Research Journal of Applied Sciences, Engineering and Technology 1(2): 54-58, 2009
ISSN: 2040-7467
© M axwell Scientific Organization, 2009
Submit Date: June 18, 2009
Accepted Date: July 21, 2009
Published Date: August 31, 2009
Measurement of Natural Radioactivity In Beach Sediments From
North East Coast of Tamilnadu, India
1
V. R amasam y, 1 S. Senthil, 2 V. Meenakshisundaram and 2 V. Gajendran
1
Departm ent of Physics, Annam alai University, Tamilnadu, Ind ia
2
HA SD , IGC AR , Kalpakkam , Tam ilnadu, Ind ia
Abstract: The distribution of natural gamma emitting 2 3 8 U, 2 3 2 Th and 4 0 K radionu clides in beach sediments
along north east coast of Tamilnad u, India has be en carried out using a NaI(Tl) gamm a ray spectrom etric
technique. The m ean activity con centrations of m easured rad ionuclides w ere compared with other literature
values. The absorbed dose rate, annual effective dose equivalent, external hazard index and representative level
index were calculated and comp ared w ith interna tionally recom men ded values.
Key w ords: Radionuclides, absorbed dose rate, hazard indices, representative level index
INTRODUCTION
The naturally occurring radion uclides are relatively
and uniformly distributed in the seas and the oceans.
Human activities like mining and milling of mineral ores,
ore processing and enrichment, nuclear fuel fabrication
and handling of the fuel cycle tail end products cause
release of additional amou nts of natural radionu clides into
the environment. Also, the discharge into the sea of low
level waste from nuclear industry has become a source of
contamination in the marine coastal environment of
countries possessing nuclear power plants and nuclear
reprocessing plants (A kram , et al., 2007). Most of the
radioa ctivity deposited on surface sediments is washed by
rains and drained through rivers to the oceans. Part of the
ground deposited activity is absorbed in the soils and
percolates with the underground waters to the oceans.
Radionuclides reaching the ocean become part of the
marine ecosystem (water, sediments, and biota) and may
transfer through seawater-sedim ent-bio ta interfac e to
human beings (Akram , et al., 2006). Accumulation of
such substances in the marine costal environment raises
many problems conc erning safety o f biotic life, food
chain and ultimately humans. To address these problems,
assessment of radioactivity concentration in the marine
environment is essential. It is necessary to quantify the
distribution of radionuclides in the main marine
constituents (sea water, sea sediments and marine
organisms) and to assess radiological impacts of the
detected radionuc lides on hum an he alth.
Beach sediments are mineral deposits formed through
weathering and erosion of either igneo us or m etamorphic
rocks. Among the rock constituent minerals are some
natural radion uclides that co ntribute to ionizing radiation
exposure on Earth. Natural radioactivity in soils comes
from U and Th series and natural K. The study of the
distribution of primordial radionuclides allows the
understanding of the radiological implication of these
elements due to the gamma-ray exposure of the body and
irradiation of lung tissue from inhalation of radon and its
daughters (Uosif, et al., 2008).
During the last few decades, the coastal environment
of North east coast of Tamilnadu in In dia has experienced
intense developme nts in ind ustry, tou rism, tran sport,
urbanization and aquaculture. This paper reports the
activity concentrations of natural radionuclides 2 3 5 U, 2 3 2 Th
and 4 0 K, for beach sediments of North east coast of
Tamilnadu, India. The objective of this paper is to
evalu ate the radiological hazards due to natural
radioa ctivity associated with beach sediments by
calculating the absorbed dose rate, annual effective dose
rate, representative level index and external hazard index.
MATERIALS AND METHODS
This study took place in North east coast of
Tamilnadu in India is bordered on the east by the Bay of
Bengal (figure 1). The total study area spread over from
Port novo (Lat: 11º 30 ’ 953”N; Long 79º 46’279”E) to
Marina beach of Chennai (Lat: 13º 03’ 974”N; Long 80º
17’362 ”E), which covers an area about 200km. The tidal
range is 1.2-1.5m for spring tides and 0.3-0.6m for neap
tides. Some famo us beache s (M arina, K ovalam, A rovil
and Silver), historical place (Mahabalipuram) and
Industries (SIPCOT) are located in this coastal area.
