URANIUM IN FISH FROM SAN MARCOS DAM, CHIHUAHUA, MEXICO

Some uranium outcrops are located around the San Marcos area, which is near to Chihuahua City. The objective of this study was to analyze the concentrations of isotopic uranium in fish collected from the San Marcos dam. This body water is placed in a semiarid region at northwest of Chihuahua city. The water of this dam is used for agriculture in the nearest areas. Sixteen fish samples were obtained in one sampling during the rainy season, from July to August of 2005. The analysis was made on the fish muscle. U-isotopes concentration was determined by high-resolution alpha spectrometry, using a PIPS detector. The activity concentrations of ²³⁸U and ²³⁴U isotopes ranged from 0.14 to 2.6 and 0.6 to 4.5 Bq kg^-1, respectively. Values reported by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) specify a ²³⁸U activity concentration ranging from 0.013 to 1.9 Bq kg^-1 in fish from the United States. Although these fish are not consumed by the population, this analysis shows an abnormal concentration of this toxic element. For the aforementioned, it is concluded that in this zone there is a natural contamination from uranium minerals outcrops.