Hydrochemistry and 222Rn Concentrations in Spring Waters in the Arid Zone El Granero, Chihuahua, Mexico

Water in arid and semi-arid environments is characterized by the presentation of complex interactions, where dissolved chemical species in high concentrations have negative effects on the water quality. Radon is present in areas with a high uranium and radium content, and it is the main contributor of the annual effective dose received by humans. The objective of this study was to evaluate concentrations of 222Rn and the water quality of spring waters. Water was classified as calcium sulfated and sodium sulfated. Most of the water samples with high radon concentrations presented higher concentrations of sulfates, fluorides, and total dissolved solids. 222Rn concentrations may be attributed to possible enhancement of 226Ra due to temperature and salinity of water, as well as evaporation rate. In 100% of the sampled spring waters the 222Rn levels exceeded the maximum acceptable limit which is proposed by international institutions. Aridity increases radiological risk related to 222Rn dose because spring waters are the main supply source for local populations. The implementation of environmental education, strategies, and technologies to remove the contaminants from the water are essential in order to reduce the health risk for local inhabitants.CIMAV (Centro de Investigación en Materiales Avanzados

Uranium series isotopes concentration in sediments at San Marcos and Luis L. Leonreservoirs, Chihuahua, Mexico

Spatial and temporal distribution of the radioisotopes concentrations were determined in sediments near the surface and core samples extracted from two reservoirs located in an arid region close to Chihuahua City, Mexico. At San Marcos reservoir one core was studied, while from Luis L. Leon reservoir one core from the entrance and another one close to the wall were investigated. 232Th-series, 238U-series, 40K and 137Cs activity concentrations (AC, Bq kg-1) were determined by gamma spectrometry with a high purity Ge detector. 238U and 234U ACs were obtained by liquid scintillation and alpha spectrometry with a surface barrier detector. Dating of core sediments was performed applying CRS method to 210Pb activities. Results were verified by 137Cs AC. Resulting activity concentrations were compared among corresponding surface and core sediments. High 238U-series AC values were found in sediments from San Marcos reservoir, because this site is located close to the Victorino uranium deposit. Low AC values found in Luis L. Leon reservoir suggest that the uranium present in the source of the Sacramento – Chuviscar Rivers is not transported up to the Conchos River. Activity ratios (AR) 234U/ 238U and 238U/226Ra in sediments have values between 0.9-1.2, showing a behavior close to radioactive equilibrium in the entire basin. 232Th/238U, 228Ra/226Ra ARs are witnesses of the different geological origin of sediments from San Marcos and Luis L. Leon reservoirs

Uranium in the Surrounding of San Marcos-Sacramento River Environment (Chihuahua, Mexico)

The main interest of this study is to assess whether uranium deposits located in the San Marcos outcrops (NW of Chihuahua City, Mexico) could be considered as a source of U-isotopes in its surrounding environment. Uranium activity concentrations were determined in biota, ground, and surface water by either alpha or liquid scintillation spectrometries. Major ions were analyzed by ICP-OES in surface water and its suspended matter. For determining uranium activity in biota, samples were divided in parts. The results have shown a possible lixiviation and infiltration of uranium from geological substrate into the ground and surface water, and consequently, a transfer to biota. Calculated annual effective doses by ingestion suggest that U-isotopes in biota could not negligibly contribute to the neighboring population dose. By all these considerations, it is concluded that in this zone there is natural enhancement of uranium in all environmental samples analyzed in the present work

Partitioning and Availability of Metals from Water Suspended Sediments: Potential Pollution Risk Assessment

