Deposition velocities of some natural radionuclides from the atmosphere at Ninh Thuan and Dong Nai of Vietnam
Nuclear Science and Technology, Vol.10, No. 1 (2020), pp. 31-39
Deposition velocities of some natural radionuclides from the
atmosphere at Ninh Thuan and Dong Nai of Vietnam
Nguyen Van Phu, Le Nhu Sieu, Tran Dinh Khoa, Nguyen Dinh Tung,
Nguyen Thi Thanh Nga, Truong Y
Dalat Nuclear Research Institute
01 Nguyen Tu Luc Str., Dalat, LamDong
Email: phunguyen.nutech @ gmail.com
(Received 07 November 2019, accepted 14 January 2020)
Abstract: The deposition velocities of Be-7, K-40, Th-232, U-238 and Pb-210 radionuclides from the
atmosphere at Ninh Thuan and Dong Nai monitoring stations of Vietnam were investigated. The
deposition velocity was calculated based on it’s specific radioactivity in aerosols and deposition
density in fallout samples. The data of the deposition velocities of radionuclides from the atmosphere
are needed as input data for the models to simulate atmospheric radioactive dispersion and assess the
public dose around nuclear facilities. The radioactivity of Be-7, K-40, Th-232, U-238 and Pb-210
nuclides in aerosols and fallout samples were analyzed by using a low level background gamma
spectrometer equipped with HPGe detector of high resolution. The results show that the deposition
velocities of Be-7, K-40, Th-232, U-238 and Pb-210 nuclides from the air are in ranges of 0.04÷1.71;
1.84÷27.46; 1.46÷23.63; 0.80÷26.13 and 0.06÷1.53 (cm/s), with average values of 0.55; 13.81; 8.22;
8.12 and 0.58 (cm/s), respectively. The deposition velocities of the radionuclides in the survey areas
are comparable with those found in tropical and subtropical regions and these results could be served
as the database of the World radioactive transport parameters.
Keywords: Deposition velocity, natural radioactivity, deposition density, aerosol, fallout.
Monitoring of the environmental
radioactivity is necessary in Vietnam
because it would create a database of the
radiation background to assess radiation
dose to the population during the
industrialization process of the country.
Besides, radiation monitoring is essential in
Vietnam by now as it needs to timely detect
possible nuclear incident that could be
happened at nuclear power plants currently
operating in southern China and Taiwan
that would affect Vietnam due to the both
Northeast and Southeast monsoons. In
I. INTRODUCTION
Research and monitoring
of
environmental radioactivity is a field of science
which began and developed along with the use
of nuclear energy in various fields of human
activity. The initial works on environmental
radioactivity research were carried out during
the 20s and 30s of the twentieth century.
These works were mainly related to the
survey for the distribution of natural
radionuclides and assessment of the impacts
of ionizing radiation on living organisms in
regions with high levels of U, Ra, Th and their
recent
years,
radioactivity
in
the
progenies.
Studies
of
environmental
atmosphere has been constantly monitoring
by radiological monitoring stations around
the world. In Vietnam, radiological
monitoring stations were also set up in
radioactivity were especially important and
necessary after the nuclear weapons tests were
conducted that caused a lot of artificial
radionuclides to disperse globally.
©2020 Vietnam Atomic Energy Society and Vietnam Atomic Energy Institute
DEPOSITION VELOCITIES OF SOME NATURAL RADIONUCLIDES FROM THE ATMOSPHERE …
numerous provinces to monitor for the
radiation background in the air. These
stations are under the control of the
was about 40000 m3 per sample; the
collection time is one month. Before
collecting, filter was dried at 60°C in a
vacuum drying oven to constant weight
(drying time was >24 hours); then it was
removed and placed in a desiccator for about
3-4 hours; balance to determine the weight of
blank filter. After the filter with aerosol was
collected and dried under the same
conditions as that for blank filters, the
sample was weighed to determine the amount
of the dust attained on the filter [2]. The
aerosol deposition density was also
monitored at the same location by using
stainless steel trays with an area of 1.0 m2
each [3]. The trays were installed at a height
of 1.5 m above the ground.
