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

García-Tenorio, R.

Montero-Cabrera, María E.

Méndez-García, Carmen G.

Rentería Villalobos, Marusia

Revista Mexicana de Física

The determination of the specific activities of210Po and isotopic uranium by alpha spectrometry was performed in a sediment core from SanMarcos Dam.The objective of this work was to analyze the vertical distribution of isotopic uranium and210Po and the behavior of these radionuclidesalong sediment core collected from the San Marcos Dam. Sample was divided into 11 sections, in which210Po and Isotopic Uranium weredetermined using liquid-liquid extraction with tributyl phosphate (TBP). Furthermore, it was made a comparison between the TBP techniqueand the technique of extraction chromatography using UTEVA resins for uranium.The results of specific activities for210Po show a trend to decrease along the core, whereas the uranium isotopic does not show a pointedtrend. The results of isotopic ratios between the234U and238U 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 TBPextraction.La determinaci ́on de las actividades espec ́ıficas de210Po y uranio isot ́opico mediante espectrometr ́ıa alfa fue realizada en un n ́ucleo desedimento de la Presa San Marcos. El objetivo de este trabajo fue analizar la distribuci ́on vertical de uranio isot ́opico y de210Po as ́ı como elcomportamiento de estos radion ́uclidos a lo largo del n ́ucleo de sedimento recolectado en la presa San Marcos.  La muestra fue dividida en11 secciones.  Para la determinaci ́on de210Po y de uranio isot ́opico en cada una de las secciones se utiliz ́o la t ́ecnica de extracci ́on l ́ıquido-l ́ıquido con tributil fosfato (TBP). Tambi ́en se realiz ́o una comparaci ́on entre la t ́ecnica del TBP y la t ́ecnica de cromatograf ́ıa de extracci ́oncon resinas UTEVA para el uranio isot ́opico.  Los resultados de las actividades espec ́ıficas para210Po muestran una tendencia decrecientea lo largo del n ́ucleo, mientras que para uranio isot ́opico muestran una tendencia no mon ́otona.  Los resultados de las relaciones isot ́opicasentre el234U y el238U muestran estar cerca del equilibrio secular en cada una de las secciones del n ́ucleo.  La comparaci ́on entre las dost ́ecnicas de extracci ́on de uranio indica que se tiene un mayor rendimiento qu ́ımico mediante empleando la t ́ecnica de UTEVA

Méndez García, Cristina

García-Tenorio García-Balmaseda, Rafael

Rentería Villalobos, M.

