Radiocarbon Dating of Marine Samples: Methodological Aspects, Applications and Case Studies

none4Radiocarbon dating by AMS (Accelerator Mass Spectrometry) is a well-established absolute dating technique widely used in different areas of research for the analysis of a wide range of organic materials. Precision levels of the order of 0.2–0.3% in the measured age are nowadays achieved while several international intercomparison exercises have shown the high degree of reproducibility of the results. This paper discusses the applications of 14C dating related to the analysis of samples up-taking carbon from marine carbon pools such as the sea and the oceans. For this kind of samples relevant methodological issues have to be properly addressed in order to correctly interpret 14C data and then obtain reliable chronological frameworks. These issues are mainly related to the so-called “marine reservoirs effects” which make radiocarbon ages obtained on marine organisms apparently older than coeval organisms fixing carbon directly from the atmosphere. We present the strategies used to correct for these effects also referring to the last internationally accepted and recently released calibration curve. Applications will be also reviewed discussing case studies such as the analysis of marine biogenic speleothems and for applications in sea level studies.openGianluca Quarta; Lucio Maruccio; Marisa D’Elia; Lucio CalcagnileQuarta, Gianluca; Maruccio, Lucio; D'Elia, Marisa; Calcagnile, Luci

A Hydrogenated amorphous silicon detector for Space Weather Applications

The characteristics of a hydrogenated amorphous silicon (a-Si:H) detector are presented here for monitoring in space solar flares and the evolution of large energetic proton events up to hundreds of MeV. The a-Si:H presents an excellent radiation hardness and finds application in harsh radiation environments for medical purposes, for particle beam characterization and in space weather science and applications. The critical flux detection threshold for solar X rays, soft gamma rays, electrons and protons is discussed in detail.Comment: 32 pages, 13 figures, submitted to Experimental Astronom

Measuring stable carbon and nitrogen isotopes by IRMS and 14C by AMS on samples with masses in the microgram range: Performances of the system installed at CEDAD-University of Salento

A new experimental set-up dedicated to the simultaneous measurements of stable carbon and nitrogen isotopic ratios by IRMS (Isotope Ratio Mass Spectrometry) and 14C by AMS (Accelerator Mass Spectrometry) has been installed at CEDAD (Centre for Dating and Diagnostics)-University of Salento. The new set-up is formed by different functional blocks: an elemental analyzer, an IRMS spectrometer, a gas handling unit and a new hybrid sputtering ion source, connected to the AMS system. The general features of the new system are presented as well as the technical solutions adopted for its integration with the existing AMS system. Different tests were performed by analyzing samples of known isotopic composition and of different masses in order to define optimal operating conditions. In particular it is shown how radiocarbon measurements with precision of 0.6–0.7% and 1% are possible with the new system on samples of mass of the order of∼20 Ug and ∼10 Ug, respectively. Background levels of the order of 10−14 (14C/12C) have been also demonstrated. The new system has then significantly extended the experimental potential of the Centre in several research fields where the possibility to date very low mass samples is either a crucial advantage or mandatory such as in environmental sciences and cultural heritage dating

Measuring stable carbon and nitrogen isotopes by IRMS and14C by AMS on samples with masses in the microgram range: Performances of the system installed at CEDAD-University of Salento

A new experimental set-up dedicated to the simultaneous measurements of stable carbon and nitrogen isotopic ratios by IRMS (Isotope Ratio Mass Spectrometry) and 14C by AMS (Accelerator Mass Spectrometry) has been installed at CEDAD (Centre for Dating and Diagnostics)-University of Salento. The new set-up is formed by different functional blocks: an elemental analyzer, an IRMS spectrometer, a gas handling unit and a new hybrid sputtering ion source, connected to the AMS system. The general features of the new system are presented as well as the technical solutions adopted for its integration with the existing AMS system. Different tests were performed by analyzing samples of known isotopic composition and of different masses in order to define optimal operating conditions. In particular it is shown how radiocarbon measurements with precision of 0.6–0.7% and 1% are possible with the new system on samples of mass of the order of ∼20 ug and∼10 ug, respectively. Background levels of the order of 10−14 (14C/12C) have been also demonstrated. The new system has then significantly extended the experimental potential of the Centre in several research fields where the possibility to date very low mass samples is either a crucial advantage or mandatory such as in environmental sciences and cultural heritage dating

