Abstract
In this work we present results of a study concerning the distribution and behaviour of several natural radionuclides (U, Th-isotopes, 210Po and gamma-emitters) in a mining river located in the southwest of Spain. Enhancements of U concentrations relative to other analysed isotopes within the U series have been observed, being due to co-precipitation of U with heavy metals in accord with increases in pH along the river. The U excess can be traced to uranium dissolution in waters that have been used as a part of a mineral treatment process within the mine, the water subsequently being released into the river.