On the radioecological issues of natural radionuclides in water and sediment of a highly contaminated lagoon from Mexico

On the radioecological issues of natural radionuclides in water and sediment of a highly contaminated lagoon from Mexico C.D. Mandujano-García 1,2,*, A.R. Nava-Huerta2, N.A. Santibañez2, O.R. Hernandez-Montoya3, D.R. Luna-Méndez3, J. Huerta-García3, J. Bluhm-Gutierrez4 and R. García-Tenorio1 1Departmento de Física Nuclear Aplicada II, Universidad de Sevilla, 41012 Sevilla, España 2Departmento de Recursos del Mar, Cinvestav, 97310 Mérida, Yucatán, México 3Laboratorio de Biología Ambiental y Molecular, Universidad Autónoma de Zacatecas, 98060 Zacatecas, México 4Unidad Académica de Ciencias de la Tierra, Universidad Autónoma de Zacatecas, 98058 Zacatecas, México INTRODUCTION RESULTS AND DISCUSSION CONCLUSION 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 [Iskander, 1994]. Contamination of water, sediment and affected biota has produced several environmental issues, including biological effects in some species of flora [Huerta-Garca, 2016]. 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 [USEPA, 1999]. 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. METODOLOGY REFERENCES 1. [Huerta-Garca, 2016] Huerta Garca, et.al... Evaluación de Mercurio y otros metales pesados en sedimentos de la presa la Zacatecana y su efecto fitotoxicolgico en maz (Zea mays) y frijol (Phaselous vulgaris L) cultivados en reas aldedaas. Informe de proyecto de investigacin UAZ-2015-36928 (2016). 2. [Iskander, 1994] Iskander F.Y., Vega-Carrillo H.R., Manzanares E. Determination of mercury and other elements in La Zacatecana Dam sediment in Mexico. The Science of the Total Environment 148: 45-48 (1994). 3. [Mireles, 2003] Mireles F, Dvila J.I., Quirino L.L. Lugo J.F., Pinedo J.L. and Ros C. Natural soil gamma Radioactivity levels and resultant population dose in the cities of Zacatecas and Guadalupe, Zacatecas, Mexico. Health Phys. 84 (3): 328-372 (2003). 4. [USEPA, 1999] United States Environmental Protection Agency. Technologically Enhanced Naturally Occurring Radioactive Materials in the Southwestern Copper Belt of Arizona. Technical Report 402-R-99-002. 5. [Villa, 2011] Villa M., Manjón G., Hurtado S., and García-Tenorio R. Uranium pollution in an estuary affected by pyrite acid mine drainage and releases of naturally occurring radioactive materials. Marine Pollution Bulletin 62 (2011) 1521–1529 Activity concentration of 210Pb, 226Ra and 228Ra in the sediment samples of the studied lagoon presented an average value of 83±26, 46±11 and 62±12 Bq/kg, respectively. This values are very similar, but also higher than levels in soil from the cities of Zacatecas and Guadalupe, which present ranges of 11-38 and 8-38 Bq/kg for radionuclides from the 238U and 232Th natural decay series, respectively [Mireles, 2003]. Activity concentrations of natural radionuclides in water and sediment from the lagoon El Pedernalillo have been determined. Levels of radium isoptopes and 210Pb in sediments are within reference levels of the studied region. On the other hand, uranium concentration levels in water are high, specially 234U exceed the USEPA guidelines levels for total uranium in natural waters (185 mBq/L). Because water from the suited lagoon is used for irrigation of nearby crops and animal consumption, radioecological implications may emerge from uranium bioaccumlation in the food chain. It is necessary to extend this study to the radioanlysis of biota and continue monitoring the levels of U in the Zacatecas environment. Activity concentration of natural radionuclides in sediment of the studied lagoon Z1 Z2 Z3 Z4 Z5 Z6 Z7 Z8 Z9 Z10 0 10 20 30 40 50 60 70 80 90 100 Bq/kg Sediment sample 226Ra Z1 Z2 Z3 Z4 Z5 Z6 Z7 Z8 Z9 Z10 0 10 20 30 40 50 60 70 80 90 100 Bq/kg 228Ra Sediment sample Z1 Z2 Z3 Z4 Z5 Z6 Z7 Z8 Z9 Z10 0 20 40 60 80 100 120 140 210Pb Bq/kg Sediment sample Sediment preparation Sampling Sediment was dried, grinded and sieved. A representative alicuote of sediment was packed in cilindrical geometry Study Area Map of Zacatecas city El Pedernalillo lagoon is located in Central México, within the mining district of Zacatecas. 10 samples of water and 10 samples of sediment were collected from the shore. Analysis of water by alpha spectrometry Actinides coprecipitation with iron hidroxide Preconcentration U-Po Separation Source preparation Radiochemical processing of water samples Liquid-liquid solvent extraction (TBP) Electrodeposition (U) or self-deposition (Po) in metalic plates Measurement with PIPS detectors in a Canberra Alpha Analyst System Spectrum Analysis with Genie 2000 Analysis of sediment by gammma-ray spectrometry High resolution gamma-ray spectrometry was used to perform the radiometric characterization of the sediment samples in a Canberra HPGe (Hyperpure Germanium) detector type XtRa (extended range), with a relative efficiency of 40% and resolution of 1.77 keV for the 1.33 MeV photopeak of 60Co. Efficiency calibration was performed using IAEA reference materials (RGU1, RGTh1). Self-absortion corrections were done for 210Pb calculations. Gamma-ray spectrometry system used in this study: HPGe detector and lead shielding. Regarding alpha-particle spectrometry measurements in water, uranium isotopes presented activity concentration average values of 155±104, 380±252 and 7.0±4.2 mBq/L for 238U, 234U and 235U, respectively. Average concentration of 210Po in water was 25±19 mBq/L. Uranium levels in the studied lagoon are lower than U levels in surface water from the Arizona cupper belt (2960~3100 mBq/L) [USEPA, 1999], but higher than U levels in water from and estuary influenced by acid mine drainage in the Iberian Pyrite Belt (1.8~131 mBq/L)[Villa, 2011]. Z1 Z2 Z3 Z4 Z5 Z6 Z7 Z8 Z9 Z10 0 100 200 300 400 500 600 700 800 900 1000 1100 mBq/L Water sample U-238 U-234 Z1 Z2 Z3 Z4 Z5 Z6 Z7 Z8 Z9 Z10 0 10 20 30 40 50 60 70 80 90 mBq/L Water sample U-235 Po-210 What about us? View publication statsView publication stats