DISTRIBUTION AND BIOACCUMULATION OF 210Po AND 210Pb IN ABIOTIC AND BIOTIC COMPONENTS OF THE BAY OF BENGAL

DISTRIBUTION AND BIOACCUMULATION OF 210Po AND 210Pb IN ABIOTIC AND BIOTIC COMPONENTS OF THE BAY... Abstract Marine environment is enriched source of heavy minerals associated with radionuclides which are largely responsible for human exposure to radiation. Bay of Bengal is one among the important marine ecosystems in the world because of its high biodiversity. The aim of this work was to generate a comprehensive data on distribution and bioaccumulation of 210Po and 210Pb in marine environment of the Bay of Bengal. For this water and sand samples (10 stations), shellfishes (21 species) and fishes (43 species) were collected and the concentrations of 210Po and 210Pb were measured by radiochemical separation followed by alpha counting method using ZnS(Ag) detector. 210Pb concentration in the marine water (mean: 7.6 ± 3.31 mBq l−1) is always higher than 210Po (mean: 4.1 ± 1.97 mBq l−1). The mean 210Po and 210Pb concentration in sand was 5.2 ± 1.87 and 3.1 ± 1.20 Bq kg−1, respectively; indicating that 210Po concentrations in the sand sample is always higher than that of 210Pb. The concentration of both 210Po and 210Pb depends on grain size of the sand. Surface samples of depth 0–10 cm recorded maximum 210Po (6.37 Bq kg−1) and 210Pb (4.07 Bq kg−1) concentration. The concentrations of 210Po and 210Pb in biota are following decreasing order: Oyster > Clam > Squid > Crab > Prawn > Fish. The committed effective dose rate calculated for shellfish species maintained a higher range of 81.0–281.2 μSv y−1. However, dose transfer rate from fish species fluctuated from 14.4 to 165.6 μSv y−1and this indicated that fish is radiologically safe as compared to shellfish. INTRODUCTION Naturally occurring, radioactive materials present in the marine environment are responsible for delivering the majority of radiation dose to marine fauna. The short-lived decay products of 226Ra (viz., 222Rn, 218Po, 214Pb, 214Bi, 214Po, 210Pb, 210Bi and 210Po) are a source of radiation dose to marine fauna, especially the alpha-emitters 218Po, 214Po and 210Po. Radium-226 in the crust of the earth decays into 222Rn gas that diffuses into seawater and is the origin of the short-lived decay products in the water. Of these, 210Pb has the longest half-life (22.2 years) and is the parent of 210Po, an alpha-emitting isotope with a half-life of only 138.4 days(1). Polonium-210 is responsible for a large fraction of the natural radiation dose delivered to many of the living species in seawater(2–5). Carvalho and Fowler(6) stated that most of the marine species are highly enriched with 210Po and 210Pb and they contribute ~8% of the total internal dose received by man. They also studied the kinetics of 210Po and 210Pb accumulation from water to seafood. Yamamoto et al.(7) observed that the 210Po and 210Pb concentrations are relatively low in meat, medium in milk, vegetables and cereals, and high in most of the marine organisms. The fact of 210Pb that enters the sea surface of North Pacific was first examined by Rama et al.(8). The concentrations of 210Po and 210Pb have been studied extensively in the biosphere and more particularly in the human environment(9–11). Indian peninsula is the second largest peninsula in the world which covers 20 72 000.85 km2 and it is the sixth largest producer of marine fishes(12). In India the annual per capita consumption of fish is ~5–6 kg, further fish is the staple food for any coastal environment so there is a distinct need for investigation of the accumulation of 210Po and 210Pb by aquatic organisms that constitute human food sources. Considering the importance of radiological status of the Bay of Bengal, the present investigation of measuring the concentration of 210Po and 210Pb in water, sediment and marine food organisms such as shellfishes like prawn, crab and molluscs and several species of fin fishes were undertaken. This data would be helpful in the future in case of any changes in the environment like Tsunami. STUDY AREA Bay of Bengal is the largest bay in the world. It forms the northeastern part of the Indian Ocean. It is roughly triangular in shape and it occupies an area of 2 172 000 km2. It has several estuaries, coral reefs and mangroves hence it is full of biological diversity. It is one of the largest marine ecosystems in the world. So it is important to measure the concentration of radioactive isotopes in biotic and abiotic components of the marine ecosystem. Hence the present study was undertaken in a 159 km coastal stretch of the Bay of Bengal (Pondycherry to Velanganni). A total of 10 different sampling stations were selected for 210Po and 210Pb measurements. The distance between each station is ~ 10–15 km (Figure 1). Figure 1. View largeDownload slide Map showing the study area. Figure 1. View largeDownload slide Map showing the study area. MATERIALS AND METHODS Methods such as radiochemical separation (co-precipitation and acid leaching), extraction chromatography, ion exchange separation (anion exchange resin) and solvent extraction have been employed for determination of 210Po and 210Pb in environmental matrices. For the present study co-precipitation (for water samples) and wet acid digestion (for biota and sand samples) followed by alpha counting has been adopted for 210Po and 210Pb measurements. Because processing of sample using wet acid digestion and co-precipitation are more conventional and cost effective than the other methods. Analysis of 210Po in water samples Seawater (~100 l) was filtered through a Whatman 40 filter paper and acidified with concentrated HCl to pH 1. Iron (ferric chloride) carrier (500 mg) was added to the filtered and acidified sample and the 210Po in the filtered water was collected on ferric hydroxide precipitate by slow addition of concentrated ammonia solution with rapid stirring until pH reached 9. Two repeat precipitations were carried out to completely carry 210Po by Fe(OH)3. The complete precipitate carrying 210Po was dissolved in 6 N HCl. A silver planchette (0.8 mm thickness and 2.5 cm diameter) of pre-determined background was suspended in the sample solution by means of a nylon thread at the end of a glass rod, connected to a stirrer. The solution is stirred for a period of 6 h. Spontaneous deposition of 210Po on both sides of the silver planchette took place under these conditions. At the end of the plating period, the planchette was taken out, rinsed with alcohol, dried under an infrared lamp and counted for activity on both sides in an alpha counter (ZnS(Ag): 28% efficiency with background count rate of 0.1 cpm). Analysis of sand Beach sand sample (~10 g) was ground to pass through 100 μm meshes and oven dried at 110°C for 24 h to remove moisture. The sample was then heated three times with con.HNO3 evaporating to near dryness each time. The residue was evaporated with con.HCl repeatedly to convert to chloride medium and taken in 0.5 N HCl for auto-deposition of 210Po on to a silver (Ag) planchette as stated above. 210Po and 210Pb activities in coastal sand at different depth In order to understand the depth-wise distribution of 210Po and 210Pb in the beach sand, core sampling of the sand was undertaken in the beach to a depth of 30 cm in six sampling stations (S1–S6). The core was sliced at various depths namely 5, 10, 15, 20, 25 and 30 cm and the activities of 210Po and 210Pb were measured in each slice. Distribution of 210Po and 210Pb in different grain sizes of coastal sand The beach sand sample was successively sifted in 105, 300 and 500 μm sieves and various fractions of sand grains were obtained (105, 300 and 500 μm) and activity of 210Po and 210Pb were measured in each fraction. Analysis of biological materials Owing to highly volatile nature of 210Po in dry ash conditions, the biological samples (~50 g) were wet processed repeatedly with con.HNO3 and H2O2 (1:1) oxidizing mixture added in small increments (5–10 ml at a time) till a white residue obtained. Then the residue was made up to 0.5 N HCl and placed on a magnetic stirrer with thermostat control at a temperature of 90–95°C. Ascorbic acid (100 mg) was added to reduce ferric ions to ferrous, thus eliminating interference in electrochemical deposition of 210Po. The 210Po activity was measured by spontaneous deposition followed by alpha counting. Determination of 210Pb The 210Pb concentrations in water, sediment and biological samples were determined by incubation method(13). Even though 210Pb is a beta emitter it can be able to measured by alpha counting. In this method the final solutions used for spontaneous deposition of 210Po (210Po is completely removed) in the above mentioned samples were incubated for a period of 138 days (equivalent to half-life period of 210Po). After the incubation period, 210Po formed from the parent 210Pb was subjected to spontaneous deposition on a silver planchette and counted for alpha radiation, i.e. whatever 210Po present in solution is proportional to 210Pb only; from the 210Po concentration 210Pb was deduced. RESULTS AND DISCUSSIONS 210Po and 210Pb distribution in coastal water Station-wise data on concentrations of 210Po, 210Pb and their activity ratios (210Po/210Pb) in the coastal water of Bay of Bengal measured are presented in Table 1. The levels of 210Po ranged in water from 1.4 to 7.4 mBq l−1 with a mean value of 4.1 ± 1.97 mBq l−1 and that of 210Pb ranged from 3.1 to 13.7 mBq l−1 with a mean value of 7.6 ± 3.31 mBq l−1. It is evident from results that 210Pb concentration in the coastal water is always higher than 210Po for a given station (Figure 2). The activity ratios of 210Po/210Pb lie within the narrow range from 0.32 to 0.81 (mean: 0.52). Among the 10 sampling stations analyzed a minimum activity levels of 210Po (1.4 ± 0.32 mBq l−1) and 210Pb (3.1 ± 0.55 mBq l−1) were recorded in Pitchavaram Mangroves (S3) and a maximum level of 210Po (7.4 ± 0.55 mBq l−1) was recorded in Nagappattinam (S9) and maximum level of 210Pb (13.7 ± 0.96 mBq l−1) in Karaikal coast (S7). In general, a higher level of 210Po and 210Pb were recorded in southern stations (S7–S10) as compared to the northern stations (S1–S6). The concentration of 210Po in Nagappattinam coastal water was five times higher than that of Pitchavaram Mangroves. The average concentration of 210Po in Bay of Bengal is lower when compare to adjacent coast, Gulf of Mannar (15 ± 9.5 mBq l−1) by Masilamani(14) and higher when compared to the mean value of 210Po (1.5 mBq l−1) in Palk Strait by Bukhari et al.(15), Ennore Creek (2.7 mBq l−1) by Musthafa and Krishnamoorthy(16) and Kalpakkam coast value (1.9 mBq l−1) by Iyengar et al.(17). 210Po concentrations in coastal water was studied by several workers in different region of the world and these values ranged from 0.29 to 2.4 mBq l−1(2) for South African waters (0.30–1.5 mBq l−1) by Shannon et al.(18), for North sea (0.37 mBq l−1) by Spencer et al.(19), for Duch coast (1.0 mBq l−1) by Koster et al.(20) for Great Yarmouth (4.0 mBq l−1) by Mc Donald et al.(21) and for USSR (9.2 mBq l−1) by Parfenov(3) which are lower than the present value. Table 1. Station-wise mean 210 Po and 210Pb activities in coastal water, sand and Kd factor. Name of the station Activity (mBq l−1) 210Po/210Pb ratio Activity (Bq kg−1) 210Po/210Pb ratio Kd factor 210Po 210Pb 210Po 210Pb 210Po 210Pb Pondycherry (S1) 3.7 ± 0.17 8.3 ± 0.88 0.44 6.1 ± 0.37 4.0 ± 0.37 1.52 1.6 × 103 4.8 × 102 Devanampattinam (S2) 2.8 ± 0.24 4.2 ± 0.60 0.66 5.7 ± 0.79 2.6 ± 0.58 2.19 2.0 × 103 6.2 × 102 Pitchavaram Mangroves (S3) 1.4 ± 0.32 3.1 ± 0.55 0.45 2.5 ± 0.63 1.3 ± 0.27 1.92 1.8 × 103 42.x 102 Tirumullaivasal (S4) 3.0 ± 0.48 7.1 ± 0.73 0.41 4.8 ± 0.59 2.9 ± 0.43 1.65 1.6 × 103 4.1 × 102 Poompukar (S5) 2.9 ± 0.41 4.5 ± 0.66 0.64 8.0 ± 0.51 4.3 ± 0.60 1.74 2.6 × 103 1.7 × 103 Tharangambadi (S6) 2.0 ± 0.43 6.0 ± 0.57 0.32 7.5 ± 0.88 4.1 ± 0.41 1.95 4.0 × 103 1.3 × 103 Karaikal (S7) 6.5 ± 0.45 13.7 ± 0.96 0.47 6.3 ± 0.58 4.5 ± 0.52 1.40 1.0 × 103 4.6 × 102 Nagore (S8) 5.0 ± 0.43 8.7 ± 0.58 0.57 5.2 ± 0.42 3.9 ± 0.57 1.33 1.0 × 103 4.5 × 102 Nagappattinam (S9) 7.4 ± 0.55 9.1 ± 0.70 0.81 3.7 ± 0.60 2.1 ± 0.30 1.76 5.0 102 2.4 × 102 Velanganni (S10) 6.0 ± 0.53 12.0 ± 0.93 0.49 2.6 ± 0.57 1.6 ± 0.32 1.62 4.3 × 102 1.3 × 102 Over all range 1.4–7.4 3.1–13.7 0.32–0.81 2.5–8.0 1.3–4.5 1.33–2.19 4.3 × 102–4.0 × 103 1.3 × 102–1.7 × 103 Over all mean ± SD 4.1 ± 1.97 7.6 ± 3.31 0.52 ± 0.14 5.2 ± 1.87 3.1 ± 1.20 1.70 ± 0.26 1.7 × 103 6.2 × 102 Name of the station Activity (mBq l−1) 210Po/210Pb ratio Activity (Bq kg−1) 210Po/210Pb ratio Kd factor 210Po 210Pb 210Po 210Pb 210Po 210Pb Pondycherry (S1) 3.7 ± 0.17 8.3 ± 0.88 0.44 6.1 ± 0.37 4.0 ± 0.37 1.52 1.6 × 103 4.8 × 102 Devanampattinam (S2) 2.8 ± 0.24 4.2 ± 0.60 0.66 5.7 ± 0.79 2.6 ± 0.58 2.19 2.0 × 103 6.2 × 102 Pitchavaram Mangroves (S3) 1.4 ± 0.32 3.1 ± 0.55 0.45 2.5 ± 0.63 1.3 ± 0.27 1.92 1.8 × 103 42.x 102 Tirumullaivasal (S4) 3.0 ± 0.48 7.1 ± 0.73 0.41 4.8 ± 0.59 2.9 ± 0.43 1.65 1.6 × 103 4.1 × 102 Poompukar (S5) 2.9 ± 0.41 4.5 ± 0.66 0.64 8.0 ± 0.51 4.3 ± 0.60 1.74 2.6 × 103 1.7 × 103 Tharangambadi (S6) 2.0 ± 0.43 6.0 ± 0.57 0.32 7.5 ± 0.88 4.1 ± 0.41 1.95 4.0 × 103 1.3 × 103 Karaikal (S7) 6.5 ± 0.45 13.7 ± 0.96 0.47 6.3 ± 0.58 4.5 ± 0.52 1.40 1.0 × 103 4.6 × 102 Nagore (S8) 5.0 ± 0.43 8.7 ± 0.58 0.57 5.2 ± 0.42 3.9 ± 0.57 1.33 1.0 × 103 4.5 × 102 Nagappattinam (S9) 7.4 ± 0.55 9.1 ± 0.70 0.81 3.7 ± 0.60 2.1 ± 0.30 1.76 5.0 102 2.4 × 102 Velanganni (S10) 6.0 ± 0.53 12.0 ± 0.93 0.49 2.6 ± 0.57 1.6 ± 0.32 1.62 4.3 × 102 1.3 × 102 Over all range 1.4–7.4 3.1–13.7 0.32–0.81 2.5–8.0 1.3–4.5 1.33–2.19 4.3 × 102–4.0 × 103 1.3 × 102–1.7 × 103 Over all mean ± SD 4.1 ± 1.97 7.6 ± 3.31 0.52 ± 0.14 5.2 ± 1.87 3.1 ± 1.20 1.70 ± 0.26 1.7 × 103 6.2 × 102 Table 1. Station-wise mean 210 Po and 210Pb activities in coastal water, sand and Kd factor. Name of the station Activity (mBq l−1) 210Po/210Pb ratio Activity (Bq kg−1) 210Po/210Pb ratio Kd factor 210Po 210Pb 210Po 210Pb 210Po 210Pb Pondycherry (S1) 3.7 ± 0.17 8.3 ± 0.88 0.44 6.1 ± 0.37 4.0 ± 0.37 1.52 1.6 × 103 4.8 × 102 Devanampattinam (S2) 2.8 ± 0.24 4.2 ± 0.60 0.66 5.7 ± 0.79 2.6 ± 0.58 2.19 2.0 × 103 6.2 × 102 Pitchavaram Mangroves (S3) 1.4 ± 0.32 3.1 ± 0.55 0.45 2.5 ± 0.63 1.3 ± 0.27 1.92 1.8 × 103 42.x 102 Tirumullaivasal (S4) 3.0 ± 0.48 7.1 ± 0.73 0.41 4.8 ± 0.59 2.9 ± 0.43 1.65 1.6 × 103 4.1 × 102 Poompukar (S5) 2.9 ± 0.41 4.5 ± 0.66 0.64 8.0 ± 0.51 4.3 ± 0.60 1.74 2.6 × 103 1.7 × 103 Tharangambadi (S6) 2.0 ± 0.43 6.0 ± 0.57 0.32 7.5 ± 0.88 4.1 ± 0.41 1.95 4.0 × 103 1.3 × 103 Karaikal (S7) 6.5 ± 0.45 13.7 ± 0.96 0.47 6.3 ± 0.58 4.5 ± 0.52 1.40 1.0 × 103 4.6 × 102 Nagore (S8) 5.0 ± 0.43 8.7 ± 0.58 0.57 5.2 ± 0.42 3.9 ± 0.57 1.33 1.0 × 103 4.5 × 102 Nagappattinam (S9) 7.4 ± 0.55 9.1 ± 0.70 0.81 3.7 ± 0.60 2.1 ± 0.30 1.76 5.0 102 2.4 × 102 Velanganni (S10) 6.0 ± 0.53 12.0 ± 0.93 0.49 2.6 ± 0.57 1.6 ± 0.32 1.62 4.3 × 102 1.3 × 102 Over all range 1.4–7.4 3.1–13.7 0.32–0.81 2.5–8.0 1.3–4.5 1.33–2.19 4.3 × 102–4.0 × 103 1.3 × 102–1.7 × 103 Over all mean ± SD 4.1 ± 1.97 7.6 ± 3.31 0.52 ± 0.14 5.2 ± 1.87 3.1 ± 1.20 1.70 ± 0.26 1.7 × 103 6.2 × 102 Name of the station Activity (mBq l−1) 210Po/210Pb ratio Activity (Bq kg−1) 210Po/210Pb ratio Kd factor 210Po 210Pb 210Po 210Pb 210Po 210Pb Pondycherry (S1) 3.7 ± 0.17 8.3 ± 0.88 0.44 6.1 ± 0.37 4.0 ± 0.37 1.52 1.6 × 103 4.8 × 102 Devanampattinam (S2) 2.8 ± 0.24 4.2 ± 0.60 0.66 5.7 ± 0.79 2.6 ± 0.58 2.19 2.0 × 103 6.2 × 102 Pitchavaram Mangroves (S3) 1.4 ± 0.32 3.1 ± 0.55 0.45 2.5 ± 0.63 1.3 ± 0.27 1.92 1.8 × 103 42.x 102 Tirumullaivasal (S4) 3.0 ± 0.48 7.1 ± 0.73 0.41 4.8 ± 0.59 2.9 ± 0.43 1.65 1.6 × 103 4.1 × 102 Poompukar (S5) 2.9 ± 0.41 4.5 ± 0.66 0.64 8.0 ± 0.51 4.3 ± 0.60 1.74 2.6 × 103 1.7 × 103 Tharangambadi (S6) 2.0 ± 0.43 6.0 ± 0.57 0.32 7.5 ± 0.88 4.1 ± 0.41 1.95 4.0 × 103 1.3 × 103 Karaikal (S7) 6.5 ± 0.45 13.7 ± 0.96 0.47 6.3 ± 0.58 4.5 ± 0.52 1.40 1.0 × 103 4.6 × 102 Nagore (S8) 5.0 ± 0.43 8.7 ± 0.58 0.57 5.2 ± 0.42 3.9 ± 0.57 1.33 1.0 × 103 4.5 × 102 Nagappattinam (S9) 7.4 ± 0.55 9.1 ± 0.70 0.81 3.7 ± 0.60 2.1 ± 0.30 1.76 5.0 102 2.4 × 102 Velanganni (S10) 6.0 ± 0.53 12.0 ± 0.93 0.49 2.6 ± 0.57 1.6 ± 0.32 1.62 4.3 × 102 1.3 × 102 Over all range 1.4–7.4 3.1–13.7 0.32–0.81 2.5–8.0 1.3–4.5 1.33–2.19 4.3 × 102–4.0 × 103 1.3 × 102–1.7 × 103 Over all mean ± SD 4.1 ± 1.97 7.6 ± 3.31 0.52 ± 0.14 5.2 ± 1.87 3.1 ± 1.20 1.70 ± 0.26 1.7 × 103 6.2 × 102 Figure 2. View largeDownload slide 210Po and 210Pb activity in water samples of Bay of Bengal. Figure 2. View largeDownload slide 210Po and 210Pb activity in water samples of Bay of Bengal. The dissolved 210Pb concentration is distinctly higher when compared to Palk Strait (2.8 mBq l−1) by Bukhari et al.(15), Point Calimere (1.3 ± 0.2 mBq l−1) by Suriyanarayanan et al.(22), Mumbai coast (2.0 mBq l−1) by Bangera and Rudran(23), Ennore Creek (1.6 mBq l−1) by Musthafa and Krishnamoorthy(16) and lower than the mean levels reported in Gulf of Manner (20.6 ± 10.6 mBq l−1) by Masilamani(14). The wide variation was largely due to atmospheric input of 210Pb which varied latitudinally(24). Also variations in 210Pb concentration with depth were reported(25, 26). However, a typical average seawater value of 1.875 mBq l−1 was derived by Cherry and Shannon(2). This value is less when compared with the present study. The calculated 210Po/210Pb ratios for the coastal waters worked out to be 0.52 showing a 48% depletion of 210Po in water samples. Bacon et al.(26) stated that the rate of binding of 210Po to organic particulates was higher and its availability in dissolved form was much reduced and hence it registered a low level in water. 210Po and 210Pb distribution in coastal sand The concentration of 210Po in sand samples varied from 2.5 to 8.0 Bq kg−1 having a mean value of 5.2 ± 1.87 Bq kg−1 and that of 210Pb ranged from 1.3 to 4.5 Bq kg−1 with a mean value of 3.1 ± 1.2 Bq kg−1 (Table 1). It is observed from results that 210Po in the coastal sand is in higher concentration than 210Pb (Figure 3). Pitchavaram Mangroves (S3) recorded minimum activity levels of 210Po (2.5 ± 0.63 Bq kg−1) and 210Pb (1.3 ± 0.27 Bq kg−1) and a maximum level of 210Po (8.0 ± 0.51 Bq kg−1) in Tharangambadi (S6) and 210Pb (4.5 ± 0.52 Bq kg−1) in Karaikkal coast (S7). The mean activity concentration of 210Po in the coastal sand of Bay of Bengal was relatively far less than the mean activity in Gulf of Mannar (35.5 Bq kg−1) by Masilamani(14), Mallipattinam coastal sand (4.0 Bq kg−1) by Suriyanarayanan et al.(27) and Kalpakkam coastal sand (44.0 Bq kg−1) by Iyengar et al.(28) and Mangalore coast (1.23–17.72 Bq kg−1) by Siddappa et al.(29) and coastal Karnataka (6.22–18.9 Bq kg−1) by Narayana et al.(30) and Ullal coast (1.7–43.2 Bq kg−1) Narayana and Prakash(31). Figure 3. View largeDownload slide 210Po and 210Pb activity in coastal sand samples of Bay of Bengal. Figure 3. View largeDownload slide 210Po and 210Pb activity in coastal sand samples of Bay of Bengal. The mean activity concentration of 210Pb was much lower than those reported for the Kalpakkam beach sand (385.0 Bq kg−1) by Iyengar et al.(28), Mallipattinam coastal (1.0 Bq kg−1) by Suriyanarayanan et al.(27) and Trombay coast (356.0 Bq kg−1) by Bangera and Patel(32) and Comparable to Southwest coast of Mangalore environment (3.6–58.13 Bq kg−1) Siddappa et al.(29) and Honnavar environment (40.01 Bq kg−1) by Narayana et al.(30). The 210Po/210Pb ratios calculated for the entire stretch to be 1.7 indicating that the 210Po concentration in sand sample is always about twice the concentration of 210Pb. The higher concentration of 210Po in sand sample may be due to deposition of organic particulates which are generally rich source of 210Po. Kd factor The fraction of 210Po and 210Pb between sand and ambient medium is termed as distribution coefficient or Kd factor. It is a ratio of the total amount of a radionuclide per unit of dry sand to the amount of same radionuclide per unit volume of water. The Kd factor for 210Po varied from 4.3 × 102 to 4.0 × 103 and 1.3 × 102 to 1.7 × 103 for 210Pb. A higher distribution coefficient indicates a stronger binding of the radionuclide to the sand and vice versa. Grain size The distribution of 210Po and 210Pb in different grain size of beach sand collected from five stations (S1 and S3 to S6) are presented in Table 2 and Figures 4 and 5. A maximum concentration of 210Po (mean: 9.5 ± 4.2 Bq kg−1) was recorded in the particle size 105 μm (range: 4.0–15.5 Bq kg−1) and minimum concentration of 210Po (mean: 3.7 ± 1.3 Bq kg−1) in the particles of 500 μm (range: 2.0–5.0 Bq kg−1). The sand grains of 300 μm size registered intermediate level of 210Po concentration (mean: 5.8 ± 2.4 Bq kg−1) with a range from 3.0 to 9.0 Bq kg−1. A similar trend was also found with respect to 210Pb activities. The sand particles of 105 μm recorded a maximum level of 210Pb activity (mean: 5.2 ± 1.65 Bq kg−1; range: 3.1–7.3 Bq kg−1) and minimum level of 1.3 ± 0.48 Bq kg−1 (range: 1.0–2.0 Bq kg−1) in 500 μm particles. The sand particles of 300 μm registered an intermediate concentration of 3.3 ± 1.59 Bq kg−1 (range: 1.8–5.6 Bq kg−1). Table 2. Distribution of 210Po and 210Pb in different grains size in coastal sand of Bay of Bengal. Name of the station 210Po activity (Bq kg−1) 210Pb activity (Bq kg−1) 105 μm 300 μm 500 μm 105 μm 300 μm 500 μm Pondycherry (S1) 9.0 7.0 5.0 6.0 4.2 2.0 Pitchavaram Mangroves (S3) 4.0 3.0 2.0 3.1 1.8 0.8 Tirumullaivasal (S4) 8.0 4.0 3.0 4.0 3.0 1.0 Poompukar (S5) 11.0 6.0 3.8 5.5 2.0 1.0 Tharangambadi (S6) 15.5 9.0 5.0 7.3 5.6 1.5 Over all range 4–15.5 3–9 2.0–5.0 3.1–7.3 1.8–5.6 1–2.0 Over all mean ± SD 9.5 ± 4.2 5.8 ± 2.4 3.7 ± 1.3 5.2 ± 1.6 3.32 ± 1.6 1.3 ± 0.5 Name of the station 210Po activity (Bq kg−1) 210Pb activity (Bq kg−1) 105 μm 300 μm 500 μm 105 μm 300 μm 500 μm Pondycherry (S1) 9.0 7.0 5.0 6.0 4.2 2.0 Pitchavaram Mangroves (S3) 4.0 3.0 2.0 3.1 1.8 0.8 Tirumullaivasal (S4) 8.0 4.0 3.0 4.0 3.0 1.0 Poompukar (S5) 11.0 6.0 3.8 5.5 2.0 1.0 Tharangambadi (S6) 15.5 9.0 5.0 7.3 5.6 1.5 Over all range 4–15.5 3–9 2.0–5.0 3.1–7.3 1.8–5.6 1–2.0 Over all mean ± SD 9.5 ± 4.2 5.8 ± 2.4 3.7 ± 1.3 5.2 ± 1.6 3.32 ± 1.6 1.3 ± 0.5 Table 2. Distribution of 210Po and 210Pb in different grains size in coastal sand of Bay of Bengal. Name of the station 210Po activity (Bq kg−1) 210Pb activity (Bq kg−1) 105 μm 300 μm 500 μm 105 μm 300 μm 500 μm Pondycherry (S1) 9.0 7.0 5.0 6.0 4.2 2.0 Pitchavaram Mangroves (S3) 4.0 3.0 2.0 3.1 1.8 0.8 Tirumullaivasal (S4) 8.0 4.0 3.0 4.0 3.0 1.0 Poompukar (S5) 11.0 6.0 3.8 5.5 2.0 1.0 Tharangambadi (S6) 15.5 9.0 5.0 7.3 5.6 1.5 Over all range 4–15.5 3–9 2.0–5.0 3.1–7.3 1.8–5.6 1–2.0 Over all mean ± SD 9.5 ± 4.2 5.8 ± 2.4 3.7 ± 1.3 5.2 ± 1.6 3.32 ± 1.6 1.3 ± 0.5 Name of the station 210Po activity (Bq kg−1) 210Pb activity (Bq kg−1) 105 μm 300 μm 500 μm 105 μm 300 μm 500 μm Pondycherry (S1) 9.0 7.0 5.0 6.0 4.2 2.0 Pitchavaram Mangroves (S3) 4.0 3.0 2.0 3.1 1.8 0.8 Tirumullaivasal (S4) 8.0 4.0 3.0 4.0 3.0 1.0 Poompukar (S5) 11.0 6.0 3.8 5.5 2.0 1.0 Tharangambadi (S6) 15.5 9.0 5.0 7.3 5.6 1.5 Over all range 4–15.5 3–9 2.0–5.0 3.1–7.3 1.8–5.6 1–2.0 Over all mean ± SD 9.5 ± 4.2 5.8 ± 2.4 3.7 ± 1.3 5.2 ± 1.6 3.32 ± 1.6 1.3 ± 0.5 Figure 4. View largeDownload slide 210Po activities in different grain size of the coastal sand of Bay of Bengal. Figure 4. View largeDownload slide 210Po activities in different grain size of the coastal sand of Bay of Bengal. Figure 5. View largeDownload slide 210Pb activities in different grain size of the coastal sand of Bay of Bengal. Figure 5. View largeDownload slide 210Pb activities in different grain size of the coastal sand of Bay of Bengal. Depth-wise distribution of 210Po and 210Pb in coastal sand The distribution of 210Po and 210Pb at different depth in beach sand is presented in Tables 3 and 4. The maximum distribution of 210Po (6.37 Bq kg−1) and 210Pb (4.07 Bq kg−1) was found at the depth of 10 cm. However, the concentrations of the two radionuclides at the depth of 20–30 cm decline drastically. Table 3. 210Po Activities in coastal sand samples at different depths (core sampling). Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 6.14 6.85 5.57 4.30 3.54 3.24 Devanampattinam(S2) 5.02 6.81 4.20 3.25 2.06 1.82 Pitchavaram Mangroves (S3) 3.42 4.85 3.85 2.57 2.28 1.42 Tirumullaivasal (S4) 4.85 5.21 4.28 4.14 3.71 3.0 Poompukar (S5) 6.14 7.12 6.42 5.71 4.85 3.82 Tharangambadi (S6) 6.41 7.42 7.04 6.28 5.72 3.21 Over all range 3.42–6.41 4.85–7.42 3.85–7.04 2.57–6.28 2.06–5.72 1.42–3.82 Over all mean ± SD 5.33 ± 1.1 6.37 ± 1.07 5.22 ± 1.31 4.37 ± 1.41 3.69 ± 1.42 2.75 ± 0.92 Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 6.14 6.85 5.57 4.30 3.54 3.24 Devanampattinam(S2) 5.02 6.81 4.20 3.25 2.06 1.82 Pitchavaram Mangroves (S3) 3.42 4.85 3.85 2.57 2.28 1.42 Tirumullaivasal (S4) 4.85 5.21 4.28 4.14 3.71 3.0 Poompukar (S5) 6.14 7.12 6.42 5.71 4.85 3.82 Tharangambadi (S6) 6.41 7.42 7.04 6.28 5.72 3.21 Over all range 3.42–6.41 4.85–7.42 3.85–7.04 2.57–6.28 2.06–5.72 1.42–3.82 Over all mean ± SD 5.33 ± 1.1 6.37 ± 1.07 5.22 ± 1.31 4.37 ± 1.41 3.69 ± 1.42 2.75 ± 0.92 Table 3. 210Po Activities in coastal sand samples at different depths (core sampling). Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 6.14 6.85 5.57 4.30 3.54 3.24 Devanampattinam(S2) 5.02 6.81 4.20 3.25 2.06 1.82 Pitchavaram Mangroves (S3) 3.42 4.85 3.85 2.57 2.28 1.42 Tirumullaivasal (S4) 4.85 5.21 4.28 4.14 3.71 3.0 Poompukar (S5) 6.14 7.12 6.42 5.71 4.85 3.82 Tharangambadi (S6) 6.41 7.42 7.04 6.28 5.72 3.21 Over all range 3.42–6.41 4.85–7.42 3.85–7.04 2.57–6.28 2.06–5.72 1.42–3.82 Over all mean ± SD 5.33 ± 1.1 6.37 ± 1.07 5.22 ± 1.31 4.37 ± 1.41 3.69 ± 1.42 2.75 ± 0.92 Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 6.14 6.85 5.57 4.30 3.54 3.24 Devanampattinam(S2) 5.02 6.81 4.20 3.25 2.06 1.82 Pitchavaram Mangroves (S3) 3.42 4.85 3.85 2.57 2.28 1.42 Tirumullaivasal (S4) 4.85 5.21 4.28 4.14 3.71 3.0 Poompukar (S5) 6.14 7.12 6.42 5.71 4.85 3.82 Tharangambadi (S6) 6.41 7.42 7.04 6.28 5.72 3.21 Over all range 3.42–6.41 4.85–7.42 3.85–7.04 2.57–6.28 2.06–5.72 1.42–3.82 Over all mean ± SD 5.33 ± 1.1 6.37 ± 1.07 5.22 ± 1.31 4.37 ± 1.41 3.69 ± 1.42 2.75 ± 0.92 Table 4. 210Pb activities in coastal sand samples at different depths (core sampling). Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 4.64 3.57 3.12 2.57 2.14 1.76 Devanampattinam(S2) 3.10 3.23 4.51 2.40 2.53 1.29 Pitchavaram Mangroves (S3) 2.29 3.86 2.34 1.86 1.29 1.0 Tirumullaivasal (S4) 3.29 2.84 2.71 2.14 1.86 1.37 Poompukar (S5) 3.21 5.10 4.57 3.14 2.0 1.86 Tharangambadi (S6) 3.14 5.83 4.71 3.42 2.0 1.57 Over all range 2.29–4.64 2.84–5.83 2.34–4.71 1.86–3.42 1.29–2.53 1.0–1.86 Over all mean ± SD 3.27 ± 0.75 4.07 ± 1.15 3.66 ± 1.05 2.58 ± 0.59 1.97 ± 0.40 1.47 ± 0.31 Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 4.64 3.57 3.12 2.57 2.14 1.76 Devanampattinam(S2) 3.10 3.23 4.51 2.40 2.53 1.29 Pitchavaram Mangroves (S3) 2.29 3.86 2.34 1.86 1.29 1.0 Tirumullaivasal (S4) 3.29 2.84 2.71 2.14 1.86 1.37 Poompukar (S5) 3.21 5.10 4.57 3.14 2.0 1.86 Tharangambadi (S6) 3.14 5.83 4.71 3.42 2.0 1.57 Over all range 2.29–4.64 2.84–5.83 2.34–4.71 1.86–3.42 1.29–2.53 1.0–1.86 Over all mean ± SD 3.27 ± 0.75 4.07 ± 1.15 3.66 ± 1.05 2.58 ± 0.59 1.97 ± 0.40 1.47 ± 0.31 Table 4. 210Pb activities in coastal sand samples at different depths (core sampling). Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 4.64 3.57 3.12 2.57 2.14 1.76 Devanampattinam(S2) 3.10 3.23 4.51 2.40 2.53 1.29 Pitchavaram Mangroves (S3) 2.29 3.86 2.34 1.86 1.29 1.0 Tirumullaivasal (S4) 3.29 2.84 2.71 2.14 1.86 1.37 Poompukar (S5) 3.21 5.10 4.57 3.14 2.0 1.86 Tharangambadi (S6) 3.14 5.83 4.71 3.42 2.0 1.57 Over all range 2.29–4.64 2.84–5.83 2.34–4.71 1.86–3.42 1.29–2.53 1.0–1.86 Over all mean ± SD 3.27 ± 0.75 4.07 ± 1.15 3.66 ± 1.05 2.58 ± 0.59 1.97 ± 0.40 1.47 ± 0.31 Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 4.64 3.57 3.12 2.57 2.14 1.76 Devanampattinam(S2) 3.10 3.23 4.51 2.40 2.53 1.29 Pitchavaram Mangroves (S3) 2.29 3.86 2.34 1.86 1.29 1.0 Tirumullaivasal (S4) 3.29 2.84 2.71 2.14 1.86 1.37 Poompukar (S5) 3.21 5.10 4.57 3.14 2.0 1.86 Tharangambadi (S6) 3.14 5.83 4.71 3.42 2.0 1.57 Over all range 2.29–4.64 2.84–5.83 2.34–4.71 1.86–3.42 1.29–2.53 1.0–1.86 Over all mean ± SD 3.27 ± 0.75 4.07 ± 1.15 3.66 ± 1.05 2.58 ± 0.59 1.97 ± 0.40 1.47 ± 0.31 Bioaccumulation of 210Po and 210Pb in seafood organisms The activity concentrations of 210Po and 210Pb accumulated in the edible parts (soft tissues and muscle) of shellfish species and fish species from three major fish landing centers of the study area namely Cuddalore (Devanampattinam), Pitchavaram Mangroves and Nagappattinam were analyzed. The shellfishes include species of prawns, crabs and mollascan species of squid, oyster and clam. The activity concentrations of 210Po and 210Pb measured in shellfish species and fin fish species were presented in Tables 5–8 and Figures 6–9. The bioaccumulation of 210Po in shellfish species ranged from 5.3 to 52.1 Bq kg−1 with overall mean of 18.4 ± 16.0 Bq kg−1 whereas bioaccumulation of 210Pb ranged from 1.6 to 11.3 Bq kg−1 with a mean value of 3.7 ± 3.0 Bq kg−1. Fish species in Devanampattinam registered relatively a low level of 210Po and 210Pb. The 210Po concentrations ranged from 2.0 to 17.6 Bq kg−1 with in the mean value of 7.3 ± 4.3 Bq kg−1. Similarly 210Pb concentration ranged from 0.6 to 11.7 Bq kg−1 with the mean value of 2.9 ± 2.0 Bq kg−1. The ratio of 210Po/210Pb is always several times higher in shellfish species (4.5) and fin fish species (5.0). Table 5. 210Po and 210Pb concentrations (Bq kg−1) in edible parts shell fishes of coast (S2). S. no. Name of the sample Devanampattinam (S2) Pitchavaram Mangroves (S3) Nagappattinam (S9) 210Po 210Pb 210Po 210Pb 210Po 210Pb Prawn 1.  Penaeus monodon 8.6 ± 1.2 2.7 ± 0.8 13.02 ± 0.3 2.2 ± 0.5 24.3 ± 1.6 11.0 ± 1.6 2.  Penaeus indicus 5.3 ± 0.8 1.6 ± 0.3 3.4 ± 0.02 0.51 ± 0.06 19.0 ± 1.4 6.5 ± 0.8 3.  Penaeus semisulcatus 6.7 ± 0.9 2.1 ± 0.5 7.6 ± 1.1 1.8 ± 0.3 17.0 ± 1.0 5.3 ± 0.3 Range 5.3–8.6 1.6–2.7 3.4–13.02 0.51–2.2 17.0–24.3 5.3–0.3 Mean ± SD 6.8 ± 1.6 2.1 ± 0.5 8.0 ± 4.8 1.5 ± 0.8 20.1 ± 3.7 7.6 ± 3.0 Crab 4.  Portunus sanguinolentus 7.6 ± 0.8 2.1 ± 0.4 5.4 ± 0.5 2.2 ± 0.2 28 ± 1.5 8.7 ± 1.3 5.  Portunus pelagicus 9.3 ± 0.6 2.4 ± 0.6 4.8 ± 0.3 1.5 ± 0.1 17.0 ± 1.3 6.4 ± 0.6 6.  Scylla serrata 26 ± 1.2 4.2 ± 0.9 11.3 ± 1.4 3.4 ± 0.6 39.3 ± 1.7 11.5 ± 1.5 Range 7.6–26 2.1–4.2 4.8–11.3 1.5–3.4 17.0–39.3 6.4–11.5 Mean ± SD 14.3 ± 10.1 2.9 ± 1.1 7.1 ± 3.5 2.3 ± 0.9 28.1 ± 11.1 8.8 ± 2.5 Molluscs 7.  Loligo duavucelli (Squid) 15.6 ± 0.3 2.8 ± 0.9 12.8 ± 1.4 1.8 ± 0.3 13.5 ± 1.1 5.0 ± 0.4 8.  Crassostrea madrasensis (Oyster) 52.1 ± 2.3 11.3 ± 1.4 45.2 ± 2.6 9.2 ± 0.9 58.6 ± 2.4 9.5 ± 1.6 9.  Meretrix casta (Clam) 34.3 ± 1.8 4.6 ± 1.1 23.7 ± 2.0 2.3 ± 0.4 29.4 ± 1.5 3.4 ± 1.4 Range 15.6–52.1 2.8–11.3 12.8–45.2 1.8–9.2 13.5–58.6 3.4–9.5 Mean ± SD 34 ± 18.2 6.2 ± 4.4 27.2 ± 16.4 4.4 ± 2.0 33.8 ± 22.8 5.9 ± 3.1 Over all range 5.3–52.1 1.6–11.3 3.4–45.2 0.51–9.2 13.5–58.6 3.4–11.5 Over all mean ± SD 18.4 ± 16.03 3.7 ± 2.99 14.1 ± 13.1 2.7 ± 2.5 27.3 ± 14.18 7.5 ± 2.82 S. no. Name of the sample Devanampattinam (S2) Pitchavaram Mangroves (S3) Nagappattinam (S9) 210Po 210Pb 210Po 210Pb 210Po 210Pb Prawn 1.  Penaeus monodon 8.6 ± 1.2 2.7 ± 0.8 13.02 ± 0.3 2.2 ± 0.5 24.3 ± 1.6 11.0 ± 1.6 2.  Penaeus indicus 5.3 ± 0.8 1.6 ± 0.3 3.4 ± 0.02 0.51 ± 0.06 19.0 ± 1.4 6.5 ± 0.8 3.  Penaeus semisulcatus 6.7 ± 0.9 2.1 ± 0.5 7.6 ± 1.1 1.8 ± 0.3 17.0 ± 1.0 5.3 ± 0.3 Range 5.3–8.6 1.6–2.7 3.4–13.02 0.51–2.2 17.0–24.3 5.3–0.3 Mean ± SD 6.8 ± 1.6 2.1 ± 0.5 8.0 ± 4.8 1.5 ± 0.8 20.1 ± 3.7 7.6 ± 3.0 Crab 4.  Portunus sanguinolentus 7.6 ± 0.8 2.1 ± 0.4 5.4 ± 0.5 2.2 ± 0.2 28 ± 1.5 8.7 ± 1.3 5.  Portunus pelagicus 9.3 ± 0.6 2.4 ± 0.6 4.8 ± 0.3 1.5 ± 0.1 17.0 ± 1.3 6.4 ± 0.6 6.  Scylla serrata 26 ± 1.2 4.2 ± 0.9 11.3 ± 1.4 3.4 ± 0.6 39.3 ± 1.7 11.5 ± 1.5 Range 7.6–26 2.1–4.2 4.8–11.3 1.5–3.4 17.0–39.3 6.4–11.5 Mean ± SD 14.3 ± 10.1 2.9 ± 1.1 7.1 ± 3.5 2.3 ± 0.9 28.1 ± 11.1 8.8 ± 2.5 Molluscs 7.  Loligo duavucelli (Squid) 15.6 ± 0.3 2.8 ± 0.9 12.8 ± 1.4 1.8 ± 0.3 13.5 ± 1.1 5.0 ± 0.4 8.  Crassostrea madrasensis (Oyster) 52.1 ± 2.3 11.3 ± 1.4 45.2 ± 2.6 9.2 ± 0.9 58.6 ± 2.4 9.5 ± 1.6 9.  Meretrix casta (Clam) 34.3 ± 1.8 4.6 ± 1.1 23.7 ± 2.0 2.3 ± 0.4 29.4 ± 1.5 3.4 ± 1.4 Range 15.6–52.1 2.8–11.3 12.8–45.2 1.8–9.2 13.5–58.6 3.4–9.5 Mean ± SD 34 ± 18.2 6.2 ± 4.4 27.2 ± 16.4 4.4 ± 2.0 33.8 ± 22.8 5.9 ± 3.1 Over all range 5.3–52.1 1.6–11.3 3.4–45.2 0.51–9.2 13.5–58.6 3.4–11.5 Over all mean ± SD 18.4 ± 16.03 3.7 ± 2.99 14.1 ± 13.1 2.7 ± 2.5 27.3 ± 14.18 7.5 ± 2.82 No. of analysis (n) = 6 – 10. Table 5. 210Po and 210Pb concentrations (Bq kg−1) in edible parts shell fishes of coast (S2). S. no. Name of the sample Devanampattinam (S2) Pitchavaram Mangroves (S3) Nagappattinam (S9) 210Po 210Pb 210Po 210Pb 210Po 210Pb Prawn 1.  Penaeus monodon 8.6 ± 1.2 2.7 ± 0.8 13.02 ± 0.3 2.2 ± 0.5 24.3 ± 1.6 11.0 ± 1.6 2.  Penaeus indicus 5.3 ± 0.8 1.6 ± 0.3 3.4 ± 0.02 0.51 ± 0.06 19.0 ± 1.4 6.5 ± 0.8 3.  Penaeus semisulcatus 6.7 ± 0.9 2.1 ± 0.5 7.6 ± 1.1 1.8 ± 0.3 17.0 ± 1.0 5.3 ± 0.3 Range 5.3–8.6 1.6–2.7 3.4–13.02 0.51–2.2 17.0–24.3 5.3–0.3 Mean ± SD 6.8 ± 1.6 2.1 ± 0.5 8.0 ± 4.8 1.5 ± 0.8 20.1 ± 3.7 7.6 ± 3.0 Crab 4.  Portunus sanguinolentus 7.6 ± 0.8 2.1 ± 0.4 5.4 ± 0.5 2.2 ± 0.2 28 ± 1.5 8.7 ± 1.3 5.  Portunus pelagicus 9.3 ± 0.6 2.4 ± 0.6 4.8 ± 0.3 1.5 ± 0.1 17.0 ± 1.3 6.4 ± 0.6 6.  Scylla serrata 26 ± 1.2 4.2 ± 0.9 11.3 ± 1.4 3.4 ± 0.6 39.3 ± 1.7 11.5 ± 1.5 Range 7.6–26 2.1–4.2 4.8–11.3 1.5–3.4 17.0–39.3 6.4–11.5 Mean ± SD 14.3 ± 10.1 2.9 ± 1.1 7.1 ± 3.5 2.3 ± 0.9 28.1 ± 11.1 8.8 ± 2.5 Molluscs 7.  Loligo duavucelli (Squid) 15.6 ± 0.3 2.8 ± 0.9 12.8 ± 1.4 1.8 ± 0.3 13.5 ± 1.1 5.0 ± 0.4 8.  Crassostrea madrasensis (Oyster) 52.1 ± 2.3 11.3 ± 1.4 45.2 ± 2.6 9.2 ± 0.9 58.6 ± 2.4 9.5 ± 1.6 9.  Meretrix casta (Clam) 34.3 ± 1.8 4.6 ± 1.1 23.7 ± 2.0 2.3 ± 0.4 29.4 ± 1.5 3.4 ± 1.4 Range 15.6–52.1 2.8–11.3 12.8–45.2 1.8–9.2 13.5–58.6 3.4–9.5 Mean ± SD 34 ± 18.2 6.2 ± 4.4 27.2 ± 16.4 4.4 ± 2.0 33.8 ± 22.8 5.9 ± 3.1 Over all range 5.3–52.1 1.6–11.3 3.4–45.2 0.51–9.2 13.5–58.6 3.4–11.5 Over all mean ± SD 18.4 ± 16.03 3.7 ± 2.99 14.1 ± 13.1 2.7 ± 2.5 27.3 ± 14.18 7.5 ± 2.82 S. no. Name of the sample Devanampattinam (S2) Pitchavaram Mangroves (S3) Nagappattinam (S9) 210Po 210Pb 210Po 210Pb 210Po 210Pb Prawn 1.  Penaeus monodon 8.6 ± 1.2 2.7 ± 0.8 13.02 ± 0.3 2.2 ± 0.5 24.3 ± 1.6 11.0 ± 1.6 2.  Penaeus indicus 5.3 ± 0.8 1.6 ± 0.3 3.4 ± 0.02 0.51 ± 0.06 19.0 ± 1.4 6.5 ± 0.8 3.  Penaeus semisulcatus 6.7 ± 0.9 2.1 ± 0.5 7.6 ± 1.1 1.8 ± 0.3 17.0 ± 1.0 5.3 ± 0.3 Range 5.3–8.6 1.6–2.7 3.4–13.02 0.51–2.2 17.0–24.3 5.3–0.3 Mean ± SD 6.8 ± 1.6 2.1 ± 0.5 8.0 ± 4.8 1.5 ± 0.8 20.1 ± 3.7 7.6 ± 3.0 Crab 4.  Portunus sanguinolentus 7.6 ± 0.8 2.1 ± 0.4 5.4 ± 0.5 2.2 ± 0.2 28 ± 1.5 8.7 ± 1.3 5.  Portunus pelagicus 9.3 ± 0.6 2.4 ± 0.6 4.8 ± 0.3 1.5 ± 0.1 17.0 ± 1.3 6.4 ± 0.6 6.  Scylla serrata 26 ± 1.2 4.2 ± 0.9 11.3 ± 1.4 3.4 ± 0.6 39.3 ± 1.7 11.5 ± 1.5 Range 7.6–26 2.1–4.2 4.8–11.3 1.5–3.4 17.0–39.3 6.4–11.5 Mean ± SD 14.3 ± 10.1 2.9 ± 1.1 7.1 ± 3.5 2.3 ± 0.9 28.1 ± 11.1 8.8 ± 2.5 Molluscs 7.  Loligo duavucelli (Squid) 15.6 ± 0.3 2.8 ± 0.9 12.8 ± 1.4 1.8 ± 0.3 13.5 ± 1.1 5.0 ± 0.4 8.  Crassostrea madrasensis (Oyster) 52.1 ± 2.3 11.3 ± 1.4 45.2 ± 2.6 9.2 ± 0.9 58.6 ± 2.4 9.5 ± 1.6 9.  Meretrix casta (Clam) 34.3 ± 1.8 4.6 ± 1.1 23.7 ± 2.0 2.3 ± 0.4 29.4 ± 1.5 3.4 ± 1.4 Range 15.6–52.1 2.8–11.3 12.8–45.2 1.8–9.2 13.5–58.6 3.4–9.5 Mean ± SD 34 ± 18.2 6.2 ± 4.4 27.2 ± 16.4 4.4 ± 2.0 33.8 ± 22.8 5.9 ± 3.1 Over all range 5.3–52.1 1.6–11.3 3.4–45.2 0.51–9.2 13.5–58.6 3.4–11.5 Over all mean ± SD 18.4 ± 16.03 3.7 ± 2.99 14.1 ± 13.1 2.7 ± 2.5 27.3 ± 14.18 7.5 ± 2.82 No. of analysis (n) = 6 – 10. Table 6. Activity concentrations of 210Po and 210Pb in muscle of fishes from Devanampattinam coast (S2). S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Rastrelliger kanagurta 17.6 ± 1.5 11.7 ± 1.1 1.50 2. Leiognathus bindus 11.2 ± 1.1 6.5 ± 1.0 1.72 3. Mugil cephalus 7.5 ± 0.8 4.2 ± 0.5 1.78 4. Euthynnus affinis 5.0 ± 0.4 1.7 ± 0.2 2.94 5. Atule mate 6.2 ± 0.5 1.2 ± 0.1 5.39 6. Pinjalo sp. 2.7 ± 0.1 0.6 ± 0.01 4.5 7. Liza sp. 5.9 ± 0.7 1.8 ± 0.3 3.27 8. Stolephorus sp 12.0 ± 1.2 2.2 ± 0.6 5.45 9. Sardinella dayiregan 4.5 ± 0.6 0.9 ± 0.04 5.0 10. Lethrinus cinereus 11.5 ± 1.1 1.2 ± 0.1 9.58 11. Scomberomorus guttauts 2.0 ± 0.1 0.6 ± 0.01 3.33 12. Alectis sp. 4.0 ± 0.2 0.7 ± 0.01 5.71 Range 2.0–17.6 0.6–11.7 1.50–9.58 Mean ± SD 7.34 ± 4.3 2.9 ± 2.01 4.89 ± 3.77 S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Rastrelliger kanagurta 17.6 ± 1.5 11.7 ± 1.1 1.50 2. Leiognathus bindus 11.2 ± 1.1 6.5 ± 1.0 1.72 3. Mugil cephalus 7.5 ± 0.8 4.2 ± 0.5 1.78 4. Euthynnus affinis 5.0 ± 0.4 1.7 ± 0.2 2.94 5. Atule mate 6.2 ± 0.5 1.2 ± 0.1 5.39 6. Pinjalo sp. 2.7 ± 0.1 0.6 ± 0.01 4.5 7. Liza sp. 5.9 ± 0.7 1.8 ± 0.3 3.27 8. Stolephorus sp 12.0 ± 1.2 2.2 ± 0.6 5.45 9. Sardinella dayiregan 4.5 ± 0.6 0.9 ± 0.04 5.0 10. Lethrinus cinereus 11.5 ± 1.1 1.2 ± 0.1 9.58 11. Scomberomorus guttauts 2.0 ± 0.1 0.6 ± 0.01 3.33 12. Alectis sp. 4.0 ± 0.2 0.7 ± 0.01 5.71 Range 2.0–17.6 0.6–11.7 1.50–9.58 Mean ± SD 7.34 ± 4.3 2.9 ± 2.01 4.89 ± 3.77 No. of analysis (n) = 6 – 10. Table 6. Activity concentrations of 210Po and 210Pb in muscle of fishes from Devanampattinam coast (S2). S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Rastrelliger kanagurta 17.6 ± 1.5 11.7 ± 1.1 1.50 2. Leiognathus bindus 11.2 ± 1.1 6.5 ± 1.0 1.72 3. Mugil cephalus 7.5 ± 0.8 4.2 ± 0.5 1.78 4. Euthynnus affinis 5.0 ± 0.4 1.7 ± 0.2 2.94 5. Atule mate 6.2 ± 0.5 1.2 ± 0.1 5.39 6. Pinjalo sp. 2.7 ± 0.1 0.6 ± 0.01 4.5 7. Liza sp. 5.9 ± 0.7 1.8 ± 0.3 3.27 8. Stolephorus sp 12.0 ± 1.2 2.2 ± 0.6 5.45 9. Sardinella dayiregan 4.5 ± 0.6 0.9 ± 0.04 5.0 10. Lethrinus cinereus 11.5 ± 1.1 1.2 ± 0.1 9.58 11. Scomberomorus guttauts 2.0 ± 0.1 0.6 ± 0.01 3.33 12. Alectis sp. 4.0 ± 0.2 0.7 ± 0.01 5.71 Range 2.0–17.6 0.6–11.7 1.50–9.58 Mean ± SD 7.34 ± 4.3 2.9 ± 2.01 4.89 ± 3.77 S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Rastrelliger kanagurta 17.6 ± 1.5 11.7 ± 1.1 1.50 2. Leiognathus bindus 11.2 ± 1.1 6.5 ± 1.0 1.72 3. Mugil cephalus 7.5 ± 0.8 4.2 ± 0.5 1.78 4. Euthynnus affinis 5.0 ± 0.4 1.7 ± 0.2 2.94 5. Atule mate 6.2 ± 0.5 1.2 ± 0.1 5.39 6. Pinjalo sp. 2.7 ± 0.1 0.6 ± 0.01 4.5 7. Liza sp. 5.9 ± 0.7 1.8 ± 0.3 3.27 8. Stolephorus sp 12.0 ± 1.2 2.2 ± 0.6 5.45 9. Sardinella dayiregan 4.5 ± 0.6 0.9 ± 0.04 5.0 10. Lethrinus cinereus 11.5 ± 1.1 1.2 ± 0.1 9.58 11. Scomberomorus guttauts 2.0 ± 0.1 0.6 ± 0.01 3.33 12. Alectis sp. 4.0 ± 0.2 0.7 ± 0.01 5.71 Range 2.0–17.6 0.6–11.7 1.50–9.58 Mean ± SD 7.34 ± 4.3 2.9 ± 2.01 4.89 ± 3.77 No. of analysis (n) = 6 – 10. Table 7. Activity concentrations of 210Po and 210Pb in muscle of fishes from Pitchavaram Mangroves. S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Arius maculatus 6.5 ± 0.7 4.02 ± 0.6 1.61 2. Gerres abbreviatus 12.5 ± 1.1 6.0 ± 0.9 2.08 3. Leiognathus daura 8.2 ± 0.6 5.3 ± 0.6 1.54 4. Scatophagus argus 16.5 ± 1.3 9.3 ± 0.8 1.77 5. Sardinella longiceps 6.2 ± 0.7 1.07 ± 0.3 5.79 6. Sarotherodon mosambicus 5.4 ± 0.5 2.7 ± 0.2 2.0 7. Chirocentrus sp. 1.5 ± 0.2 0.5 ± 0.02 3.0 8. Synaptura commersoniana 8.5 ± 1.1 2.5 ± 0.5 3.4 9. Pinjalo Sp. 6.2 ± 0.8 2.4 ± 0.6 2.58 10. Liza Sp. 2.7 ± 0.3 0.6 ± 0.05 4.5 11. Stolephorus indicus 5.9 ± 0.9 1.9 ± 0.2 3.10 12. Therapon jarbua 2.0 ± 0.4 0.4 ± 0.02 5.0 13. Upeneus sulphureus 1.0 ± 0.2 0.3 ± 0.02 3.33 14. Kathala axillaris 8.0 ± 1.3 0.6 ± 0.04 1.33 15. Thrissina baelama 16.0 ± 1.5 1.2 ± 0.3 13.33 16. Valamugil speigeri 2.0 ± 0.6 0.8 ± 0.06 0.25 17. Mene maculata 6.0 ± 0.9 1.3 ± 0.2 4.61 18. Nematalosa nasus 7.0 ± 1.1 0.8 ± 0.05 8.33 19. Nemipterus japonicus 4.0 ± 0.8 1.9 ± 0.4 2.10 Range 1.0–16.5 0.3–9.3 0.25–13.33 Mean ± SD 6.6 ± 4.43 2.3 ± 2.2 4.29 ± 3.67 S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Arius maculatus 6.5 ± 0.7 4.02 ± 0.6 1.61 2. Gerres abbreviatus 12.5 ± 1.1 6.0 ± 0.9 2.08 3. Leiognathus daura 8.2 ± 0.6 5.3 ± 0.6 1.54 4. Scatophagus argus 16.5 ± 1.3 9.3 ± 0.8 1.77 5. Sardinella longiceps 6.2 ± 0.7 1.07 ± 0.3 5.79 6. Sarotherodon mosambicus 5.4 ± 0.5 2.7 ± 0.2 2.0 7. Chirocentrus sp. 1.5 ± 0.2 0.5 ± 0.02 3.0 8. Synaptura commersoniana 8.5 ± 1.1 2.5 ± 0.5 3.4 9. Pinjalo Sp. 6.2 ± 0.8 2.4 ± 0.6 2.58 10. Liza Sp. 2.7 ± 0.3 0.6 ± 0.05 4.5 11. Stolephorus indicus 5.9 ± 0.9 1.9 ± 0.2 3.10 12. Therapon jarbua 2.0 ± 0.4 0.4 ± 0.02 5.0 13. Upeneus sulphureus 1.0 ± 0.2 0.3 ± 0.02 3.33 14. Kathala axillaris 8.0 ± 1.3 0.6 ± 0.04 1.33 15. Thrissina baelama 16.0 ± 1.5 1.2 ± 0.3 13.33 16. Valamugil speigeri 2.0 ± 0.6 0.8 ± 0.06 0.25 17. Mene maculata 6.0 ± 0.9 1.3 ± 0.2 4.61 18. Nematalosa nasus 7.0 ± 1.1 0.8 ± 0.05 8.33 19. Nemipterus japonicus 4.0 ± 0.8 1.9 ± 0.4 2.10 Range 1.0–16.5 0.3–9.3 0.25–13.33 Mean ± SD 6.6 ± 4.43 2.3 ± 2.2 4.29 ± 3.67 No. of analysis (n) = 6 – 10. Table 7. Activity concentrations of 210Po and 210Pb in muscle of fishes from Pitchavaram Mangroves. S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Arius maculatus 6.5 ± 0.7 4.02 ± 0.6 1.61 2. Gerres abbreviatus 12.5 ± 1.1 6.0 ± 0.9 2.08 3. Leiognathus daura 8.2 ± 0.6 5.3 ± 0.6 1.54 4. Scatophagus argus 16.5 ± 1.3 9.3 ± 0.8 1.77 5. Sardinella longiceps 6.2 ± 0.7 1.07 ± 0.3 5.79 6. Sarotherodon mosambicus 5.4 ± 0.5 2.7 ± 0.2 2.0 7. Chirocentrus sp. 1.5 ± 0.2 0.5 ± 0.02 3.0 8. Synaptura commersoniana 8.5 ± 1.1 2.5 ± 0.5 3.4 9. Pinjalo Sp. 6.2 ± 0.8 2.4 ± 0.6 2.58 10. Liza Sp. 2.7 ± 0.3 0.6 ± 0.05 4.5 11. Stolephorus indicus 5.9 ± 0.9 1.9 ± 0.2 3.10 12. Therapon jarbua 2.0 ± 0.4 0.4 ± 0.02 5.0 13. Upeneus sulphureus 1.0 ± 0.2 0.3 ± 0.02 3.33 14. Kathala axillaris 8.0 ± 1.3 0.6 ± 0.04 1.33 15. Thrissina baelama 16.0 ± 1.5 1.2 ± 0.3 13.33 16. Valamugil speigeri 2.0 ± 0.6 0.8 ± 0.06 0.25 17. Mene maculata 6.0 ± 0.9 1.3 ± 0.2 4.61 18. Nematalosa nasus 7.0 ± 1.1 0.8 ± 0.05 8.33 19. Nemipterus japonicus 4.0 ± 0.8 1.9 ± 0.4 2.10 Range 1.0–16.5 0.3–9.3 0.25–13.33 Mean ± SD 6.6 ± 4.43 2.3 ± 2.2 4.29 ± 3.67 S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Arius maculatus 6.5 ± 0.7 4.02 ± 0.6 1.61 2. Gerres abbreviatus 12.5 ± 1.1 6.0 ± 0.9 2.08 3. Leiognathus daura 8.2 ± 0.6 5.3 ± 0.6 1.54 4. Scatophagus