Institute
of
Nuclear
Science
and
Technology (Hanoi) and the Nuclear
Research Institute (Dalat) [1].
From the atmosphere, radionuclides
fall to the ground and the ocean. They are
essentially stored and accumulated long
term in these environments until complete
decay. From the soil, radioactive substances
cause external radiation and penetrate living
organisms through the food chain causing
internal radiation. Therefore, observing the
radionuclides due to the deposition is very
important to establish a relationship between
the source and the effective radiation dose
on humans [1].
The analytical methods applied to
quantify activities of the radionuclides in the
samples were those which were in accordance
to the procedures established by the Laboratory
of the Center for Environment Research and
Monitoring, Nuclear Research Institute (Da
Lat). The Laboratory has been evaluated and
accredited to be conformable to the ISO/IEC
17025:2017 with the national code of VILAS
525 [2,3].
The objective of this research is to
obtain the transport parameters of some
radionuclides in the air to create the input
data for
a
model to simulate the
atmospheric dispersion of the radioactive
materials and to assess the public dose
around nuclear facilities.
II. CONTENT
In this study, the measurements for
activities of the radionuclides in aerosols and
fallout samples were performed for 24 hours
to obtain sufficient uncertainty. The samples
were measured on a low background gamma
spectrometer equipped with a HPGe detector
model GX3019 (CANBERRA) having a
relative efficiency of 30%, and an energy
resolution of 1.90 keV at the 1333 keV and a
peak-to-Compton ratio of 56:1. Computer
software MAESTRO-32 was used to process
obtained spectrums.
A. Object and method
In this research, aerosols and fallout
samples were collected monthly at the Center
for Hydro-Meteorological Forecasting in Ninh
Thuan province (11o34'51''N, 108o58'25''E) and
Dong Nai province (10o50'42''N, 107o14'09''E).
Samples of aerosols were collected on
604LB Cellulose filters by using a high-
volume air sampler HV3000 with a flow rate
of 100 m3/h. The sampling point was 1.5 m
above the ground. The total sampling volume
32
NGUYEN VAN PHU et al.
Quality control programme for the
measurements was conducted by using the
IAEA-CU-2006-03 standard reference
(1)
Where Afallout is the deposition density in
a fallout sample, Bq/m2/s;
materials (SRM) sample. The counting time for
each measurement was around 90,000s in order
to obtain good counting statistics.
Aaerosol is the specific radioactivity of
concerned radionuclide in the aerosol
sample, Bq/m3;
The activity of Be-7 was quantified based
on the photopeak of 477.59 keV (10.358%), for
Pb-210 it was based on the peak of 46.5 keV
(4.058%). The activity of K-40 was quantified
based on it’s photopeak of 1460.83 keV
(10.671%). The activities of Th-232 and U-238
were quantified based on photo peaks of their
progenies Ac-228 at 911.205 keV (26.607%),
338.32 keV (11.254%) and Th-234 at 63.0 keV
(3.81%), respectively.
V is the deposition
velocity
of
radionuclide from the atmosphere, m/s.
B. Result
1. Natural radioactivity from the atmosphere
Average values and ranges of
radioactivity of Be-7, K-40, Th-232, U-238
and Pb-210 radionuclides detected in the
aerosols at Ninh Thuan and Dong Nai
monitoring stations are presented in Tables I
and II.
The deposition velocity of radionuclides
from the atmosphere was calculated by the
formula [4]:
Table I. Average values and ranges of radioactivity of Be-7, K-40, Th-232, U-238 and Pb-210 nuclides
detected in aerosols at Ninh Thuan (from January 2017 to December 2018) and Dong Nai monitoring stations
(from November 2018 to July 2019).