Montero Cabrera, María Elena

idUS. Depósito de Investigación Universidad de Sevilla

RADIATION PHYSICS Revista Mexicana de Fı́sica58 (2012) 234–237 JUNIO 2012Application of the alpha spectrometry for the study of core sediment extracted inthe San Marcos dam in ChihuahuaC. Méndez Garćıa1, R.Garćıa-Tenorio2, M. Renteŕıa Villalobos1, Maŕıa Elena Montero Cabrera1,∗1Centro de Investigación en Materiales Avanzados, CIMAV,Miguel de Cervantes 120, 31109, Chihuahua, Chih., Mexico.2Applied Nuclear Physics Group, Universidad de Sevilla, ETS Arquitectura,Avda. Reina Mercedes s/n, 41012 Seville, Spain.Corresponding author: elena.montero@cimav.edu.mxRecibido el 3 de junio de 2011; aceptado el 1 de febrero de 2012The determination of the specific activities of210Po and isotopic uranium by alpha spectrometry was performed in a sediment core from SanMarcos Dam.The objective of this work was to analyze the vertical distribution of isotopic uranium and210Po and the behavior of these radionuclidesalong sediment core collected from the San Marcos Dam. Sample was divided into 11 sections, in which210Po and Isotopic Uranium weredetermined using liquid-liquid extraction with tributyl phosphate (TBP). Furthermore, it was made a comparison between the TBP techniqueand the technique of extraction chromatography using UTEVA resins for uranium.The results of specific activities for210Po show a trend to decrease along the core, whereas the uranium isotopic does not show a pointedtrend. The results of isotopic ratios between the234U and238U 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 TBPextraction.Keywords:alpha spectrometry; uranium; polonium; sediment core.La determinacíon de las actividades especı́fi as de210Po y uranio isot́opico mediante espectrometrı́a alfa fue realizada en un núcleo desedimento de la Presa San Marcos. El objetivo de este trabajo fue analizar la distribución vertical de uranio isot´ pico y de210Po aśı como elcomportamiento de estos radionúclidos a lo largo del ńucleo de sedimento recolectado en la presa San Marcos. La muestra fue dividida en11 secciones. Para la determinación de210Po y de uranio isot´ pico en cada una de las secciones se utilizó la t́ecnica de extracción ĺıquido-lı́quido con tributil fosfato (TBP). También se realiźo una comparación entre la t́ecnica del TBP y la t́ecnica de cromatografı́ de extraccíoncon resinas UTEVA para el uranio isotópico. Los resultados de las actividades especı́ficas para210Po muestran una tendencia decrecientea lo largo del ńucleo, mientras que para uranio isotópico muestran una tendencia no monótona. Los resultados de las relaciones isotópicasentre el234U y el 238U muestran estar cerca del equilibrio secular en cada una de las secciones del núcleo. La comparación entre las dostécnicas de extracción de uranio indica que se tiene un mayor rendimiento quı́mico mediante empleando la técnica de UTEVA.Descriptores:Espectrometrı́a alfa; uranio; polonio; ńucleo de sedimento.PACS: 91.67.Pq; 91.67.Qr; 91.67.Ty.1. IntroductionIn the state of Chihuahua there are known about 30 uraniumanomalies [1], almost all located in the vicinity of ChihuahuaCity, the state capital, at the center of the homonym state inMexico. At north-west of Chihuahua City, Majalca Area,are two well-established major uranium deposits: Victorinoand San Marcos, both in the San Marcos Area. There is alsothe San Marcos dam, namesake of the surrounding mountain.The San Marcos mountain formation is a caldera [2], whichincludes several outcrops of uranium ore and the dam. Ge-ological investigations suggest that these uranium ores con-tribute to uranium deposits in sediments at the Chihuahua-Sacramento Valley [3-5].Previous studies in the area have shown the presence ofuranium in superficial waters, fish, and some plants [6-9].Data about the superficial water contamination shows highuranium specific activities by up to 7.7 Bq/L [10]. This valueis above to the reference level of 0.001 Bq/L for drinkingwater reported in UNSCEAR [11]. The high uranium con-centrations in the area are attributed to the lixiviation and/orerosion of the uraniferous deposits located in San Marcos [3,7].As foregoing mentioned, there are several studies in dif-ferent matrices in the study area, but there have been no de-terminations of radionuclides in a sediment core. The im-portance of determining uranium in this work is to know itsbehavior in different sections of the