Y. Narayana

Distribution of some natural and artificial radionuclides in Mangalore environment of South India

Abstract The activities of 40 K, 226 Ra, 228 Ra, 210 Po, 210 Pb, 137 Cs and 90 Sr were determined in a number of natural samples in the environment of Mangalore, South India where large-scale industrial activities are envisaged. Well-established nuclear techniques were employed to measure the activities and wherever necessary radiochemical methods were also followed. The measurement of transfer coefficients indicated that the uptake of 226 Ra, 228 Ra and 210 Pb in paddy is higher than that in vegetables. The measured activity ratios of 210 Po: 210 Pb and 228 Ra: 226 Ra in soil samples suggest the existence of equilibrium between the corresponding radionuclides in normal background areas and disequilibrium in high background areas. The intake of radionuclides by the population and the internal dose were estimated. The annual internal effective dose for the population is found to be 341 μSv year −1 which mainly arises from 40 K and 210 Pb.

226Ra, 40K and 7Be activity concentrations in plants in the environment of Kaiga, India

Leaves, stem and bark samples from several plant species were collected from tropical forest of Kaiga, in the west coast of India where two nuclear power reactors of 220 MW each have just been commissioned and another two are under construction, and analysed for their (226)Ra, (40)K and (7)Be concentrations. The activities of (226)Ra and (40)K in plants were found to vary in the range BDL-13.2 and 12.0-797.3 Bq kg(-1), respectively. Plants show significant (7)Be activity in leaves, the activity varies in 72.5-1,060.8 Bq kg(-1). Stem and bark of plants show higher levels of (226)Ra and (40)K when compared to leaves. Soil-to-plant transfer factor for (226)Ra and (40)K were found to vary in the range BDL-0.37 and 0.09-5.61, respectively for different plants. The concentration of (226)Ra and (40)K in leaves depends on the age of the leaves.

Distribution of some natural and artificial radionuclides in the environment of coastal Karnataka of south India

Coastal Karnataka, which is an important region of the south-west coast of India, is poised to become a region of major industrial activity with the construction of nuclear and thermal power stations, oil refineries and petrochemical complexes. This is in addition to existing chemical and fertilizer factories and a host of other industries. Systematic studies on radiation levels and radionuclide distributions in the environment of this region were undertaken to provide baseline data on the radiation levels for future assessment of the impact of these industrial activities and to throw light on the basic aspects of transportation of radionuclides in the environment and their uptake by vegetation species. The activities of 40K, 226Ra, 210Po, 210Pb, 228Ra, 137Cs and 90Sr were determined in a number of environmental samples of the region by employing well established nuclear techniques and standard radiochemical methods. The internal dose to the population of the region from ingestion of different radionuclides was estimated. The results of these systematic investigations, which form the first ever report on the radionuclide distribution of coastal Karnataka, are presented and discussed in this paper.

External gamma radiation dose rates in coastal Karnataka

External gamma-ray dose rates in air have been measured using a sensitive plastic scintillometer in the environment of coastal Karnataka, on the south west coast of India, where intensive industrial activities including a nuclear power plant, a super thermal power station and a petrochemical complex are envisaged. The gamma dose rates in air range from 26 to 174 nGy h-1 with a geometric mean of 74 nGy h-1 and geometric standard deviation of 1.4. The activity of primordial radionuclides in soil samples of the region were measured using an HPGe gamma ray spectrometer and the resulting doses in air were calculated. The mean absorbed dose rate due to primordial radionuclides was 41.4 nGy h-1 with a geometric standard deviation of 1.4. A correlation was found between doses measured using scintillometer and doses estimated from the measured activity of primordial radionuclides when the cosmic ray component is taken into account. The concentration of primordial radionuclides in soil and sand show considerable variation in their vertical depth distribution in the high background area of the region.

Study of 210Po and 210Pb in the riverine environments of coastal Karnataka.

Activity of (210)Po and (210)Pb were measured in soil and sediment samples collected from the major rivers Kali, Sharavathi and Netravathi of Coastal Karnataka. The activity of these two radionuclides were determined by radiochemical separation of (210)Po and counting the activity using a ZnS(Ag) Alpha counter. The activity of (210)Pb was higher than that of (210)Po in the riverine environs. The (210)Po and (210)Pb content in sediment was found to increase with silt/clay and organic matter contents. However no significant correlation was found between the activity (210)Po and (210)Pb with pH in sediments. The activity of (210)Po and (210)Pb and influence of physico-chemical parameters on these radionuclides were studied and discussed in this paper.

Bioindicators in the tropical forest of Kaiga environment

Abstract Investigations on the natural and artificial fallout radionuclides 210 Po and 137 Cs and the primordial radionuclide 40 K in the prominent tree species of Western Ghat tropical forests near Kaiga have been carried out as a part of baseline background radiation studies in the environment of Kaiga where nuclear power reactors are being installed. The prominent tree species of the region Tectona grandis L.f. and Terminalia paniculata Roth., and the commonly available epiphytic plant species Pterobryopsis tumida (Hook.) Dix. and Cymbidium aliofolium (Lo) Swartz. were chosen and concentrations of 40 K, 210 Po and 137 Cs were measured employing well-established nuclear techniques. The different parts of Cumbidium aloifolium (Lo) Swartz. such as leaves, stem, etc. were analysed to understand the absorption mechanism of fallout radionuclides. From a careful analysis of the results, the epiphytic plant species are identified as bioindicators to monitor fallout radionuclides.