Ninh Thuan monitoring station
µBq/m3
Dong Nai monitoring station
µBq/m3
Radionuclide
Average (n)
1666 (24)
4384 (9)
Be-7
K-40
Range
Average (n)
Range
607 ÷ 3831
32.7 (24)
2335 ÷ 7000
73.7 (9)
11.4 ÷ 57.2
2.89 (24)
10.8 ÷ 151.7
5.76 (9)
Average (n)
Range
Th-232
U-238
Pb-210
1.05 ÷ 5.21
3.01 (24)
0.60 ÷ 9.72
5.04 (9)
Average (n)
Range
0.68 ÷ 5.86
358 (24)
1.20 ÷ 9.78
703 (9)
Average (n)
Range
172 ÷ 780
418 ÷ 925
Note: n is number of measurement
33
DEPOSITION VELOCITIES OF SOME NATURAL RADIONUCLIDES FROM THE ATMOSPHERE …
Table II. Average values and ranges of deposition density of Be-7, K-40, Th-232, U-238 and Pb-210
nuclides detected in fallout samples at Ninh Thuan (from January 2017 to December 2018) and Dong Nai
monitoring stations (from November 2018 to July 2019).
Ninh Thuan monitoring station
Bq/m2/month
17.79 (24)
Dong Nai monitoring station
Bq/m2/month
34.38 (9)
Radionuclide
Average (n)
Be-7
K-40
Range
Average (n)
Range
2.55 ÷ 36.98
10.47 (24)
1.23 ÷ 100.20
3.87 (9)
2.82 ÷ 18.63
0.51 (24)
0.49 ÷ 7.71
0.16 (9)
Average (n)
Range
Th-232
U-238
Pb-210
0.14 ÷ 1.19
0.05 ÷ 0.23
0.25 (9)
Average (n)
Range
0.49 (24)
0.08 ÷ 1.19
0.06 ÷ 0.60
6.47 (9)
Average (n)
Range
4.62 (24)
1.16 ÷ 12.42
0.61 ÷ 16.51
Note: n is number of measurement
velocities of the radionuclides were
calculated (Eq.1) and the results were
presented in Tables III and IV. The
temporal variation of the deposition
velocities of radionuclides were shown in
Figures 1, 2, 3 and 4.
2. Deposition velocity of radionuclide from
the atmosphere
From the data of specific radioactivity and
deposition densities of radionuclides obtained at
Ninh Thuan and Dong Nai monitoring stations
(Table
I
and
II),
the
deposition
Table III. Deposition velocities of Be-7, K-40, Th-232, U-238 and Pb-210 radionuclides from the
atmosphere at Ninh Thuan monitoring station (from January 2017 to December 2018).
Be-7
K-40
Th-232
cm/s
U-238
Pb-210
Time
cm/s
cm/s
cm/s
cm/s
01/17
02/17
03/17
04/17
05/17
06/17
07/17
08/17
09/17
10/17
0.41 ± 0.05
0.17 ± 0.01
0.07 ± 0.03
0.20 ± 0.09
1.71 ± 0.22
0.26 ± 0.07
0.53 ± 0.14
1.22 ± 0.17
1.18 ± 0.30
1.00 ± 0.14
14.23 ± 3.12
14.9 ± 3.31
13.2 ± 4.52
10.22 ± 3.45
24.14 ± 5.47
11.63 ± 3.11
12.94 ± 3.16
1.84 ± 0.39
16.53 ± 5.11
26.51 ± 3.22
15.93 ±11.63
23.63 ±11.13
4.63 ± 2.94
5.73 ± 5.04
5.07 ± 2.10
3.16 ± 1.60
4.13 ± 2.05
1.46 ± 0.53
3.63 ± 1.70
11.43 ± 3.46
26.13 ± 8.99
25.55 ± 6.85
3.04 ± 1.49
7.16 ± 4.97
4.38 ± 1.68
4.51 ± 2.16
2.95 ± 1.05
1.94 ± 0.41
14.91 ± 5.21
23.65 ± 7.80
0.81 ± 0.14
0.35 ± 0.07
0.18 ± 0.08
0.26 ± 0.08
1.01 ± 0.20
0.39 ± 0.14
0.48 ± 0.12
0.71 ± 0.08
0.87 ± 0.19
0.52 ± 0.06
34
NGUYEN VAN PHU et al.
