Deposition velocities of some natural radionuclides from the atmosphere at Ninh Thuan and Dong Nai of Vietnam

tical 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]. 
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. 
NGUYEN VAN PHU et al. 
33 
Quality control programme for the 
measurements was conducted by using the 
IAEA-CU-2006-03 standard reference 
materials (SRM) sample. The counting time for 
each measurement was around 90,000s in order 
to obtain good counting statistics. 
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. 
The deposition velocity of radionuclides 
from the atmosphere was calculated by the 
formula [4]: 
 (1) 
Where Afallout is the deposition density in 
a fallout sample, Bq/m
2
/s; 
Aaerosol is the specific radioactivity of 
concerned radionuclide in the aerosol 
sample, Bq/m
3
; 
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. 
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). 
Radionuclide 
Ninh Thuan monitoring station Dong Nai monitoring station 
µBq/m
3
 µBq/m
3
Be-7 
Average (n) 1666 (24) 4384 (9) 
Range 607 ÷ 3831 2335 ÷ 7000 
K-40 
Average (n) 32.7 (24) 73.7 (9) 
Range 11.4 ÷ 57.2 10.8 ÷ 151.7 
Th-232 
Average (n) 2.89 (24) 5.76 (9) 
Range 1.05 ÷ 5.21 0.60 ÷ 9.72 
U-238 
Average (n) 3.01 (24) 5.04 (9) 
Range 0.68 ÷ 5.86 1.20 ÷ 9.78 
Pb-210 
Average (n) 358 (24) 703 (9) 
Range 172 ÷ 780 418 ÷ 925 
 Note: n is number of measurement 
DEPOSITION VELOCITIES OF SOME NATURAL RADIONUCLIDES FROM THE ATMOSPHERE  
34 
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). 
Radionuclide 
Ninh Thuan monitoring station Dong Nai monitoring station 
Bq/m
2
/month Bq/m
2
/month 
Be-7 
Average (n) 17.79 (24) 34.38 (9) 
Range 2.55 ÷ 36.98 1.23 ÷ 100.20 
K-40 
Average (n) 10.47 (24) 3.87 (9) 
Range 2.82 ÷ 18.63 0.49 ÷ 7.71 
Th-232 
Average (n) 0.51 (24) 0.16 (9) 
Range 0.14 ÷ 1.19 0.05 ÷ 0.23 
U-238 
Average (n) 0.49 (24) 0.25 (9) 
Range 0.08 ÷ 1.19 0.06 ÷ 0.60 
Pb-210 
Average (n) 4.62 (24) 6.47 (9) 
Range 1.16 ÷ 12.42 0.61 ÷ 16.51 
 Note: n is number of measurement 
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 
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. 
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). 
Time 
Be-7 K-40 Th-232 U-238 Pb-210 
cm/s cm/s cm/s cm/s cm/s 
01/17 0.41 ± 0.05 14.23 ± 3.12 15.93 ±11.63 26.13 ± 8.99 0.81 ± 0.14 
02/17 0.17 ± 0.01 14.9 ± 3.31 23.63 ±11.13 25.55 ± 6.85 0.35 ± 0.07 
03/17 0.07 ± 0.03 13.2 ± 4.52 4.63 ± 2.94 3.04 ± 1.49 0.18 ± 0.08 
04/17 0.20 ± 0.09 10.22 ± 3.45 5.73 ± 5.04 7.16 ± 4.97 0.26 ± 0.08 
05/17 1.71 ± 0.22 24.14 ± 5.47 5.07 ± 2.10 4.38 ± 1.68 1.01 ± 0.20 
06/17 0.26 ± 0.07 11.63 ± 3.11 3.16 ± 1.60 4.51 ± 2.16 0.39 ± 0.14 
07/17 0.53 ± 0.14 12.94 ± 3.16 4.13 ± 2.05 2.95 ± 1.05 0.48 ± 0.12 
08/17 1.22 ± 0.17 1.84 ± 0.39 1.46 ± 0.53 1.94 ± 0.41 0.71 ± 0.08 
09/17 1.18 ± 0.30 16.53 ± 5.11 3.63 ± 1.70 14.91 ± 5.21 0.87 ± 0.19 
10/17 1.00 ± 0.14 26.51 ± 3.22 11.43 ± 3.46 23.65 ± 7.80 0.52 ± 0.06 
NGUYEN VAN PHU et al. 