Sam ple collection and preparation: Beach sediment
samples were collected during April 2008. The total study
area covers about 200km, from which at the distance of 56km interval, 35 sampling locations [S1 -S 3 5 ] are selected.
The exact position of each sampling site was recorded
using Hand held GARMIN GPS (Global Positioning
System, Mo del no 12).The samples were collected from
10-20m away from the high tide, when it makes towards
the road side. Five sa mples w ere collected from each site
covering an area of one meter square, at a depth of 5cm
and pack ed in plastic pouches.
Corresponding Author: V. Ramasamy, Department of Physics, Annamalai University, Tamilnadu, India
54
Res. J. Appl. Sci. Eng. Technol., 1(2): 54-58, 2009
Fig 1: Geographic location of North east coast of Tamilnadu in India where the beach sediment samples were collected
The collected samples were dried in an oven at 100-110 ºC
for about 24h and sieved through a 2-mm mesh-size sieve
to remove stone, pebbles and other macro-impurities. The
homogenized sample was placed in a 500g airtight PVC
container. The inner lid was place d in and closed tightly
with outer cap. The container was sealed hermetically and
extern ally using cellophane tape and kept aside for about
a month to ensure eq uilibrium betw een R a and its
daughter products before being taken for gamma ray
spectrome tric analysis (R ama samy, et al., 2004).
Gamma spectroscopic an alysis: To estimate the activity
levels of the 2 3 8 U, 2 3 2 Th and 4 0 K in the samples, a gamma
ray spectrometer in the laboratory of Health and Safety
55
Res. J. Appl. Sci. Eng. Technol., 1(2): 54-58, 2009
presented in table 1. Activity is reported in Bqkg - 1 on the
basis of the sedime nt’s dry weight. Th e measured activity
concentrations range from BD L to 30.42±7.90 BqkgG 1 for
238
U, BDL to 218.64±8.02 BqkgG 1 for 2 3 2 Th and
212.6±24.68 BqkgG 1 to 423.43±26.52 BqkgG 1 for 4 0 K.
The maxim um activity concentration of 2 3 8 U
(30.42±7.90 BqkgG 1 ) and 2 3 2 Th (218.64±8.02 BqkgG 1 )
were observed in Mahabalipuram (S-22), which is one of
the famous historical and tourism place. The highest
activity concen tration of 4 0 K (423.43±26.52 BqkgG 1 ) was
found in Kovalam beach (S-29) nearer to Chennai metro
city. The lowest concentration of all radionuclides was
found at Pudhucherry beach (S-10) (table 1), which may
be due to high comp osition of Si (M arija Jankovic, et al.,
2008).
Table 3 presents the absorbed dose rate, annual
effective dose equiv alent, external hazard index and
representative level index values. The
calculated
absorbed gamma dose rate varied from 156.73 nGy hG 1
(S-22, Mahabalipuram beach) to 15.63 nGy hG 1 (S- 10,
Pudhucherry beach) with a mean of 30.15 nGy hG 1 . The
mean absorbed dose rate is found to be 0.59 times the
world average value (51 nGy hG 1 : UNSCEAR, 2000). The
calculated values of annual effective dose rate ranging
from 0.08 to 0.77mSv, with a mean value of 0.15mSv,
which is lower than the world average value of 0.48mSv
(UNSCEAR, 2000). The calculated value of external
hazard index range s from 0.08 to 0.98.The representative
level index value being 0.24 to 2.56, with the average of
0.48, lower than the world average (0.66 Bq kgG 1 :Harb,
2008).
Div ision, Indira Gandhi Centre for Atomic Research,
Kalpakkam was used in the present investigations. NaI
(Tl) crystal detector of size 3” X 3” along with a 8K multi
channel analyzer was used to record the gamma spectra.