The importance of physico-chemical parameters on the speciation of natural radionuclides in riverine ecosystems.

External gamma radiation levels were measured in the catchment areas of the Sharavathi River and the dose rates in air were found to be in the range 26.0-61.0 nGy h(-1). Soil and sediment samples of the riverine environment were analysed for natural radionuclides such as (226)Ra, (232)Th and (40)K using a NaI(Tl) gamma spectrometer. The activity concentration of (210)Pb and (210)Po in soil and sediment samples was determined by radiochemical separation techniques. Evaluation of the activity concentration of radionuclides with grain size revealed an increase in the activity of (226)Ra, (232)Th and (40)K towards fine grain size. The activity concentrations for all isotopes in all samples were not significantly correlated with pH. However, the activity of (210)Po and (210)Pb in sediment showed a moderate positive correlation with organic matter content and a good correlation with clay content of sediment.

Variation of radiation level and radionuclide enrichment in high background area

Significantly high radiation level and radionuclide concentration along Quilon beach area of coastal Kerala have been reported by several investigators. Detailed gamma radiation level survey was carried out using a portable scintillometer. Detailed studies on radionuclides concentration in different environmental matrices of high background areas were undertaken in the coastal areas of Karunagapalli, Kayankulam, Chavara, Neendakara and Kollam to study the distribution and enrichment of the radionuclides in the region. The absorbed gamma dose rates in air in high background area are in the range 43-17,400nGyh⁻¹. Gamma radiation level is found to be maximum at a distance of 20m from the sea waterline in all beaches. The soil samples collected from different locations were analysed for primordial radionuclides by gamma spectrometry. The activity of primordial radionuclides was determined for the different size fractions of soil to study the enrichment pattern. The highest activity of (232)Th and (226)Ra was found to be enriched in 125-63μ size fraction. The preferential accumulation of (40)K was found in <63μ fraction. The minimum (232)Th activity was 30.2Bqkg⁻¹, found in 1000-500μ particle size fraction at Kollam and maximum activity of 3250.4Bqkg⁻¹ was observed in grains of size 125-63μ at Neendakara. The lowest (226)Ra activity observed was 33.9Bqkg⁻¹ at Neendakara in grains of size 1000-500μ and the highest activity observed was 482.6Bqkg⁻¹ in grains of size 125-63μ in Neendakara. The highest (40)K activity found was 1923Bqkg⁻¹ in grains of size <63μ for a sample collected from Neendakara. A good correlation was observed between computed dose and measured dose in air. The correlation between (232)Th and (226)Ra was also moderately high. The results of these investigations are presented and discussed in this paper.

Atmospheric radon levels and its emanation rate in the environment of Kaiga

Abstract A systematic study of atmospheric radon levels and of radon emanation rates was conducted in the environment of Kaiga on the south-west coast of India where the installation of nuclear power reactors is in progress. 222 Rn emanation rates were estimated employing the accumulating chamber method and were found to vary from 5.6 to 62.9 mBq m −2 s −1 with a geometric mean of 30.0 mBq m −2 s −1 . The atmospheric concentrations were estimated using CR-39 solid state nuclear track detectors (SSNTDs) and found to vary from 4.7 to 27.9 Bq m −3 with a geometric mean of 13.4 Bq m −3 . The results show a strong correlation between emanation rate and atmospheric concentration while showing a poor correlation between 226 Ra concentration in surface soil and atmospheric concentration of 222 Rn. The results are also compared and discussed in the light of relevant literature reported for other environments.

Distribution and behaviour of natural radionuclides in soil samples of Goa on the southwest coast of India

Publisher Summary Human beings have always been exposed to natural background radiation. The natural background radiation has two components: one originating from extra terrestrial sources such as cosmic rays and the other from terrestrial sources that derive essentially from the Earths strata. This chapter discusses the program of studies on natural radiation in the environment of Goa that was conducted by the research group in the period 1995–1999 to establish the natural background radiation level and radionuclide distribution in the environment. Soil samples were collected and analyzed for their gamma radionuclides—namely, 226 Ra, 232 Th and 40 K using an HPGe spectrometer. 210 Pb and 210 Po were determined employing radiochemical techniques. Activity ratios and correlation studies of 226 Ra, 210 Pb and 210 Po in surface soil clearly indicate the presence of unsupported 210 Pb and 210 Po in surface soil. Significant correlation observed between the concentrations of 210 Pb and 210 Po and soil organic matter content confirms the adsorption of these radionuclides from atmospheric precipitation, hence causing higher concentrations in surface soil.