35 
Time 
Be-7 K-40 Th-232 U-238 Pb-210 
cm/s cm/s cm/s cm/s cm/s 
11/17 1.20 ± 0.11 27.46 ± 6.11 12.62 ± 3.90 4.73 ± 1.16 1.53 ± 0.18 
12/17 0.43 ± 0.05 10.74 ± 2.66 8.81 ± 2.82 7.83 ± 3.08 0.71 ± 0.11 
01/18 0.13 ± 0.03 12.54 ± 2.78 18.17 ± 7.95 5.11 ± 1.67 0.92 ± 0.14 
02/18 0.04 ± 0.02 13.89 ± 2.85 1.95 ± 0.83 1.91 ± 0.65 0.06 ± 0.01 
03/18 0.05 ± 0.01 8.21 ± 1.74 1.90 ± 0.94 0.80 ± 0.24 0.16 ± 0.03 
04/18 0.18 ± 0.05 18.35 ± 4.46 9.10 ± 2.88 16.89 ± 6.25 0.60 ± 0.10 
05/18 0.46 ± 0.11 9.21 ± 2.03 18.72 ± 6.06 9.66 ± 2.43 0.44 ± 0.10 
06/18 0.35 ± 0.06 8.46 ± 1.65 4.10 ± 1.48 5.73 ± 1.25 0.36 ± 0.06 
07/18 0.95 ± 0.12 17.07 ± 3.77 5.67 ± 2.12 4.57 ± 1.00 1.01 ± 0.17 
08/18 0.34 ± 0.08 5.57 ± 1.39 4.39 ± 1.47 2.96 ± 0.65 0.27 ± 0.06 
09/18 0.79 ± 0.07 6.37 ± 1.19 6.89 ± 2.33 3.45 ± 0.91 0.40 ± 0.08 
10/18 0.26 ± 0.04 13.64 ± 4.76 14.91 ± 7.28 3.75 ± 1.36 0.20 ± 0.09 
11/18 0.76 ± 0.16 21.37 ± 6.35 2.07 ± 0.96 4.07 ± 1.39 0.82 ± 0.18 
12/18 0.57 ± 0.09 12.44 ± 2.79 9.16 ± 3.54 9.28 ± 2.54 0.85 ± 0.22 
Min - Max 0.04  1.71 1.84  27.46 1.46  23.63 0.80  26.13 0.06  1.53 
Mean ± 
SD 
0.55 ± 0.45 13.81 ± 6.36 8.22 ± 6.18 8.12 ± 7.60 0.58 ± 0.35 
Geomean 0.37 12.17 6.19 5.63 0.47 
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). 
Time 
Be-7 K-40 Th-232 U-238 Pb-210 
cm/s cm/s cm/s cm/s cm/s 
11/18 0.10 ± 0.02 7.55 ± 2.40 13.84 ± 3.75 9.07 ± 1.53 0.16 ± 0.04 
12/18 0.35 ± 0.08 1.48 ± 0.35 0.84 ± 0.25 5.81 ± 0.95 0.34 ± 0.06 
01/19 0.04 ± 0.01 4.24 ± 1.34 0.28 ± 0.14 0.83 ± 0.18 0.03 ± 0.01 
02/19 0.02 ± 0.01 2.47 ± 0.96 1.04 ± 0.33 5.37 ± 1.83 0.22 ± 0.08 
03/19 0.08 ± 0.01 3.17 ± 1.10 2.33 ± 0.99 0.77 ± 0.18 0.13 ± 0.06 
04/19 0.02 ± 0.01 0.83 ± 0.32 0.74 ± 0.27 0.56 ± 0.47 0.11 ± 0.04 
05/19 0.62 ± 0.06 0.27 ± 0.08 0.78 ± 0.23 1.89 ± 0.46 0.55 ± 0.16 
06/19 1.41 ± 0.29 3.50 ± 1.13 1.40 ± 0.53 1.30 ± 0.29 1.04 ± 0.26 
07/19 0.65 ± 0.06 0.28 ± 0.07 0.52 ± 0.16 1.48 ± 0.26 0.74 ± 0.18 
Min - Max 0.02  1.41 0.27  7.55 0.28  13.84 0.56  9.07 0.03  1.04 
Mean ± SD 0.37 ± 0.47 2.64 ± 2.33 2.42 ± 4.32 3.01 ± 3.01 0.37 ± 0.34 
Geomean 0.14 1.63 1.14 1.93 0.23 
DEPOSITION VELOCITIES OF SOME NATURAL RADIONUCLIDES FROM THE ATMOSPHERE  
36 
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.
NGUYEN VAN PHU et al. 
37 
Frequency distribution of the deposition 
velocity for Be-7 and Pb-210 from the 
atmosphere at Ninh Thuan and Dong Nai were 
shown in Figure 5 and 6. 
