M. Rentería Villalobosª, M.E. Montero Cabreraª , *, M. Reyes Cortésª , b, E.F. Herrera Perazaª, A. Rodríguez Pinedac, G. Manjón Colladod, R. García Tenoriod, T. Crespoe, and M. Valenzuela Hernándezª
ª Centro de Investigación en Materiales Avanzados, Miguel de Cervantes 120, 31109 Chihuahua, Chih., México,
b Facultad de Ingeniería, Universidad Autónoma de Chihuahua, Nuevo Campus Universitario s/n, Chihuahua, Chih, México,
c World Wildlife Fund (WWF), Chihuahuan Desert Program, Coronado 1005, 31000 Chihuahua, Chih. México,
d Universidad de Sevilla, Departamento de Física Aplicada II, ETS Arquitectura, Av. Reina Mercedes 2, 41012 Sevilla, Spain,
e Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Av. Complutense 22, 28040 Madrid, Spain *e-mail: elena.montero@cimav.edu.mx
]]> Recibido el 2 de marzo de 2006
Abstract
As part of a scientific research project about alpha radioactivity in groundwater for human consumption at the Chihuahua City, the characterization of rock sources of radioactivity around de Chihuahua valley was developed. The radioactivity of groundwater and sediments was determined, too. The radioactivity of uranium- and thorium- series isotopes contained in rocks was obtained by high resolution gamma-ray spectroscopy. Some representative values are 50 Bq/kg for the mean value of Bi-214 activity, and 121.5 Bq/kg for the highest value at West of the city. The activity of sediments, extracted during wells perforation, was determined using a NaI(Tl) detector. A non-reported before uranium ore was localized at the San Marcos range formation. Its outcrops are inside the Chihuahua-Sacramento valley basin and its activity characterization was performed. Unusually high specific uranium activities, determined by alpha spectrometry, were obtained in water, plants, sediments and fish extracted at locations close to outcrops of uranium minerals. The activity of water of the San Marcos dam reached 7.7 Bq/L. The activity offish, trapped at San Marcos dam, is 0.99 Bq/kg. Conclusions about the contamination of groundwater at North of Chihuahua City were obtained.
Keywords: Radioactivity; groundwater; uranium-series disequilibrium; gamma-ray spectrometry; alpha-ray spectrometry.
Resumen
Como parte de un proyecto científico sobre actividad alfa en agua subterranea de consumo humano en la ciudad de Chihuahua, se ha desarrollado la caracterización de las rocas fuentes de la radiactividad en el valle de Chihuahua. Se determinó también la actividad de muestras de agua subterránea y de sedimentos. La actividad de los isótopos de las series radiactivas en las rocas se obtuvo usando espectroscopía gamma de alta resolución. Algunos valores representativos son 50 Bq/kg para el valor medio de la actividad del Bi-214 y 121.5 Bq/kg para el valor más alto al oeste de la ciudad. La actividad de los sedimentos extraídos durante la perforación de pozos para agua potable, se determinó usando un detector de NaI(Tl). En la formacion montañosa de San Marcos se localizó un depósito de uranio no publicado. Sus afloramientos se encuentran dentro de la cuenca del valle Chihuahua-Sacramento y se realizó la caracterización de su radiactividad. Se determinaron actividades por espectrometría alfa de agua, plantas, sedimentos y peces extraídos en emplazamientos cercanos a los afloramientos de minerales de uranio. La actividad del agua en la presa de san Marcos llegó a 7.7 Bq/L. La actividad de pescados de la misma presa alcanza 0.99 Bq/kg. Se obtuvieron conclusiones sobre la contaminacion del agua subterránea al norte de la ciudad de Chihuahua.
Descriptores: Radiactividad; agua subterránea; desequilibrio U-234/U-238; espectrometría gamma; espectrometría alfa.
]]>PACS: 89.60-k; 91.65.Rg; 92.40.kc; 92.40.Gc; 92.40.Q
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Acknowledgement
The support given by Junta Central de Agua y Saneamiento del Estado de Chihuahua and by M. Alemán, L. Fuentes Montero, D. Burciaga Valencia, J. Mantero Cabrera, and E. Torres Moye is acknowledged.
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