Be-7
K-40
Th-232
U-238
Pb-210
Time
cm/s
cm/s
cm/s
cm/s
cm/s
11/17
12/17
01/18
02/18
03/18
04/18
05/18
06/18
07/18
08/18
09/18
10/18
11/18
12/18
1.20 ± 0.11
0.43 ± 0.05
0.13 ± 0.03
0.04 ± 0.02
0.05 ± 0.01
0.18 ± 0.05
0.46 ± 0.11
0.35 ± 0.06
0.95 ± 0.12
0.34 ± 0.08
0.79 ± 0.07
0.26 ± 0.04
0.76 ± 0.16
0.57 ± 0.09
27.46 ± 6.11
10.74 ± 2.66
12.54 ± 2.78
13.89 ± 2.85
8.21 ± 1.74
18.35 ± 4.46
9.21 ± 2.03
8.46 ± 1.65
17.07 ± 3.77
5.57 ± 1.39
6.37 ± 1.19
13.64 ± 4.76
21.37 ± 6.35
12.44 ± 2.79
1.84 27.46
12.62 ± 3.90
8.81 ± 2.82
18.17 ± 7.95
1.95 ± 0.83
1.90 ± 0.94
9.10 ± 2.88
18.72 ± 6.06
4.10 ± 1.48
5.67 ± 2.12
4.39 ± 1.47
6.89 ± 2.33
14.91 ± 7.28
2.07 ± 0.96
9.16 ± 3.54
1.46 23.63
4.73 ± 1.16
7.83 ± 3.08
5.11 ± 1.67
1.91 ± 0.65
0.80 ± 0.24
16.89 ± 6.25
9.66 ± 2.43
5.73 ± 1.25
4.57 ± 1.00
2.96 ± 0.65
3.45 ± 0.91
3.75 ± 1.36
4.07 ± 1.39
9.28 ± 2.54
0.80 26.13
1.53 ± 0.18
0.71 ± 0.11
0.92 ± 0.14
0.06 ± 0.01
0.16 ± 0.03
0.60 ± 0.10
0.44 ± 0.10
0.36 ± 0.06
1.01 ± 0.17
0.27 ± 0.06
0.40 ± 0.08
0.20 ± 0.09
0.82 ± 0.18
0.85 ± 0.22
0.06 1.53
Min - Max 0.04 1.71
Mean ±
0.55 ± 0.45
SD
13.81 ± 6.36
12.17
8.22 ± 6.18
6.19
8.12 ± 7.60
5.63
0.58 ± 0.35
0.47
0.37
Geomean
Table IV. Deposition velocities of Be-7, K-40, Th-232, U-238 and Pb-210 radionuclides from the
atmosphere at Dong Nai station (from November 2018 to July 2019).
