Scholarly article on topic 'Estimation of Polonium-210 activity in marine and terrestrial samples and computation of ingestion dose to the public in and around Kanyakumari coast, India'

Estimation of Polonium-210 activity in marine and terrestrial samples and computation of ingestion dose to the public in and around Kanyakumari coast, India Academic research paper on "Chemical sciences"

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Abstract of research paper on Chemical sciences, author of scientific article — L. Macklin Rani, R.K. Jeevanram, V. Kannan, M. Govindaraju

Abstract The brown mussel Perna perna, an effective bioindicator species for monitoring radioactive pollution, was used to evaluate the concentration of 210Po in and around the coastal areas of Kanyakumari, a Monazite rich region. 210Po concentration in P. perna collected from ten different locations in this region exhibited values ranging between 78.09 ± 5.5 and 320.00 ± 18.1 Bq/kg (wet). Kalluvilai recorded the maximum concentration of 210Po (320.00 ± 18.1Bq/kg), and hence further studies involving the activity of 210Po in other marine organisms and terrestrial samples were carried out from this site. The annual intake of 210Po by the population residing in this location via dietary sources was estimated. Similarly, the total annual committed effective dose to the public was found to be 2.24mSv/year. The results obtained were compared to the values reported by earlier studies in India and also in other countries.

Academic research paper on topic "Estimation of Polonium-210 activity in marine and terrestrial samples and computation of ingestion dose to the public in and around Kanyakumari coast, India"

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Journal of Radiation Research and Applied

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Estimation of Polonium-210 activity in marine and terrestrial samples and computation of ingestion dose to the public in and around Kanyakumari coast, India

L. Macklin Rania'*, R.K. Jeevanram b, V. Kannanc, M. Govindaraju a

a Department of Environmental Biotechnology, Bharathidasan University, Tiruchirappalli, 620 024, Tamil Nadu, India

b Department of Medical Physics, Bharathidasan University, Tiruchirappalli, 620 024, Tamil Nadu, India c Institute of Ocean Management, Anna University, Chennai, 600 025, Tamil Nadu, India

ARTICLE INFO

ABSTRACT

Article history: Received 17 January 2014 Received in revised form 21 February 2014 Accepted 24 February 2014 Available online xxx

Keywords:

Perna perna Annual intake

Annual committed effective dose

The brown mussel Perna perna, an effective bioindicator species for monitoring radioactive pollution, was used to evaluate the concentration of 210Po in and around the coastal areas of Kanyakumari, a Monazite rich region. 210Po concentration in P. perna collected from ten different locations in this region exhibited values ranging between 78.09 ± 5.5 and 320.00 ± 18.1 Bq/kg (wet). Kalluvilai recorded the maximum concentration of 210Po (320.00 ± 18.1 Bq/kg), and hence further studies involving the activity of 210Po in other marine organisms and terrestrial samples were carried out from this site. The annual intake of 210Po by the population residing in this location via dietary sources was estimated. Similarly, the total annual committed effective dose to the public was found to be 2.24 mSv/year. The results obtained were compared to the values reported by earlier studies in India and also in other countries.

Copyright © 2014, The Egyptian Society of Radiation Sciences and Applications. Production

and hosting by Elsevier B.V. All rights reserved.

Introduction

Polonium-210 (210Po), an a-emitting naturally occurring radionuclide (Bustamante, Germain, Leclerc, & Miramand, 2002;

Cherry & Shannon, 1974), exists in the environment as a result of Uranium-238 (238U) decay chain. It is ubiquitously distributed in rocks, soils, makingup earth's crust, in the atmosphere and in natural waters (Matthews, Kim, & Martin, 2007). 210Po enters in marine organisms via adsorption, absorption and ingestion

* Corresponding author. Tel.: +91 431 2407088x632.

E-mail address: macklinranil@gmail.com (L. Macklin Rani). Peer review under responsibility of The Egyptian Society of Radiation Sciences and Applications

http://dx.doi.org/10.1016/j.jrras.2014.02.006

1687-8507/Copyright © 2014, The Egyptian Society of Radiation Sciences and Applications. Production and hosting by Elsevier B.V. All rights reserved.