sample, correspondingto different sedimentation depths in the dam. Moreover, thedetermination of210Po will allow a future dating work. Dif-ferent uranium extraction procedures were tested for deter-mining the best parameters for future works.2. Materials and methods2.1. Study areaThe San Marcos River, which rises in the dam of the samename, is tributary to the Sacramento River in Chihuahua City.The San Marcos River basin covers approximately 175 km2.APPLICATION OF THE ALPHA SPECTROMETRY FOR THE STUDY OF CORE SEDIMENT EXTRACTED IN... 235FIGURE 1. San Marcos Dam study area. Sediment core was col-lected at point B.Figure 1 shows a satellite image from San Marcos dam;point B shows the place where core was extracted. The damwall is showed as an angle, which can be seen close to points5 and B.2.2. Sediment Core SampleFigure 2 shows the sediment core sample extracted from SanMarcos Dam.Sampling of sediment core was carried out in July 2007.The core length was 30 cm, and it was divided into 11 sec-tions of 2 – 4 cm width, the sample closest to the surfacewas designated as MTA1 and MTA 11 is the deepest frac-tion; each section had a mass about 50 g. In the laboratory,samples were dried at 55 ˚ C during 24 hours as general pro-cedure.2.3. Determination of radionuclides by alpha spectrom-etryFor the determination of both210Po and uranium extractionthe technique of liquid-liquid extraction with tributyl phos-phate (TBP) was used. This method was initially developedby Holm and Fukai [12] and slightly modified by El-Daoushyet al [13]. To obtain the best parameters, the technique of ura-nium by extraction chromatography using UTEVA resins wastested for comparison.FIGURE 2. Sediment core sample.The samples were spiked with209Po standard solution forthe determination of210Po, and for isotopic uranium determi-nation a solution standard of232U was used.Isotopic uranium and210Po contents of each section ofthe simple were determined by alpha spectrometry using aspectrometry chain Alpha Analyst (CANBERRA), based onPIPS type detector.2.4. Extraction of isotopic uranium and 210Po by trib-utyl phosphate (TBP)For this procedure, samples were dried at 55oC, sievedthrough a 2 mm mesh and homogenized. Aliquots of 0.5 gfrom every core sections were taken. Samples were digestedin a hot plate with aqua regia and the dry residue was redis-solved using HNO38M.Afterwards, the extraction of polonium and uranium wascarried out with TBP. The210Po alpha source is obtained byself-deposition onto copper discs from a 1.5M HCl solution[13], while the final solutions of U, after their isolation, wereelectrodeposited onto stainless-steel discs by the Hallstadius(1984) [14] method.2.5. Extraction of isotopic uranium by extraction chro-matography with UTEVA resins.For the extraction of isotopic uranium by UTEVA, sampleswere calcined at 600oC during 24 hours. After calcination,the samples were sieved to 2 mm mesh and homogenized.Aliquots of 0.2 g were taken. Samples were digestedwith HF and HN03, and then the dry residue was dissolvedwith 3 M HN03. The sample solution was passed throughthe UTEVA column. In this condition, U (VI) is retained.Uranium is eluted with HCl 0.01 M, and then it is electrode-posited.3. Results and discussion.Table 1 shows the results of specific activities of210Po andthe obtained chemical yield for TBP technique. Figure 3 plotthe specific activities of210Po, and shows that the specific ac-tivity of 210Po decreases when the core fraction of sedimentis deeper, as was expected.The result of the specific activity of210Po in the MTA1,is that corresponding to the fraction of lead in excess.Figure 4 shows alpha spectra characteristic for poloniumand uranium respectively. Note the peak corresponding topolonium extracted from the sample210Po and the peak ofthe tracer209Po (a). The peaks corresponding to uranium iso-topes from the sample and232U peak of the tracer are shownin (b).Rev. Mex. Fis.58 (2012) 234–237236 C. MÉNDEZ GARĆIA, R.GARĆIA-TENORIO, M. RENTEŔIA VILLALOBOS, MAR ÍA ELENA MONTERO CABRERATABLE I. Specific activities of210Po obtained in fractions of thecore sample.CODE 210Po (Bq/kg) YIELD (%)MTA 1 167± 6 55MTA 2 200± 6 59MTA 3 183± 6 56MTA 4 162± 5 60MTA 5 148± 6 43MTA 6 133± 5 60MTA 7 134± 4 53MTA 8 107± 3 51MTA 9 89± 3 59MTA 10 89± 4 58MTA 11 84± 3 54FIGURE 3. 