|Year : 2010 | Volume
| Issue : 3 | Page : 150-154
Radioactivity study in Nagapattinam coastal area (Nagapattinam, Velankanni and Karaikal) in Bay of Bengal
P Shahul Hameed1, P Raja2, G Satheeshkumar1
1 Environmental Research Centre, J.J. College of Engineering and Technology, Ammapettai, Tiruchirappalli, India
2 P.G and Research department of Zoology, Periyar E.V.R. College, Tiruchirappalli, India
|Date of Web Publication||22-Oct-2011|
P.G and Research department of Zoology, Periyar E.V.R. College, Tiruchirappalli
Source of Support: None, Conflict of Interest: None
A study on the distribution and bioaccumulation of radionuclides has been undertaken in the abiotic and biotic matrices of the Nagapattinam coast (Bay of Bengal). The measurement of ambient gamma radiation levels in the coastal regions showed a rapidly changing non-uniform radiation regime ranging from 6.56 to 24.59 μR/hr. During the survey irregular and discontinuous radiation profile could be observed even in a narrow stretch of coastal area. The gross alpha and beta activities in sediments were indicative of the relative abundance of naturally occurring alpha and beta radionuclides. The mean value of gross alpha activity in the coastal area was 6.0 Bq/kg and gross beta activity in the coastal area was 16.8 Bq/kg. Gross alpha activity was non-uniformly distributed among the stations while beta activity was almost uniformly distributed. Among the several species of fishes taken for the study, Sardinella sp., accumulated higher level of 210 Po in it's muscle (15.7 Bq/kg). The study on the distribution and bioaccumulation of alpha emitting radionuclides such as 210 Po in the Nagapattinam, Velankanni and Karaikal coastal ecosystem, showed that the activity from this radionuclide is well within the safe limits, since there are no anthropogenic nuclear inputs.
Keywords: Gamma radiation, gross alpha, gross beta activity and 210 Po in fish
|How to cite this article:|
Hameed P S, Raja P, Satheeshkumar G. Radioactivity study in Nagapattinam coastal area (Nagapattinam, Velankanni and Karaikal) in Bay of Bengal. Radiat Prot Environ 2010;33:150-4
|How to cite this URL:|
Hameed P S, Raja P, Satheeshkumar G. Radioactivity study in Nagapattinam coastal area (Nagapattinam, Velankanni and Karaikal) in Bay of Bengal. Radiat Prot Environ [serial online] 2010 [cited 2022 May 20];33:150-4. Available from: https://www.rpe.org.in/text.asp?2010/33/3/150/86294
| 1. Introduction|| |
Radiation may be defined as the spontaneous emission of high energy particles (or) electromagnetic radiation from the unstable atomic nuclei, until they become stable one. Most nuclei are unstable. A stable nucleus contains the correct proportion of neutron and protons. If a particular nucleus contains excess of neutron or proton, it becomes electrically imbalanced. The imbalanced nucleuses become radioactive and emit particles of alpha, beta or gamma rays (Shah, 1985). The environment normally has some amount of natural radioactivity resulting from cosmic rays and ionizing radiations from naturally occurring radioactive substances in soil, air, water and biota. 210 Po, belong to naturally occurring 238 U series having considerable half lives (138.4 days respectively) and are present in almost all environmental matrices. The main source of 210 Po entering the environment is the exhalation of 222 Rn, a daughter product of Ra-226 which continuously escapes from the surface of the earth. Radon-222 decays to 210 Pb, 210 Bi and 210 Po which attach themselves to atmospheric particulates and are transported back to the earth's surface. 238 U and 232 Th decay series isotopes have been used to address a range of problems in fluvial geomorphology, including provenance determination of coastal sediments (Roberta and Plater, 1999), resolution of sedimentation rate of fluvial sands (Murray et al., 1990), and resolution of fluvival sediment sources (Yeager and Santschi, 2003; Yeager, et al., 2006). The later three decay naturally to produce other important radioactive isotopes of elements; including radium, radon, Polonium and lead (Qureshi, 2002; Akram et al., 2006 and Ajayi, 2008). No scientific investigation was carried out on the distribution and accumulation of natural radionuclides in the Nagappattinam, Velankanni and Karaikal coastal area. Hence, the present investigation was attempted to determine the accumulation of 210 Po in the abiotic and biotic components of above coastal area.