(Alam et al., 1999). The concentration of 210Po in the edible portions of marine organisms may be many folds higher than that in the seawater because of biological reconcentration processes (Saiyad Musthafa & Krishnamoorthy, 2012). This is specially so with filter feeders mussels, which ingest detritus material with a high degree of radionuclide association. It has been recognized internationally, that filter feeding bivalve molluscs act as a first order biological indicators of radioactive pollution (Alam et al., 1999; Phillips, 1980).

There are a few regions in the world, which are known for high background radiation areas (HBRAs), are due to the local geological controls and geochemical effects and cause enhanced levels of terrestrial radiation (UNSCEAR, 1993; 2000). Monazite sands have been found to be the source of such high background radiation levels in certain parts of Brazil, China, Egypt and India (Ghiassi-nejad, Mortazavi, Cameron, Niroomand-rad, & Karam, 2002; Paschoa, 2000; UNSCEAR, 2000).

In India, there are quite a few monazite sand bearing placer deposits causing natural HBRAs along its long coastline (UNSCEAR, 2000). Coastal parts of Tamil Nadu, Kerala and the south western coast of India are known for HBRAs (Mishra, 1993; Mohanty, Sengupta, Das, Vijayan, & Saha, 2004; Sunta, 1993). Though seafood is consumed widely by the people in coastal area of India, the pattern of consumption varies in different regions of the country and also even within the state of Tamil Nadu. Dose estimation studies have been carried out in HBRAs universally. However, our knowledge on the radiation dose received by the fishermen population mainly due to their food habits is quite limited. It is therefore of interest to study the intake of 210Po through specific dietary habit of this

region, as the sand of Kanyakumari coast is richly composed of monazite ore, a rich source of uranium. An interesting fact is that the mussel, a bioindicator species, is a prominent diet of the local people residing in Kanyakumari coast, but not in other parts of Tamil Nadu. This maybe due to the non-availability of mussel in other parts of Tamil Nadu. Among the ten different locations studied for 210Po concentration in this region, Kallu-vilai exhibited the maximum concentration in mussel (Perna perna) and hence the concentration in other marine organisms such as fish, prawn and crab, terrestrial and sediment samples in this location was studied and annual committed effective dose amongst the local people was also estimated.

2. Study area

The study area is located in the southern part of peninsular India (8° 09'48"N77°41'22"Eto 8°13'01"N77°11'17" E), surrounded by the Bay of Bengal in the East, the Indian Ocean in the South and the Arabian Sea in the West. The study area includes Kanyakumari, one of the tourist destinations of India (Fig. 1).

3. Materials and methods

3.1. Collection and preparation of samples

3.1.1. Seafood samples

Fresh seafood samples were collected from 10 different locations along the Kanyakumari coast (Table 1). All the collected

Fig. 1 - Location map of the study area.

Table. 1 - Characteristics and Geographic coordinates of the sampling sites.

Sampling sites Characteristics of Latitude Longitude

sampling site

Kudankulam Fishing village, 8°09'48''N 77°41'22'' E

Near Atomic

Power station

Kalluvilai Fishing village 8°06'36''N 77°33'25''E

Chinnamuttam Fishing village, very close to fishing Harbour 8°05'43'' N 77°33'36'' E

Kanyakumari Fishing town, fishing Harbour, Tourist spot 8°04'41'' N 77°33'03'' E

Kovalam Fishing village 8°04'42'' N 77°31'54'' E

Keelamanakudi Fishing village 8°05'16'' N 77°29'19'' E

Kadiyapattanam Fishing village 8° 08 '06 ' ' N 77°18'17'' E

Manavalakurichi Near Indian Rare Earths Limited, Fishing village 8°08'35'' N 77°18'09'' E

Collachel Fishing Harbour 8°10'22'' N 77°15'19'' E

Inayam Fishing village 8°13'01'' N 77°11'17''E

seafood samples were placed in an icebox, then transported to the laboratory, washed with tap water and freed of adhering soil particles. The whole soft tissues were segregated from the shells of the mussels and blotted dry. The wet weights of the samples were recorded and used for further analysis.