210Po activity as function of sample depth.FIGURE 4. Alpha spectrum of Polonium and uranium respectively.TABLE II. Specific activities of234U and238U, and activity ratiosin each fraction extracted by UTEVA.CODE 234U 238U (234U/238U) YIELD(Bq/kg) (Bq/kg) (%)MTA 1 125± 9 107± 8 1.2 58MTA 2 126± 8 93± 6 1.4 71MTA 3 102± 7 79± 5 1.3 76MTA 4 100± 7 79± 5 1.3 79MTA 5 119± 8 92± 6 1.3 80MTA 6 108± 8 95± 7 1.1 69MTA 7 125± 9 106± 8 1.2 75MTA 8 119± 8 98± 7 1.2 76MTA 9 120± 8 96± 7 1.2 77MTA 10 107± 7 94± 6 1.1 84MTA 11 92± 6 83± 6 1.1 81Table 2 shows the results obtained by UTEVAS techniquefor isotopic uranium.Results from Table 2 and Fig 5 show that the234U and238U activity ratios are close to secular equilibrium alongthe sediment core. This behavior probably means that ura-nium content of sediments comes from suspended particu-lated matter instead of precipitation from dissolved uraniumcontent in water. The results of the activities for235U wereexcluded in this report, due to the high errors found in themeasurements.Table 3 shows the comparison between the two uraniumextraction techniques. Results indicate that chemical yieldsare better using the technique of UTEVA extraction. Thistechnique would be the best for sediment core uranium anal-ysis in future work.FIGURE 5. Isotopic Uranium activity as function of sample depth.Rev. Mex. Fis.58 (2012) 234–237APPLICATION OF THE ALPHA SPECTROMETRY FOR THE STUDY OF CORE SEDIMENT EXTRACTED IN... 237TABLE III. Comparation between techniques for uranium extrac-tion.CODE UTEVA TBP UTEVA TBP UTEVA TBPMTA 1 126 67 107 38 58 55MTA 4 100 66 79 19 79 59MTA 5 119 112 92 39 80 55MTA 7 125 82 106 51 75 52MTA 9 120 60 96 36 77 484. ConclusionsSpecific activities of isotopic uranium and210Po were deter-mined by alpha spectrometry.In sediment core, the highest concentration of210Po is inthe samples near to the surface, whereas the lowest concen-tration is in the deeper fraction, as expected.The behavior of238U and234U activities is close to sec-ular equilibrium, as expected in case of sediment formationfrom solid fragments.The extraction technique by UTEVA resins gives higherchemical yields for isotopic uranium analysis.1. P.C. Goodell, inTechnical Committee Meeting, Uranium de-posits in volcanic rocksVol. TC-490/3. (STI/PUB/690), IAEAEl Paso, Texas. , 1985, p. 97.2. H. Ferŕız, in Technical Committee Meeting, Uranium depositsin volcanic rocks, Vol. TC-490/3. (STI/PUB/690), IAEA ElPaso, Texas, 1985, p. 197.3. M. Reyes-Cortes, M.E. Montero-Cabrera, M. Renteria-Villalobos, L. Fuentes-Montero, L. Fuentes-Cobas, E.F.Herrera-Peraza, H. Esparza-Ponce,et al., Rev. Mex. FisS53(2007) 23.4. Manuel Reyes Cortés, Caracterización de los minerales deuranio delárea de San Marcos, Chihuahua. Influencia hidro-geoĺogica., Thesis in Doctor en Ciencia de Materiales, Fı́sicade Materiales, Centro de Investigación en Materiales Avanza-dos, (2009)5. Manuel Reyes-Cortés, Luis Fuentes-Cobas, Enrique Torres-Moye, Hilda Esparza-Ponce, and Marı́a Montero-Cabrera,MinPe99 (2010) 121.6. Marusia Renterı́a Villalobos, Modelo conceptual de las concen-traciones de uranio en agua superficial y subterránea en la zonade San Marcos-Sacramento Thesis in Doctorado en Ciencia yTecnoloǵıa Ambiental, Medio Ambiente y Energı́a, Centro deInvestigacíon en Materiales Avanzados, (2007)7. M. Renteŕıa Villalobos, M. Silva, M. Reyes, C. G. Ḿendez,D. Burciaga, E. F. Herrera, and M. E. Montero, in10 Interna-tional Conference on the Biogeochemistry of Trace Elements(ICOBTE), Centro de Investigación en Materiales Avanzados,Chihuahua, Mexico, 2009.8. Maxa Yadira Silva Śaenz, Actividad de los iśotopos 234U-238U Y 226Ra en el rio San Marcos-Sacramento Norte, Chi-huahua, Ḿexico, Thesis in Maestrı́a en Ciencia y Tecnologı́aAmbiental, Medio Ambiente y Energı́a, Centro de Investi-gacíon en Materiales Avanzados, (2008)9. Diana Pamela Nev́arez Ronquillo, Estudio de las concentra-ciones de iśotopos de uranio, radio y radón en aguas superfi-ciales y subterŕaneas en la zona San Marcos-Sacramento, The-sis in M Sc, Enerǵıas renovables y Conservación del MedioAmbiente, Centro de Investigación en Materiales Avanzados,(2010)10. B. Markert, of Trace Elements in Medicine and Biology21(2007) 7.11. United Nation Scientific Committee on the Effect of AtomicRadiation. UNSCEAR., UNSCEAR, New York, USA., 2000.12. Fukai R. Holm E,Talanta24 (1977) 659.13. Olsson K El-Daoushy F, Garcı́a-Tenorio R.,Hydrobiologia214(1991) 43.14. Lars Hallstadius,NIM Phys Res223(1984) 266.Rev. Mex. Fis.58 (2012) 234–237View publication stats