| 2. Materials and Methods|| |
The present study area includes sea coast of Nagapattinam, Velanganni and Karaikal in Bay of Bengal between Northern Latitude 10.7906 degrees and 79.8428 degrees Eastern Longitude an area of 2715.83 square kilometers in it's fold [Figure 1].They are important centres of fishery activities in Tamil Nadu, Nagapattinam and Velanganni belong to Tamil Nadu while Karaikal is small coastal enclave Puducherry union territory. Large number of mechanized boats and country boats are put into fishing operation and fishes are exported to different parts of the country and aboard. Sediment samples and fishes were collected the sea coast of Nagapattinam, Velankanni and Karaikal coast. Sediment samples were collected directly from sea coast and nine fish's species of fishes were collecting from fishing vessels operating in the study area namely Nagapattinam, Velankanni and Karaikal (Scomberomorus guttatus, Alectis sp., Euthynus affinis, Stolephorus indicus, Sardinella sp., Nematalosa nasus, Nemipterus japonicus, Pinjalo sp. and Apolectus niger).
The ambient gamma radiation levels were measured with a calibrated SM141E ECIL Scintillometer (NaI (Ti) crystal with a reading range of 0.1 to 15555 counts per second). The measurement of gross alpha and gross beta activity, the coastal sediment samples collected from the sampling station and samples was dried in an oven at 105°-110°C for 24 h. 10 mg (for alpha) 100 mg (for beta) of the powdered dry sample was uniformly spread over a clean background counted aluminium planchette (3cm diameter) using a micro sieve and the radioactivity was measured in alpha and beta counter (Kannan, 1983; Ganapathy, 1984). Polonium-210 determinations were made by the standard technique of acid digestion, spontaneous deposition of Po-210 from an acid solution on to both side of a polished silver disc and counting of the 210 Po alpha activity on the disc (Flynn, 1968; Iyengar, 1983). The counting instruments used were an alpha counter with ZnS (Ag) detector with a background of 0.1-0.2 cpm and a counting efficiency of 25%.
| 3. Results and Discussion|| |
In the present study the terrestrial gamma radiation, gross alpha, gross beta activities in sediment and 210 Po activities in fish's samples of Nagapattinam, Velankanni and Karaikal coastal (Bay of Bengal) environment are given in [Table 1], [Table 2] and [Table 3]. In general, terrestrial gamma radiation level of Nagappattinam coast ranged from 6.3 to 6.8 μR/h; Karaikal coast from 20.2 to 29.3μR/h and Velankanni coast from 6.0 to 6.8 μR/hr. In the present study gamma radiation level rapidly changing a non-uniform distribution of radiation regime ranging from as low as 6.0μR/h to as much as 29.3μR/h. This value is low when compared to world range (28-120 μ R/h) and Gulf of Mannar coastal region (10-450μR/h). The mean value of gamma radiation levels in the Nagapattinam coast (6.3-6.8 μR/h), Karaikal coast (20.2-29.3 μR/h) and Velankanni coast (6.0-6.8 μ R/h is lower when compared to the mean value of coastal environment of Karnataka (74 μ R/h; Narayana et. al., 1995) and also reported for different regions of India (80.7 μR/h; Mishra and Sadasivan, 1971), Pichavaram mangroves (6 to 39 μ R/h; Raja and Shahul Hameed, 2007) Gulf of Mannar (range: 10-450 μ R/h; Ravikumar, 2001) this value higher as compared to the adjacent coast of Palk Strait (range: 5-25 μR/h; Shahul Hameed, 2002). The values for coastal sediment of Nagapattinam, Velankanni and Karaikal coastal are less than the world average reported to the normal background area and this clearly established that Nagapattinam, Velankanni and Karaikal coastal area register a minimum level of terrestrial gamma radiation. From the present study it is concluded that Nagapattinam ecosystem maintains a non-uniform distribution and a low level of gamma radiation in the entire stations.
