～1.45
16.9～373
177～676
Soil in Jiuquan[13]
mean
80.0
25.4
35.7
429.2
range
20.1～200.0
14.4～46.1
16.4～70.3
115.5～711.8
Soil in Beishan[14]
mean
34.1
34.3
38.8
652.1
19.8
1255.5
861.4
range
19.3～76.4
20.2～76.8
16.2～64.9
496～861
4.58～49.7
641～3157
640～1130
Plant in Beishan[14]
mean
130.1
0.4
8.4
136.2
range
26.8～243
0.086～1.43
0.7～35.7
37.2～238 From the analysis results of plant samples, the contents of 238U, 226Ra, 232Th, 40K, total α and total β of plant samples are in the range of environmental background compared with the soil background level in Jiuquan and Beishan. A small amount of artificial radionuclide 137Cs is detected in plant samples, and the total α and total β are slightly higher in some samples due to there are activities of nuclear research and nuclear waste disposal near the study area.
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[6]
The analysis of rock sample A total of 15 rock samples are collected from boreholes of BS15 ~ BS19 which were taken from three different depths (100m, 300m and 500m). The analysis results of rock samples are shown in Table 6. Table 6 The analysis results of rock samples Location
238U (Bq/kg)
226Ra (Bq/kg)
232Th (Bq/kg)
40K (Bq/kg)
137Cs (Bq/kg)
Total α (Bq/kg)
Total β (Bq/kg)
External exposure index(Ir)
Internal exposure index(IRa)
Xinchang and jijicao rock
Mean
50.3
50.9
120.1
911
0.11
1153.7
1389.9
0.8
0.3
Range
6.68～194
10.3～184
4.91～232
386～1936
0.07～0.27
78.8～2048
42.5～2465
0.2～1.5
0.1～0.9
Soil in Jiuquan[13]
mean Range
80.0
25.4
35.7
429.2
20.1～200.0
14.4～46.1
16.4～70.3
115.5～711.8
Soil in Beishan[14]
mean range
34.1
34.3
38.8
652.1
19.8
1255.5
861.4
19.3～76.4
20.2～76.8
16.2～64.9
496～861
4.58～49.7
641～3157
640～1130
From the analysis results of rock sample, the contents of 226Ra, 232Th, 40K and total β in rock samples are higher than the soil background in Jiuquan and Beishan, and the content of 137Cs is very low. The contents of 238U, 232Th, 40K are within the normal range compared to their average content in the crust of the earth. Most of the external, internal exposure index of each sample are small, which can meet the requirement of Limit of Radionuclides in Building Materials(GB6566-2001), and the use of soil is unrestricted. The artificial radionuclides 137Cs is detected with trace amounts in rock samples, and total β is high in several samples which may be related to activities of nuclear research and nuclear waste disposal near the study area.
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[7]
The analysis of water samples The analysis results of water samples are shown in table 7. Table 7 The analysis results of water samples Sequence number
Results of analysis (mBq/L)
Sampling location
238U
226Ra
232Th
40K
137Cs
90Sr
Total α
Total β
1
32.9
<9
0.024
533
5080
8820
Sishili well, well water
2
7.38
40
0.003
1674
1755
4680
Jinmiaogou mine, adit water
3
22.2
30
not detected
411
5360
3150
Jinmiaogou mine, adit water
4
79.1
10
not detected
283
1175
9450
Jiujing, well water
5
155
10
0.001
510
4902
7670
Yuanyanggou, well water
6
88.7
10
not detected
223
2859
6780
Xinchang, grove, well water
7
69.1
10
0.001
372
1819
4180
Xinchang, ravine, well water
8
96.1
20
not detected
561
1480
7990
Fluorite mine, well water
9
403
24.1
0.098
533
<4.0
30.4
1750
5920
Borehole BS05,291.29-301.45m
10
0.09
29.4
not detected
1674
<4.0
10.6
5920
1940
Borehole BS15,320.75-342.63m
11
0.272
54.3
not detected
411
<4.0
12.8
6040
1630
Borehole BS15,404.75-426.63m
12
0.968
117
not detected
283
<4.0
10
6090
2690
Borehole BS15,509.76-538.26m
mean
79.6
30.9
0.025
622
<4.0
16.0
3685.8
5408.3
range
0.09～403
10～117
0.001～0.098
223～1674
<4.0
10～30.4
1175～6090
1630～9450
Jiuquan Well water[[] G.F. Zhao, Q. Sun, S.M. Bai,etc.: Investigation of Natural Radioactivity Level of Water in Gansu Province, Natural Environmental Radioactivity Level in China (The Chinese National Environmental Protection Agency, China 1995). ]
range
24.8～111.9
19.9～52.8
0.29～0.45
82.4～779.8
Mean
68.3
36.4
0.37
131.1
Beishan well water[14]
Range
3.4～12
12～67
330～2100
631～1340
mean
6.25
30.8
1056
942.8