English

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

Montero-Cabrera, Maria Elena

Digital.CSIC

RADIATION PHYSICS Revista Mexicana de Fı´sica 58 (2012) 234–237 JUNIO 2012Application of the alpha spectrometry for the study of core sediment extracted inthe San Marcos dam in ChihuahuaC. Me´ndez Garcı´a1, R.Garcı´a-Tenorio2, M. Renterı´a Villalobos1, Marı´a Elena Montero Cabrera1,∗1Centro de Investigacio´n en Materiales Avanzados, CIMAV,Miguel de Cervantes 120, 31109, Chihuahua, Chih., Mexico.2Applied Nuclear Physics Group, Universidad de Sevilla, ETS Arquitectura,Avda. Reina Mercedes s/n, 41012 Seville, Spain.Corresponding author: elena.montero@cimav.edu.mxRecibido el 3 de junio de 2011; aceptado el 1 de febrero de 2012The determination of the specific activities of 210Po and isotopic uranium by alpha spectrometry was performed in a sediment core from SanMarcos Dam.The objective of this work was to analyze the vertical distribution of isotopic uranium and 210Po and the behavior of these radionuclidesalong sediment core collected from the San Marcos Dam. Sample was divided into 11 sections, in which 210Po and Isotopic Uranium weredetermined using liquid-liquid extraction with tributyl phosphate (TBP). Furthermore, it was made a comparison between the TBP techniqueand 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 pointedtrend. 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 TBPextraction.Keywords: alpha spectrometry; uranium; polonium; sediment core.La determinacio´n de las actividades especı´ficas de 210Po y uranio isoto´pico mediante espectrometrı´a alfa fue realizada en un nu´cleo desedimento de la Presa San Marcos. El objetivo de este trabajo fue analizar la distribucio´n vertical de uranio isoto´pico y de 210Po ası´ como elcomportamiento de estos radionu´clidos a lo largo del nu´cleo de sedimento recolectado en la presa San Marcos. La muestra fue dividida en11 secciones. Para la determinacio´n de 210Po y de uranio isoto´pico en cada una de las secciones se utilizo´ la te´cnica de extraccio´n lı´quido-lı´quido con tributil fosfato (TBP). Tambie´n se realizo´ una comparacio´n entre la te´cnica del TBP y la te´cnica de cromatografı´a de extraccio´ncon resinas UTEVA para el uranio isoto´pico. Los resultados de las actividades especı´ficas para 210Po muestran una tendencia decrecientea lo largo del nu´cleo, mientras que para uranio isoto´pico muestran una tendencia no mono´tona. Los resultados de las relaciones isoto´picasentre el 234U y el 238U muestran estar cerca del equilibrio secular en cada una de las secciones del nu´cleo. La comparacio´n entre las doste´cnicas de extraccio´n de uranio indica que se tiene un mayor rendimiento quı´mico mediante empleando la te´cnica de UTEVA.Descriptores: Espectrometrı´a alfa; uranio; polonio; nu´cleo de sedimento.PACS: 91.67.Pq; 91.67.Qr; 91.67.Ty.1. IntroductionIn the state of Chihuahua there are known about 30 uraniumanomalies [1], almost all located in the vicinity of ChihuahuaCity, the state capital, at the center of the homonym state inMexico. At north-west of Chihuahua City, Majalca Area,are two well-established major uranium deposits: Victorinoand San Marcos, both in the San Marcos Area. There is alsothe San Marcos dam, namesake of the surrounding mountain.The San Marcos mountain formation is a caldera [2], whichincludes several outcrops of uranium ore and the dam. Ge-ological investigations suggest that these uranium ores con-tribute to uranium deposits in sediments at the Chihuahua-Sacramento Valley [3-5].Previous studies in the area have shown the presence ofuranium in superficial waters, fish, and some plants [6-9].Data about the superficial water contamination shows highuranium specific activities by up to 7.7 Bq/L [10]. This valueis above to the reference level of 0.001 Bq/L for drinkingwater reported in UNSCEAR [11]. The high uranium con-centrations in the area are attributed to the lixiviation and/orerosion of the uraniferous deposits located in San Marcos [3,7].As foregoing mentioned, there are several studies in dif-ferent matrices in the study area, but there have been no de-terminations of radionuclides in a sediment core. The im-portance of determining uranium in this work is to know itsbehavior in different sections of the sample, correspondingto different sedimentation depths in the dam. Moreover, thedetermination of 210Po will allow a future dating work. Dif-ferent uranium extraction procedures were tested for deter-mining the best parameters for future works.2. Materials and methods2.1. Study areaThe San Marcos River, which rises in the dam of the samename, is tributary to the Sacramento River in Chihuahua City.The San Marcos River basin covers approximately 175 km2.APPLICATION OF THE ALPHA SPECTROMETRY FOR THE STUDY OF CORE SEDIMENT EXTRACTED IN... 235FIGURE 1. San Marcos Dam study area. Sediment core was col-lected at point B.Figure 1 shows a satellite image from San Marcos dam;point B shows the place where core was extracted. The damwall is showed as an angle, which can be seen close to points5 and B.2.2. Sediment Core SampleFigure 2 shows the sediment core sample extracted from SanMarcos Dam.Sampling of sediment core was carried out in July 2007.The core length was 30 cm, and it was divided into 11 sec-tions of 2 – 4 cm width, the sample closest to the surfacewas designated as MTA1 and MTA 11 is the deepest frac-tion; each section had a mass about 50 g. In the laboratory,samples were dried at 55 ˚ C during 24 hours as general pro-cedure.2.3. Determination of radionuclides by alpha spectrom-etryFor the determination of both210Po and uranium extractionthe technique of liquid-liquid extraction with tributyl phos-phate (TBP) was used. This method was initially developedby Holm and Fukai [12] and slightly modified by El-Daoushyet al [13]. To obtain the best parameters, the technique of ura-nium by extraction chromatography using UTEVA resins wastested for comparison.FIGURE 2. Sediment core sample.The samples were spiked with 209Po standard solution forthe determination of 210Po, and for isotopic uranium determi-nation a solution standard of 232U was used.Isotopic uranium and 210Po contents of each section ofthe simple were determined by alpha spectrometry using aspectrometry chain Alpha Analyst (CANBERRA), based onPIPS type detector.2.4. Extraction of isotopic uranium and 210Po by trib-utyl phosphate (TBP)For this procedure, samples were dried at 55oC, sievedthrough a 2 mm mesh and homogenized. Aliquots of 0.5 gfrom every core sections were taken. Samples were digestedin a hot plate with aqua regia and the dry residue was redis-solved using HNO38M.Afterwards, the