• ZAGRADA—The New Zagreb Radiocarbon Database

      Porter, Antun; Obelić, Bogomil; Krajcar Bronić, Ines (Department of Geosciences, The University of Arizona, 2010-01-01)
      After introducing the liquid scintillation counting (LSC) method and graphite target preparation for accelerator mass spectrometry (AMS) measurements in the Zagreb Radiocarbon Laboratory, the existing database software designed only for gas proportional counting (GPC) (using a DOS operating system) could not satisfy the requirements for parallel conduction of several techniques. This has been enabled recently by the development of the new relational database ZAGRADA, which--using SQL scripts and constraints defined by primary and foreign keys--enforces high data integrity and provides better performances in data filtering and sorting. The structural scheme of this database conceptually comprises 4 basic modules with data on the samples, chemical pretreatment and preparation, measurements and data on the final results. A user-friendly graphical user interface has been designed to perform various actions and data manipulation to the database. The implementation of a new database for 14C samples has significant contribution to scientific research performed in the Radiocarbon and Tritium Laboratory and to quality assurance and quality control, and will enable better and easier communication with customers.
    • Zero BP Plus 34: 25 Years of Radiocarbon

      Deevey, Edward S. (American Journal of Science, 1984-01-01)
    • Zinc Reduction as an Alternative Method for AMS Radiocarbon Dating: Process Optimization at CIRCE

      Marzaioli, F.; Borriello, G.; Passariello, I.; Lubritto, C.; De Cesare, N.; D'Onofrio, A.; Terrasi, F. (Department of Geosciences, The University of Arizona, 2008-01-01)
      The pretreatment of samples for radiocarbon measurements, transforming a variety of materials into graphite solid targets, represents a critical point in the accelerator mass spectrometry (AMS) procedure. We describe the new, state-of-the-art CIRCE AMS preparation laboratory, particularly the setup and optimization of an alternative method, the zinc reduction method, for graphite target production, compared to the more common hydrogen reduction method. Measured 14C values on standard and blank samples reduced via zinc reaction revealed mean background levels, accuracy, and sensitivity comparable to those obtained by our conventional hydrogen reaction lines. Zinc line reduction at the CIRCE laboratory represents an effective and powerful alternative to the conventional hydrogen reduction, ensuring higher sample throughput with lower costs at a comparable performance level.
    • Łódź Radiocarbon Dates III

      Kanwiszer, Andrzej; Trzeciak, Pawet (Department of Geosciences, The University of Arizona, 1991-01-01)
    • Δ14C and δ13C of Seawater DIC as Tracers of Coastal Upwelling: A 5-Year Time Series from Southern California

      Santos, Guaciara M.; Ferguson, Julie; Acaylar, Kayla; Johnson, Kathleen R.; Griffin, Sheila; Druffel, Ellen (Department of Geosciences, The University of Arizona, 2011-12-16)
      Marine radiocarbon (14C) is a widely used tracer of past ocean circulation, but very few high-resolution records have been obtained. Here, we report a time series of carbon isotope abundances of dissolved inorganic carbon (DIC) in surface seawater collected from the Newport Beach pier in Orange County, within the Southern California Bight, from 2005 to 2010. Surface seawater was collected bimonthly and analyzed for 14C, 13C, and salinity. Results from May 2005 to November 2010 show no long-term changes in 13C DIC values and no consistent variability that can be attributed to upwelling. 14C DIC values have lowered from ~34 to about ~16, an 18 decrease from the beginning of this project in 2005, and is consistent with the overall 14C depletion from the atmospheric thermonuclear bomb pulse at the end of the 1950s. 14C DIC values, paired with salinity, do appear to be suitable indicators of upwelling strength with periods of upwelling characterized by more saline and lower DIC 14C values. However, a similar signal was not observed during the strong upwelling event of 2010. These results were obtained in the Southern California Bight where upwelling is fairly weak and there is a complex oceanographic circulation in comparison with the remaining western USA coastline. It is therefore likely that the link between DIC 14C, salinity, and upwelling would be even stronger at other sites. These data represent the longest time series of 14C data from a coastal Southern California site performed to date.