Determination of the activity concentration of 131I in the middle basin of the Bogota river

This research presents an approximation to determine the presence of I-131 (a reagent used in diagnosis and metabolic therapy of thyroid cancer) in the Bogota River, the body of water located on the border of the Colombian capital. Samples were taken along the middle river basin and analyzed using the high-resolution gamma-ray spectrometry technique. A maximum concentration of 16.8 Bq L-1 was obtained at the point called Guadua bridge, near the PTAR El Salitre, followed by the measures in point Gibraltar, with 16.1 Bq L-1. These results are considered relevant because of their proximity to the maximum concentration established for discharges in liquid form to sewers, rivers and other large bodies of water, stipulated in the Colombian regulations. They also exceed the World Health Organization reference value for drinking water. The presence of I-131 can be associated to the activity of the medical sector, as a consequence of the transport of the radioisotope from the facilities where it is applied, through the sewerage networks, to the wastewater treatment plant of the city and finally to the river.