Fig. 5. Frequency distribution of the deposition velocity for Be-7 in the air at Ninh Thuan and Dong Nai. 
Fig. 6. Frequency distribution of the deposition velocity for Pb-210 in the air at Ninh Thuan and Dong Nai. 
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. 
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). 
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 
0%
25%
50%
75%
100%
0
2
4
6
8
0
.1 0.
3
0
.5
0
.7
0
.9
1
.1
1
.3
1
.5
M
o
re
Fr
eq
u
e
n
cy
Be-7 (NT) 
Frequency
0%
25%
50%
75%
100%
0
2
4
6
0.
0
1
0
.3
0
.5
0
.7
0
.9
1
.1
1
.3
M
o
re
Fr
eq
u
e
n
cy
Be-7 (DN) 
Frequency Cumulative %
0%
25%
50%
75%
100%
0
2
4
6
8
0.
1
0.
3
0.
5
0.
7
0.
9
1.
1
1.
3
1.
5
M
o
re
Fr
eq
u
en
cy
Pb-210 (NT) 
Frequency
0%
25%
50%
75%
100%
0
2
4
6
0.
0
1
0.
3
0.
5
0.
7
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1.
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Frequency Cumulative %
DEPOSITION VELOCITIES OF SOME NATURAL RADIONUCLIDES FROM THE ATMOSPHERE  
38 
nuclear interactions between galactic cosmic 
rays and solar protons with atmospheric 
nitrogen and oxygen nuclei. Pb-210 is one of 
the progenies of 
222
Rn which formed from the 
U-238 radioactive series. Because 
222
Rn 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. 
Usually K-40, Th-232 and U-238 
deposit from the atmosphere with their 
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. 
Table V. A comparison of the deposition velocities of radionuclides from the atmosphere in different tropical 
and subtropical regions. 
Location 
Deposition velocity, cm/s 
Reference 
Be-7 Pb-210 
Toki, Japan (35
o19’N, 137o10’E) 1.48 [5] 
Atlantic and Mediterranean coasts, Spain (37
o16’N, 6o55’W) 0.50 0.51 [4] 
Southeastern Michigan, USA (42
o25’N, 83o1’W) 1.57 1.05 [6] 
Ninh Thuan, Vietnam (11
o
34'51''N, 108
o
58'25''E) 0.37 0.47 
This study 
Dong Nai, Vietnam (10
o
50'42''N, 107
o
14'09''E). 0.14 0.23 
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 
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 
NGUYEN VAN PHU et al. 
39 
beginning of rainy season, which indicates that 
aerosols cleaning process in the atmosphere is 
more efficient during the first rains. 
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. 
REFERENCES 
[1]. Station of Chemical and Radioactive 
Environment Monitoring and Analysis No. 3, 
Nuclear Research Institute, Report on the 
implementation of Annually National Projects: 
“Monitoring and analyzing environmental 
radioactivity at 8 monitoring points: Dalat, 
Ninh Thuan, Hochiminh city, Binh Thuan, 
Vung Tau, Ca Mau, Tay Ninh and Bac My 
Thuan (Tien Giang)”. 
[2]. Laboratory of Environmental Analyses 
(VILAS 525), Center for Environment 
Research and Monitoring, Nuclear Research 
Institute, TCCS-BK-03: 2017. 
[3]. Laboratory of Environmental Analyses 
(VILAS 525), Center for Environment 
Research and Monitoring, Nuclear Research 
Institute, TCCS-RL-05: 2017. 
[4]. R. L. Lozano, E. G. San Miguel, J. P. Bolívar, 
and M. Baskaran, “Depositional fluxes and 
concentrations of 
7
Be and 
210
Pb in bulk 
precipitation and aerosols at the interface of 
Atlantic and Mediterranean coasts in Spain”, 
Journal of Geophysical Research, Vol. 116, 
D18213, 2011. 
[5]. Naofumi Akata, Yoshitaka Shiroma, 
Norihiro Ikemoto, Akemi Kato, Miklos 
Hegedus, Masahiro Tanaka, Hideki 
Kakiuchi and Tibor Kovacs, “Atmospheric 
Concentration and Deposition Flux of 
Cosmogenic Beryllium-7 at Toki, Central 
Part of Japan”, Radiation Environment and 
Medicine Vol.7, No.1, 47-52, 2018. 
[6]. D. McNeary and M. Baskaran, “Depositional 
characteristics of 
7
Be and 
210
Pb in southeastern 
Michigan”, Journal of Geophysical Research, 
Vol. 108, No. D7, 4210, 2003.