Standard sources of natural Uranium (1997.56Bq), natural
Thorium (1237.28 Bq) and KCl (5181.59 Bq) with a
standard 250ml container from International Atomic
Energy Agency (IAEA) were used for calibrating the
gamma ray spectrometer. These standards were obtained
from environmental survey laboratory, Indira Gandhi
Centre for Atomic Research, Kalpakkam. With the
counting time of 10,000 seconds for each sample, the
below detectable limit (BDL) limits were 21.2BqkgG 1 for
40
K, 5.5 BqkgG 1 for 2 3 8 U and 2 3 2 Th.
Calculation of radiological effects:
Dose rate calculation: The absorbed dose rate was
calculated from the measured activities of 2 3 8 U, 2 3 2 Th and
40
K in the surface sediment samples using the below
formula (Pa paefth ymio u, et al., 2008)
D (nGy hG 1 ) = 0.462 CU +0.604C T h +0.042C K
(1)
W here D is the absorbed dose rate (nGy hG 1 ). C U , C T h
and C K are the activity concentrations (BqkgG 1 ) of 2 3 8 U,
232
Th and 4 0 K respectively.
To estimate the annual effective dose rates, the conversion
coefficient from absorbed dose to effective dose, 0.7
SvGyG 1 and outdoor occupancy factor of 0.2 proposed by
UNSCEAR, 2000 were used. The effective dose rate in
units of m Sv yG 1 was calculated by the follow ing form ula
Effective dose rate (m Sv yG 1 ) = D (nGy hG 1 ) x 8760 h x
0.2 x 0.7 SvGyG 1 x 10G 6
(2)
DISCUSSION
Large variation among the radioactivity concentration
for different sites has been observed . It may be du e to
geological condition and drainage pattern of the study
area since four river estuaries were located. According to
Harb (2008), large variation of radionuclides in beach
sedim ents may be du e to the continuous wa ve action, as
the waves reaches up to about 10m from the waterline
during high tide and results in the fresh deposition of
heavy minerals along the seashore. The high v alues could
be explained as due to the presence of black sands, which
are enriched in the mineral monazite containing a
significant amou nt of 2 3 2 Th. The enrichment occurs
because of the specific gravity of monazite allows its
concentration along bea ches w here lighter materials are
swept aw ay (U osif, et al., 2008).
The mean activity concen trations of 2 3 8 U, 2 3 2 Th and
40
K is 0.33, 0.98 and 0.74 times the world average values
and 0.29, 0.98 and 0.38 times the Indian average values
respectively (UNSCEAR, 2000). Table 2 shows the
comparison of observed activity concentration of 2 3 8 U,
232
Th and 4 0 K in the present samples with literature values
of different beaches.
Calculation of hazard indexes: The external hazard
index , H e x , is defined as (Marija Jankovic et al., 2008)
H ex = (C U /370 + C T h /259 + C K /4810) # 1
(3)
An additional hazard index so called representative
level index is calculated by using the formula (Harb,
2008),
I(r = (C U /150 + C T h /100 + C K /1500)
(4)
W here C U ,C T h and C K are the specific activities
(BqkgG 1 ) of 2 3 8 U, 2 3 2 Th and 4 0 K, respectively. The value of
these index es must be less than unity in order to keep the
radiation haz ard insignificant.