The new gas ion source at CEDAD: Improved performances and first 14C environmental applications

none4noA new sputtering ion source has been installed at CEDAD (Centre for Dating and Diagnostics) at the University of Salento in Lecce, Italy. The installation of the new ion source, capable of accepting both solid and gas samples, required significant modifications of the existing low energy injector of the accelerator mass spectrometry (AMS) system. The new ion source is connected, through an in-house designed gas handling interface, to an elemental analyzer which combusts the samples to carbon dioxide and splits the gas into an IRMS system and also to the gas feed line of the ion source. This arrangement allows the simultaneous measurement of C, N content (in the EA), carbon and nitrogen stable isotopic ratios by IRMS and radiocarbon (14C) by AMS on samples with masses in the microgram range. The results of different tests performed to find optimal operational conditions and to improve the system performances are presented. The performances of the system as a function of the diameter of the glass capillary used to feed the source and the pressure of the gas mixture in the syringe are also presented. The achievable precision and blank levels are discussed together with the results obtained in environmental studiesrestrictedCalcagnile, Lucio; Maruccio, Lucio; Braione, Eugenia; Quarta, Gianluca*Calcagnile, Lucio; Maruccio, Lucio; Braione, Eugenia; Quarta, Gianluc

A new system for the simultaneous measurement of δ13C and δ15N by IRMS and radiocarbon by AMS on gaseous samples: Design features and performances of the gas handling interface

We present the general design features and preliminary performances of a new system for the simultaneous AMS-14C and IRMS δ13C and δ15N measurements on samples with masses in the μg range. The system consists of an elemental analyzer (EA), a gas splitting unit (GSU), a IRMS system, a gas handling interface (GHI) and a sputtering ion source capable of accepting gaseous samples. A detailed description of the system and of the control software supporting unattended operation are presented together with the first performance tests carried out by analyzing samples with masses ranging from 8 μgC to 2.4 mgC. The performances of the system were tested in term of stability of the ion beam extracted from the ion source, precision and accuracy of the results by comparing the measured isotopic ratios with those expected for reference materials

Design features of the new multi isotope AMS beamline at CEDAD

We present the general layout and the design features of the new beam line at CEDAD (Centre for Dating and Diagnostics) of the University of Salento, Italy, dedicated to the analysis of the rare isotope 10Be optimized for the 10B isobar suppression using the passive degrader in combination with a high resolution gas ionization detector. The layout of the beam line will also offer the possibility to analyze 26Al, 129I and actinide isotopes. The ion optics simulations, the characteristics of the dispersive elements, the detection and control systems are presented together with the expected performances

A combined PIXE–PIGE approach for the assessment of the diagenetic state of cremated bones submitted to AMS radiocarbon dating

Bone samples from a Bronze age necropolis in Northern Italy, exposed to different combustion temperatures,were submitted to XRD (X-ray Diffraction), PIXE (Particle Induced X-ray Emission) and PIGE (Particle Induced Gamma Ray Emission) analyses in order to obtain information about their diagenetic state. Structural carbonate was then extracted by acid hydrolysis and used for 14C-AMS (Accelerator Mass Spectrometry) dating. These analytical techniques permitted the study of the effects of the combustion temperature on the crystallinity of the bone apatite and on its elemental chemical composition in terms of major, minor and trace elements. The results indicate that combustion at temperatures above 700 C induces changes in the bone crystalline structure, reducing the diagenetic uptake of elements from the burial environment