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In recent decades, interest in the measurement of 10Be has increased due to its relevance in various fields of science. Trace amounts of 10Be produced from meteoric sources require sensitive accelerator mass spectrometry (AMS) measurements and robust sample preparation. The extraction, separation, and preparation of the appropriate oxide form for AMS require extensive and careful laboratory processing and certified reference materials to validate the chemical performance of the protocols used and the calibration of the AMS system in the measurement. In this work, the meteoric 10Be concentrations in two certified reference materials are characterized to establish their suitability as internal control standards for laboratory chemical preparation and AMS measurements of this radioisotope in our laboratory and the whole AMS community. [ABSTRACT FROM AUTHOR]

Stable isotopes have been used historically to track food webs. Our approach used a combination of δ13C and radiocarbon (14C) dating to identify carbon sources in cave shrimp within caves of the Karstic Yucatan Peninsula, Mexico. Three sister species of stygobitic Typhlatya shrimps were collected from the cenote pool (cenote hereafter), cavern and cave hydro regions. New and previously reported 14C and δ13C values of whole tissues from the organisms were determined at the AMS laboratory (LEMA) of the Institute of Physics of the Universidad Nacional Autónoma de México. This new set of isotopic values of biomass and potential sources were incorporated into the Bayesian Mixing Modeling Software SIAR. In two hypothetical scenarios, the contribution from each feeding source among three species of the Typhlatya genus was determined. Slight differences were also observed between isotopic values of two groups of the same species collected in two distant cenote pools, suggesting this species may feed on a wider array of sources than previously found, and that the oligotrophic environment may have a strong influence on cave shrimp diet. [ABSTRACT FROM AUTHOR]

The 1MV AMS system installed at National Accelerator Mass Spectrometry Laboratory (LEMA) has been used to determine the meteoric 10Be concentrations from particulate matter at the center of Mexico during 2012. The meteoric 10Be concentration range between (1.1 ± 14%, and 5.1 ± 12%) × 104 atoms m−3. In this work, we presented the first data of concentrations of meteoric 10Be found in this kind of samples by using AMS technique in Mexico. [ABSTRACT FROM AUTHOR]

AMS- 14 C applications often require the analysis of small samples. Such is the case of atmospheric aerosols where frequently only a small amount of sample is available. The ion beam physics group at the ETH, Zurich, has designed an Automated Graphitization Equipment (AGE III) for routine graphite production for AMS analysis from organic samples of approximately 1 mg. In this study, we explore the potential use of the AGE III for graphitization of particulate carbon collected in quartz filters. In order to test the methodology, samples of reference materials and blanks with different sizes were prepared in the AGE III and the graphite was analyzed in a MICADAS AMS (ETH) system. The graphite samples prepared in the AGE III showed recovery yields higher than 80% and reproducible 14 C values for masses ranging from 50 to 300 μg. Also, reproducible radiocarbon values were obtained for aerosol filters of small sizes that had been graphitized in the AGE III. As a study case, the tested methodology was applied to PM 10 samples collected in two urban cities in Mexico in order to compare the source apportionment of biomass and fossil fuel combustion. The obtained 14 C data showed that carbonaceous aerosols from Mexico City have much lower biogenic signature than the smaller city of Cuernavaca. [ABSTRACT FROM AUTHOR]

Analysis of ancient human bones found in “El Cóporo”, an archaeological site in Guanajuato, Mexico; were performed using a multi techniques scheme: 14C radiocarbon dating, IBA (Ion Beam Analysis), SEM-EDS (Scanning Electron Microscope Energy Dispersive X-ray Spectroscopy). We measured the elemental composition of the bones, especially some with a superficial black pigmentation. Soil samples collected from the burial place were also analyzed. The 14C dating was performed with a new High Voltage Europe 1MV Tandentron Accelerator Mass Spectrometer (AMS) recently installed in the IFUNAM (Instituto de Física, Universidad Nacional Autónoma de México). The radiocarbon dating allowed us to determine the date of death of the individual in a period between the year 890 and 975AD, which is consistent with the late period of the Cóporo civilization. The element sample analysis of bones with the surface black pigmentation show higher levels of Fe, Mn and Ba compared when bone’s black surface was mechanically removed. These three elements were found in soil samples from the skeleton burial place. These results indicate more likely that the bone black coloration is due to a postmortem alteration occurring in the burial environment. [ABSTRACT FROM AUTHOR]

Abstract: A new Accelerator Mass Spectrometry system has been installed at the Institute of Physics of the National Autonomous University of Mexico (UNAM). A sample preparation chemistry laboratory equipped with computer controlled graphitization equipment (AGEIII) has also been established. Together both facilities constitute the LEMA (Laboratorio de Espectrometría de Masas con Aceleradores) first of its kind in Mexico. High sensitivity characterization of the concentration in a sample of 14C as well as 10Be, 26Al, 129I and Pu are now possible. Since the demand for 14C dating is far more abundant, a data analysis program was developed in the cross-platform programming language Python in order to calculate radiocarbon age. Results from installation, acceptance tests and the first results of 14C analyses of reference materials prepared in our own facility are presented. [Copyright &y& Elsevier]

The optimization of preparation techniques for 10Be in rainfall samples and the approaches applied to improve the measurement of this radionuclide with the accelerator mass spectrometry (AMS) system were carried out at LEMA-UNAM. A radiochemical procedure has been realized to measure 10Be in smaller samples than those reported in similar studies, reducing the sample volume from 2 L to 250 mL. The 10Be concentrations in the dissolved and particulate fraction of rain from the high-altitude rural site Altzomoni (Mexico) during 2017–2018 were determined for the first time at LEMA. The results show that the presence of particulate material is four orders of magnitude greater than the content of 10Be in the rainfall from Altzomoni. This work shows a mean concentration of (1.9 ± 0.2) × 104 and (3.3 ± 0.6) × 108 atoms per gram of rainfall in dissolved and particulate fractions. [ABSTRACT FROM AUTHOR]

In this work we determine the 14 C content in a graphite bar used in the core of the research nuclear reactor TRIGA MARK III, at the "Instituto Nacional de Investigaciones Nucleares" (ININ) in México. The 14 C / 12 C ratio was measured, using Accelerator Mass Spectrometry (AMS) at the Laboratorio Nacional de Espectrometría de Masas con Aceleradores (LEMA) at the "Instituto de Física de la Universidad Nacional Autónoma de México" (IFUNAM). Our results show a 14 C ratio over three orders of magnitude higher than that found in modern organic matter. A γ -ray spectroscopy study of the graphite bar with a High Purity Germanium detector (HPGe) shows the presence of the same radioactive isotopes reported in previous studies of similar bars. [ABSTRACT FROM AUTHOR]