The Table 7 shows that the contents of 238U, 226Ra, 232Th, 40K in well water are within the normal range of radioactive background. Except 40K and total β of Jinmiaogou coal mine, total α and β of Jinmiaogou gold mine in tunnel water, other radioactive indicators are in the normal range of the well water background. Except 232Th and total β, other radioactive indicators are high in borehole water which may be related to the relatively high radioactive content of granite and there are activities of nuclear research and nuclear waste disposal near the study area. The contents of total α and β of all water samples do not meet the requirements of Health Standards for Drinking Water (GB5749-2006) (total α＜0.5Bq/L, total β＜1Bq/L), so they can not be as drinking water. Dose estimation and evaluation Dose estimation models and related parameters used in dose estimation process are from the report of UNSCEAR and ICRP. Based on radioactive background investigation, the annual effective doses to the public caused by background radiation are preliminary estimated. External exposure mainly includes terrestrial γ radiation and cosmic rays. Internal exposure mainly includes: (1) Internal exposure by inhalation of radon and its daughters in the air; (2) Internal exposure by intake of natural radionuclides in food and water. According to the results of investigation, Xinchang and Jijicao rocks are sparsely populated, and only one family to the south of Xinchang rock. The radiation dose to herdsman from natural background is preliminary estimated.
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[1]
External exposure dose According to measurement results of γ radiation dose rate, γ radiation dose rate of outdoor and indoor environment are respectively 112nGy/h and 119 n Gy/h in the study area. The total effective dose to herdsman by external exposure was 0.721 mSv/a, slightly less than the average annual effective dose(0.87mSv/a) by external exposure in Jiuquan[7].
DOI: 10.1021/acs.jproteome.1c00638.s001
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[2]
Internal exposure dose l The doses to the public caused by inhalation of radon According to the measurement results of radon concentration in the air and the average concentration of 222Rn of bungalow in Gansu province, the mean of radon concentration in the outdoor air is 6.1 Bq/m3 and the concentration of radon in indoor air is 33.3 Bq/m3. The occupancy factor of indoor and outdoor are 0.77 and 0.23 respectively[[] P.Y. Gao, Y.F. Tao, J.L. Huo, etc.: Chinese J. Radiological Medicine and Protection, Vol. 11(1)( 1991), pp.32-35
DOI: 10.1109/ifost.2007.4798552
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[3]
The analysis of total dose The total effective dose to the public from the background radiation by internal exposure and external exposure is 2.074mSv/a which is obtained by the results of dose estimate of external exposure and internal exposure in Xinchang and Jijicao rock. It is lower than the effective dose (2.3mSv/a[19]) to the public by natural radiation in China. And the radiation dose to the public by natural background is mainly from the external exposure of γ radiation and internal exposure of radon inhalation. From the result of dose estimation, the study area belongs to the normal natural radioactive background region. Conclusions The environmental radioactivity background of Xinchang and Jijicao rock in Beishan preselected region has been preliminary investigated and evaluated, and the public dose from local natural background radiation is estimated in this paper which can provide basic data and information for siting of geological disposal, construction of underground research laboratory, environmental impact assessment and safety assessment of HLW disposal repository in the future. The investigation results of environmental radioactivity background of Xinchang and Jijicao rock show that the results of the field monitoring and radioactive analysis of samples are generally within normal environment background. The effective dose to local residents from natural background radiation is 2.074mSv/a by internal and external exposure which is less than the effective dose(2.3mSv/a) to the public in China . In conclusion, the results of investigation and evaluation show that the environmental radioactivity of Xinchang and Jijicao rock is generally within normal natural background. References
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