A study of the distribution of U and Th-isotopes in different fractions of intertidal sediments collected in a marsh area has been carried out. This marsh area is affected by the releases of natural radionuclides from fertilizer industries carried out into the Odiel river. The study has shown that uranium is mainly located in non-residual fractions of the sediments and particularly coprecipitated with amorphous ferromanganese oxyhydroxides. In the case of Th isotopes, the contribution of residual fractions is higher than that of non-residual fractions, being the main non- residual fraction again the amourphous ferromanganese oxyhydroxides. However, all fractions seems to reflect the same pattern of contamination. Thus, those sediments located along the Odiel river basin have the higher concentration in all sequentially extracted fractions. Some interesting activity and mass ratios have also been investigated.
U, Th and Ra isotopic activities have been measured in water and sediment samples collected over three years from the Guadalquivir river channel (South of Spain). The study of the radioactivity levels and activity ratios evolution in space and time has provided information on the behavior of the radionuclides mentioned above in the estuarine and non-estuarine zones of the river.
The occurrence of anomalous enhancements of U-isotope activities in the surrounding environment of a phosphate fertilizer factory complex at the southwest of Spain has been established. It seems that significant amounts of U, released by such industries, are being accumulated in the environment, which may substantially contribute to the collective radiation dose received by the local population.
Authors:A. Martínez-Aguirre, M. García-León, C. Gascó, and A. Travesi
An extensive study on the distribution of natural radionuclides in an estuarine ecosystem located in Southwestern Spain is presented. This environment is highly affected by the wastes released by a phosphoric acid industry which uses phosphate rocks as raw material for fertilizer production. This rock has generally high concentrations of U and its daughters. The estuary is formed by two rivers, Odiel and Tinto, which have a common mouth into the Atlanic Ocean and a salt marsh (Odiel marsh) affected by the income of Odiel riverwaters. This river receives directly the liquid and part of the solid (gypsum) wastes released from the industries. Besides that, most of the phosphogypsum wastes are stored in uncovered piles at the right margin of the Tinto river. The study has concluded that the wastes from such industries are the cause of the enhanced concentrations found at the bed of both river channels as well as the enhancement found in surface soils in certain zones of the Odiel wet marshland. Indeed, the Northern marsh and the Mojarrera channel at the Odiel marsh seem to be the main sinks of the contaminant released by the phosphoric acid industry.
Authors:A. Martínez-Aguirre, M. Morón, and M. García-León
Concentrations of U- and Ra-isotopes in rainwater samples taken in the South Spanish atmospheric environment during the years 1986, 1987 and 1988 are presented. Such data have been obtained by applying a simple method for the simultaneous determination of such radionuclides from the same rainwater sample. Ra is firstly coprecipitated as Ba–Ra sulfate. Then two alternatives can be used for U analysis: a coprecipitation of U with Fe, followed by a selective redissolution of the precipitate with ammonium carbonate, or a solvent extraction technique by using tributyl phosphate. Levels of 0.99 to 1.81 g/l, 3.4 to 17.9 mBq/l and 0.5 to 5.5 mBq/l, respectively for U,226Ra and224Ra are found during the studied time period. The dependence of such concentration variability on meteorological parameters is discussed.
Authors:J. Martín, A. Martínez-Aguirre, M. Respaldiza, and M. da Silva
The studied marsh area is located at the southwest of Spain in an estuarine system formed by the confluence of the Odiel river and the Atlantic ocean. 23 samples collected in the marsh have been analysed by Thick Target Proton Induced X-ray Emission using 2 MeV protons from the 3 MV Van de Graaff accelerator of the ITN. Elemental concentrations in the samples are affected by the Atlantic ocean, the materials transported by the Odiel river and the wastes discharged by the factories of a nearby industrial area. The study has shown that certain areas of the estuary present high concentrations of P, Cu, Zn, As and Pb, which were attributed to the operation of a phosphate fertilizer factory and a Cu extraction factory. The mining activity carried out near the source of the river could be also responsible of part of this contamination. Finally, the spatial distribution of the contamination has reflected the dinamic of the Odiel river waters, due to tidal movements, into the marsh area.
Authors:M. García-León, A. Martínez-Aguirre, R. Periáñez, J. Bolívar, and R. García-Tenorio
Phosphate rocks are used for phosphoric acid production, which is the basis of agricultural phosphate fertilizers. It is known that phosphate ores contain, due to geological reasons, important amounts of natural radioactivity, mainly U-isotopes and daughters. By studying a specific case in Southwestern Spain, it is shown that the operation of phosphate fertilizer factories clearly enhance the natural radiation levels of its close environment. Levels of U-, Th-isotopes, and other natural radionuclides are given for a wide set of different samples, which support such a conclusion. In addition, the study of isotopic ratios gives information on the environmental behavior of such radionuclides.