extraction of polonium and uranium wascarried out with TBP. The 210Po alpha source is obtained byself-deposition onto copper discs from a 1.5M HCl solution[13], while the final solutions of U, after their isolation, wereelectrodeposited onto stainless-steel discs by the Hallstadius(1984) [14] method.2.5. Extraction of isotopic uranium by extraction chro-matography with UTEVA resins.For the extraction of isotopic uranium by UTEVA, sampleswere calcined at 600oC during 24 hours. After calcination,the samples were sieved to 2 mm mesh and homogenized.Aliquots of 0.2 g were taken. Samples were digestedwith HF and HN03, and then the dry residue was dissolvedwith 3 M HN03. The sample solution was passed throughthe UTEVA column. In this condition, U (VI) is retained.Uranium is eluted with HCl 0.01 M, and then it is electrode-posited.3. Results and discussion.Table 1 shows the results of specific activities of 210Po andthe obtained chemical yield for TBP technique. Figure 3 plotthe specific activities of 210Po, and shows that the specific ac-tivity of 210Po decreases when the core fraction of sedimentis deeper, as was expected.The result of the specific activity of 210Po in the MTA1,is that corresponding to the fraction of lead in excess.Figure 4 shows alpha spectra characteristic for poloniumand uranium respectively. Note the peak corresponding topolonium extracted from the sample 210Po and the peak ofthe tracer 209Po (a). The peaks corresponding to uranium iso-topes from the sample and 232U peak of the tracer are shownin (b).Rev. Mex. Fis. 58 (2012) 234–237236 C. M ´ENDEZ GARC´IA, R.GARC´IA-TENORIO, M. RENTER´IA VILLALOBOS, MAR´IA ELENA MONTERO CABRERATABLE I. Specific activities of 210Po obtained in fractions of thecore sample.CODE 210Po (Bq/kg) YIELD (%)MTA 1 167 ± 6 55MTA 2 200 ± 6 59MTA 3 183 ± 6 56MTA 4 162 ± 5 60MTA 5 148 ± 6 43MTA 6 133 ± 5 60MTA 7 134 ± 4 53MTA 8 107 ± 3 51MTA 9 89 ± 3 59MTA 10 89 ± 4 58MTA 11 84 ± 3 54FIGURE 3. 210Po activity as function of sample depth.FIGURE 4. Alpha spectrum of Polonium and uranium respectively.TABLE II. Specific activities of 234U and 238U, and activity ratiosin each fraction extracted by UTEVA.CODE 234U 238U (234U/238U) YIELD(Bq/kg) (Bq/kg) (%)MTA 1 125 ± 9 107 ± 8 1.2 58MTA 2 126 ± 8 93 ± 6 1.4 71MTA 3 102 ± 7 79 ± 5 1.3 76MTA 4 100 ± 7 79 ± 5 1.3 79MTA 5 119 ± 8 92 ± 6 1.3 80MTA 6 108 ± 8 95 ± 7 1.1 69MTA 7 125 ± 9 106 ± 8 1.2 75MTA 8 119 ± 8 98 ± 7 1.2 76MTA 9 120 ± 8 96 ± 7 1.2 77MTA 10 107 ± 7 94 ± 6 1.1 84MTA 11 92 ± 6 83 ± 6 1.1 81Table 2 shows the results obtained by UTEVAS techniquefor isotopic uranium.Results from Table 2 and Fig 5 show that the 234U and238U activity ratios are close to secular equilibrium alongthe sediment core. This behavior probably means that ura-nium content of sediments comes from suspended particu-lated matter instead of precipitation from dissolved uraniumcontent in water. The results of the activities for 235U wereexcluded in this report, due to the high errors found in themeasurements.Table 3 shows the comparison between the two uraniumextraction techniques. Results indicate that chemical yieldsare better using the technique of UTEVA extraction. Thistechnique would be the best for sediment core uranium anal-ysis in future work.FIGURE 5. Isotopic Uranium activity as function of sample