RESUL TS
The results of analysis of activity concentration of
U, 2 3 2 Th and 4 0 K radionuclides in beach sediment
samples for different locations of the study area are
238
56
Res. J. Appl. Sci. Eng. Technol., 1(2): 54-58, 2009
Tab le 1: Geog raphical location and activity concentration of
India
S l.N o
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
Na me o f the S ite
Port novo
Samiyarpettai
Periyakkupam
Rajapettai
Sonankuppam
Devanamp attainam
Moo rthy Kuppam
Pannithittau
Veeramam Pattinam
Pud huch erry
Na duth ittu
Periyakalapattau
Koonimedu K uppam
Chitti kuppam
Mandavai (pudhukkuppam)
Anum andhai
Kadappkam
Panaiyur kuppam
Paramankeni kuppam
Thenpattinam
Kadaluar gramam
Mahabalipuram
Kolliyur
Dev neri
Pattipulam
Th enn eme li
Va dan eme li
Thiruvedanthai
Kovalam
Karikattukuppam
Panniyur
Eanchapakkam
Palavakkam
Thiruvanmyur
Marina
238
U , 2 3 2 Th and
Latitude
11/30’.953
11º32’.991
11º36’.233
11º41’.017
11º43’.279
11º44’.317
11º47’.356
11º49’.612
11º53’.614
11º55’391
11º57’.442
12º01’.660
12º04’.543
12º06’.697
12º09’.735
12º11’.901
12º16’.269
12º17’.962
12º20’.965
12º23’.976
12º16’.734
12º35’.657
12º37’.208
12º38’.746
12º41’.244
12º42’.292
12º43’.778
12º45’.332
12º47’.451
12º49’.899
12º53’.068
12º55’.138
12º57’.617
12º59’.918
13º03’.974
40
K in the beach sediment samples of the North east of Tamilnadu,
Longitude
79º 46’.279
79º45’.595
79º45’.505
79º46’.378
79º46’.952
79º47’.221
79º47’.799
79º48’.312
79º49’.659
79º50’.043
79º50’.452
79º52’.030
79º53’.565
79º’54’.931
79º56’.894
79º58’.358
80º 00’.980
80º01’.915
80º04’.104
80º06’.652
80º08’.566
80º11.359
80º11’.905
80º12’.385
80º13’.307
80º13’.654
80º14’.220
80º14’.707
80º15’.111
80º14’.851
80º15’.112
80º15’.425
80º15’.839
80º16’.742
80º17’.362
Average
Maximum
Minimum
Activity concentration (Bq/ kg)
----------------------------------------------------------238
40
U
232
K
Th
7.94±5.58
12.33±4.33
243.74±25.54
7.28±4.38
10.58±4.63
224.48±24.62
6.46±4.62
11.24±4.74
214.36±24.86
6.31±4.42
9.46±4.34
236.68±24.71
15 .16 ±5 .4
96 .42 ±6 .6
242.27±24.76
26.99±7.23
185.46±7.68
238.32±34.21
11.42±5.62
10.69±4.64
224.46±24.38
6.37±4.47
7.8±4.05
23 8.3 3± 24 .5
6.24±4.46
6.72±4.08
216.51±24.64
BDL
BDL
212.6±24.68
6.33±4.39
8.34±4.28
239.44±24.72
6.5 1± 4.3
65±4.06
226.67±24.74
6.6 8± 4.4
5.98±4.08
234.91±24.74
6.34±4.52
7.36±4.62
222.62±25.64
6.4 2± 4.4
6.98±4.48
232.47±25.04
6.54±4.57
7.04±4.56
218.72±24.34
6.44±4.56
6.84±4.24
213.36±24.18
7.0 2± 4.6
7.94±4.84
226.74±25.43
6.98±4.84
7.26±4.26
24 6.4 ±2 6.4
6.51±4.72
7.42±4.17
241.59±24.36
8.96±5.26
10.94±4.92
246.54±25.06
30 .42 ±7 .9
218.64±8.02
254.62±26.08
7.36±5.02
19.79±4.48
335.29±26.58
6.89±4.51
16.63±4.62
324.65±24.67
6.36±4.48
12.61±4.48
294.65±25.12
6.49±4.57
9.45±4.69
304.72±24.69
5.21±4.48
16.28±4.76
326.24±24.96
6.06±4.42
18.73±4.62
348.61±24.89
8.78±5.06
24.33±4.75
423.43±26.52
7.84±5.02
17.68±4.64
376.45±27.96
7.04±5.51
13 .92 ±4 .4
353.49±26.86
6.38±4.61
14.67±4.31
340.44±25.49
BDL
15.48±4.24
34 8.0 3± 25 .8
6.34±4.49
12 .37 ±4 .8
364.82±25.68
BDL
8.56±4.94
423.43±26
8.39±4.87
24.52±4.73
274.87±25.58
30.42±7.90
218.64±8.02
423.43±26.52
BDL
BDL
212.6±24.68
Tab le 2: Com parison of activity concentrations of 2 3 8 U , 2 3 2 Th and 4 0 K in beach sediment samples of North east coast of Tamilnadu, India and
other studies in different beaches of the world.