argus 16.5 ± 1.3 9.3 ± 0.8 1.77 5. Sardinella longiceps 6.2 ± 0.7 1.07 ± 0.3 5.79 6. Sarotherodon mosambicus 5.4 ± 0.5 2.7 ± 0.2 2.0 7. Chirocentrus sp. 1.5 ± 0.2 0.5 ± 0.02 3.0 8. Synaptura commersoniana 8.5 ± 1.1 2.5 ± 0.5 3.4 9. Pinjalo Sp. 6.2 ± 0.8 2.4 ± 0.6 2.58 10. Liza Sp. 2.7 ± 0.3 0.6 ± 0.05 4.5 11. Stolephorus indicus 5.9 ± 0.9 1.9 ± 0.2 3.10 12. Therapon jarbua 2.0 ± 0.4 0.4 ± 0.02 5.0 13. Upeneus sulphureus 1.0 ± 0.2 0.3 ± 0.02 3.33 14. Kathala axillaris 8.0 ± 1.3 0.6 ± 0.04 1.33 15. Thrissina baelama 16.0 ± 1.5 1.2 ± 0.3 13.33 16. Valamugil speigeri 2.0 ± 0.6 0.8 ± 0.06 0.25 17. Mene maculata 6.0 ± 0.9 1.3 ± 0.2 4.61 18. Nematalosa nasus 7.0 ± 1.1 0.8 ± 0.05 8.33 19. Nemipterus japonicus 4.0 ± 0.8 1.9 ± 0.4 2.10 Range 1.0–16.5 0.3–9.3 0.25–13.33 Mean ± SD 6.6 ± 4.43 2.3 ± 2.2 4.29 ± 3.67 No. of analysis (n) = 6 – 10. Table 8. Activity concentrations of 210Po and 210Pb in muscle of fishes from Nagappattinam. S. no. Species analyzed Activity (Bq /kg) dry 210Po/210Pb ratio 210Po 210Pb 1. Pampus argenteus 10.0 ± 1.4 3.0 ± 0.6 3.33 2. Carangoides armatus 3.0 ± 0.8 2.0 ± 0.5 1.5 3. Hirundichthys coromandelenesis 5.0 ± 1.2 1.8 ± 0.3 3.33 4. Scomberomorus guttatus 3.0 ± 0.9 1.0 ± 0.2 3.0 5. Nemipterus japonicus 8.0 ± 1.8 2.1 ± 0.4 3.81 6. Rastrelliger kanakurta 23.0 ± 2.1 9.5 ± 1.4 2.42 7. Megalops cyprinoides 4.0 ± 0.6 1.6 ± 0.2 2.5 8. Ambassis commersoni 12.0 ± 1.5 3.0 ± 0.6 4.0 9. Sarotherodon mosambicus 8.6 ± 1.1 2.5 ± 0.4 3.44 10. Synaptura commersoniana 15.6 ± 1.7 4.2 ± 1.1 3.71 11. Stolephorus indicus 9.0 ± 0.8 3.6 ± 0.9 2.5 12. Therapon jarbua 7.3 ± 0.4 2.1 ± 0.3 3.47 Range 3.0–23.0 1.0–9.5 1.5–4.0 Mean ± SD 9.04 ± 5.7 3.03 ± 2.2 3.08 ± 0.7 S. no. Species analyzed Activity (Bq /kg) dry 210Po/210Pb ratio 210Po 210Pb 1. Pampus argenteus 10.0 ± 1.4 3.0 ± 0.6 3.33 2. Carangoides armatus 3.0 ± 0.8 2.0 ± 0.5 1.5 3. Hirundichthys coromandelenesis 5.0 ± 1.2 1.8 ± 0.3 3.33 4. Scomberomorus guttatus 3.0 ± 0.9 1.0 ± 0.2 3.0 5. Nemipterus japonicus 8.0 ± 1.8 2.1 ± 0.4 3.81 6. Rastrelliger kanakurta 23.0 ± 2.1 9.5 ± 1.4 2.42 7. Megalops cyprinoides 4.0 ± 0.6 1.6 ± 0.2 2.5 8. Ambassis commersoni 12.0 ± 1.5 3.0 ± 0.6 4.0 9. Sarotherodon mosambicus 8.6 ± 1.1 2.5 ± 0.4 3.44 10. Synaptura commersoniana 15.6 ± 1.7 4.2 ± 1.1 3.71 11. Stolephorus indicus 9.0 ± 0.8 3.6 ± 0.9 2.5 12. Therapon jarbua 7.3 ± 0.4 2.1 ± 0.3 3.47 Range 3.0–23.0 1.0–9.5 1.5–4.0 Mean ± SD 9.04 ± 5.7 3.03 ± 2.2 3.08 ± 0.7 No. of analysis (n) = 6 – 10. Table 8. Activity concentrations of 210Po and 210Pb in muscle of fishes from Nagappattinam. S. no. Species analyzed Activity (Bq /kg) dry 210Po/210Pb ratio 210Po 210Pb 1. Pampus argenteus 10.0 ± 1.4 3.0 ± 0.6 3.33 2. Carangoides armatus 3.0 ± 0.8 2.0 ± 0.5 1.5 3. Hirundichthys coromandelenesis 5.0 ± 1.2 1.8 ± 0.3 3.33 4. Scomberomorus guttatus 3.0 ± 0.9 1.0 ± 0.2 3.0 5. Nemipterus japonicus 8.0 ± 1.8 2.1 ± 0.4 3.81 6. Rastrelliger kanakurta 23.0 ± 2.1 9.5 ± 1.4 2.42 7. Megalops cyprinoides 4.0 ± 0.6 1.6 ± 0.2 2.5 8. Ambassis commersoni 12.0 ± 1.5 3.0 ± 0.6 4.0 9. Sarotherodon mosambicus 8.6 ± 1.1 2.5 ± 0.4 3.44 10. Synaptura commersoniana 15.6 ± 1.7 4.2 ± 1.1 3.71 11. Stolephorus indicus 9.0 ± 0.8 3.6 ± 0.9 2.5 12. Therapon jarbua 7.3 ± 0.4 2.1 ± 0.3 3.47 Range 3.0–23.0 1.0–9.5 1.5–4.0 Mean ± SD 9.04 ± 5.7 3.03 ± 2.2 3.08 ± 0.7 S. no. Species analyzed Activity (Bq /kg) dry 210Po/210Pb ratio 210Po 210Pb 1. Pampus argenteus 10.0 ± 1.4 3.0 ± 0.6 3.33 2. Carangoides armatus 3.0 ± 0.8 2.0 ± 0.5 1.5 3. Hirundichthys coromandelenesis 5.0 ± 1.2 1.8 ± 0.3 3.33 4. Scomberomorus guttatus 3.0 ± 0.9 1.0 ± 0.2 3.0 5. Nemipterus japonicus 8.0 ± 1.8 2.1 ± 0.4 3.81 6. Rastrelliger kanakurta 23.0 ± 2.1 9.5 ± 1.4 2.42 7. Megalops cyprinoides 4.0 ± 0.6 1.6 ± 0.2 2.5 8. Ambassis commersoni 12.0 ± 1.5 3.0 ± 0.6 4.0 9. Sarotherodon mosambicus 8.6 ± 1.1 2.5 ± 0.4 3.44 10. Synaptura commersoniana 15.6 ± 1.7 4.2 ± 1.1 3.71 11. Stolephorus indicus 9.0 ± 0.8 3.6 ± 0.9 2.5 12. Therapon jarbua 7.3 ± 0.4 2.1 ± 0.3 3.47 Range 3.0–23.0 1.0–9.5 1.5–4.0 Mean ± SD 9.04 ± 5.7 3.03 ± 2.2 3.08 ± 0.7 No. of analysis (n) = 6 – 10. Figure 6. View largeDownload slide Mean concentrations of 210Po and 210Pb in seafood organisms of Bay of Bengal. Figure 6. View largeDownload slide Mean concentrations of 210Po and 210Pb in seafood organisms of Bay of Bengal. Figure 7. View largeDownload slide Percentage of 210Po content in different body components of the oyster, Crassostrea madrasensis. Figure 7. View largeDownload slide Percentage of 210Po content in different body components of the oyster, Crassostrea madrasensis. Figure 8. View largeDownload slide Percentage of 210Po content in different body components of the clam, Meretrix casta. Figure 8. View largeDownload slide Percentage of 210Po content in different body components of the clam, Meretrix casta. Figure 9. View largeDownload slide Percentage of 210Po content in different body components of the fish, Sardinella longiceps. Figure 9. View largeDownload slide Percentage of 210Po content in different body components of the fish, Sardinella longiceps. The bioaccumulation of 210Po in shellfish species of Pitchavaram fluctuated from 3.4 to 45.2 Bq kg−1 with mean value of 14.1 ± 13.1 Bq kg−1 whereas bioaccumulation of 210Pb ranged from 0.51 to 9.2 Bq kg−1 with a mean value of 2.7 ± 2.5 Bq kg−1. Fish species in Pitchavaram Mangroves registered relatively a low level of 210Po and 210Pb. 210Po concentrations ranged from 1.0 to 16.5 Bq kg−1 with the mean value of 6.6 ± 4.4 Bq kg−1. Similarly 210Pb concentration ranged from 0.3 to 9.3 Bq kg−1 with the mean value of 2.3 ± 2.2 Bq kg−1. The ratio of 210Po/210Pb is always several times higher both in shellfish species (5.3) and fin fish species (4.2). The bioaccumulated concentration of 210Po in shellfish species of Nagappatinam ranged from 13.5 to 58.6 Bq kg−1 with overall mean value of 27.3 ± 14.2 Bq kg−1 and bioaccumulation of 210Pb ranged from 5.0 to 11.5 Bq kg−1 with a mean value of 7.5 ± 2.82 Bq kg−1. Fish species from Nagappattinam landing center registered relatively a low level of 210Po and 210Pb. The 210Po concentrations ranged from 3.0 to 23.0 Bq kg−1 with the mean value of 9.0 ± 5.7 Bq kg−1. Similarly 210Pb concentration ranged from 1.0 to 9.5 Bq kg−1 with the mean value of 3.0 ± 2.2 Bq kg−1. The ratio 210Po/210Pb registered higher values both in shellfish species (6.0) and fin fish species (3.1). Figure 6 indicated that among the shellfish species prawns registered a minimum mean activity concentration of 11.6 Bq kg−1 of 210Po. In contrast ~32.0 Bq kg−1 of 210Po was found to be accumulated in the molluscan species and crab species maintained an intermediated level of 16.5 Bq kg−1. However, fish species registered 7.6 Bq kg−1. A similar trend was also observed for the bioaccumulation of 210Pb in shellfish species and fishes. The accumulated level of 210Pb was found to be maximum (5.5 Bq kg−1) among mollascan species. The activity concentrations of 4.7 and 3.7 Bq kg−1 of 210Pb were recorded in the species of crab and prawn respectively. Fishes maintained a low level of 2.7 Bq kg−1 of 210Pb. The shellfish species analyzed in the present study fall into two groups of organisms namely crustaceans which include prawns and crabs, and molluscs which include bivalves, oyster, clam and squid. The bioaccumulation of 210Po in seafood organisms follows the descending order: The bioaccumulation of 210Po in the soft tissue of molluscan species (oyster, calm and squid) analyzed was found to be distinctly higher (31.6 Bq kg−1) as compared to crustacean species. Analysis of 210Po in 33 fish species revealed that fish muscle accumulated relatively a minimum average level of 7.6 Bq kg−1 210Po (range: 6.6–9.9 Bq kg−1). In general the bioaccumulation of 210Po largely depends on the nature of food and feeding habits of the organisms. Prawns and crabs largely feed on small organisms such as fish, copepods and other crustaceans in zooplankton(33). On the other hand bivalve molluscs such as oysters and clams are benthic organisms and they live buried in the bottom sand and feed on small organic particulate matters which are enriched with 210Po and therefore, the bioaccumulation of 210Po in molluscs is very high. Analysis of 210Pb concentration in shellfish species of prawn, crab and molluscs and a number of fish species indicated a similar trend as that of 210Po. This means that 210Pb concentration was relatively higher in shellfishes than in fish species. The situation clearly indicated that muscles are poor accumulators of 210Pb as compared to 210Po. The 210Pb concentration in crustacean species under the present study, ranged from 0.5 to 11.5 Bq kg−1 in muscle and these values are distinctly higher than the reported values of several investigators. Holtzman(34) reported 0.05 Bq kg−1 of 210Pb in muscle of prawns from Great Lakes in Alaska. 210Pb in prawns of the Mediterranean Sea was 0.024 Bq kg−1(35) and prawns and crabs of Kalpakkam coastal waters ranged from 0.22 to 1.2 Bq kg−1 for muscle and 0.78 to 2.4 Bq kg−1 for exoskeleton(28). The chemical affinity of 210Pb with calcified shells and bones is responsible for the higher level of concentration in bones and other mineralized parts of animals such as exoskeleton and shell as reported by several others(34, 36, 37). The prawn undergoes a phenomenon of ecdysis or periodic molting of exoskeleton. This shedding of the exoskeleton and formation of new one could possibly be attributed for lower level of 210Pb in the exoskeleton of prawn and it is also considered as natural mechanisms of shedding the body burden of 210Pb. Moreover, organic particulates are richer in 210Po than in 210Pb. This could also be attributed for the observed higher concentration of 210Po than 210Pb in these organisms. Intra-organismic distribution of 210Po In order to understand the biodistribution capacity of different internal organs of edible seafood organisms, the activity concentration of 210Po in various internal organs of an oyster (Crassostrea madrasensis), a clam (Meretrix casta) and a fish (Sardinella longiceps) were analyzed and reported in Figures 7–9. The data show the following descending orders: Oyster (Crassostrea madrasensis) Digestive Glands > Gills > Viscera > Mantle > Adductor Muscle Clam (Meretrix casta) Digestive Glands > Gills > Mantle > Viscera > Adductor Muscle Fish (Sardinella longiceps) Liver > Gills > Muscle > Intestine > Bone The biodistribution of 210Po was maximum in the digestive glands of the oyster (90 Bq kg−1 dry) and clam (42 Bq kg−1 dry). It may be concluded that the higher distribution of 210Po in digestive glands of bivalves is due to their dominant role in the digestive process of food particles which contain appreciable levels of 210Po. Next to digestive glands the gills in oyster distributed a higher amount of 210Po (61 Bq kg−1 dry). The gills act both as food filter and as a respiratory organ and hence form the site of uptake. Water loaded with oxygen and food material is drawn through the gills facilitating entry of radionuclides. Moreover, composition of the surrounding water might also play an equally important role because of its variation in radionuclide concentration. The mantle is also active sites of 210Po distribution. This is mainly due to an intimate contact with food particles on these organs. Further, the mucous has complex sulfate carbohydrate with the ion exchange of radionuclides across the cell membrane(38, 39). The per capita intake of seafood components is assessed by survey method. It was carried out in coastal population of the study area covering 150 families in three coastal villages. Detailed information about the diet was known from the population consisting mainly of fishermen and per capita consumption of major seafood species are assessed. From the radioactivity data of the seafood and the data on the diet information survey, the intake of 210Po and 210Pb was derived. Using the activity intake data and ICRP(40) dose factors, the dose to the individual member of the population was calculated (210Po: 1.2 × 10−6 Sv Bq−1: 210Pb: 6.9 × 10−7 Sv Bq−1). The committed effective dose rate (CEDE) recorded for shellfish species maintained a higher range (81.0–281.2 μSv y−1). However, dose transfer rate from fish species varied from 14.4 to 165.6 μSv y−1. Though the average consumption of fish is found to be higher than the shellfish, fish transfer lesser CEDE to the public. The work on measurements of 210Po and 210Pb in other terrestrial food items is in progress. CONCLUSIONS It is concluded from the results that distribution of 210Po and 210Pb in water, sand and their bioaccumulation in seafood organisms from the Bay of Bengal was non-uniform and widely fluctuating. The 210Pb concentration in the coastal water is always higher than 210Po for a given station. On contrary, the mean 210Po/210Pb ratios in sand was 1.7 indicating the 210Po concentrations in the sand sample is always about twice the concentration of 210Pb in sand sample. Further small sand grains (105 μm) has stronger chemical affinity to both 210Po (9.5 Bq kg−1) and 210Pb (5.2 Bq kg−1) and this may be due to the deposition of organic compound which are generally rich source of 210Po. The maximum activity of the two radionuclides was observed up to 10 cm depth (210Po: 6.4 Bq kg−1 and 210Pb: 4.1 Bq kg−1) and the activity declined with increasing depth. The bioaccumulation capability in seafood organisms maintain the following trend: Oyster> Clam > Squid > Crab > Prawn > Fish. It is concluded that in sand and biota, 210Po/210Pb ratios always exceeded unity indicating that unsupported nature of 210Po, i.e. not depend on parent 210Pb. Among the seafood organisms shellfish intake decisively augmented dose to consumer as compared to fish intake. In conclusion finfish is radiologically safer than shellfishes. ACKNOWLEDGEMENTS The authors thankfully acknowledge Shri S. Chandrasekaran, RSD, Dr K. Sivasubramanian, Head, RAMS, Dr R. Baskaran, Head, RSD Dr B. Venkatraman, Director, HSEG and Dr A.K. Bhaduri, Director, IGCAR, Kalpakkam for their academic and technical support. FUNDING This work was supported by Board of Research in Nuclear Sciences (BRNS), Mumbai, Department of Atomic Energy. Government of India. Project No. 2006/37/36/BRNS. REFERENCES 1 UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) . 2000 . Sources, effects and risks of ionizing radiation. 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DISTRIBUTION AND BIOACCUMULATION OF 210Po AND 210Pb IN ABIOTIC AND BIOTIC COMPONENTS OF THE BAY OF BENGAL