depth.Rev. Mex. Fis. 58 (2012) 234–237APPLICATION OF THE ALPHA SPECTROMETRY FOR THE STUDY OF CORE SEDIMENT EXTRACTED IN... 237TABLE III. Comparation between techniques for uranium extrac-tion.CODE UTEVA TBP UTEVA TBP UTEVA TBPMTA 1 126 67 107 38 58 55MTA 4 100 66 79 19 79 59MTA 5 119 112 92 39 80 55MTA 7 125 82 106 51 75 52MTA 9 120 60 96 36 77 484. ConclusionsSpecific activities of isotopic uranium and 210Po were deter-mined by alpha spectrometry.In sediment core, the highest concentration of 210Po is inthe samples near to the surface, whereas the lowest concen-tration is in the deeper fraction, as expected.The behavior of 238U and 234U activities is close to sec-ular equilibrium, as expected in case of sediment formationfrom solid fragments.The extraction technique by UTEVA resins gives higherchemical yields for isotopic uranium analysis.1. P.C. Goodell, in Technical Committee Meeting, Uranium de-posits in volcanic rocksVol. TC-490/3. (STI/PUB/690), IAEAEl Paso, Texas. , 1985, p. 97.2. H. Ferrı´z, in Technical Committee Meeting, Uranium depositsin volcanic rocks, Vol. TC-490/3. (STI/PUB/690), IAEA ElPaso, Texas, 1985, p. 197.3. M. Reyes-Cortes, M.E. Montero-Cabrera, M. Renteria-Villalobos, L. Fuentes-Montero, L. Fuentes-Cobas, E.F.Herrera-Peraza, H. Esparza-Ponce, et al., Rev. Mex. FisS53(2007) 23.4. Manuel Reyes Corte´s, Caracterizacio´n de los minerales deuranio del a´rea de San Marcos, Chihuahua. Influencia hidro-geolo´gica., Thesis in Doctor en Ciencia de Materiales, Fı´sicade Materiales, Centro de Investigacio´n en Materiales Avanza-dos, (2009)5. Manuel Reyes-Corte´s, Luis Fuentes-Cobas, Enrique Torres-Moye, Hilda Esparza-Ponce, and Marı´a Montero-Cabrera,MinPe 99 (2010) 121.6. Marusia Renterı´a Villalobos, Modelo conceptual de las concen-traciones de uranio en agua superficial y subterra´nea en la zonade San Marcos-Sacramento Thesis in Doctorado en Ciencia yTecnologı´a Ambiental, Medio Ambiente y Energı´a, Centro deInvestigacio´n en Materiales Avanzados, (2007)7. M. Renterı´a Villalobos, M. Silva, M. Reyes, C. G. Me´ndez,D. Burciaga, E. F. Herrera, and M. E. Montero, in 10 Interna-tional Conference on the Biogeochemistry of Trace Elements(ICOBTE), Centro de Investigacio´n en Materiales Avanzados,Chihuahua, Mexico, 2009.8. Maxa Yadira Silva Sa´enz, Actividad de los iso´topos 234U-238U Y 226Ra en el rio San Marcos-Sacramento Norte, Chi-huahua, Me´xico, Thesis in Maestrı´a en Ciencia y Tecnologı´aAmbiental, Medio Ambiente y Energı´a, Centro de Investi-gacio´n en Materiales Avanzados, (2008)9. Diana Pamela Neva´rez Ronquillo, Estudio de las concentra-ciones de iso´topos de uranio, radio y rado´n en aguas superfi-ciales y subterra´neas en la zona San Marcos-Sacramento, The-sis in M Sc, Energı´as renovables y Conservacio´n del MedioAmbiente, Centro de Investigacio´n en Materiales Avanzados,(2010)10. B. Markert, of Trace Elements in Medicine and Biology21(2007) 7.11. United Nation Scientific Committee on the Effect of AtomicRadiation. UNSCEAR., UNSCEAR, New York, USA., 2000.12. Fukai R. Holm E, Talanta 24 (1977) 659.13. Olsson K El-Daoushy F, Garcı´a-Tenorio R., Hydrobiologia 214(1991) 43.14. Lars Hallstadius, NIM Phys Res 223 (1984) 266.Rev. Mex. Fis. 58 (2012) 234–237

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

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