|Table 1: Terrestrial gamma radiation levels at Nagappattinam, Velanganni and Karaikal coastal area|
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|Table 2: Gross alpha and gross beta activity in the coastal sediment samples|
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|Table 3: Comparison of 210Po activity in chosen fishes of nagappattinam velanganni and karaikal coastal environment|
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The gross alpha activity ranged from 4.0 to 8.0 Bq/kg with a mean value of 6.0 Bq/kg and gross beta activity was distinctly higher and narrowly fluctuating from 15.9 to 17.5 Bq/g with a mean value of 16.8 Bq/kg. In the Velankanni coastal area, higher level of gross alpha activity (8 Bq/kg) could be observed and lower level of (4.0 Bq/kg) at Nagappattinam coastal area. The gross beta activity was higher level at Nagappattinam coast (17.5 Bq/kg), and minimum level of (15.9 Bq/kg) Karaikal coast was recorded. Gross alpha activity was non-uniformly distributed among the stations, while beta activity was almost uniformly distributed. This value low when compared to gross alpha (11 mBq/g); gross beta (34 mBq/g) were recorded in the sediment samples of Mandapam coast (Palk Strait) reported by Sadiq Bukhari (2002) and gross alpha activity (12Bq/kg); gross beta activity (46 Bq/kg) in the sediment sample of Pichavaram mangrove ecosystem reported by Raja (2004). The higher activity observed in the sediment could possibly be due to higher concentrations of 40 K and thorium in sediments as suggested by Moore (1981).
The Gulf of Mannar coastal sediment registered gross alpha activity of 86 mBq/g and gross beta of 818 mBq/g as investigated by Somasumdaram (1998). The gross alpha and gross beta of sediment observed in the present study are much lower compared to adjacent coast Gulf of Mannar, Pichavaram mangrove ecosystem, Palk Strait and other marine environment. In the presence of alpha and beta activities in the coastal sediment is indicative of the occurrence of naturally occurring radionuclides and their relative abundance [Table 3]. The mean concentration of 210 Po in alpha emitting radionuclide in fish species collected from Nagapattinam, Velankanni and Karaikal coastal area ranged from 1.7 to 15.7 Bg/kg. These values are lower than those reported for the fish muscle adjacent coast, Gulf of Mannar by Masilamani (2001); Pichavaram Mangrove by Raja (2004) and Kalpakkam Coast by Iyengar (1983). In all the fishes analysed the highest 210 Po concentration was recorded in the muscle of detrivore bottom feeder Sardinella sp. (FAO, 1974). Among the several species of fishes taken for the study, the fish Sardinella sp., accumulated higher level of 210 Po in it's muscle (15.7 Bq/kg).
The higher concentration of 210 Po observed in this fish can be correlated to it's plankton feeding habit. As 210 Po has a high degree of association with organic moiety of fish which feeds on organic detritus and tend to accumulate higher level of 210 Po in their muscle. The variability in the accumulation of these radionuclides could also be based on bioavailability, feeding habits, age, sex and reproductive cycle of fish (Hameed, 2001). In the fish species analysed higher 210 Po content was found in the muscle of Sardinella sp (15.7), Apolectus niger (12.9 Bq/kg), Nemipterus japonicus (14.2 Bq/kg) and Stolephorus indicus (12.6 Bq/kg) as compared to other species [Figure 2]. The present study has generated a database on the distribution and bioaccumulation of natural radionuclides in the marine province of Nagapattinam, Velankanni and Karaikal for the first time in the marine environment. The results indicate the Nagapattinam, Velankanni and Karaikal coastal environment is relatively a low background radiation region. In this accumulation of these radionuclides by abiotic and biotic components of this region is at low level, compared to relatively high background radiation coasts such as Gulf of Mannar on the South and Kalpakkam coast on the North.
|Figure 2: Mean value of 210Po activity in chosen fishes of Nagappattinam, Velankanni and Karaikal coastal area|
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| 4. Acknowledgements|| |
Our sincere thanks are due to Dr. N. Anbusaravanan, Reader & Head, and Dr.George John, P. G. and Research Department of Zoology and Principal, Periyar E.V.R. College Trichirappalli, for the constant encouragement in this works. Dr. V. Kannan, Officer-in-charge, ESL, Indira Gandhi Centre for Atomic Research, Kalpakkam for technical support and Principal, J.J. College of Engineering and Technology, Ammapettai, Tiruchirappalli for institutional support.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]