Letter to the Editor: Radon isotope assessment of Submarine Groundwater Discharge (SGD) in Coleroon River Estuary,Tamil Nadu,India

Journal of Radioanalytical and Nuclear Chemistry -     

Identification of groundwater discharge in Cuddalore coast,Tamil Nadu using radium isotopes

For the optimal exploitation and management of coastal aquifers of Tamil Nadu, it is essential to evaluate the groundwater outflow into the sea also called as submarine groundwater discharge. In this study, radium isotopes (^223,224Ra) were employed to understand the groundwater discharge in coastal areas of Cuddalore district, Tamil Nadu. Sea water samples (100 L) were collected from various locations of Cuddalore coast in October 2011 and passed through Mn-impregnated acrylic fiber columns. These acrylic columns were analyzed for ^223,224Ra activities using radium delayed coincidence counter. The observed higher activities of ^223,224Ra excess (0.02 ± 0.001–3.28 ± 0.16 and 64 ± 3–380 ± 19 mBq/100 L respectively) indicate that groundwater discharge occurs in this coastal region.     

Occurrence of the radionuclides in groundwater of crystalline hard rock regions of central Tamil Nadu,India

A study was conducted to understand the occurrence of the radionuclides in groundwater of crystalline hard rock region. Samples were collected to analyze major cations, anions, U, ²²²Rn and stable isotopes of oxygen, hydrogen. It was inferred that few samples have U and ²²²Rn concentrations higher than the permissible limit of drinking water standard. High degree of weathering of granitic rocks and long contact time of groundwater with the aquifer matrix could be the reason for enhanced U and ²²²Rn levels in groundwater. The association of U with SO₄ also proves that there exists anthropogenic influence in groundwater composition.     

Estimation of submarine groundwater discharge using radium mass-balance in Mumbai Harbour Bay,Mumbai, India

Journal of Radioanalytical and Nuclear Chemistry - The Mumbai Harbour Bay (MHB), Mumbai, India houses a large number of ports, industrial units and urban settlements thus the groundwater may be...     

Evaluation of natural gamma radiation and absorbed gamma dose in soil and rocks of Perambalur district (Tamil Nadu,India)

The activity concentrations and absorbed gamma dose of primordial radionuclides ²³⁸U, ²³²Th and ⁴⁰K were determined employing γ-ray spectrometry in 31 soil samples from the land area earmarked for house construction in Perambalur district and 14 rock samples from quarries that supply stones for the entire district. The soil samples registered relatively a higher mean value of 13.2 Bq kg^?1 for ²³⁸U, 66 Bq kg^?1 for ²³²Th and 340.3 Bq kg^?1 for ⁴⁰K as compared to mean values for rock samples (²³⁸U—8.0 Bq kg^?1; ²³²Th—65.1 Bq kg^?1; ⁴⁰K—199.1 Bq kg^?1). The mean absorbed gamma dose rate for soil (61.4 nGy h^?1) marginally exceeded the prescribed limit of 55 nGy h^?1 while, rocks registered the mean absorbed gamma dose rate of 10.4 nGy h^?1. The mean radium equivalent activity was distinctly higher in soil (130.6 Bq kg^?1) than in rock (20.0 Bq kg^?1). However, these values were lower than the limit (370 Bq kg^?1) set by OECD for building materials. It is evident from the data that the soil and rocks do not pose any radiological risk for house constructions in Perambalur district.     

Measurement of gamma radiation from rocks used as building material in Tiruchirappalli district,Tamil Nadu,India