The water management initiatives in freshwater systems focus on water availability to preserve this resource for human uses and the health of aquatic ecosystems. This work presents an assessment of the potential pollution risk caused by the metal availability in suspended sediments. The objective of this study was to determine the partitioning, association, and geochemical fractionation of metals in suspended sediments from a surface water body. Additionally, the environmental assessment for this reservoir was estimated using geoaccumulation, enrichment, and pollution indices of metals and the related potential risk by their elemental availability (RAC). Chemical, mineralogical, and morphological characterizations were obtained by inductively coupled plasma spectrometry, alpha spectroscopy, X-ray crystallography, and scanning electron microscopy. Clay, quartz, montmorillonite, and calcite were the main minerals of suspended sediments. Chemical fractionation was the parameter affecting the concentrations of metals in suspended sediments. The sediment composition is of natural origin; however, these finer particles can promote the scavenging of toxic metals. It contributes to obtaining moderate to high levels for enrichment/contamination indices. Although Ca, Mg, and U were the most accessible metals for aquatic biota, metals such as Sr, Mn, Li, Cu, and Ni in the exchangeable phase of suspended sediments are the potentially toxic elements in this aquatic ecosystem

Uranium in the surrounding of San Marcos-Sacramento river environment (Chihuahua,Mexico)

The main interest of this study is to assess whether uranium deposits located in the San Marcos outcrops (NW of Chihuahua City,Mexico) could be considered as a source of U-isotopes in its surrounding environment. Uranium activity concentrations weredetermined in biota, ground, and surface water by either alpha or liquid scintillation spectrometries. Major ions were analyzedby ICP-OES in surface water and its suspended matter. For determining uranium activity in biota, samples were divided in parts.The results have shown a possible lixiviation and infiltration of uranium from geological substrate into the ground and surfacewater, and consequently, a transfer to biota. Calculated annual effective doses by ingestion suggest that U-isotopes in biota couldnot negligibly contribute to the neighboring population dose. By all these considerations, it is concluded that in this zone there isnatural enhancement of uranium in all environmental samples analyzed in the present work.Consejo Nacional de Ciencia y Tecnología (CONACYT), Project SEP-CONACYT 2604

Determination of 234U and 238U Activities in Soil by Liquid Scintillation and High-Resolution Alpha Spectrometry

Uranium is a radioactive element with a special presence in the rocks, waters, sediments, soils, and plants at the state of Chihuahua. The activity ratio of 238U/234U is used to explain the uranium transport by surface water and its deposition in arid environments. In this work, the activity concentration of natural U isotopes is determined by PERALS liquid scintillation and high-resolution alpha spectrometry (AS, Canberra camera 7401VR) in the Environmental Radiological Surveillance Laboratory (LVRA) at CIMAV, Chihuahua. Uranium is extracted from soils through the scintillating liquid extractor URAEX for PERALS, with chemical recovery (CR) of 80 - 85 %, and through the ion exchange resin UTEVA + electrode position by the Hallstadius method, with CR of 85 - 90 %, for AS. The procedures of 234U and 238U activity concentration (AC) determination in soils were validated by their application to the certified reference material IAEA-375. The resulting values were in the reference range of the certified or informative values. Both procedures were applied to 6 representative soil samples, with AC of the same order of magnitude or greater, and similar CR and compatible results. Both procedures are satisfactory for the purposes of LVRA research and in general

Characterization of source rocks and groundwater radioactivity at the Chihuahua valley

