Results 1 - 10 of 906
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[en] This article is the first one in a series of three articles dedicated to radioecology. After an introduction to the field covered by radioecology, it deals with the dispersion of radionuclides in air, their deposition on surfaces, their migration in soils and their dispersion in watercourses. For each mode of transfer, the associated phenomena are firstly presented, followed by the parameters or the models that allow to take them into account. Quantitative illustrations and parameter values show the intensity of these transfers and to make rough assessments of volume, surface or mass activities in the concerned environmental components
[en] The meteoric cosmogenic beryllium has been used as an essential geophysical tracer in the analysis of atmospheric flows and erosion soils since 1960. The first measurements 7Be and 10Be concentrations in rainwater from Mexico, have been carried out by using gamma decay spectroscopy and AMS techniques, respectively for each isotope. With this it was possible to report a preliminar value for the 10Be/7Be isotopic ratio in such environmental samples. The present work described preliminary results related to rainwater collected at mountain and metropolitan areas. Results are compared with predictions and previous measurements for both radioisotopes, observing a very sensible behavior particularly for the case of 7Be activities. (author)
[en] In the present study, an attempt has been made to measure the radionuclide contents in soil samples from the region around coal-based thermal power plant (TPP) in Tarn Taran district of Punjab state in India and to assess the impact of coal-based TPP on the radionuclide distribution in surrounding areas. For this purpose, soil samples collected from the region, coal samples, and fly-ash samples collected from the plant were analyzed using the gamma spectrometry technique employing thallium-activated sodium iodide detector. The activity concentration of radionuclides was observed to be higher for the samples collected from the locations nearer to the power plant and decreased as the distance from power plant increased indicating an increase in soil radioactivity due to TPP. (author)
[en] The low level tritium, released to marine environment from nuclear facilities, incorporated by marine matrices as tissue free water tritium (TFWT) and organically bound tritium (OBT), was studies for 3 years at Tarapur, situated on the west coast of India. Results show that the tritium concentration in sea water was correlated with TFWT concentration in sea weeds, sediment and marine animals as, with correlation coefficients of 0.6, 0.8 and 0.96 respectively. The TFWT to OBT ratios were observed to be 5.7, 4.9 and 3.6 respectively in seaweed, sediment and marine animals. (author)
[en] A Short-Term Emergency Assessment system of the Marine Environmental Radioactivity (STEAMER) was developed at the Japan Atomic Energy Agency (JAEA) to forecast or reanalyze the oceanic dispersion of radionuclides that are released into the ocean around Japan from nuclear facilities during routine operation or in an emergency. STEAMER is currently in daily operation at JAEA to conduct single forecast simulation. The predictability of STEAMER is validated by utilizing oceanographic forecast and reanalysis data in this study. The oceanic dispersion simulations that use oceanographic reanalysis data as input data are assumed to have true solutions. Reanalysis data that has been optimized by data assimilation is the most reliable input for post-analysis. Rigorous oceanic dispersion simulations are conducted for the hypothetical release of Cs-137 from the Fukushima Daiichi Nuclear Power Plant. The predictability of the Cs-137 oceanic dispersion is quantitatively estimated over a forecast period. Moreover, ensemble forecast simulations are also performed applying the Lagged Average Forecast methodology and they successfully improve the predictability of the Cs-137 oceanic dispersion over that obtained using single forecast simulation. The ensemble forecast simulations need to be installed in STEAMER in the future. (author)
[en] This study focused on the composition and species diversity of plants during different succession periods based on a field investigation in Houzhai Valley in Puding County, a karst area in Guizhou Province in Southwest China. The results showed that the vegetation in this area was mainly in four succession stages: grassland, shrub grassland, shrub forest and arbour forest. There were also some artificial fruit-bearing forests. In summary, 97 families, 230 genera and 382 species were investigated and recorded in the studied region. The predominant three families with the largest number of species were the Rosaceae, Compositae and Poaceae. The percentage of the life forms as arbour, shrub, herb and rattan accounted for 14.66%, 29.84%, 43.46% and 11.52% of the total species, respectively. The species richness index and Simpson's diversity index were as follows: arbour forest > shrub forest > shrub grassland > fruit-bearing forest > grassland. The species evenness and Shannon–Wiener index were as follows: arbour forest > shrub forest > shrub grassland > grass > fruit-bearing forest. In different stages of vegetation succession in the karst area, the measures taken for the restoration of vegetation and afforestation should be based on the specific species. (author)
[en] In general, groundwater flow and transport models are being applied to investigate a wide variety of hydrogeological conditions besides to calculate the rate and direction of movement of groundwater through aquifers and confining units in the subsurface. Transport models estimate the concentration of a chemical in groundwater which requires the development of a calibrated groundwater flow model or, at a minimum, an accurate determination of the velocity and direction of groundwater flow that is based on field data. All the available hydrogeological, geophysical and water quality data in Musi basin, Hyderabad, India, were fed as input to the model to obtain the groundwater flow velocities and the interaction of surface water and groundwater and thereby seepage loss was estimated. This in turn paved the way to calculate the capacity of the storage treatment plants (STP) to be established at the inlets of six major lakes of the basin. The total dissolved solid was given as the pollutant load in the mass transport model, and through model simulation, its migration at present and futuristic scenarios was brought out by groundwater flow and mass transport modeling. The average groundwater velocity estimated through the flow model was 0.26 m/day. The capacities of STP of various lakes in the study area were estimated based on the lake seepage and evaporation loss. Based on the groundwater velocity and TDS as pollutant load in the lakes, the likely contamination from lakes at present and for the next 20 years was predicted.
[en] In the context of proposed uranium mining area, it is very important to evaluate the presence of certain trace metals in groundwater around a proposed uranium mining area at Peddagattu and Seripally areas of Nalgonda district, Telangana (India). The concentrations of certain metals (Cu, Zn, Ni, Pb, Fe, Mn, Cd, Co, Sr, Ba, Cr, Cs and As) were measured in 37 groundwater locations and 10 surface water locations for seven times during 2 years around proposed uranium mining areas. The risk of the chemical toxicant [may be characterized using a hazard quotient (HQ)] is calculated by the results obtained during the study. The HQs of both groundwater (37) and surface water (10) all the considered trace metals were well below the threshold value of 1 as suggested by USEPA.
[en] The vertical fraction variation of eddy diffusivity was taken into consideration in the dispersion of pollutants from a point source. A power-law profile was used to describe the variation of wind speed and vertical eddy diffusivity with height above ground surface. The dry deposition of the diffusing particles at the ground surface is taken into account through the boundary conditions. The concentration of pollutants was derived assuming that the vertical diffusion is limited by an elevated inversion layer located at the top of the boundary layer “h”. Also, the decay distance of a pollutant along the wind direction was estimated. The resulting analytical solutions have been applied on the emissions from Egypt ’s First Research Reactor at Inshas in unstable condition and Hanford diffusion experiment in stable condition. Comparisons between proposed and observed concentrations show a good agreement between the proposed and observed concentrations whenα=0.81 than other fractions and integer value. The results are discussed and presented in illustrative figures