Be-7
K-40
Th-232
cm/s
U-238
Pb-210
cm/s
Time
cm/s
cm/s
cm/s
11/18
12/18
0.10 ± 0.02
0.35 ± 0.08
0.04 ± 0.01
0.02 ± 0.01
0.08 ± 0.01
0.02 ± 0.01
0.62 ± 0.06
1.41 ± 0.29
0.65 ± 0.06
0.02 1.41
0.37 ± 0.47
0.14
7.55 ± 2.40
1.48 ± 0.35
4.24 ± 1.34
2.47 ± 0.96
3.17 ± 1.10
0.83 ± 0.32
0.27 ± 0.08
3.50 ± 1.13
0.28 ± 0.07
0.27 7.55
2.64 ± 2.33
1.63
13.84 ± 3.75
0.84 ± 0.25
0.28 ± 0.14
1.04 ± 0.33
2.33 ± 0.99
0.74 ± 0.27
0.78 ± 0.23
1.40 ± 0.53
0.52 ± 0.16
0.28 13.84
2.42 ± 4.32
1.14
9.07 ± 1.53
5.81 ± 0.95
0.83 ± 0.18
5.37 ± 1.83
0.77 ± 0.18
0.56 ± 0.47
1.89 ± 0.46
1.30 ± 0.29
1.48 ± 0.26
0.56 9.07
3.01 ± 3.01
1.93
0.16 ± 0.04
0.34 ± 0.06
0.03 ± 0.01
0.22 ± 0.08
0.13 ± 0.06
0.11 ± 0.04
0.55 ± 0.16
1.04 ± 0.26
0.74 ± 0.18
0.03 1.04
0.37 ± 0.34
0.23
01/19
02/19
03/19
04/19
05/19
06/19
07/19
Min - Max
Mean ± SD
Geomean
35
DEPOSITION VELOCITIES OF SOME NATURAL RADIONUCLIDES FROM THE ATMOSPHERE …
Fig. 1. Deposition velocities of Be-7 and Pb-210 at Ninh Thuan.
Fig. 2. Deposition velocities of K-40, Th-232 and U-238 at Ninh Thuan.
Fig. 3. Deposition velocities of Be-7 and Pb-210 at Dong Nai.
Fig. 4. Deposition velocities of K-40, Th-232 and U-238 at Dong Nai.
36
NGUYEN VAN PHU et al.
Frequency distribution of the deposition
atmosphere at Ninh Thuan and Dong Nai were
shown in Figure 5 and 6.
velocity for Be-7 and Pb-210 from the
Be-7 (DN)
Be-7 (NT)
6
4
2
0
100%
75%
50%
25%
0%
8
6
4
2
0
100%
75%
50%
25%
0%
Frequency
Frequency
Cumulative %
Fig. 5. Frequency distribution of the deposition velocity for Be-7 in the air at Ninh Thuan and Dong Nai.
Pb-210 (DN)
Pb-210 (NT)
6
4
2
0
100%
75%
50%
25%
0%
8
6
4
2
0
100%
75%
50%
25%
0%
Frequency
Frequency
Cumulative %
Fig. 6. Frequency distribution of the deposition velocity for Pb-210 in the air at Ninh Thuan and Dong Nai.
Deposition velocities of Be-7 and Pb-
210 tend to be similar to each other: it was
higher in the rainy season (from May to
October), but it was lower in the dry season
(from November to April of the following
year). The deposition velocities of the
radionuclides from the atmosphere in the rainy
season were about two times higher than that in
the dry season (Figs. 1 and 3).
C. Discussion
Experimental data show that the
deposition velocities of radionuclides Be-7,
K-40, Th-232, U-238 and Pb-210 in the air at
Ninh Thuan are 0.04 ÷ 1.71; 1.48 ÷ 27.46;
1.46 ÷ 23.63; 0.80 ÷ 26.13 and 0.06 ÷
1.53cm/s with the average values of 0.55;
13.81; 8.22; 8.12 and 0.58 cm/s, and at Dong
Nai are 0.02 ÷ 1.41; 0.27 ÷ 7.55; 0.28 ÷
13.84; 0.56 ÷ 9.07 and 0.03 ÷ 1.04 with the
average values of 0.37; 2.64; 2.42; 3.01 and
0.37 cm/s, respectively.
As seen from Table III and IV the
deposition velocities of Be-7 and Pb-210 were
from 15 to 25 times lower than that of K-40,
Th-232, and U-238. Be-7 is formed from the
37
DEPOSITION VELOCITIES OF SOME NATURAL RADIONUCLIDES FROM THE ATMOSPHERE …
nuclear interactions between galactic cosmic
rays and solar protons with atmospheric
nitrogen and oxygen nuclei. Pb-210 is one of
the progenies of 222Rn which formed from the
U-238 radioactive series. Because 222Rn is an
inert gas so it could be able to emanate from
the ground into the atmosphere where it decays
to form Pb-210. In the atmosphere, Be-7 and
Pb-210 are attached to fine aerosols which are
easily soluble in water, and therefore the rain
has the same effect in washing out both of
these radionuclides from the atmosphere.