3.1.2. Sediment sample

Sediment samples were collected from the seashore of the samplinglocations. Dry sediment samples were sieved using a stainless steel mesh with the size of 600 mm in order to obtain the sediment fine grain size fraction for radionuclide analyses.

3.1.3. Terrestrial samples

The terrestrial samples (plant originated edibles) were collected within a radius of 1 km from the seashore and transported to the laboratory, washed with tap water. The wet weights of the samples were recorded and then stored until processed further.

3.1.4. Number of samples

About 60 mussel samples were collected from ten different sites (6 samples from each site). For further studies, 24 samples of marine origin (6 samples each of sediment, fish, prawn and crab) and 72 samples of terrestrial origin (6 samples each

Table. 3 - Mean concentration of 210Po in sediment and

seafood samples of Kalluvilai.

Sample Mean 210Po Activity (Bq/kg)

Surface sediment 2.30 ± 0.3

Fish ( Lethrinus lentjan) 1.20 ± 0.3

Prawn (Fenneropenaeus indicus) 53.97 ± 3.7

Crab (Portinus sanguinolentus) 40.10 ± 4.4

of 12 different food item) were collected from the site, Kallu-vilai for the analysis. Various species of seafood and terrestrial samples were collected from November, 2011 to January, 2013 based on their availability.

3.2. Analysis of 210Po

For the analysis of 210Po, 100 g of wet sample (seafood, plant origins and sediment) was oven dried at 100-110 °C, repeatedly digested with concentrated HNO3 and H2O2 until its complete digestion. Then concentrated HCl was added with heating to transform it to a chloride medium. The digested sample was taken up with 0.5 N HCl, filtered through Whatman-40 filter paper. This filtrate was then subjected to electrochemical displacement on a silver planchette of 2.5 cm diameter using ascorbic acid (Flynn, 1968; Kannan, Iyengar, & Ramesh, 2001; Yamamoto et al., 1994) with constant stirring for 6 h. Ascorbic acid was added to reduce ferric ions to ferrous ions, thereby eliminating its interference in electrochemical deposition of 210Po.

Then 210Po was spontaneously deposited onto the rotating silver planchette. For each sample, after the first plating was over, a fresh silver planchette was suspended in the same sample and plating was repeated second time for about 6 h. After its completion, plating for a third time was continued in the same sample. It was found that an average of 95% of 210Po was plated during the first plating itself. The accuracy of radi-oanalytical results is further ensured by using this procedure on double distilled water samples spiked with an addition of standardized amount of tracer 209Po activity. Since the double distilled water samples showed only background counts, the contribution of sample alpha activity will be negligible.

3.3. Measurement of210Po concentration

After the spontaneous deposition of 210Po on the silver planchette, a-activity of 210Po was measured on both sides of silver planchette, using an alpha counter (Counting system CS-201) having ZnS (Ag) detector (counting efficiency of 27.7% and background of 0.1 cpm). After the application of required decay corrections, 210Po concentration of samples was expressed in Bq/kg of wet sample.

3.4. Dietary survey

Dietary habit of the inhabitants residing in this coastal area was collected from the response of two hundred respondents to a questionnaire based survey. The contribution of different dietary sources obtained by this method was used to assess the intake of 210Po from habitual food intake. This data was

Table. 2 - Mean concentration of 210Po in mussel sample.

Sampling sites Mean 210Po activity (Bq/kg)

Kudankulam 78.09 ± 5.5

Kalluvilai 320.00 ± 18.1

Chinnamuttam 231.51 ± 12.4

Kanyakumari 210.00 ± 7.8

Kovalam 300.15 ± 15.3

Keelamanakudi 169.14 ± 8.2

Kadiyapattanam 111.50 ± 6.5

Manavalakurichi 200.72 ± 11.8

Collachel 180.40 ± 9.2

Inayam 120.15 ± 4.4

Table. 4 - Mean concentration of Po in edibles, and total annual committed effective dose for inhabitants of Kalluvilai.