Tiruchirappalli district is naturally endowed with rich building material resources which are also used in neighboring districts. Hence, measurements of activity concentrations and absorbed dose rate of primordial radionuclides (²³⁸U, ²³²Th and ⁴⁰K) in the rock samples collected from 14 sedimentary rocks and 9 igneous rocks were carried out employing gamma ray spectrometry. In sedimentary rocks the geometric mean activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K were found to be 7.4, 29.5 and 233.6 Bq kg^?1, respectively. On the other hand in igneous rocks geometric mean activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K were distinctly higher and found to be 13.1, 105.7 and 888.8 Bq kg^?1, respectively. The mean radium equivalent activity (Ra_eq) recorded in both sedimentary (20.8 Bq kg^?1) and igneous rocks (245.4 Bq kg^?1) were well within the limit prescribed for dwellings (370 Bq kg^?1) except Vilathupatti (689.3 Bq kg^?1) and Narthamalai (371.6 Bq kg^?1). The mean absorbed dose rate from igneous rock (115 nGy h^?1) exceeded the prescribed limit of 55 nGy h^?1. The mean indoor annual effective dose from the sedimentary rock (0.056 mSv y^?1) and igneous rock (0.580 mSv y^?1) did not exceed the prescribed limit (1 mSv y^?1) except the igneous rock from Vilathupatti (1.51 mSv y^?1). The study concludes that sedimentary and igneous rocks analyzed were radiologically safe when used as building materials except igneous rock from Vilathupatti and Narthamalai.     

Natural radioactivity in soil samples of Yelagiri Hills,Tamil Nadu,India and the associated radiation hazards

The natural radioactivity of soils at Yelagiri hills has been studied in this paper. The radioactivities of 25 samples have been measured with a NaI(Tl) detector. The radioactivity concentrations of ²³⁸U, ²³²Th and ⁴⁰K ranged from ≤2.17 to 53.23, 13.54 to 89.89 and from 625.09 to 2207.3 Bq kg^?1, respectively. The measured activity concentrations for these radionuclides were compared with world average activity of soil. The average activity concentration of ²³²Th in the present study is 1.19 times higher than world median value while the activity of ²³⁸U and ⁴⁰K is found to be lower. In order to evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity Ra_eq, the absorbed dose rate D_R, the annual effective dose rate and the external hazard index (H_ex) have been calculated and compared with the internationally approved values. The study provides background radioactivity concentrations in Yelagiri hills.     

Radon concentration in groundwater of Varahi and Markandeya river basins, Karnataka State, India

The present study presents an overview of the distribution of radon (²²²Rn) activity concentration in the groundwater samples and their annual effective dose exposure in the Varahi and Markandeya command areas. Radon measurement was made using Durridge RAD-7 radon-in-air monitor, using RAD H₂O technique with closed loop aeration concept. The measured ²²²Rn activities in 16 groundwater samples of Varahi command area ranged between 0.2 ± 0.4 and 10.1 ± 1.7 Bq L⁻¹ with an average value of 2.07 ± 0.84 Bq L⁻¹, well within the EPA’s maximum contaminant level (MCL) of 11.1 Bq L⁻¹. In contrast, the recorded ²²²Rn activities in 14 groundwater samples of Markandeya command area found to vary from 2.21 ± 1.66 to 27.3 ± 0.787 Bq L⁻¹ with an average value of 9.30 ± 1.45 Bq L⁻¹. 21.4% of the samples (sample no. RMR5, RMR11 and RMR12) in the Markandeya command area exceeded the EPA’s MCL of 11.1 Bq L⁻¹ and it was found that some samples in both the command areas were found to have radon values close to MCL value. The spatial variation in the radon concentration in the Varahi and Markandeya command area were delineated by constructing the contour map. The total annual effective dose resulting from radon in groundwater of both Varahi and Markandeya command areas were significantly lower than the UNSCEAR and WHO recommended limit for members of the public of 1 mSv year⁻¹.     

Activity concentration of polonium-210 and lead-210 in tobacco products and annual committed effective dose to tobacco users in Tiruchirappalli District (Tamil Nadu,India)

The present study has carried out with an objective of determining the activity concentrations of two radionuclides namely polonium-210 (²¹⁰Po) and lead-210 (²¹⁰Pb) in smoke tobacco products (cigarette, bidi and cigar) and smokeless tobacco products (chewing tobacco and snuff) consumed in Tiruchirappalli District, Tamil Nadu (India) and their annual committed effective dose to tobacco consumers. The concentration of ²¹⁰Po was always higher than that of ²¹⁰Pb in all the analyzed tobacco products. It also revealed that 79% of Annual committed effective dose comes from ²¹⁰Po and about 21% from ²¹⁰Pb. Maximum concentration (13.2 mBq g^?1) of ²¹⁰Po recorded in cigarette and lowest concentration was observed in snuff (6.4 mBq g^?1). The highest mean committed effective dose of ²¹⁰Po and ²¹⁰Pb in various tobacco products were found in cigarette followed by bidi, cigar, chewing tobacco and snuff. The study revealed that the tobacco products available in Tiruchirappalli District contain a relatively lower concentration of radionuclides when compared to other regional studies. Since this kind of study in India is fragmentary, the present study has generated a base data for the first time for entire Tiruchirappalli District.