As part of a scientific research project about alpha radioactivity in groundwater for human consumption at the Chihuahua City, the charac-terization of rock sources of radioactivity around de Chihuahua valley was developed. The radioactivity of groundwater and sediments wasdetermined, too. The radioactivity of uranium- and thorium- series isotopes contained in rocks was obtained by high resolution gamma-rayspectroscopy. Some representative values are 50 Bq/kg for the mean value of Bi-214 activity, and 121.5 Bq/kg for the highest value at Westof the city. The activity of sediments, extracted during wells perforation, was determined using a NaI(Tl) detector. A non-reported beforeuranium ore was localized at the San Marcos range formation. Its outcrops are inside the Chihuahua-Sacramento valley basin and its activ-ity characterization was performed. Unusually high specific uranium activities, determined by alpha spectrometry, were obtained in water,plants, sediments and fish extracted at locations close to outcrops of uranium minerals. The activity of water of the San Marcos dam reached7.7 Bq/L. The activity of fish, trapped at San Marcos dam, is 0.99 Bq/kg. Conclusions about the contamination of groundwater at North ofChihuahua City were obtained.Como parte de un proyecto cient ́ıfico sobre actividad alfa en agua subterr ́anea de consumo humano en la ciudad de Chihuahua, se hadesarrollado la caracterizaci ́on de las rocas fuentes de la radiactividad en el valle de Chihuahua. Se determin ́o tambi ́en la actividad de muestrasde agua subterr ́anea y de sedimentos. La actividad de los is ́otopos de las series radiactivas en las rocas se obtuvo usando espectroscop ́ıagamma de alta resoluci ́on. Algunos valores representativos son 50 Bq/kg para el valor medio de la actividad del Bi-214 y 121.5 Bq/kg para elvalor m ́as alto al oeste de la ciudad. La actividad de los sedimentos extra ́ıdos durante la perforaci ́on de pozos para agua potable, se determin ́ousando un detector de NaI(Tl). En la formaci ́on monta ̃nosa de San Marcos se localiz ́o un dep ́osito de uranio no publicado. Sus afloramientosse encuentran dentro de la cuenca del valle Chihuahua-Sacramento y se realiz ́o la caracterizaci ́on de su radiactividad. Se determinaronactividades por espectrometr ́ıa alfa de agua, plantas, sedimentos y peces extra ́ıdos en emplazamientos cercanos a los afloramientos deminerales de uranio. La actividad del agua en la presa de san Marcos lleg ́o a 7.7 Bq/L. La actividad de pescados de la misma presa alcanza0.99 Bq/kg. Se obtuvieron conclusiones sobre la contaminaci ́on del agua subterr ́anea al norte de la ciudad de Chihuahua

Application of the alpha spectrometry for the study of core sediment extracted in the San Marcos dam in Chihuahua

4 páginas, 4 figuras, 3 tablas.-- PACS: 91.67.Pq; 91.67.Qr; 91.67.Ty.[EN]: The determination of the specific activities of 210Po and isotopic uranium by alpha spectrometry was performed in a sediment core from San Marcos Dam. The objective of this work was to analyze the vertical distribution of isotopic uranium and 210Po and the behavior of these radionuclides along sediment core collected from the San Marcos Dam. Sample was divided into 11 sections, in which 210Po and Isotopic Uranium were determined using liquid-liquid extraction with tributyl phosphate (TBP). Furthermore, it was made a comparison between the TBP technique and the technique of extraction chromatography using UTEVA resins for uranium. The results of specific activities for 210Po show a trend to decrease along the core, whereas the uranium isotopic does not show a pointed trend. The results of isotopic ratios between the 234U and 238U show that they are close to secular equilibrium in each of the core sections. The comparison between the two uranium extraction techniques indicates that chemical yield is better using the UTEVA technique than TBP extraction.[ES]: La determinación de las actividades específicas de 210Po y uranio isotópico mediante espectrometría alfa fue realizada en un núcleo de sedimento de la Presa San Marcos. El objetivo de este trabajo fue analizar la distribución vertical de uranio isotópico y de 210Po así como el comportamiento de estos radionúclidos a lo largo del núcleo de sedimento recolectado en la presa San Marcos. La muestra fue dividida en 11 secciones. Para la determinación de 210Po y de uranio isotópico en cada una de las secciones se utilizó la técnica de extracción líquido-líquido con tributil fosfato (TBP). También se realizó una comparación entre la técnica del TBP y la técnica de cromatografía de extracción con resinas UTEVA para el uranio isotópico. Los resultados de las actividades específicas para 210Po muestran una tendencia decreciente a lo largo del núcleo, mientras que para uranio isotópico muestran una tendencia no monótona. Los resultados de las relaciones isotópicas entre el 234U y el 238U muestran estar cerca del equilibrio secular en cada una de las secciones del núcleo. La comparación entre las dos técnicas de extracción de uranio indica que se tiene un mayor rendimiento químico mediante empleando la técnica de UTEVA.Peer reviewe

