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Caracterización radiológica de las aguas subterráneas de la Sierra de Gádor (Almería)
J.L. Guerrero1, A. Vallejos2, J.C. Cerón3, F. Sánchez-Martos2, A. Pulido-Bosch2 y J.P. Bolívar1
1Departamento de Ciencias Integradas (Física Aplicada), Universidad de Huelva. 2Departamento de Biología y Geología. Universidad de Almería. 3Centro de Investigación para la Ingeniería en Minería Sostenible, Escuela Técnica Superior de Ingeniería. Univ. de Huelva.
resumen: La Sierra de Gádor es un sistema acuífero kárstico localizado en Almería, sometido a gran estrés ambiental ya que sustenta las principales actividades económicas de la zona (agricultura y turismo). El objetivo de este trabajo ha sido estudiar los niveles y el comportamiento de los isótopos naturales de U y 226Ra en sus aguas subterráneas. Para ello, se recogieron 28 muestras de manantiales y sondeos, y se determinó la concentración de actividad de los isótopos naturales de U y 226Ra mediante espectrometría alfa.
La concentración de actividad de 238U osciló entre 2,8 y 42 mBq L-1, con cocientes 234U/238U mayores que la unidad en todos los casos. El 226Ra osciló en dos órdenes de magnitud, con un máximo de 4·102 mBq L-1. En general, mostró una movilidad muy inferior a la del U en estas aguas. Se observaron tres grupos de aguas en función de sus características hidroquímicas y concentración de radionucleidos, los cuales se discuten en este trabajo.
Se concluye que el U aparece principalmente disuelto formando complejos de carbonato de uranilo, estando todas las muestras subsaturadas respecto a las principales fases minerales de U. Finalmente, las dosis efectivas comprometidas calculadas demuestran la ausencia de riesgo radiológico para la población debido a los radionucleidos analizados.
ABstrAct: Sierra de Gádor is a karst aquifer system located in Almería, under great environmental stress, supporting the main economi- cal activities of the area (agriculture and tourism). The objective of this work is to study the levels and behavior of natural U-isotopes and 226Ra in the groundwater. For that, 28 samples from springs and boreholes were collected, and the activity concentrations of the natural U-isotopes and 226Ra by alpha spectrometry were determined.
The activity concentration of 238U ranges between 2.8 y 42 mBq L-1, and the 234U/238U activity ratio were higher than unity for all samples. 226Ra ranges two orders of magnitude with a maximum of 4·102 mBq L-1. In general it showed a much lower mobility than U in those waters. Three groups of water were observed on the basis of their hydrochemical characteristics and radionuclide concentration which are discussed in this work.
It concludes that U mainly existed as uranyl carbonate complexes, and all samples are clearly undersaturated with respect to the main U mineral phases. Finally, the calculated committed effective doses reveals the absence of risk for the population due to the analyzed radionuclides.
Palabras clave: acuífero kárstico, isótopos de uranio, 226Ra, dosis efectiva comprometida. Keywords: Karst Aquifer, Uranium Isotopes, 226Ra, Committed Effective Dose.
introducciÓn
La Sierra de Gádor es un macizo montañoso situado en el extremo suroccidental de la provincia de Almería donde existe un macrosistema acuífero kárstico localizado (Figura 1). Este sistema, de edad triásica (250-200 Ma), ocupa un área de más de 900 km2 y está principalmente formado por calizas (CaCO3), y dolomías \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\[CaMg(CO3)2\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\], con intercala- ciones de yeso (CaSO4·2H2O). Los materiales carbonatados pueden alcanzar espesores de hasta 1000 m y se encuen- tran fracturados y karstificados, presentando una elevada permeabilidad \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\[1\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\].
Debido al clima semiárido de la zona, con una precipi- tación media anual de entorno a 400 mm para el conjun- to de la Sierra de Gádor y una temperatura media anual de 17,2oC en su vertiente Sur, este sistema acuífero es
explotado actualmente para regar más de 2,0·104 ha de invernaderos, localizados en el Campo de Dalías, el cual está hidráulicamente conectado con la Sierra de Gádor. Además, abastece de agua potable a más de 2,0·105 personas, y más del doble en los meses de verano \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\[2\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\]. La intensa explotación a la cual ha sido sometido este sistema acuífero, excediendo la recarga media anual, ha producido caídas en los niveles piezómetricos, deterioro de calidad de las aguas e intrusión marina en algunos sectores del borde sur \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\[3\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\].
Teniendo en cuenta los hechos anteriores, así como el escaso conocimiento de los radionucleidos naturales en esta área, el objetivo de este trabajo ha sido conocer los niveles y el comportamiento de los isótopos naturales de U y 226Ra en el sistema acuífero de la Sierra de Gádor.
CARACTERIzACIóN RADIOLóGICA DE LAS AGUAS SUBTERRáNEAS DE LA SIERRA DE GáDOR (ALMERíA)
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