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Abstract

Abstract Marine environment is enriched source of heavy minerals associated with radionuclides which are largely responsible for human exposure to radiation. Bay of Bengal is one among the important marine ecosystems in the world because of its high biodiversity. The aim of this work was to generate a comprehensive data on distribution and bioaccumulation of 210Po and 210Pb in marine environment of the Bay of Bengal. For this water and sand samples (10 stations), shellfishes (21 species) and fishes (43 species) were collected and the concentrations of 210Po and 210Pb were measured by radiochemical separation followed by alpha counting method using ZnS(Ag) detector. 210Pb concentration in the marine water (mean: 7.6 ± 3.31 mBq l−1) is always higher than 210Po (mean: 4.1 ± 1.97 mBq l−1). The mean 210Po and 210Pb concentration in sand was 5.2 ± 1.87 and 3.1 ± 1.20 Bq kg−1, respectively; indicating that 210Po concentrations in the sand sample is always higher than that of 210Pb. The concentration of both 210Po and 210Pb depends on grain size of the sand. Surface samples of depth 0–10 cm recorded maximum 210Po (6.37 Bq kg−1) and 210Pb (4.07 Bq kg−1) concentration. The concentrations of 210Po and 210Pb in biota are following decreasing order: Oyster > Clam > Squid > Crab > Prawn > Fish. The committed effective dose rate calculated for shellfish species maintained a higher range of 81.0–281.2 μSv y−1. However, dose transfer rate from fish species fluctuated from 14.4 to 165.6 μSv y−1and this indicated that fish is radiologically safe as compared to shellfish. INTRODUCTION Naturally occurring, radioactive materials present in the marine environment are responsible for delivering the majority of radiation dose to marine fauna. The short-lived decay products of 226Ra (viz., 222Rn, 218Po, 214Pb, 214Bi, 214Po, 210Pb, 210Bi and 210Po) are a source of radiation dose to marine fauna, especially the alpha-emitters 218Po, 214Po and 210Po. Radium-226 in the crust of the earth decays into 222Rn gas that diffuses into seawater and is the origin of the short-lived decay products in the water. Of these, 210Pb has the longest half-life (22.2 years) and is the parent of 210Po, an alpha-emitting isotope with a half-life of only 138.4 days(1). Polonium-210 is responsible for a large fraction of the natural radiation dose delivered to many of the living species in seawater(2–5). Carvalho and Fowler(6) stated that most of the marine species are highly enriched with 210Po and 210Pb and they contribute ~8% of the total internal dose received by man. They also studied the kinetics of 210Po and 210Pb accumulation from water to seafood. Yamamoto et al.(7) observed that the 210Po and 210Pb concentrations are relatively low in meat, medium in milk, vegetables and cereals, and high in most of the marine organisms. The fact of 210Pb that enters the sea surface of North Pacific was first examined by Rama et al.(8). The concentrations of 210Po and 210Pb have been studied extensively in the biosphere and more particularly in the human environment(9–11). Indian peninsula is the second largest peninsula in the world which covers 20 72 000.85 km2 and it is the sixth largest producer of marine fishes(12). In India the annual per capita consumption of fish is ~5–6 kg, further fish is the staple food for any coastal environment so there is a distinct need for investigation of the accumulation of 210Po and 210Pb by aquatic organisms that constitute human food sources. Considering the importance of radiological status of the Bay of Bengal, the present investigation of measuring the concentration of 210Po and 210Pb in water, sediment and marine food organisms such as shellfishes like prawn, crab and molluscs and several species of fin fishes were undertaken. This data would be helpful in the future in case of any changes in the environment like Tsunami. STUDY AREA Bay of Bengal is the largest bay in the world. It forms the northeastern part of the Indian Ocean. It is roughly triangular in shape and it occupies an area of 2 172 000 km2. It has several estuaries, coral reefs and mangroves hence it is full of biological diversity. It is one of the largest marine ecosystems in the world. So it is important to measure the concentration of radioactive isotopes in biotic and abiotic components of the marine ecosystem. Hence the present study was undertaken in a 159 km coastal stretch of the Bay of Bengal (Pondycherry to Velanganni). A total of 10 different sampling stations were selected for 210Po and 210Pb measurements. The distance between each station is ~ 10–15 km (Figure 1). Figure 1. View largeDownload slide Map showing the study area. Figure 1. View largeDownload slide Map showing the study area. MATERIALS AND METHODS Methods such as radiochemical separation (co-precipitation and acid leaching), extraction chromatography, ion exchange separation (anion exchange resin) and solvent extraction have been employed for determination of 210Po and 210Pb in environmental matrices. For the present study co-precipitation (for water samples) and wet acid digestion (for biota and sand samples) followed by alpha counting has been adopted for 210Po and 210Pb measurements. Because processing of sample using wet acid digestion and co-precipitation are more conventional and cost effective than the other methods. Analysis of 210Po in water samples Seawater (~100 l) was filtered through a Whatman 40 filter paper and acidified with concentrated HCl to pH 1. Iron (ferric chloride) carrier (500 mg) was added to the filtered and acidified sample and the 210Po in the filtered water was collected on ferric hydroxide precipitate by slow addition of concentrated ammonia solution with rapid stirring until pH reached 9. Two repeat precipitations were carried out to completely carry 210Po by Fe(OH)3. The complete precipitate carrying 210Po was dissolved in 6 N HCl. A silver planchette (0.8 mm thickness and 2.5 cm diameter) of pre-determined background was suspended in the sample solution by means of a nylon thread at the end of a glass rod, connected to a stirrer. The solution is stirred for a period of 6 h. Spontaneous deposition of 210Po on both sides of the silver planchette took place under these conditions. At the end of the plating period, the planchette was taken out, rinsed with alcohol, dried under an infrared lamp and counted for activity on both sides in an alpha counter (ZnS(Ag): 28% efficiency with background count rate of 0.1 cpm). Analysis of sand Beach sand sample (~10 g) was ground to pass through 100 μm meshes and oven dried at 110°C for 24 h to remove moisture. The sample was then heated three times with con.HNO3 evaporating to near dryness each time. The residue was evaporated with con.HCl repeatedly to convert to chloride medium and taken in 0.5 N HCl for auto-deposition of 210Po on to a silver (Ag) planchette as stated above. 210Po and 210Pb activities in coastal sand at different depth In order to understand the depth-wise distribution of 210Po and 210Pb in the beach sand, core sampling of the sand was undertaken in the beach to a depth of 30 cm in six sampling stations (S1–S6). The core was sliced at various depths namely 5, 10, 15, 20, 25 and 30 cm and the activities of 210Po and 210Pb were measured in each slice. Distribution of 210Po and 210Pb in different grain sizes of coastal sand The beach sand sample was successively sifted in 105, 300 and 500 μm sieves and various fractions of sand grains were obtained (105, 300 and 500 μm) and activity of 210Po and 210Pb were measured in each fraction. Analysis of biological materials Owing to highly volatile nature of 210Po in dry ash conditions, the biological samples (~50 g) were wet processed repeatedly with con.HNO3 and H2O2 (1:1) oxidizing mixture added in small increments (5–10 ml at a time) till a white residue obtained. Then the residue was made up to 0.5 N HCl and placed on a magnetic stirrer with thermostat control at a temperature of 90–95°C. Ascorbic acid (100 mg) was added to reduce ferric ions to ferrous, thus eliminating interference in electrochemical deposition of 210Po. The 210Po activity was measured by spontaneous deposition followed by alpha counting. Determination of 210Pb The 210Pb concentrations in water, sediment and biological samples were determined by incubation method(13). Even though 210Pb is a beta emitter it can be able to measured by alpha counting. In this method the final solutions used for spontaneous deposition of 210Po (210Po is completely removed) in the above mentioned samples were incubated for a period of 138 days (equivalent to half-life period of 210Po). After the incubation period, 210Po formed from the parent 210Pb was subjected to spontaneous deposition on a silver planchette and counted for alpha radiation, i.e. whatever 210Po present in solution is proportional to 210Pb only; from the 210Po concentration 210Pb was deduced. RESULTS AND DISCUSSIONS 210Po and 210Pb distribution in coastal water Station-wise data on concentrations of 210Po, 210Pb and their activity ratios (210Po/210Pb) in the coastal water of Bay of Bengal measured are presented in Table 1. The levels of 210Po ranged in water from 1.4 to 7.4 mBq l−1 with a mean value of 4.1 ± 1.97 mBq l−1 and that of 210Pb ranged from 3.1 to 13.7 mBq l−1 with a mean value of 7.6 ± 3.31 mBq l−1. It is evident from results that 210Pb concentration in the coastal water is always higher than 210Po for a given station (Figure 2). The activity ratios of 210Po/210Pb lie within the narrow range from 0.32 to 0.81 (mean: 0.52). Among the 10 sampling stations analyzed a minimum activity levels of 210Po (1.4 ± 0.32 mBq l−1) and 210Pb (3.1 ± 0.55 mBq l−1) were recorded in Pitchavaram Mangroves (S3) and a maximum level of 210Po (7.4 ± 0.55 mBq l−1) was recorded in Nagappattinam (S9) and maximum level of 210Pb (13.7 ± 0.96 mBq l−1) in Karaikal coast (S7). In general, a higher level of 210Po and 210Pb were recorded in southern stations (S7–S10) as compared to the northern stations (S1–S6). The concentration of 210Po in Nagappattinam coastal water was five times higher than that of Pitchavaram Mangroves. The average concentration of 210Po in Bay of Bengal is lower when compare to adjacent coast, Gulf of Mannar (15 ± 9.5 mBq l−1) by Masilamani(14) and higher when compared to the mean value of 210Po (1.5 mBq l−1) in Palk Strait by Bukhari et al.(15), Ennore Creek (2.7 mBq l−1) by Musthafa and Krishnamoorthy(16) and Kalpakkam coast value (1.9 mBq l−1) by Iyengar et al.(17). 210Po concentrations in coastal water was studied by several workers in different region of the world and these values ranged from 0.29 to 2.4 mBq l−1(2) for South African waters (0.30–1.5 mBq l−1) by Shannon et al.(18), for North sea (0.37 mBq l−1) by Spencer et al.(19), for Duch coast (1.0 mBq l−1) by Koster et al.(20) for Great Yarmouth (4.0 mBq l−1) by Mc Donald et al.(21) and for USSR (9.2 mBq l−1) by Parfenov(3) which are lower than the present value. Table 1. Station-wise mean 210 Po and 210Pb activities in coastal water, sand and Kd factor. Name of the station Activity (mBq l−1) 210Po/210Pb ratio Activity (Bq kg−1) 210Po/210Pb ratio Kd factor 210Po 210Pb 210Po 210Pb 210Po 210Pb Pondycherry (S1) 3.7 ± 0.17 8.3 ± 0.88 0.44 6.1 ± 0.37 4.0 ± 0.37 1.52 1.6 × 103 4.8 × 102 Devanampattinam (S2) 2.8 ± 0.24 4.2 ± 0.60 0.66 5.7 ± 0.79 2.6 ± 0.58 2.19 2.0 × 103 6.2 × 102 Pitchavaram Mangroves (S3) 1.4 ± 0.32 3.1 ± 0.55 0.45 2.5 ± 0.63 1.3 ± 0.27 1.92 1.8 × 103 42.x 102 Tirumullaivasal (S4) 3.0 ± 0.48 7.1 ± 0.73 0.41 4.8 ± 0.59 2.9 ± 0.43 1.65 1.6 × 103 4.1 × 102 Poompukar (S5) 2.9 ± 0.41 4.5 ± 0.66 0.64 8.0 ± 0.51 4.3 ± 0.60 1.74 2.6 × 103 1.7 × 103 Tharangambadi (S6) 2.0 ± 0.43 6.0 ± 0.57 0.32 7.5 ± 0.88 4.1 ± 0.41 1.95 4.0 × 103 1.3 × 103 Karaikal (S7) 6.5 ± 0.45 13.7 ± 0.96 0.47 6.3 ± 0.58 4.5 ± 0.52 1.40 1.0 × 103 4.6 × 102 Nagore (S8) 5.0 ± 0.43 8.7 ± 0.58 0.57 5.2 ± 0.42 3.9 ± 0.57 1.33 1.0 × 103 4.5 × 102 Nagappattinam (S9) 7.4 ± 0.55 9.1 ± 0.70 0.81 3.7 ± 0.60 2.1 ± 0.30 1.76 5.0 102 2.4 × 102 Velanganni (S10) 6.0 ± 0.53 12.0 ± 0.93 0.49 2.6 ± 0.57 1.6 ± 0.32 1.62 4.3 × 102 1.3 × 102 Over all range 1.4–7.4 3.1–13.7 0.32–0.81 2.5–8.0 1.3–4.5 1.33–2.19 4.3 × 102–4.0 × 103 1.3 × 102–1.7 × 103 Over all mean ± SD 4.1 ± 1.97 7.6 ± 3.31 0.52 ± 0.14 5.2 ± 1.87 3.1 ± 1.20 1.70 ± 0.26 1.7 × 103 6.2 × 102 Name of the station Activity (mBq l−1) 210Po/210Pb ratio Activity (Bq kg−1) 210Po/210Pb ratio Kd factor 210Po 210Pb 210Po 210Pb 210Po 210Pb Pondycherry (S1) 3.7 ± 0.17 8.3 ± 0.88 0.44 6.1 ± 0.37 4.0 ± 0.37 1.52 1.6 × 103 4.8 × 102 Devanampattinam (S2) 2.8 ± 0.24 4.2 ± 0.60 0.66 5.7 ± 0.79 2.6 ± 0.58 2.19 2.0 × 103 6.2 × 102 Pitchavaram Mangroves (S3) 1.4 ± 0.32 3.1 ± 0.55 0.45 2.5 ± 0.63 1.3 ± 0.27 1.92 1.8 × 103 42.x 102 Tirumullaivasal (S4) 3.0 ± 0.48 7.1 ± 0.73 0.41 4.8 ± 0.59 2.9 ± 0.43 1.65 1.6 × 103 4.1 × 102 Poompukar (S5) 2.9 ± 0.41 4.5 ± 0.66 0.64 8.0 ± 0.51 4.3 ± 0.60 1.74 2.6 × 103 1.7 × 103 Tharangambadi (S6) 2.0 ± 0.43 6.0 ± 0.57 0.32 7.5 ± 0.88 4.1 ± 0.41 1.95 4.0 × 103 1.3 × 103 Karaikal (S7) 6.5 ± 0.45 13.7 ± 0.96 0.47 6.3 ± 0.58 4.5 ± 0.52 1.40 1.0 × 103 4.6 × 102 Nagore (S8) 5.0 ± 0.43 8.7 ± 0.58 0.57 5.2 ± 0.42 3.9 ± 0.57 1.33 1.0 × 103 4.5 × 102 Nagappattinam (S9) 7.4 ± 0.55 9.1 ± 0.70 0.81 3.7 ± 0.60 2.1 ± 0.30 1.76 5.0 102 2.4 × 102 Velanganni (S10) 6.0 ± 0.53 12.0 ± 0.93 0.49 2.6 ± 0.57 1.6 ± 0.32 1.62 4.3 × 102 1.3 × 102 Over all range 1.4–7.4 3.1–13.7 0.32–0.81 2.5–8.0 1.3–4.5 1.33–2.19 4.3 × 102–4.0 × 103 1.3 × 102–1.7 × 103 Over all mean ± SD 4.1 ± 1.97 7.6 ± 3.31 0.52 ± 0.14 