Some aquatic ecosystems from Mexico, such as rivers and lagoons, are affected by wastes enriched with potentially toxic elements generated by precious metal mining activities. Contamination of water, sediment and affected biota has produced several environmental issues, including biological effects in some species of flora. On the other hand, mineral processing activities may also generate effluents containing high activity concentration levels of natural radionuclides and, in this case, the wastes may be considered as technologically enhanced naturally occurring radioactive materials (TENORM). The release of TENORM in the aquatic environment may represent a radiological and ecological contamination issue. Therefore, the need for monitoring and assessing the radioecological impact of mining activities has been increased. In this study, measurements of the activity concentration levels of natural radionuclides in water and sediment from a continental lagoon in Central Mexico are performed. Methods include the use of alpha-particle spectrometry with passivated implanted planar silicon detectors for the analysis of uranium and polonium in water. For isolation of U and Po of water samples, a radiochemical process based in co-precipitation with iron hydroxide and liquid-liquid solvent extraction using tributyl phosphate was employed. High-resolution gamma-ray spectrometry with hyper-pure germanium (HPGe) detectors was used to analyse gamma emitter radionuclides in sediment samples. Preliminary results show that levels of uranium isotopes in surface water are 1-5 orders of magnitude higher than reported levels for drinking water from North America. Because water from the suited lagoon is used for irrigation of nearby crops, a discussion of the radioecological implications of the obtained results is presented.