Edibles Intake (kg/year) 210Po Activity (Bq/kg) Annual committed effective dose (mSv/year)

Banana 40.00 0.04 ± 0.01 1.92 x 10"3

Guava 2.70 0.05 ± 0.02 0.16 x 10"3

Curry leaves 7.30 0.10 ± 0.02 0.87 x 10"3

Bitter gourd 1.00 0.07 ± 0.02 0.08 x 10"3

Bottle gourd 2.25 0.05 ± 0.02 0.13 x 10"3

Tomato 18.25 0.06 ± 0.02 1.31 x 10"3

Papaya 11.25 0.04 ± 0.01 0.54 x 10"3

Cassava 27.00 0.07 ± 0.03 2.26 x 10"3

Green Chilli 1.50 0.18 ± 0.06 0.32 x 10"3

Drumstick 7.50 0.04 ± 0.02 0.36 x 10"3

Rice 182.50 0.21 ± 0.04 45.99 x 10"3

Coconut 18.25 0.04 ± 0.01 0.87 x 10"3

Fish (Lethrinus lentjan) 109.55 1.20 ± 0.10 157.75 x 10"3

Mussel (Perna perna) 4.50 320.00 ± 18.1 1728.00 x 10"3

Prawn (Fenneropenaeus indicus) 2.70 53.97 ± 3.7 174.86 x 10"3

Crab (Portinus sanguinolentus) 2.70 40.10 ± 4.4 129.92 x 10"3

Total annual committed effective dose 2245.34 x 10" -3

also used to assess the role of marine samples like mussel, fish, prawn, crab and other terrestrial food items in contributing towards the annual committed effective dose.

3.5. Dose calculations

The annual committed effective dose was estimated based on the dose coefficients as reported in the ICRP publication 72 (International Commission on Radiological Protection, 1996). The annual effective dose calculation for the intake of radio-nuclides through ingestion and inhalation for adults has been calculated by the following method.

Annual effective dose(Sv/year) = A x B x C

where, A = Food consumption (kg/year), B = 210Po concentration (Bq/kg),C = Annual committed effective dose conversion factor (1.2 x 10-6 Sv/Bq) (Data from ICRP 72)

4. Results and discussion

4.1. 210Po concentration study

Among the seafood, fishes and mussels are largely consumed by the local people in daily diet. The concentration of 210Po in

the bioindicator species, brown mussel, P. perna collected from the ten sampling sites are given in Table 2. The concentration of 210Po varied between 78.09 ± 5.5 (Kudankulam) and 320.00 ± 18.1 Bq/kg (Kalluvilai). It was observed that the locations of Kanyakumari, Kalluvilai, Chinnamuttam and Kovalam exhibited a higher 210Po concentration. This might be due to the fact that these regions are prominently located close to the end point of Western Ghats and also in the rain water runoff direction. The highest concentration of 210Po obtained in the present study (320.00 ± 18.1 Bq/kg) is found to be lower than that of the values recorded in Brazil for P. perna (1995 ± 363 Bq/Kg Dry) (Gouvea, Santos, & Dutra, 1992). The activity concentration and accumulation potential of 210Po in P. perna is due to the filter feeding pattern of bivalves. The 210Po concentration in P. perna in the present study (320.00 ± 18.1 Bq/kg) in Kalluvilai is three fold higher than that obtained with Perna viridis 113.32 ± 7.10 as reported by Saiyad Musthafa and Krishnamoorthy (2012) in Ennore Creek, South India (Table 3). Since, brown mussel P. perna is the most abundant and commonly consumed variety in this region, this study is primarily focused on the concentration of 210Po in the above said species.