5.2 ± 1.87 3.1 ± 1.20 1.70 ± 0.26 1.7 × 103 6.2 × 102 Table 1. Station-wise mean 210 Po and 210Pb activities in coastal water, sand and Kd factor. Name of the station Activity (mBq l−1) 210Po/210Pb ratio Activity (Bq kg−1) 210Po/210Pb ratio Kd factor 210Po 210Pb 210Po 210Pb 210Po 210Pb Pondycherry (S1) 3.7 ± 0.17 8.3 ± 0.88 0.44 6.1 ± 0.37 4.0 ± 0.37 1.52 1.6 × 103 4.8 × 102 Devanampattinam (S2) 2.8 ± 0.24 4.2 ± 0.60 0.66 5.7 ± 0.79 2.6 ± 0.58 2.19 2.0 × 103 6.2 × 102 Pitchavaram Mangroves (S3) 1.4 ± 0.32 3.1 ± 0.55 0.45 2.5 ± 0.63 1.3 ± 0.27 1.92 1.8 × 103 42.x 102 Tirumullaivasal (S4) 3.0 ± 0.48 7.1 ± 0.73 0.41 4.8 ± 0.59 2.9 ± 0.43 1.65 1.6 × 103 4.1 × 102 Poompukar (S5) 2.9 ± 0.41 4.5 ± 0.66 0.64 8.0 ± 0.51 4.3 ± 0.60 1.74 2.6 × 103 1.7 × 103 Tharangambadi (S6) 2.0 ± 0.43 6.0 ± 0.57 0.32 7.5 ± 0.88 4.1 ± 0.41 1.95 4.0 × 103 1.3 × 103 Karaikal (S7) 6.5 ± 0.45 13.7 ± 0.96 0.47 6.3 ± 0.58 4.5 ± 0.52 1.40 1.0 × 103 4.6 × 102 Nagore (S8) 5.0 ± 0.43 8.7 ± 0.58 0.57 5.2 ± 0.42 3.9 ± 0.57 1.33 1.0 × 103 4.5 × 102 Nagappattinam (S9) 7.4 ± 0.55 9.1 ± 0.70 0.81 3.7 ± 0.60 2.1 ± 0.30 1.76 5.0 102 2.4 × 102 Velanganni (S10) 6.0 ± 0.53 12.0 ± 0.93 0.49 2.6 ± 0.57 1.6 ± 0.32 1.62 4.3 × 102 1.3 × 102 Over all range 1.4–7.4 3.1–13.7 0.32–0.81 2.5–8.0 1.3–4.5 1.33–2.19 4.3 × 102–4.0 × 103 1.3 × 102–1.7 × 103 Over all mean ± SD 4.1 ± 1.97 7.6 ± 3.31 0.52 ± 0.14 5.2 ± 1.87 3.1 ± 1.20 1.70 ± 0.26 1.7 × 103 6.2 × 102 Name of the station Activity (mBq l−1) 210Po/210Pb ratio Activity (Bq kg−1) 210Po/210Pb ratio Kd factor 210Po 210Pb 210Po 210Pb 210Po 210Pb Pondycherry (S1) 3.7 ± 0.17 8.3 ± 0.88 0.44 6.1 ± 0.37 4.0 ± 0.37 1.52 1.6 × 103 4.8 × 102 Devanampattinam (S2) 2.8 ± 0.24 4.2 ± 0.60 0.66 5.7 ± 0.79 2.6 ± 0.58 2.19 2.0 × 103 6.2 × 102 Pitchavaram Mangroves (S3) 1.4 ± 0.32 3.1 ± 0.55 0.45 2.5 ± 0.63 1.3 ± 0.27 1.92 1.8 × 103 42.x 102 Tirumullaivasal (S4) 3.0 ± 0.48 7.1 ± 0.73 0.41 4.8 ± 0.59 2.9 ± 0.43 1.65 1.6 × 103 4.1 × 102 Poompukar (S5) 2.9 ± 0.41 4.5 ± 0.66 0.64 8.0 ± 0.51 4.3 ± 0.60 1.74 2.6 × 103 1.7 × 103 Tharangambadi (S6) 2.0 ± 0.43 6.0 ± 0.57 0.32 7.5 ± 0.88 4.1 ± 0.41 1.95 4.0 × 103 1.3 × 103 Karaikal (S7) 6.5 ± 0.45 13.7 ± 0.96 0.47 6.3 ± 0.58 4.5 ± 0.52 1.40 1.0 × 103 4.6 × 102 Nagore (S8) 5.0 ± 0.43 8.7 ± 0.58 0.57 5.2 ± 0.42 3.9 ± 0.57 1.33 1.0 × 103 4.5 × 102 Nagappattinam (S9) 7.4 ± 0.55 9.1 ± 0.70 0.81 3.7 ± 0.60 2.1 ± 0.30 1.76 5.0 102 2.4 × 102 Velanganni (S10) 6.0 ± 0.53 12.0 ± 0.93 0.49 2.6 ± 0.57 1.6 ± 0.32 1.62 4.3 × 102 1.3 × 102 Over all range 1.4–7.4 3.1–13.7 0.32–0.81 2.5–8.0 1.3–4.5 1.33–2.19 4.3 × 102–4.0 × 103 1.3 × 102–1.7 × 103 Over all mean ± SD 4.1 ± 1.97 7.6 ± 3.31 0.52 ± 0.14 5.2 ± 1.87 3.1 ± 1.20 1.70 ± 0.26 1.7 × 103 6.2 × 102 Figure 2. View largeDownload slide 210Po and 210Pb activity in water samples of Bay of Bengal. Figure 2. View largeDownload slide 210Po and 210Pb activity in water samples of Bay of Bengal. The dissolved 210Pb concentration is distinctly higher when compared to Palk Strait (2.8 mBq l−1) by Bukhari et al.(15), Point Calimere (1.3 ± 0.2 mBq l−1) by Suriyanarayanan et al.(22), Mumbai coast (2.0 mBq l−1) by Bangera and Rudran(23), Ennore Creek (1.6 mBq l−1) by Musthafa and Krishnamoorthy(16) and lower than the mean levels reported in Gulf of Manner (20.6 ± 10.6 mBq l−1) by Masilamani(14). The wide variation was largely due to atmospheric input of 210Pb which varied latitudinally(24). Also variations in 210Pb concentration with depth were reported(25, 26). However, a typical average seawater value of 1.875 mBq l−1 was derived by Cherry and Shannon(2). This value is less when compared with the present study. The calculated 210Po/210Pb ratios for the coastal waters worked out to be 0.52 showing a 48% depletion of 210Po in water samples. Bacon et al.(26) stated that the rate of binding of 210Po to organic particulates was higher and its availability in dissolved form was much reduced and hence it registered a low level in water. 210Po and 210Pb distribution in coastal sand The concentration of 210Po in sand samples varied from 2.5 to 8.0 Bq kg−1 having a mean value of 5.2 ± 1.87 Bq kg−1 and that of 210Pb ranged from 1.3 to 4.5 Bq kg−1 with a mean value of 3.1 ± 1.2 Bq kg−1 (Table 1). It is observed from results that 210Po in the coastal sand is in higher concentration than 210Pb (Figure 3). Pitchavaram Mangroves (S3) recorded minimum activity levels of 210Po (2.5 ± 0.63 Bq kg−1) and 210Pb (1.3 ± 0.27 Bq kg−1) and a maximum level of 210Po (8.0 ± 0.51 Bq kg−1) in Tharangambadi (S6) and 210Pb (4.5 ± 0.52 Bq kg−1) in Karaikkal coast (S7). The mean activity concentration of 210Po in the coastal sand of Bay of Bengal was relatively far less than the mean activity in Gulf of Mannar (35.5 Bq kg−1) by Masilamani(14), Mallipattinam coastal sand (4.0 Bq kg−1) by Suriyanarayanan et al.(27) and Kalpakkam coastal sand (44.0 Bq kg−1) by Iyengar et al.(28) and Mangalore coast (1.23–17.72 Bq kg−1) by Siddappa et al.(29) and coastal Karnataka (6.22–18.9 Bq kg−1) by Narayana et al.(30) and Ullal coast (1.7–43.2 Bq kg−1) Narayana and Prakash(31). Figure 3. View largeDownload slide 210Po and 210Pb activity in coastal sand samples of Bay of Bengal. Figure 3. View largeDownload slide 210Po and 210Pb activity in coastal sand samples of Bay of Bengal. The mean activity concentration of 210Pb was much lower than those reported for the Kalpakkam beach sand (385.0 Bq kg−1) by Iyengar et al.(28), Mallipattinam coastal (1.0 Bq kg−1) by Suriyanarayanan et al.(27) and Trombay coast (356.0 Bq kg−1) by Bangera and Patel(32) and Comparable to Southwest coast of Mangalore environment (3.6–58.13 Bq kg−1) Siddappa et al.(29) and Honnavar environment (40.01 Bq kg−1) by Narayana et al.(30). The 210Po/210Pb ratios calculated for the entire stretch to be 1.7 indicating that the 210Po concentration in sand sample is always about twice the concentration of 210Pb. The higher concentration of 210Po in sand sample may be due to deposition of organic particulates which are generally rich source of 210Po. Kd factor The fraction of 210Po and 210Pb between sand and ambient medium is termed as distribution coefficient or Kd factor. It is a ratio of the total amount of a radionuclide per unit of dry sand to the amount of same radionuclide per unit volume of water. The Kd factor for 210Po varied from 4.3 × 102 to 4.0 × 103 and 1.3 × 102 to 1.7 × 103 for 210Pb. A higher distribution coefficient indicates a stronger binding of the radionuclide to the sand and vice versa. Grain size The distribution of 210Po and 210Pb in different grain size of beach sand collected from five stations (S1 and S3 to S6) are presented in Table 2 and Figures 4 and 5. A maximum concentration of 210Po (mean: 9.5 ± 4.2 Bq kg−1) was recorded in the particle size 105 μm (range: 4.0–15.5 Bq kg−1) and minimum concentration of 210Po (mean: 3.7 ± 1.3 Bq kg−1) in the particles of 500 μm (range: 2.0–5.0 Bq kg−1). The sand grains of 300 μm size registered intermediate level of 210Po concentration (mean: 5.8 ± 2.4 Bq kg−1) with a range from 3.0 to 9.0 Bq kg−1. A similar trend was also found with respect to 210Pb activities. The sand particles of 105 μm recorded a maximum level of 210Pb activity (mean: 5.2 ± 1.65 Bq kg−1; range: 3.1–7.3 Bq kg−1) and minimum level of 1.3 ± 0.48 Bq kg−1 (range: 1.0–2.0 Bq kg−1) in 500 μm particles. The sand particles of 300 μm registered an intermediate concentration of 3.3 ± 1.59 Bq kg−1 (range: 1.8–5.6 Bq kg−1). Table 2. Distribution of 210Po and 210Pb in different grains size in coastal sand of Bay of Bengal. Name of the station 210Po activity (Bq kg−1) 210Pb activity (Bq kg−1) 105 μm 300 μm 500 μm 105 μm 300 μm 500 μm Pondycherry (S1) 9.0 7.0 5.0 6.0 4.2 2.0 Pitchavaram Mangroves (S3) 4.0 3.0 2.0 3.1 1.8 0.8 Tirumullaivasal (S4) 8.0 4.0 3.0 4.0 3.0 1.0 Poompukar (S5) 11.0 6.0 3.8 5.5 2.0 1.0 Tharangambadi (S6) 15.5 9.0 5.0 7.3 5.6 1.5 Over all range 4–15.5 3–9 2.0–5.0 3.1–7.3 1.8–5.6 1–2.0 Over all mean ± SD 9.5 ± 4.2 5.8 ± 2.4 3.7 ± 1.3 5.2 ± 1.6 3.32 ± 1.6 1.3 ± 0.5 Name of the station 210Po activity (Bq kg−1) 210Pb activity (Bq kg−1) 105 μm 300 μm 500 μm 105 μm 300 μm 500 μm Pondycherry (S1) 9.0 7.0 5.0 6.0 4.2 2.0 Pitchavaram Mangroves (S3) 4.0 3.0 2.0 3.1 1.8 0.8 Tirumullaivasal (S4) 8.0 4.0 3.0 4.0 3.0 1.0 Poompukar (S5) 11.0 6.0 3.8 5.5 2.0 1.0 Tharangambadi (S6) 15.5 9.0 5.0 7.3 5.6 1.5 Over all range 4–15.5 3–9 2.0–5.0 3.1–7.3 1.8–5.6 1–2.0 Over all mean ± SD 9.5 ± 4.2 5.8 ± 2.4 3.7 ± 1.3 5.2 ± 1.6 3.32 ± 1.6 1.3 ± 0.5 Table 2. Distribution of 210Po and 210Pb in different grains size in coastal sand of Bay of Bengal. Name of the station 210Po activity (Bq kg−1) 210Pb activity (Bq kg−1) 105 μm 300 μm 500 μm 105 μm 300 μm 500 μm Pondycherry (S1) 9.0 7.0 5.0 6.0 4.2 2.0 Pitchavaram Mangroves (S3) 4.0 3.0 2.0 3.1 1.8 0.8 Tirumullaivasal (S4) 8.0 4.0 3.0 4.0 3.0 1.0 Poompukar (S5) 11.0 6.0 3.8 5.5 2.0 1.0 Tharangambadi (S6) 15.5 9.0 5.0 7.3 5.6 1.5 Over all range 4–15.5 3–9 2.0–5.0 3.1–7.3 1.8–5.6 1–2.0 Over all mean ± SD 9.5 ± 4.2 5.8 ± 2.4 3.7 ± 1.3 5.2 ± 1.6 3.32 ± 1.6 1.3 ± 0.5 Name of the station 210Po activity (Bq kg−1) 210Pb activity (Bq kg−1) 105 μm 300 μm 500 μm 105 μm 300 μm 500 μm Pondycherry (S1) 9.0 7.0 5.0 6.0 4.2 2.0 Pitchavaram Mangroves (S3) 4.0 3.0 2.0 3.1 1.8 0.8 Tirumullaivasal (S4) 8.0 4.0 3.0 4.0 3.0 1.0 Poompukar (S5) 11.0 6.0 3.8 5.5 2.0 1.0 Tharangambadi (S6) 15.5 9.0 5.0 7.3 5.6 1.5 Over all range 4–15.5 3–9 2.0–5.0 3.1–7.3 1.8–5.6 1–2.0 Over all mean ± SD 9.5 ± 4.2 5.8 ± 2.4 3.7 ± 1.3 5.2 ± 1.6 3.32 ± 1.6 1.3 ± 0.5 Figure 4. View largeDownload slide 210Po activities in different grain size of the coastal sand of Bay of Bengal. Figure 4. View largeDownload slide 210Po activities in different grain size of the coastal sand of Bay of Bengal. Figure 5. View largeDownload slide 210Pb activities in different grain size of the coastal sand of Bay of Bengal. Figure 5. View largeDownload slide 210Pb activities in different grain size of the coastal sand of Bay of Bengal. Depth-wise distribution of 210Po and 210Pb in coastal sand The distribution of 210Po and 210Pb at different depth in beach sand is presented in Tables 3 and 4. The maximum distribution of 210Po (6.37 Bq kg−1) and 210Pb (4.07 Bq kg−1) was found at the depth of 10 cm. However, the concentrations of the two radionuclides at the depth of 20–30 cm decline drastically. Table 3. 210Po Activities in coastal sand samples at different depths (core sampling). Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 6.14 6.85 5.57 4.30 3.54 3.24 Devanampattinam(S2) 5.02 6.81 4.20 3.25 2.06 1.82 Pitchavaram Mangroves (S3) 3.42 4.85 3.85 2.57 2.28 1.42 Tirumullaivasal (S4) 4.85 5.21 4.28 4.14 3.71 3.0 Poompukar (S5) 6.14 7.12 6.42 5.71 4.85 3.82 Tharangambadi (S6) 6.41 7.42 7.04 6.28 5.72 3.21 Over all range 3.42–6.41 4.85–7.42 3.85–7.04 2.57–6.28 2.06–5.72 1.42–3.82 Over all mean ± SD 5.33 ± 1.1 6.37 ± 1.07 5.22 ± 1.31 4.37 ± 1.41 3.69 ± 1.42 2.75 ± 0.92 Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 6.14 6.85 5.57 4.30 3.54 3.24 Devanampattinam(S2) 5.02 6.81 4.20 3.25 2.06 1.82 Pitchavaram Mangroves (S3) 3.42 4.85 3.85 2.57 2.28 1.42 Tirumullaivasal (S4) 4.85 5.21 4.28 4.14 3.71 3.0 Poompukar (S5) 6.14 7.12 6.42 5.71 4.85 3.82 Tharangambadi (S6) 6.41 7.42 7.04 6.28 5.72 3.21 Over all range 3.42–6.41 4.85–7.42 3.85–7.04 2.57–6.28 2.06–5.72 1.42–3.82 Over all mean ± SD 5.33 ± 1.1 6.37 ± 1.07 5.22 ± 1.31 4.37 ± 1.41 3.69 ± 1.42 2.75 ± 0.92 Table 3. 210Po Activities in coastal sand samples at different depths (core sampling). Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 6.14 6.85 5.57 4.30 3.54 3.24 Devanampattinam(S2) 5.02 6.81 4.20 3.25 2.06 1.82 Pitchavaram Mangroves (S3) 3.42 4.85 3.85 2.57 2.28 1.42 Tirumullaivasal (S4) 4.85 5.21 4.28 4.14 3.71 3.0 Poompukar (S5) 6.14 7.12 6.42 5.71 4.85 3.82 Tharangambadi (S6) 6.41 7.42 7.04 6.28 5.72 3.21 Over all range 3.42–6.41 4.85–7.42 3.85–7.04 2.57–6.28 2.06–5.72 1.42–3.82 Over all mean ± SD 5.33 ± 1.1 6.37 ± 1.07 5.22 ± 1.31 4.37 ± 1.41 3.69 ± 1.42 2.75 ± 0.92 Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 6.14 6.85 5.57 4.30 3.54 3.24 Devanampattinam(S2) 5.02 6.81 4.20 3.25 2.06 1.82 Pitchavaram Mangroves (S3) 3.42 4.85 3.85 2.57 2.28 1.42 Tirumullaivasal (S4) 4.85 5.21 4.28 4.14 3.71 3.0 Poompukar (S5) 6.14 7.12 6.42 5.71 4.85 3.82 Tharangambadi (S6) 6.41 7.42 7.04 6.28 5.72 3.21 Over all range 3.42–6.41 4.85–7.42 3.85–7.04 2.57–6.28 2.06–5.72 1.42–3.82 Over all mean ± SD 5.33 ± 1.1 6.37 ± 1.07 5.22 ± 1.31 4.37 ± 1.41 3.69 ± 1.42 2.75 ± 0.92 Table 4. 210Pb activities in coastal sand samples at different depths (core sampling). Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 4.64 3.57 3.12 2.57 2.14 1.76 Devanampattinam(S2) 3.10 3.23 4.51 2.40 2.53 1.29 Pitchavaram Mangroves (S3) 2.29 3.86 2.34 1.86 1.29 1.0 Tirumullaivasal (S4) 3.29 2.84 2.71 2.14 1.86 1.37 Poompukar (S5) 3.21 5.10 4.57 3.14 2.0 1.86 Tharangambadi (S6) 3.14 5.83 4.71 3.42 2.0 1.57 Over all range 2.29–4.64 2.84–5.83 2.34–4.71 1.86–3.42 1.29–2.53 1.0–1.86 Over all mean ± SD 3.27 ± 0.75 4.07 ± 1.15 3.66 ± 1.05 2.58 ± 0.59 1.97 ± 0.40 1.47 ± 0.31 Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 4.64 3.57 3.12 2.57 2.14 1.76 Devanampattinam(S2) 3.10 3.23 4.51 2.40 2.53 1.29 Pitchavaram Mangroves (S3) 2.29 3.86 2.34 1.86 1.29 1.0 Tirumullaivasal (S4) 3.29 2.84 2.71 2.14 1.86 1.37 Poompukar (S5) 3.21 5.10 4.57 3.14 2.0 1.86 Tharangambadi (S6) 3.14 5.83 4.71 3.42 2.0 1.57 Over all range 2.29–4.64 2.84–5.83 2.34–4.71 1.86–3.42 1.29–2.53 1.0–1.86 Over all mean ± SD 3.27 ± 0.75 4.07 ± 1.15 3.66 ± 1.05 2.58 ± 0.59 1.97 ± 0.40 1.47 ± 0.31 Table 4. 210Pb activities in coastal sand samples at different depths (core sampling). Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 4.64 3.57 3.12 2.57 2.14 1.76 Devanampattinam(S2) 3.10 3.23 4.51 2.40 2.53 1.29 Pitchavaram Mangroves (S3) 2.29 3.86 2.34 1.86 1.29 1.0 Tirumullaivasal (S4) 3.29 2.84 2.71 2.14 1.86 1.37 Poompukar (S5) 3.21 5.10 4.57 3.14 2.0 1.86 Tharangambadi (S6) 3.14 5.83 4.71 3.42 2.0 1.57 Over all range 2.29–4.64 2.84–5.83 2.34–4.71 1.86–3.42 1.29–2.53 1.0–1.86 Over all mean ± SD 3.27 ± 0.75 4.07 ± 1.15 3.66 ± 1.05 2.58 ± 0.59 1.97 ± 0.40 1.47 ± 0.31 Name of the station Different depth (Bq kg−1) 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm Pondycherry (S1) 4.64 3.57 3.12 2.57 2.14 1.76 Devanampattinam(S2) 3.10 3.23 4.51 2.40 2.53 1.29 Pitchavaram Mangroves (S3) 2.29 3.86 2.34 1.86 1.29 1.0 Tirumullaivasal (S4) 3.29 2.84 2.71 2.14 1.86 1.37 Poompukar (S5) 3.21 5.10 4.57 3.14 2.0 1.86 Tharangambadi (S6) 3.14 5.83 4.71 3.42 2.0 1.57 Over all range 2.29–4.64 2.84–5.83 2.34–4.71 1.86–3.42 1.29–2.53 1.0–1.86 Over all mean ± SD 3.27 ± 0.75 4.07 ± 1.15 3.66 ± 1.05 2.58 ± 0.59 1.97 ± 0.40 1.47 ± 0.31 Bioaccumulation of 210Po and 210Pb in seafood organisms The activity concentrations of 210Po and 210Pb accumulated in the edible parts (soft tissues and muscle) of shellfish species and fish species from three major fish landing centers of the study area namely Cuddalore (Devanampattinam), Pitchavaram Mangroves and Nagappattinam were analyzed. The shellfishes include species of prawns, crabs and mollascan species of squid, oyster and clam. The activity concentrations of 210Po and 210Pb measured in shellfish species and fin fish species were presented in Tables 5–8 and Figures 6–9. The bioaccumulation of 210Po in shellfish species ranged from 5.3 to 52.1 Bq kg−1 with overall mean of 18.4 ± 16.0 Bq kg−1 whereas bioaccumulation of 210Pb ranged from 1.6 to 11.3 Bq kg−1 with a mean value of 3.7 ± 3.0 Bq kg−1. Fish species in Devanampattinam registered relatively a low level of 210Po and 210Pb. The 210Po concentrations ranged from 2.0 to 17.6 Bq kg−1 with in the mean value of 7.3 ± 4.3 Bq kg−1. Similarly 210Pb concentration ranged from 0.6 to 11.7 Bq kg−1 with the mean value of 2.9 ± 2.0 Bq kg−1. The ratio of 210Po/210Pb is always several times higher in shellfish species (4.5) and fin fish species (5.0). Table 5. 210Po and 210Pb concentrations (Bq kg−1) in edible parts shell fishes of coast (S2). S. no. Name of the sample Devanampattinam (S2) Pitchavaram Mangroves (S3) Nagappattinam (S9) 210Po 210Pb 210Po 210Pb 210Po 210Pb Prawn 1.  Penaeus monodon 8.6 ± 1.2 2.7 ± 0.8 13.02 ± 0.3 2.2 ± 0.5 24.3 ± 1.6 11.0 ± 1.6 2.  Penaeus indicus 5.3 ± 0.8 1.6 ± 0.3 3.4 ± 0.02 0.51 ± 0.06 19.0 ± 1.4 6.5 ± 0.8 3.  Penaeus semisulcatus 6.7 ± 0.9 2.1 ± 0.5 7.6 ± 1.1 1.8 ± 0.3 17.0 ± 1.0 5.3 ± 0.3 Range 5.3–8.6 1.6–2.7 3.4–13.02 0.51–2.2 17.0–24.3 5.3–0.3 Mean ± SD 6.8 ± 1.6 2.1 ± 0.5 8.0 ± 4.8 1.5 ± 0.8 20.1 ± 3.7 7.6 ± 3.0 Crab 4.  Portunus sanguinolentus 7.6 ± 0.8 2.1 ± 0.4 5.4 ± 0.5 2.2 ± 0.2 28 ± 1.5 8.7 ± 1.3 5.  Portunus pelagicus 9.3 ± 0.6 2.4 ± 0.6 4.8 ± 0.3 1.5 ± 0.1 17.0 ± 1.3 6.4 ± 0.6 6.  Scylla serrata 26 ± 1.2 4.2 ± 0.9 11.3 ± 1.4 3.4 ± 0.6 39.3 ± 1.7 11.5 ± 1.5 Range 7.6–26 2.1–4.2 4.8–11.3 1.5–3.4 17.0–39.3 6.4–11.5 Mean ± SD 14.3 ± 10.1 2.9 ± 1.1 7.1 ± 3.5 2.3 ± 0.9 28.1 ± 11.1 8.8 ± 2.5 Molluscs 7.  Loligo duavucelli (Squid) 15.6 ± 0.3 2.8 ± 0.9 12.8 ± 1.4 1.8 ± 0.3 13.5 ± 1.1 5.0 ± 0.4 8.  Crassostrea madrasensis (Oyster) 52.1 ± 2.3 11.3 ± 1.4 45.2 ± 2.6 9.2 ± 0.9 58.6 ± 2.4 9.5 ± 1.6 9.  Meretrix casta (Clam) 34.3 ± 1.8 4.6 ± 1.1 23.7 ± 2.0 2.3 ± 0.4 29.4 ± 1.5 3.4 ± 1.4 Range 15.6–52.1 2.8–11.3 12.8–45.2 1.8–9.2 13.5–58.6 3.4–9.5 Mean ± SD 34 ± 18.2 6.2 ± 4.4 27.2 ± 16.4 4.4 ± 2.0 33.8 ± 22.8 5.9 ± 3.1 Over all range 5.3–52.1 1.6–11.3 3.4–45.2 0.51–9.2 13.5–58.6 3.4–11.5 Over all mean ± SD 18.4 ± 16.03 3.7 ± 2.99 14.1 ± 13.1 2.7 ± 2.5 27.3 ± 14.18 7.5 ± 2.82 S. no. Name of the sample Devanampattinam (S2) Pitchavaram Mangroves (S3) Nagappattinam (S9) 210Po 210Pb 210Po 210Pb 210Po 210Pb Prawn 1.  Penaeus monodon 8.6 ± 1.2 2.7 ± 0.8 13.02 ± 0.3 2.2 ± 0.5 24.3 ± 1.6 11.0 ± 1.6 2.  Penaeus indicus 5.3 ± 0.8 1.6 ± 0.3 3.4 ± 0.02 0.51 ± 0.06 19.0 ± 1.4 6.5 ± 0.8 3.  Penaeus semisulcatus 6.7 ± 0.9 2.1 ± 0.5 7.6 ± 1.1 1.8 ± 0.3 17.0 ± 1.0 5.3 ± 0.3 Range 5.3–8.6 1.6–2.7 3.4–13.02 0.51–2.2 17.0–24.3 5.3–0.3 Mean ± SD 6.8 ± 1.6 2.1 ± 0.5 8.0 ± 4.8 1.5 ± 0.8 20.1 ± 3.7 7.6 ± 3.0 Crab 4.  Portunus sanguinolentus 7.6 ± 0.8 2.1 ± 0.4 5.4 ± 0.5 2.2 ± 0.2 28 ± 1.5 8.7 ± 1.3 5.  Portunus pelagicus 9.3 ± 0.6 2.4 ± 0.6 4.8 ± 0.3 1.5 ± 0.1 17.0 ± 1.3 6.4 ± 0.6 6.  Scylla serrata 26 ± 1.2 4.2 ± 0.9 11.3 ± 1.4 3.4 ± 0.6 39.3 ± 1.7 11.5 ± 1.5 Range 7.6–26 2.1–4.2 4.8–11.3 1.5–3.4 17.0–39.3 6.4–11.5 Mean ± SD 14.3 ± 10.1 2.9 ± 1.1 7.1 ± 3.5 2.3 ± 0.9 28.1 ± 11.1 8.8 ± 2.5 Molluscs 7.  Loligo duavucelli (Squid) 15.6 ± 0.3 2.8 ± 0.9 12.8 ± 1.4 1.8 ± 0.3 13.5 ± 1.1 5.0 ± 0.4 8.  Crassostrea madrasensis (Oyster) 52.1 ± 2.3 11.3 ± 1.4 45.2 ± 2.6 9.2 ± 0.9 58.6 ± 2.4 9.5 ± 1.6 9.  Meretrix casta (Clam) 34.3 ± 1.8 4.6 ± 1.1 23.7 ± 2.0 2.3 ± 0.4 29.4 ± 1.5 3.4 ± 1.4 Range 15.6–52.1 2.8–11.3 12.8–45.2 1.8–9.2 13.5–58.6 3.4–9.5 Mean ± SD 34 ± 18.2 6.2 ± 4.4 27.2 ± 16.4 4.4 ± 2.0 33.8 ± 22.8 5.9 ± 3.1 Over all range 5.3–52.1 1.6–11.3 3.4–45.2 0.51–9.2 13.5–58.6 3.4–11.5 Over all mean ± SD 18.4 ± 16.03 3.7 ± 2.99 14.1 ± 13.1 2.7 ± 2.5 27.3 ± 14.18 7.5 ± 2.82 No. of analysis (n) = 6 – 10. Table 5. 210Po and 210Pb concentrations (Bq kg−1) in edible parts shell fishes of coast (S2). S. no. Name of the sample Devanampattinam (S2) Pitchavaram Mangroves (S3) Nagappattinam (S9) 210Po 210Pb 210Po 210Pb 210Po 210Pb Prawn 1.  Penaeus monodon 8.6 ± 1.2 2.7 ± 0.8 13.02 ± 0.3 2.2 ± 0.5 24.3 ± 1.6 11.0 ± 1.6 2.  Penaeus indicus 5.3 ± 0.8 1.6 ± 0.3 3.4 ± 0.02 0.51 ± 0.06 19.0 ± 1.4 6.5 ± 0.8 3.  Penaeus semisulcatus 6.7 ± 0.9 2.1 ± 0.5 7.6 ± 1.1 1.8 ± 0.3 17.0 ± 1.0 5.3 ± 0.3 Range 5.3–8.6 1.6–2.7 3.4–13.02 0.51–2.2 17.0–24.3 5.3–0.3 Mean ± SD 6.8 ± 1.6 2.1 ± 0.5 8.0 ± 4.8 1.5 ± 0.8 20.1 ± 3.7 7.6 ± 3.0 Crab 4.  Portunus sanguinolentus 7.6 ± 0.8 2.1 ± 0.4 5.4 ± 0.5 2.2 ± 0.2 28 ± 1.5 8.7 ± 1.3 5.  Portunus pelagicus 9.3 ± 0.6 2.4 ± 0.6 4.8 ± 0.3 1.5 ± 0.1 17.0 ± 1.3 6.4 ± 0.6 6.  Scylla serrata 26 ± 1.2 4.2 ± 0.9 11.3 ± 1.4 3.4 ± 0.6 39.3 ± 1.7 11.5 ± 1.5 Range 7.6–26 2.1–4.2 4.8–11.3 1.5–3.4 17.0–39.3 6.4–11.5 Mean ± SD 14.3 ± 10.1 2.9 ± 1.1 7.1 ± 3.5 2.3 ± 0.9 28.1 ± 11.1 8.8 ± 2.5 Molluscs 7.  Loligo duavucelli (Squid) 15.6 ± 0.3 2.8 ± 0.9 12.8 ± 1.4 1.8 ± 0.3 13.5 ± 1.1 5.0 ± 0.4 8.  Crassostrea madrasensis (Oyster) 52.1 ± 2.3 11.3 ± 1.4 45.2 ± 2.6 9.2 ± 0.9 58.6 ± 2.4 9.5 ± 1.6 9.  Meretrix casta (Clam) 34.3 ± 1.8 4.6 ± 1.1 23.7 ± 2.0 2.3 ± 0.4 29.4 ± 1.5 3.4 ± 1.4 Range 15.6–52.1 2.8–11.3 12.8–45.2 1.8–9.2 13.5–58.6 3.4–9.5 Mean ± SD 34 ± 18.2 6.2 ± 4.4 27.2 ± 16.4 4.4 ± 2.0 33.8 ± 22.8 5.9 ± 3.1 Over all range 5.3–52.1 1.6–11.3 3.4–45.2 0.51–9.2 13.5–58.6 3.4–11.5 Over all mean ± SD 18.4 ± 16.03 3.7 ± 2.99 14.1 ± 13.1 2.7 ± 2.5 27.3 ± 14.18 7.5 ± 2.82 S. no. Name of the sample Devanampattinam (S2) Pitchavaram Mangroves (S3) Nagappattinam (S9) 210Po 210Pb 210Po 210Pb 210Po 210Pb Prawn 1.  Penaeus monodon 8.6 ± 1.2 2.7 ± 0.8 13.02 ± 0.3 2.2 ± 0.5 24.3 ± 1.6 11.0 ± 1.6 2.  Penaeus indicus 5.3 ± 0.8 1.6 ± 0.3 3.4 ± 0.02 0.51 ± 0.06 19.0 ± 1.4 6.5 ± 0.8 3.  Penaeus semisulcatus 6.7 ± 0.9 2.1 ± 0.5 7.6 ± 1.1 1.8 ± 0.3 17.0 ± 1.0 5.3 ± 0.3 Range 5.3–8.6 1.6–2.7 3.4–13.02 0.51–2.2 17.0–24.3 5.3–0.3 Mean ± SD 6.8 ± 1.6 2.1 ± 0.5 8.0 ± 4.8 1.5 ± 0.8 20.1 ± 3.7 7.6 ± 3.0 Crab 4.  Portunus sanguinolentus 7.6 ± 0.8 2.1 ± 0.4 5.4 ± 0.5 2.2 ± 0.2 28 ± 1.5 8.7 ± 1.3 5.  Portunus pelagicus 9.3 ± 0.6 2.4 ± 0.6 4.8 ± 0.3 1.5 ± 0.1 17.0 ± 1.3 6.4 ± 0.6 6.  Scylla serrata 26 ± 1.2 4.2 ± 0.9 11.3 ± 1.4 3.4 ± 0.6 39.3 ± 1.7 11.5 ± 1.5 Range 7.6–26 2.1–4.2 4.8–11.3 1.5–3.4 17.0–39.3 6.4–11.5 Mean ± SD 14.3 ± 10.1 2.9 ± 1.1 7.1 ± 3.5 2.3 ± 0.9 28.1 ± 11.1 8.8 ± 2.5 Molluscs 7.  Loligo duavucelli (Squid) 15.6 ± 0.3 2.8 ± 0.9 12.8 ± 1.4 1.8 ± 0.3 13.5 ± 1.1 5.0 ± 0.4 8.  Crassostrea madrasensis (Oyster) 52.1 ± 2.3 11.3 ± 1.4 45.2 ± 2.6 9.2 ± 0.9 58.6 ± 2.4 9.5 ± 1.6 9.  Meretrix casta (Clam) 34.3 ± 1.8 4.6 ± 1.1 23.7 ± 2.0 2.3 ± 0.4 29.4 ± 1.5 3.4 ± 1.4 Range 15.6–52.1 2.8–11.3 12.8–45.2 1.8–9.2 13.5–58.6 3.4–9.5 Mean ± SD 34 ± 18.2 6.2 ± 4.4 27.2 ± 16.4 4.4 ± 2.0 33.8 ± 22.8 5.9 ± 3.1 Over all range 5.3–52.1 1.6–11.3 3.4–45.2 0.51–9.2 13.5–58.6 3.4–11.5 Over all mean ± SD 18.4 ± 16.03 3.7 ± 2.99 14.1 ± 13.1 2.7 ± 2.5 27.3 ± 14.18 7.5 ± 2.82 No. of analysis (n) = 6 – 10. Table 6. Activity concentrations of 210Po and 210Pb in muscle of fishes from Devanampattinam coast (S2). S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Rastrelliger kanagurta 17.6 ± 1.5 11.7 ± 1.1 1.50 2. Leiognathus bindus 11.2 ± 1.1 6.5 ± 1.0 1.72 3. Mugil cephalus 7.5 ± 0.8 4.2 ± 0.5 1.78 4. Euthynnus affinis 5.0 ± 0.4 1.7 ± 0.2 2.94 5. Atule mate 6.2 ± 0.5 1.2 ± 0.1 5.39 6. Pinjalo sp. 2.7 ± 0.1 0.6 ± 0.01 4.5 7. Liza sp. 5.9 ± 0.7 1.8 ± 0.3 3.27 8. Stolephorus sp 12.0 ± 1.2 2.2 ± 0.6 5.45 9. Sardinella dayiregan 4.5 ± 0.6 0.9 ± 0.04 5.0 10. Lethrinus cinereus 11.5 ± 1.1 1.2 ± 0.1 9.58 11. Scomberomorus guttauts 2.0 ± 0.1 0.6 ± 0.01 3.33 12. Alectis sp. 4.0 ± 0.2 0.7 ± 0.01 5.71 Range 2.0–17.6 0.6–11.7 1.50–9.58 Mean ± SD 7.34 ± 4.3 2.9 ± 2.01 4.89 ± 3.77 S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Rastrelliger kanagurta 17.6 ± 1.5 11.7 ± 1.1 1.50 2. Leiognathus bindus 11.2 ± 1.1 6.5 ± 1.0 1.72 3. Mugil cephalus 7.5 ± 0.8 4.2 ± 0.5 1.78 4. Euthynnus affinis 5.0 ± 0.4 1.7 ± 0.2 2.94 5. Atule mate 6.2 ± 0.5 1.2 ± 0.1 5.39 6. Pinjalo sp. 2.7 ± 0.1 0.6 ± 0.01 4.5 7. Liza sp. 5.9 ± 0.7 1.8 ± 0.3 3.27 8. Stolephorus sp 12.0 ± 1.2 2.2 ± 0.6 5.45 9. Sardinella dayiregan 4.5 ± 0.6 0.9 ± 0.04 5.0 10. Lethrinus cinereus 11.5 ± 1.1 1.2 ± 0.1 9.58 11. Scomberomorus guttauts 2.0 ± 0.1 0.6 ± 0.01 3.33 12. Alectis sp. 4.0 ± 0.2 0.7 ± 0.01 5.71 Range 2.0–17.6 0.6–11.7 1.50–9.58 Mean ± SD 7.34 ± 4.3 2.9 ± 2.01 4.89 ± 3.77 No. of analysis (n) = 6 – 10. Table 6. Activity concentrations of 210Po and 210Pb in muscle of fishes from Devanampattinam coast (S2). S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Rastrelliger kanagurta 17.6 ± 1.5 11.7 ± 1.1 1.50 2. Leiognathus bindus 11.2 ± 1.1 6.5 ± 1.0 1.72 3. Mugil cephalus 7.5 ± 0.8 4.2 ± 0.5 1.78 4. Euthynnus affinis 5.0 ± 0.4 1.7 ± 0.2 2.94 5. Atule mate 6.2 ± 0.5 1.2 ± 0.1 5.39 6. Pinjalo sp. 2.7 ± 0.1 0.6 ± 0.01 4.5 7. Liza sp. 5.9 ± 0.7 1.8 ± 0.3 3.27 8. Stolephorus sp 12.0 ± 1.2 2.2 ± 0.6 5.45 9. Sardinella dayiregan 4.5 ± 0.6 0.9 ± 0.04 5.0 10. Lethrinus cinereus 11.5 ± 1.1 1.2 ± 0.1 9.58 11. Scomberomorus guttauts 2.0 ± 0.1 0.6 ± 0.01 3.33 12. Alectis sp. 4.0 ± 0.2 0.7 ± 0.01 5.71 Range 2.0–17.6 0.6–11.7 1.50–9.58 Mean ± SD 7.34 ± 4.3 2.9 ± 2.01 4.89 ± 3.77 S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Rastrelliger kanagurta 17.6 ± 1.5 11.7 ± 1.1 1.50 2. Leiognathus bindus 11.2 ± 1.1 6.5 ± 1.0 1.72 3. Mugil cephalus 7.5 ± 0.8 4.2 ± 0.5 1.78 4. Euthynnus affinis 5.0 ± 0.4 1.7 ± 0.2 2.94 5. Atule mate 6.2 ± 0.5 1.2 ± 0.1 5.39 6. Pinjalo sp. 2.7 ± 0.1 0.6 ± 0.01 4.5 7. Liza sp. 5.9 ± 0.7 1.8 ± 0.3 3.27 8. Stolephorus sp 12.0 ± 1.2 2.2 ± 0.6 5.45 9. Sardinella dayiregan 4.5 ± 0.6 0.9 ± 0.04 5.0 10. Lethrinus cinereus 11.5 ± 1.1 1.2 ± 0.1 9.58 11. Scomberomorus guttauts 2.0 ± 0.1 0.6 ± 0.01 3.33 12. Alectis sp. 4.0 ± 0.2 0.7 ± 0.01 5.71 Range 2.0–17.6 0.6–11.7 1.50–9.58 Mean ± SD 7.34 ± 4.3 2.9 ± 2.01 4.89 ± 3.77 No. of analysis (n) = 6 – 10. Table 7. Activity concentrations of 210Po and 210Pb in muscle of fishes from Pitchavaram Mangroves. S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Arius maculatus 6.5 ± 0.7 4.02 ± 0.6 1.61 2. Gerres abbreviatus 12.5 ± 1.1 6.0 ± 0.9 2.08 3. Leiognathus daura 8.2 ± 0.6 5.3 ± 0.6 1.54 4. Scatophagus argus 16.5 ± 1.3 9.3 ± 0.8 1.77 5. Sardinella longiceps 6.2 ± 0.7 1.07 ± 0.3 5.79 6. Sarotherodon mosambicus 5.4 ± 0.5 2.7 ± 0.2 2.0 7. Chirocentrus sp. 1.5 ± 0.2 0.5 ± 0.02 3.0 8. Synaptura commersoniana 8.5 ± 1.1 2.5 ± 0.5 3.4 9. Pinjalo Sp. 6.2 ± 0.8 2.4 ± 0.6 2.58 10. Liza Sp. 2.7 ± 0.3 0.6 ± 0.05 4.5 11. Stolephorus indicus 5.9 ± 0.9 1.9 ± 0.2 3.10 12. Therapon jarbua 2.0 ± 0.4 0.4 ± 0.02 5.0 13. Upeneus sulphureus 1.0 ± 0.2 0.3 ± 0.02 3.33 14. Kathala axillaris 8.0 ± 1.3 0.6 ± 0.04 1.33 15. Thrissina baelama 16.0 ± 1.5 1.2 ± 0.3 13.33 16. Valamugil speigeri 2.0 ± 0.6 0.8 ± 0.06 0.25 17. Mene maculata 6.0 ± 0.9 1.3 ± 0.2 4.61 18. Nematalosa nasus 7.0 ± 1.1 0.8 ± 0.05 8.33 19. Nemipterus japonicus 4.0 ± 0.8 1.9 ± 0.4 2.10 Range 1.0–16.5 0.3–9.3 0.25–13.33 Mean ± SD 6.6 ± 4.43 2.3 ± 2.2 4.29 ± 3.67 S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Arius maculatus 6.5 ± 0.7 4.02 ± 0.6 1.61 2. Gerres abbreviatus 12.5 ± 1.1 6.0 ± 0.9 2.08 3. Leiognathus daura 8.2 ± 0.6 5.3 ± 0.6 1.54 4. Scatophagus argus 16.5 ± 1.3 9.3 ± 0.8 1.77 5. Sardinella longiceps 6.2 ± 0.7 1.07 ± 0.3 5.79 6. Sarotherodon mosambicus 5.4 ± 0.5 2.7 ± 0.2 2.0 7. Chirocentrus sp. 1.5 ± 0.2 0.5 ± 0.02 3.0 8. Synaptura commersoniana 8.5 ± 1.1 2.5 ± 0.5 3.4 9. Pinjalo Sp. 6.2 ± 0.8 2.4 ± 0.6 2.58 10. Liza Sp. 2.7 ± 0.3 0.6 ± 0.05 4.5 11. Stolephorus indicus 5.9 ± 0.9 1.9 ± 0.2 3.10 12. Therapon jarbua 2.0 ± 0.4 0.4 ± 0.02 5.0 13. Upeneus sulphureus 1.0 ± 0.2 0.3 ± 0.02 3.33 14. Kathala axillaris 8.0 ± 1.3 0.6 ± 0.04 1.33 15. Thrissina baelama 16.0 ± 1.5 1.2 ± 0.3 13.33 16. Valamugil speigeri 2.0 ± 0.6 0.8 ± 0.06 0.25 17. Mene maculata 6.0 ± 0.9 1.3 ± 0.2 4.61 18. Nematalosa nasus 7.0 ± 1.1 0.8 ± 0.05 8.33 19. Nemipterus japonicus 4.0 ± 0.8 1.9 ± 0.4 2.10 Range 1.0–16.5 0.3–9.3 0.25–13.33 Mean ± SD 6.6 ± 4.43 2.3 ± 2.2 4.29 ± 3.67 No. of analysis (n) = 6 – 10. Table 7. Activity concentrations of 210Po and 210Pb in muscle of fishes from Pitchavaram Mangroves. S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Arius maculatus 6.5 ± 0.7 4.02 ± 0.6 1.61 2. Gerres abbreviatus 12.5 ± 1.1 6.0 ± 0.9 2.08 3. Leiognathus daura 8.2 ± 0.6 5.3 ± 0.6 1.54 4. Scatophagus argus 16.5 ± 1.3 9.3 ± 0.8 1.77 5. Sardinella longiceps 6.2 ± 0.7 1.07 ± 0.3 5.79 6. Sarotherodon mosambicus 5.4 ± 0.5 2.7 ± 0.2 2.0 7. Chirocentrus sp. 1.5 ± 0.2 0.5 ± 0.02 3.0 8. Synaptura commersoniana 8.5 ± 1.1 2.5 ± 0.5 3.4 9. Pinjalo Sp. 6.2 ± 0.8 2.4 ± 0.6 2.58 10. Liza Sp. 2.7 ± 0.3 0.6 ± 0.05 4.5 11. Stolephorus indicus 5.9 ± 0.9 1.9 ± 0.2 3.10 12. Therapon jarbua 2.0 ± 0.4 0.4 ± 0.02 5.0 13. Upeneus sulphureus 1.0 ± 0.2 0.3 ± 0.02 3.33 14. Kathala axillaris 8.0 ± 1.3 0.6 ± 0.04 1.33 15. Thrissina baelama 16.0 ± 1.5 1.2 ± 0.3 13.33 16. Valamugil speigeri 2.0 ± 0.6 0.8 ± 0.06 0.25 17. Mene maculata 6.0 ± 0.9 1.3 ± 0.2 