Determination of uranium and polonium in Sparus aurata by alpha spectrometry

The aim of this study was optimizing conditions for the specific activities determination of some uranium-series radionuclides present in Sparus aurata by alpha spectrometry. Determinations of specific activities were conducted varying the type of digestion: acid attack on hot plate, controlled microwave digestion and acid attack after calcination of the sample. The latter procedure was applied only to the case of uranium isotopes determination. The variation in the isotope extraction method consisted of applying the techniques of liquid-liquid extraction using Tributyl phosphate (TBP) or chromatographic UTEVA resin. Results depending on the type of treatment given to the samples were compared based on obtained chemical yields. The results reveal a higher bioaccumulation of polonium in the liver sample, with activities of 0.809, 2.495 and 2.439 Bq kg-1 fresh wt compared with the fillet. The best chemical yields for polonium were close to 60% for samples that were digested by microwave. In the case of uranium the best chemical yields, close to 80% for fillet, were obtained with a previous calcination of the sample and using the UTEVA resin.El objetivo de este estudio fue la optimización de las condiciones para la determinación de las actividades específicas de algunos radionúclidos de la serie del uranio presente en Sparus aurata por espectrometría alfa. Las determinaciones de las actividades específicas se realizaron variando el tipo de digestión: ataque ácido en parrilla, en microondas y ataque ácido después de la calcinación de la muestra. Este último procedimiento fue aplicado solamente en el caso de la determinación de los isótopos de uranio. La variación en el método de extracción del isótopo, consistió en la aplicación de las técnicas de extracción líquido-líquido utilizando el fosfato de tributilo (TBP) o separación cromatográfica empleando la resina UTEVA. Los resultados obtenidos en los diferentes tipos de tratamientos que se les dio a las muestras, fueron comparados con los rendimientos químicos obtenidos. Los resultados revelan una mayor bioacumulación de polonio en la muestra de hígado, con actividades de 0.809, 2.495 y 2.439 Bq kg-1 de peso fresco en comparación con el filete. Los mejores rendimientos químicos para el polonio fueron cercanos al 60% para las muestras que se sometieron a digestión por microondas. En el caso del uranio los mejores rendimientos químicos, cercanos al 80% en filete, se obtuvieron con una calcinación previa de la muestra y el uso de la resina UTEVA

Distribution of Chemical Species in the Water-Soil-Plant (Carya illinoiensis) System near a Mineralization Area in Chihuahua, Mexico—Health Risk Implications

The aim of this study was to quantify major and trace elements in the water, soil, and plants (Carya illionensis) in an agricultural area; and to determine the health risks associated with the walnuts ingestion by calculating the risk quotient. Samples of water, soil, tree leaves, and walnuts were collected; in total, 135 samples were analyzed. Physicochemical parameters were obtained in irrigation water and soil samples. Elemental measurements were performed in an ICP, -OES and -MS. In addition, the distribution coefficient (soil–water), transfer factor (soil–plant), and hazard quotient were evaluated. In the irrigation water, As, Cr, and Pb, showed concentrations above the maximum allowable limits. Likewise, high concentrations of As, Cr, Pb, and Sb were found in tree leave samples, indicating a possible tendency of hyperaccumulation of those elements. Furthermore, Cr concentrations in walnuts were high by far than the reference value (FAO/WHO). A possible competition between chemical congeners were detected from transfer factors. Although, Sb concentrations in walnuts were also high, and no legislation for it in fruits exists. The hazard risk quotient for Sb did indicate a potential health risk. Finally, it is important to consider that the health risk increases when exposure through consumption takes place over a prolonged period of time, even in low concentrations