The 210Po concentration in the carnivorous fish species (Lethrinus lentjan) was studied as it is the commonly consumed fish variety of this region. The concentration of 210Po observed

Table. 5 - 210Po concentration in mussel samples from different regions of the world.

Species 210Po Activity (Bq/kg) Location Reference

Perna viridis 45.69 ± 1.17 to 96.44 ± 2.19 (wet wt) Malaysia Lubna, Nikazlin, Afiza Suriani,

and Mohamed (2011)

Perna perna 1995 ± 363 (dry wt) Brazil Gouvea et al. (1992)

M. galloprovincialis 428-459 (dry wt) Monaco McDonald, Fowler, Heyraud, and

Baxter (1986)

M. edulis 149 ± 82 (dry wt) Denmark Dahlgaard (1996)

M. trossulus 272 ± 28 (dry wt) Baltic Sea Stepnowski and Skwarzec (2000)

Perna indica 100.3 ± 2.8 (wet wt) Chinnamuttam and Feroz Khan and Godwin Wesley (2011)

Kuthankuzhi, South India

Perna viridis 113.32 ± 7.10 (wet wt) Ennore Creek, South India Saiyad Musthafa and Krishnamoorthy (2012)

Perna perna 78.09 ± 5.5 to 320.00 ± 18.1 (wet wt) Kanyakumari Coast, South India Present study

Fig. 2 - Map showing Annual committed effective dose due to the consumption of Perna perna in sampling sites.

in L. lentjan is 1.20 ± 0.3 Bq/kg (Table 4). This value is marginally lower than the previously reported value (3.42 ± 0.9 Bq/kg) from the nearby sites (Feroz Khan & Godwin Wesley, 2011). The concentration of 210Po for prawn (Fenner-openaeus indicus) obtained in our study (53.97 ± 3.7 Bq/kg), is lower than the value reported by Saiyad Musthafa and Krishnamoorthy (2012) for Ennore Creek (61.3 ± 4.3 Bq/kg). The value of 210Po concentration in the crab, Portinus sangui-nolentus (40.1 ± 4.4 Bq/kg) is comparable to those reported by Feroz Khan & Godwin Wesley, 2011 (42.3 ± 1.1 Bq/kg). The difference in the level of 210Po accumulation in different groups of seafood could be due to the differences in metabolism and feeding pattern (Alam & Mohamed, 2011).

The 210Po concentration in the surface sediment was 2.30 ± 0.3 Bq/kg. This value is comparable to those reported by Suriyanarayanan et al. (2008) for the coastal area of Naga-pattinam (1.9 ± 0.3 Bq/Kg) which is about 300 km away from the present study area. To compare 210Po in seafood samples with that of dietary items in the terrestrial environment, some locally grown dietary items were also evaluated for their 210Po concentration. Table 5 shows the concentration of 210Po observed in terrestrial edible items ranged from 0.04 ± 0.01 to 0.21 ± 0.04 Bq/kg, which is comparable with the results obtained for vegetable edibles in Kalpakkam (0.013 ± 0.005-0.485 ± 0.12 Bq/kg) (Kannan et al., 2001) as well as in Meghalaya, India (0.020 ± 0.002-0.056 ± 0.003 Bq/kg) (Deswyn Marbaniang, Raj Poddar, Nongkynrih, & Darlando Khathing, 2010).

4.2. Dietary survey and dose calculations

The dietary survey of the local population revealed the consumption of various edibles which in turn helped to assess the annual committed effective dose. Based on the dietary survey, it was observed that the seafood especially fish, mussel, prawn and crab comprise a major portion in daily dietary intake and the edibles of plant origin play a minor

Fig. 3 - Contribution of Annual committed effective dose from different dietary sources.

Table. 6 - Committed effective dose due to Po from different locations of the world.