4.61 18. Nematalosa nasus 7.0 ± 1.1 0.8 ± 0.05 8.33 19. Nemipterus japonicus 4.0 ± 0.8 1.9 ± 0.4 2.10 Range 1.0–16.5 0.3–9.3 0.25–13.33 Mean ± SD 6.6 ± 4.43 2.3 ± 2.2 4.29 ± 3.67 S. no. Species analyzed Activity (Bq kg−1) dry 210Po/210Pb ratio 210Po 210Pb 1. Arius maculatus 6.5 ± 0.7 4.02 ± 0.6 1.61 2. Gerres abbreviatus 12.5 ± 1.1 6.0 ± 0.9 2.08 3. Leiognathus daura 8.2 ± 0.6 5.3 ± 0.6 1.54 4. Scatophagus argus 16.5 ± 1.3 9.3 ± 0.8 1.77 5. Sardinella longiceps 6.2 ± 0.7 1.07 ± 0.3 5.79 6. Sarotherodon mosambicus 5.4 ± 0.5 2.7 ± 0.2 2.0 7. Chirocentrus sp. 1.5 ± 0.2 0.5 ± 0.02 3.0 8. Synaptura commersoniana 8.5 ± 1.1 2.5 ± 0.5 3.4 9. Pinjalo Sp. 6.2 ± 0.8 2.4 ± 0.6 2.58 10. Liza Sp. 2.7 ± 0.3 0.6 ± 0.05 4.5 11. Stolephorus indicus 5.9 ± 0.9 1.9 ± 0.2 3.10 12. Therapon jarbua 2.0 ± 0.4 0.4 ± 0.02 5.0 13. Upeneus sulphureus 1.0 ± 0.2 0.3 ± 0.02 3.33 14. Kathala axillaris 8.0 ± 1.3 0.6 ± 0.04 1.33 15. Thrissina baelama 16.0 ± 1.5 1.2 ± 0.3 13.33 16. Valamugil speigeri 2.0 ± 0.6 0.8 ± 0.06 0.25 17. Mene maculata 6.0 ± 0.9 1.3 ± 0.2 4.61 18. Nematalosa nasus 7.0 ± 1.1 0.8 ± 0.05 8.33 19. Nemipterus japonicus 4.0 ± 0.8 1.9 ± 0.4 2.10 Range 1.0–16.5 0.3–9.3 0.25–13.33 Mean ± SD 6.6 ± 4.43 2.3 ± 2.2 4.29 ± 3.67 No. of analysis (n) = 6 – 10. Table 8. Activity concentrations of 210Po and 210Pb in muscle of fishes from Nagappattinam. S. no. Species analyzed Activity (Bq /kg) dry 210Po/210Pb ratio 210Po 210Pb 1. Pampus argenteus 10.0 ± 1.4 3.0 ± 0.6 3.33 2. Carangoides armatus 3.0 ± 0.8 2.0 ± 0.5 1.5 3. Hirundichthys coromandelenesis 5.0 ± 1.2 1.8 ± 0.3 3.33 4. Scomberomorus guttatus 3.0 ± 0.9 1.0 ± 0.2 3.0 5. Nemipterus japonicus 8.0 ± 1.8 2.1 ± 0.4 3.81 6. Rastrelliger kanakurta 23.0 ± 2.1 9.5 ± 1.4 2.42 7. Megalops cyprinoides 4.0 ± 0.6 1.6 ± 0.2 2.5 8. Ambassis commersoni 12.0 ± 1.5 3.0 ± 0.6 4.0 9. Sarotherodon mosambicus 8.6 ± 1.1 2.5 ± 0.4 3.44 10. Synaptura commersoniana 15.6 ± 1.7 4.2 ± 1.1 3.71 11. Stolephorus indicus 9.0 ± 0.8 3.6 ± 0.9 2.5 12. Therapon jarbua 7.3 ± 0.4 2.1 ± 0.3 3.47 Range 3.0–23.0 1.0–9.5 1.5–4.0 Mean ± SD 9.04 ± 5.7 3.03 ± 2.2 3.08 ± 0.7 S. no. Species analyzed Activity (Bq /kg) dry 210Po/210Pb ratio 210Po 210Pb 1. Pampus argenteus 10.0 ± 1.4 3.0 ± 0.6 3.33 2. Carangoides armatus 3.0 ± 0.8 2.0 ± 0.5 1.5 3. Hirundichthys coromandelenesis 5.0 ± 1.2 1.8 ± 0.3 3.33 4. Scomberomorus guttatus 3.0 ± 0.9 1.0 ± 0.2 3.0 5. Nemipterus japonicus 8.0 ± 1.8 2.1 ± 0.4 3.81 6. Rastrelliger kanakurta 23.0 ± 2.1 9.5 ± 1.4 2.42 7. Megalops cyprinoides 4.0 ± 0.6 1.6 ± 0.2 2.5 8. Ambassis commersoni 12.0 ± 1.5 3.0 ± 0.6 4.0 9. Sarotherodon mosambicus 8.6 ± 1.1 2.5 ± 0.4 3.44 10. Synaptura commersoniana 15.6 ± 1.7 4.2 ± 1.1 3.71 11. Stolephorus indicus 9.0 ± 0.8 3.6 ± 0.9 2.5 12. Therapon jarbua 7.3 ± 0.4 2.1 ± 0.3 3.47 Range 3.0–23.0 1.0–9.5 1.5–4.0 Mean ± SD 9.04 ± 5.7 3.03 ± 2.2 3.08 ± 0.7 No. of analysis (n) = 6 – 10. Table 8. Activity concentrations of 210Po and 210Pb in muscle of fishes from Nagappattinam. S. no. Species analyzed Activity (Bq /kg) dry 210Po/210Pb ratio 210Po 210Pb 1. Pampus argenteus 10.0 ± 1.4 3.0 ± 0.6 3.33 2. Carangoides armatus 3.0 ± 0.8 2.0 ± 0.5 1.5 3. Hirundichthys coromandelenesis 5.0 ± 1.2 1.8 ± 0.3 3.33 4. Scomberomorus guttatus 3.0 ± 0.9 1.0 ± 0.2 3.0 5. Nemipterus japonicus 8.0 ± 1.8 2.1 ± 0.4 3.81 6. Rastrelliger kanakurta 23.0 ± 2.1 9.5 ± 1.4 2.42 7. Megalops cyprinoides 4.0 ± 0.6 1.6 ± 0.2 2.5 8. Ambassis commersoni 12.0 ± 1.5 3.0 ± 0.6 4.0 9. Sarotherodon mosambicus 8.6 ± 1.1 2.5 ± 0.4 3.44 10. Synaptura commersoniana 15.6 ± 1.7 4.2 ± 1.1 3.71 11. Stolephorus indicus 9.0 ± 0.8 3.6 ± 0.9 2.5 12. Therapon jarbua 7.3 ± 0.4 2.1 ± 0.3 3.47 Range 3.0–23.0 1.0–9.5 1.5–4.0 Mean ± SD 9.04 ± 5.7 3.03 ± 2.2 3.08 ± 0.7 S. no. Species analyzed Activity (Bq /kg) dry 210Po/210Pb ratio 210Po 210Pb 1. Pampus argenteus 10.0 ± 1.4 3.0 ± 0.6 3.33 2. Carangoides armatus 3.0 ± 0.8 2.0 ± 0.5 1.5 3. Hirundichthys coromandelenesis 5.0 ± 1.2 1.8 ± 0.3 3.33 4. Scomberomorus guttatus 3.0 ± 0.9 1.0 ± 0.2 3.0 5. Nemipterus japonicus 8.0 ± 1.8 2.1 ± 0.4 3.81 6. Rastrelliger kanakurta 23.0 ± 2.1 9.5 ± 1.4 2.42 7. Megalops cyprinoides 4.0 ± 0.6 1.6 ± 0.2 2.5 8. Ambassis commersoni 12.0 ± 1.5 3.0 ± 0.6 4.0 9. Sarotherodon mosambicus 8.6 ± 1.1 2.5 ± 0.4 3.44 10. Synaptura commersoniana 15.6 ± 1.7 4.2 ± 1.1 3.71 11. Stolephorus indicus 9.0 ± 0.8 3.6 ± 0.9 2.5 12. Therapon jarbua 7.3 ± 0.4 2.1 ± 0.3 3.47 Range 3.0–23.0 1.0–9.5 1.5–4.0 Mean ± SD 9.04 ± 5.7 3.03 ± 2.2 3.08 ± 0.7 No. of analysis (n) = 6 – 10. Figure 6. View largeDownload slide Mean concentrations of 210Po and 210Pb in seafood organisms of Bay of Bengal. Figure 6. View largeDownload slide Mean concentrations of 210Po and 210Pb in seafood organisms of Bay of Bengal. Figure 7. View largeDownload slide Percentage of 210Po content in different body components of the oyster, Crassostrea madrasensis. Figure 7. View largeDownload slide Percentage of 210Po content in different body components of the oyster, Crassostrea madrasensis. Figure 8. View largeDownload slide Percentage of 210Po content in different body components of the clam, Meretrix casta. Figure 8. View largeDownload slide Percentage of 210Po content in different body components of the clam, Meretrix casta. Figure 9. View largeDownload slide Percentage of 210Po content in different body components of the fish, Sardinella longiceps. Figure 9. View largeDownload slide Percentage of 210Po content in different body components of the fish, Sardinella longiceps. The bioaccumulation of 210Po in shellfish species of Pitchavaram fluctuated from 3.4 to 45.2 Bq kg−1 with mean value of 14.1 ± 13.1 Bq kg−1 whereas bioaccumulation of 210Pb ranged from 0.51 to 9.2 Bq kg−1 with a mean value of 2.7 ± 2.5 Bq kg−1. Fish species in Pitchavaram Mangroves registered relatively a low level of 210Po and 210Pb. 210Po concentrations ranged from 1.0 to 16.5 Bq kg−1 with the mean value of 6.6 ± 4.4 Bq kg−1. Similarly 210Pb concentration ranged from 0.3 to 9.3 Bq kg−1 with the mean value of 2.3 ± 2.2 Bq kg−1. The ratio of 210Po/210Pb is always several times higher both in shellfish species (5.3) and fin fish species (4.2). The bioaccumulated concentration of 210Po in shellfish species of Nagappatinam ranged from 13.5 to 58.6 Bq kg−1 with overall mean value of 27.3 ± 14.2 Bq kg−1 and bioaccumulation of 210Pb ranged from 5.0 to 11.5 Bq kg−1 with a mean value of 7.5 ± 2.82 Bq kg−1. Fish species from Nagappattinam landing center registered relatively a low level of 210Po and 210Pb. The 210Po concentrations ranged from 3.0 to 23.0 Bq kg−1 with the mean value of 9.0 ± 5.7 Bq kg−1. Similarly 210Pb concentration ranged from 1.0 to 9.5 Bq kg−1 with the mean value of 3.0 ± 2.2 Bq kg−1. The ratio 210Po/210Pb registered higher values both in shellfish species (6.0) and fin fish species (3.1). Figure 6 indicated that among the shellfish species prawns registered a minimum mean activity concentration of 11.6 Bq kg−1 of 210Po. In contrast ~32.0 Bq kg−1 of 210Po was found to be accumulated in the molluscan species and crab species maintained an intermediated level of 16.5 Bq kg−1. However, fish species registered 7.6 Bq kg−1. A similar trend was also observed for the bioaccumulation of 210Pb in shellfish species and fishes. The accumulated level of 210Pb was found to be maximum (5.5 Bq kg−1) among mollascan species. The activity concentrations of 4.7 and 3.7 Bq kg−1 of 210Pb were recorded in the species of crab and prawn respectively. Fishes maintained a low level of 2.7 Bq kg−1 of 210Pb. The shellfish species analyzed in the present study fall into two groups of organisms namely crustaceans which include prawns and crabs, and molluscs which include bivalves, oyster, clam and squid. The bioaccumulation of 210Po in seafood organisms follows the descending order: The bioaccumulation of 210Po in the soft tissue of molluscan species (oyster, calm and squid) analyzed was found to be distinctly higher (31.6 Bq kg−1) as compared to crustacean species. Analysis of 210Po in 33 fish species revealed that fish muscle accumulated relatively a minimum average level of 7.6 Bq kg−1 210Po (range: 6.6–9.9 Bq kg−1). In general the bioaccumulation of 210Po largely depends on the nature of food and feeding habits of the organisms. Prawns and crabs largely feed on small organisms such as fish, copepods and other crustaceans in zooplankton(33). On the other hand bivalve molluscs such as oysters and clams are benthic organisms and they live buried in the bottom sand and feed on small organic particulate matters which are enriched with 210Po and therefore, the bioaccumulation of 210Po in molluscs is very high. Analysis of 210Pb concentration in shellfish species of prawn, crab and molluscs and a number of fish species indicated a similar trend as that of 210Po. This means that 210Pb concentration was relatively higher in shellfishes than in fish species. The situation clearly indicated that muscles are poor accumulators of 210Pb as compared to 210Po. The 210Pb concentration in crustacean species under the present study, ranged from 0.5 to 11.5 Bq kg−1 in muscle and these values are distinctly higher than the reported values of several investigators. Holtzman(34) reported 0.05 Bq kg−1 of 210Pb in muscle of prawns from Great Lakes in Alaska. 210Pb in prawns of the Mediterranean Sea was 0.024 Bq kg−1(35) and prawns and crabs of Kalpakkam coastal waters ranged from 0.22 to 1.2 Bq kg−1 for muscle and 0.78 to 2.4 Bq kg−1 for exoskeleton(28). The chemical affinity of 210Pb with calcified shells and bones is responsible for the higher level of concentration in bones and other mineralized parts of animals such as exoskeleton and shell as reported by several others(34, 36, 37). The prawn undergoes a phenomenon of ecdysis or periodic molting of exoskeleton. This shedding of the exoskeleton and formation of new one could possibly be attributed for lower level of 210Pb in the exoskeleton of prawn and it is also considered as natural mechanisms of shedding the body burden of 210Pb. Moreover, organic particulates are richer in 210Po than in 210Pb. This could also be attributed for the observed higher concentration of 210Po than 210Pb in these organisms. Intra-organismic distribution of 210Po In order to understand the biodistribution capacity of different internal organs of edible seafood organisms, the activity concentration of 210Po in various internal organs of an oyster (Crassostrea madrasensis), a clam (Meretrix casta) and a fish (Sardinella longiceps) were analyzed and reported in Figures 7–9. The data show the following descending orders: Oyster (Crassostrea madrasensis) Digestive Glands > Gills > Viscera > Mantle > Adductor Muscle Clam (Meretrix casta) Digestive Glands > Gills > Mantle > Viscera > Adductor Muscle Fish (Sardinella longiceps) Liver > Gills > Muscle > Intestine > Bone The biodistribution of 210Po was maximum in the digestive glands of the oyster (90 Bq kg−1 dry) and clam (42 Bq kg−1 dry). It may be concluded that the higher distribution of 210Po in digestive glands of bivalves is due to their dominant role in the digestive process of food particles which contain appreciable levels of 210Po. Next to digestive glands the gills in oyster distributed a higher amount of 210Po (61 Bq kg−1 dry). The gills act both as food filter and as a respiratory organ and hence form the site of uptake. Water loaded with oxygen and food material is drawn through the gills facilitating entry of radionuclides. Moreover, composition of the surrounding water might also play an equally important role because of its variation in radionuclide concentration. The mantle is also active sites of 210Po distribution. This is mainly due to an intimate contact with food particles on these organs. Further, the mucous has complex sulfate carbohydrate with the ion exchange of radionuclides across the cell membrane(38, 39). The per capita intake of seafood components is assessed by survey method. It was carried out in coastal population of the study area covering 150 families in three coastal villages. Detailed information about the diet was known from the population consisting mainly of fishermen and per capita consumption of major seafood species are assessed. From the radioactivity data of the seafood and the data on the diet information survey, the intake of 210Po and 210Pb was derived. Using the activity intake data and ICRP(40) dose factors, the dose to the individual member of the population was calculated (210Po: 1.2 × 10−6 Sv Bq−1: 210Pb: 6.9 × 10−7 Sv Bq−1). The committed effective dose rate (CEDE) recorded for shellfish species maintained a higher range (81.0–281.2 μSv y−1). However, dose transfer rate from fish species varied from 14.4 to 165.6 μSv y−1. Though the average consumption of fish is found to be higher than the shellfish, fish transfer lesser CEDE to the public. The work on measurements of 210Po and 210Pb in other terrestrial food items is in progress. CONCLUSIONS It is concluded from the results that distribution of 210Po and 210Pb in water, sand and their bioaccumulation in seafood organisms from the Bay of Bengal was non-uniform and widely fluctuating. The 210Pb concentration in the coastal water is always higher than 210Po for a given station. On contrary, the mean 210Po/210Pb ratios in sand was 1.7 indicating the 210Po concentrations in the sand sample is always about twice the concentration of 210Pb in sand sample. Further small sand grains (105 μm) has stronger chemical affinity to both 210Po (9.5 Bq kg−1) and 210Pb (5.2 Bq kg−1) and this may be due to the deposition of organic compound which are generally rich source of 210Po. The maximum activity of the two radionuclides was observed up to 10 cm depth (210Po: 6.4 Bq kg−1 and 210Pb: 4.1 Bq kg−1) and the activity declined with increasing depth. The bioaccumulation capability in seafood organisms maintain the following trend: Oyster> Clam > Squid > Crab > Prawn > Fish. 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Radiation Protection DosimetryOxford University Press

Published: Apr 23, 2018

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