     

Radiological impact assessment of soil and groundwater of Himalayan regions in Uttarakhand,India

Journal of Radioanalytical and Nuclear Chemistry - In this study, we present the results of measurements and radiological impact of natural radioactivity in soil and groundwater of the Himalayan...     

Use of 222Rn to trace submarine groundwater discharge in a tidal period along the coast of Xiangshan, Zhejiang, China

²²²Rn is one of the operative tracers for submarine groundwater discharge (SGD), which plays a significant role in the land–ocean interaction of the estuarine and coastal regions. By the distribution pattern of ²²²Rn in atmosphere, groundwater and surface seawater, in a full tidal period (25 h) in March 2012, SGD was estimated along the coast of Xiangshan, Zhejiang, China. ²²²Rn activity in Xiangshan coast was in range of 2.4 × 10⁴–1.7 × 10⁵ Bq/m³ with an average of 9.6 × 10⁴ Bq/m³ for groundwater; 0.2 × 10²–2.8 × 10² Bq/m³ with an average of 1.1 × 10² Bq/m³ for surface seawater. ²²²Rn activities in groundwater were much greater than those in surface water, suggesting that the major source of radon came from coastal groundwater discharge. Rn fluxes of atmospheric emissions, sediment, and of ²²⁶Ra in situ decay can be negligible in this study, but the tidal effects play a crucial role in Rn fluxes. Using a radon inventory equilibrium model, we estimated that the average SGD was 13.2 cm/day and the average terrestrial SGD flux was 1.8 × 10⁸ m³/day. Furthermore, SGD may have a vital impact on the composition and structure of nutrients in seawater, and contribute to eutrophication events occurring in spring season along the coast of the East China Sea.     

Assessment of indoor radiation dose received by the residents of natural high background radiation areas of coastal villages of Kanyakumari district,Tamil Nadu,India

Radiation exposure and effective dose received through two routes of exposure, viz. external and internal, via inhalation, by residents of 10 villages belonging to Natural High Background Radiation Areas (NHBRA) of coastal regions of Kanyakumari District and Tamil Nadu in India were studied. While the indoor gamma radiation levels were monitored using Thermo Luminescent Dosimeters (TLDs), the indoor radon and thoron gas concentrations were measured using twin chamber dosimeters employing Solid State Nuclear Track Detectors (SSNTDs, LR-115-II). The average total annual effective dose was estimated and found to be varying from 2.59 to 8.76 mSv.     

Impact of season and location on the natural radioactivity in marine macroalgae (<Emphasis Type="Italic">Gracilaria edulis)</Emphasis> of coastal Tamil Nadu,India

Gracilaria edulis, an edible red marine macro algae from three high background radiation areas (Arockiapuram, Kadiapattinam and Kurumpanai) on the southwest coast of Tamil Nadu, and one low background radiation area (Mandapam) on the southeast coast of Tamil Nadu, in India, were studied for variations in average gross alpha and beta radiation activities. Significant variations in average gross beta activities were observed while alpha activities showed only marginal variation. The average gross alpha activity was recorded high (61.51 Bq kg ⁻¹) during the post southwest monsoon season, while it recorded lowest (25.48 Bq kg ⁻¹) during the post northeast monsoon season. Average gross beta activity varied between seasons with the lowest level (211.55 Bq Kg⁻¹) during post southwest monsoon season and the highest (413.33 Bq kg ⁻¹) during post northeast monsoon season. Among the four locations, the gross alpha activity was high (70.95 ± 26.74 Bq Kg⁻¹) in Arockiapuram and low (18.74 ± 6.32 Bq Kg⁻¹) in Mandapam, while the gross beta activity was high (442.25 ± 168.53 Bq Kg⁻¹) in Kurumpanai and low (158.63 ± 34.37 Bq Kg⁻¹) in Mandapam. Average gross alpha activity in G. edulis was found significantly varying in terms of locations, while average gross beta activity for the same species recorded significant seasonal variation.