Location Dose (mSv/ year) Reference

Kalpakkam, 0.74 ± 0.153 Kannan et al. (2001)

Kudankulam 0.01-0.51 Feroz Khan and Godwin Wesley

coast (2011)

Meghalaya, 0.34 Deswyn Marbaniang et al. (2010)

Sudan, Red Sea 0.003-0.004 Hassona et al. (2008)

France 0.04-0.01 Connan et al. (2007)

Baltic Sea 0.70 Nielsen et al. (1999)

Kanyakumari 2.24 Present study

contribution in the diet of the local people. Among the sea food samples, although the mussel species would be available only for a short period (3-4 months in a year), the per capita consumption of mussel by each adult has been found to be about 4.5 kg/year (Table . 4). The total annual committed effective dose was estimated to be 2.24 mSv/year, whereas, the consumption of only the mussels by an adult resulted in an annual committed effective dose varying between the average range of 0.42-1.72 mSv/year (Fig. 2). Since coconut, banana and cassava are the commonly available terrestrial plant edibles of this region, these food items play a major role in daily diet among plant edibles. However, the annual committed effective dose through the consumption of terrestrial food items by an adult accounted for only 0.05 mSv/ year (Kalluvilai). The study has shown clearly that the contribution of 210Po is primarily due to the intake of mussel (76.98%), and the other seafood (20.58%) (Fig. 3). The average annual committed effective dose obtained from the present study, excluding the mussel species was only 0.51 mSv/year, which is comparable to the value obtained from Baltic sea (0.70 mSv/year) (Nielsen et al., 1999). However the annual committed effective doses obtained from countries like Sudan (0.003-0.004 mSv/year) (Hassona, Sam, Osman, Sirelkhatim, & Larosa, 2008) and France (0.04-0.12 mSv/year) (Connan, Germain, Solier, & Gouret, 2007) are much lower (Table. 6). The lower annual effective dose reported in Sudan may be due to the fact that the study has included the consumption of only the sea fish, in which the 210Po concentration is less compared to other sea food items such as prawn, crab and mussel. Similarly the lower 210Po concentration in mussel, oyster and fish in France might have contributed to the lower annual effective dose. In the present study, the higher concentration of 210Po in bioindicator bivalve mussel species and higher intake of bivalve mussel (4.5 kg/year) in diet of the local people are the major factors for its higher contribution in annual committed effective dose when compared to other sea food such as fish, prawn and crab. The studies on dose calculations are essential not only in evaluating the dose to humans by the consumption of seafood but also in providing additional knowledge about the behaviour of radionuclides (Mat Catal, Ugur, Ozden, & Filizok, 2012). Thus the present study clearly reveals the role of 210Po in annual committed effective dose through the high human consumption of bivalve mussel.

5. Conclusion

In the present study, 210Po concentration observed in bio-indicator mussel samples from Kalluvilai area (320.00 ± 18.1 Bq/kg) is comparatively higher than other sites. The activity of 210Po was non-uniformly distributed in selected foodstuffs. The concentration of 210Po in food is in the order of mollusk > crustacean > fish > terrestrial plant edibles. The annual committed effective dose amongst fishermen population residing in Kanyakumari coastal area was calculated with concern to their unique habitual intake of diets which is different from other population of the same area (2.24 mSv/ year). The annual committed effective dose estimated in Kanyakumari coast is comparable to other reported values apart from the intake of mussel (0.51 mSv/year). The consumption of bivalve mussel is much higher in this region compared to other parts of the country and hence the slightly higher annual committed effective dose obtained in the present study is mainly due to the intake of bivalve mussel by the local people. However, the annual committed effective dose estimated in the present study is lower than the values reported for the public residing in areas with high natural background radiation like Brazil (annual effective dose > 7 mSv/year) and China (6.4 mSv/year) (Jolyon Hendry et al., 2009). No radiation induced effect has been reported in people residing in areas with slightly elevated background radiation and hence it may be concluded that the annual committed effective dose calculated for this region might not cause any health hazards to the general public.

Acknowledgement

The authors would like to express their thanks to the University Grants Commission, New Delhi for providing financial assistance through major research project and Dr. S. Dha-nuskodi, Professor and Head, Department of Physics, Bhar-athidasan University, Tiruchirappalli for providing access to alpha-counter instrumentation facility.

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