Sl.no
Location
Mean activity concentration(Bq/ kg)
Reference
--------------------------------------------------238
232
40
U
Th
K
1
W orld
25
25
370
UNSC EAR2000
2
Ind ia
28.67
63.83
32 7.6
UNSC EAR2000
3
Beach sand Egypt
-177
815
Uosif et al (2008)
4
Beach sand Read sea coast Egypt
23 .1
7.2
338
Harb (2008)
5
Hu ngary
28.67
27.96
30 2.4
UNSC EAR2000
6
Ku wa it
36
6
227
Saad and Al-Azmi (2002)
7
Nig eria
16
24
35
Arogunjo et al (2004)
8
Ka lpak kam in T amiln adu Ind ia
112
14 55 .8
351
Kannan et al (2002)
9
Ulla l in K arna taka , India
374
158
158
Radhakrishna et al (1993)
10
No rth ea st coa st of T amiln adu , India
7.82
24.52
274.87
Present study
concluded that no harmful radiation effects are pose to the
public and tourists going to the beaches for recreation or
to the sailors and fisherm en inv olved in their activities in
the area as a results of the activity of beach sediments.
CONCLUSION
The mean activity concen trations of 2 3 8 U, 2 3 2 Th
and K in beach sediments and other calculated hazard
indices are lower than the world and Indian average
values. How ever, the activity concentration of 2 3 8 U, 2 3 2 Th
and 4 0 K values are higher in S-6 an d S-22. On the basis
of lower levels of natural radioactivity, beaches of the
north east coast of Tamilnadu in India can be considered
as a less natural back g round radiation area.
It is
40
ACKNOWLEDGEMENT
The authors are thankful to the Director,
IGCAR and Head, HASD, IGCAR, Kalpakkam,
Tamilnadu, for permission to use the facilities.
57
Res. J. Appl. Sci. Eng. Technol., 1(2): 54-58, 2009
Table 3: The Absorbed d ose rate, Annual effective dose rate and Hazard indices of all sites
Site number
Ab sorbe d do se rate
Annual effective dose rate |
(nGy h G 1)
(m Sv yG 1)
1
21.28
0.1
2
19.11
0.09
3
18.71
0.09
4
18.5
0.09
5
75.34
0.37
6
134.43
0.66
7
21.09
0.1
8
17.59
0.08
9
15.97
0.08
10
15.63
0.08
11
17.95
0.09
12
16.48
0.08
13
16.49
0.08
14
16.66
0.08
15
16.88
0.08
16
16.14
0.08
17
16
0.08
18
17.49
0.08
19
17.88
0.09
20
17.56
0.08
21
21.03
0.1
22
156.73
0.77
23
29.34
0.14
24
26.77
0.13
25
22.84
0.11
26
21.41
0.1
27
25.84
0.13
28
28.65
0.14
29
34.76
0.17
30
30
0.15
31
26.4
0.13
32
26
0.13
33
26.75
0.13
34
25.61
0.12
35
25.97
0.13
Average
30.15
0.15
Maximum
156.73
0.77
Minimum
15.63
0.08
Hazard indices
H ex
0.12
0.11
0.1
0.1
0.46
0.84
0.12
0.1
0.09
0.08
0.1
0.09
0.09
0.09
0.09
0.09
0.09
0.1
0.1
0.09
0.12
0.98
0.16
0.15
0.13
0.12
0.14
0.16
0.2
0.17
0.14
0.14
0.15
0.14
0.14
0.17
0.98
0.08
I(r
0.33
0.3
0.29
0.29
1.22
2.19
0.33
0.28
0.25
0.24
0.28
0.26
0.26
0.26
0.26
0.25
0.25
0.27
0.28
0.27
0.33
2.56
0.47
0.42
0.36
0.34
0.42
0.46
0.55
0.48
0.42
0.41
0.42
0.41
0.41
0.48
2.56
0.24
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