Because Be-7 and Pb-210 are all associated
with fine aerosols, while K-40, Th-232 and U-
238 in the atmosphere were originated from the
dust and they mainly associated with large
aerosols. This made the deposition velocities of
Be-7 and Pb-210 to be from 15 to 25 times
lower than those of K-40, Th-232 and U-238 as
mentioned earlier.
highest velocities during the months of low
rainfall. In contrast, during the months of
high rainfall they deposit with the lowest
velocities the ratios between the highest and
lowest deposition velocities of K-40, Th-232
and U-238 range from 5.09 to 49.18. The
deposition velocities of these radionuclides
are also high at the beginning of the rainy
season indicating that the aerosol cleaning
process in the atmosphere is more efficient
during the first rain.
The deposition velocities determined
for Be-7, K-40, Th-232, U-238 and Pb-210
from the atmosphere at Ninh Thuan location
in this study are similar to those that
observed in [4]. Also it was revealed that the
deposition velocities of the natural
radionuclides from the atmosphere found in
this study are comparable with those found in
other tropical and subtropical regions [4-6]
as shown in Table V.
Usually K-40, Th-232 and U-238
deposit from the atmosphere with their
Table V. A comparison of the deposition velocities of radionuclides from the atmosphere in different tropical
and subtropical regions.
Deposition velocity, cm/s
Location
Reference
Be-7
1.48
0.50
1.57
0.37
0.14
Pb-210
Toki, Japan (35o19’N, 137o10’E)
[5]
[4]
[6]
Atlantic and Mediterranean coasts, Spain (37o16’N, 6o55’W)
Southeastern Michigan, USA (42o25’N, 83o1’W)
Ninh Thuan, Vietnam (11o34'51''N, 108o58'25''E)
Dong Nai, Vietnam (10o50'42''N, 107o14'09''E).
0.51
1.05
0.47
0.23
This study
Nai locations. The results show that the
deposition velocities of Be-7 and Pb-210 in
rainy season is much greater than in dry season.
Meanwhile, the highest deposition velocities of
K-40, Th-232 and U-238 occur in months with
hard rain and the lowest values were in the rainy
months. These values are also high at the
III. CONCLUSIONS
In this research, the radioactivity
monitoring for Be-7, K-40, Th-232, U-238 and
Pb-210 nuclides in the atmosphere has been
carried out from Jan 2017 to Dec 2018 at Ninh
Thuan and from Nov 2018 to Mar 2019 at Dong
38
NGUYEN VAN PHU et al.
[3]. Laboratory of Environmental Analyses
beginning of rainy season, which indicates that
aerosols cleaning process in the atmosphere is
more efficient during the first rains.
(VILAS 525), Center for Environment
Research and Monitoring, Nuclear Research
Institute, TCCS-RL-05: 2017.
The deposition velocities of the natural
radionuclides from the atmosphere in the
survey areas are in ranges for other tropical and
subtropical regions and these results could be
contributed to the database of world
radioactive transport parameters.
[4]. R. L. Lozano, E. G. San Miguel, J. P. Bolívar,
and M. Baskaran, “Depositional fluxes and
concentrations of 7Be and 210Pb in bulk
precipitation and aerosols at the interface of
Atlantic and Mediterranean coasts in Spain”,
Journal of Geophysical Research, Vol. 116,
D18213, 2011.
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Vung Tau, Ca Mau, Tay Ninh and Bac My
Thuan (Tien Giang)”.
Hegedus,
Masahiro
Tanaka,
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Kakiuchi and Tibor Kovacs, “Atmospheric
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[6]. D. McNeary and M. Baskaran, “Depositional
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