Alfred Priller

14C dating with the bomb peak: An application to forensic medicine

Abstract Samples originating from the time period after 1950 can be radiocarbon dated utilising the 14C bomb peak as a calibration curve. The applicability of “radiocarbon dating” of recent organic human material for the determination of the time of death of humans was tested. The radiocarbon results from hair and lipid samples from individuals with known date of death were compared with the results from two individuals with unknown time of death. An estimate of the year of death for the unknowns could be derived by this way. Due to the long turnover time of collagen in human bones it is not possible to use the radiocarbon content of bone collagen for a reliable estimate. In order to study the time dependence of the collagen turnover we tested “soft” chemical methods for the isolation of collagen from the bone matrix. First radiocarbon results of this investigation are presented.

Accelerator mass spectrometry of heavy long-lived radionuclides

Abstract This paper describes the upgrade of the Vienna Environmental Research Accelerator (VERA) to a universal facility for accelerator mass spectrometry (AMS). As a result, it is now possible to measure many long-lived radionuclides at natural abundances across the nuclear chart, from the lightest ( 10 Be ) to the heaviest ( 244 Pu ). Particular emphasis is placed on measurements to understand the ion optics and the origin of background ions, which ultimately limit the sensitivity. VERA is now ready to venture into the realm of actinides (e.g., 236 U , 244 Pu ), and other heavy radionuclides (e.g., 182 Hf ), which promise interesting applications in astrophysics and other fields.

An estimate of the impact of Stratosphere to Troposphere Transport (STT) on the lower free tropospheric ozone over the Alps using 10Be and 7Be measurements

Jungfraujoch (JUN), Switzerland and Zugspitze (ZUG), Germany. Inspection of the variability of the ratio 10 Be/ 7 Be in relation to 10 Be, 7 Be, and relative humidity (RH) reveals that the ratio is independent from processes that have a clear effect on both radionuclides, such as wet scavenging. High ratio values are generally met under cyclonic or northerly advective conditions, which are the synoptic situations mostly related to stratosphere-to-troposphere transport (STT) events over central Europe, while the 10-day back trajectories indicate a stratospheric source for the majority of the cases within the upper 10% quantile of 10 Be/ 7 Be ratios. The monthly 10 Be/ 7 Be ratios show a clear May and June peak at JUN and a much weaker seasonality at ZUG. A simple mixing model is used for an independent estimate of the strength of STT throughout the year based on the 7 Be and 10 Be measurements. In spite of the various uncertainties, the results indicate a seasonal cycle of stratospheric ozone percentage contribution with an early spring maximum (3– 11%) and autumn minimum (1–2%) at ZUG, while at JUN, a primary maximum in May and June (6–18%), a secondary maximum in March (4–13%), and a minimum again in autumn (1–4%) are revealed. Although the simple method applied here provides an independent estimate for the impact of STT to the lower troposphere, it nevertheless shows relatively good agreement with Lagrangian model calculations, especially for ZUG. INDEX TERMS: 0341 Atmospheric Composition and Structure: Middle atmosphere—constituent transport and chemistry (3334); 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry; 3329 Meteorology and Atmospheric Dynamics: Mesoscale meteorology; 3362 Meteorology and Atmospheric Dynamics: Stratosphere/troposphere interactions; KEYWORDS: stratospheric intrusions, cosmogenic radionuclides, tropospheric ozone, 7 Be, 10 Be, Alps Citation: Zanis, P., et al., An estimate of the impact of stratosphere-to-troposphere transport (STT) on the lower free tropospheric ozone over the Alps using 10 Be and 7 Be measurements, J. Geophys. Res., 108(D12), 8520, doi:10.1029/2002JD002604, 2003.

Disentangling Geomagnetic and Precipitation Signals in an 80-kyr Chinese Loess Record of 10Be

The cosmogenic radionuclide 10 Be is produced by cosmic-ray spallation in Earths atmosphere. Its production rate is regulated by the geomagnetic field intensity, so that its accumulation rate in aeolian sediments can, in principle, be used to derive high-resolution records of geomagnetic field changes. However, 10 Be atmospheric fallout rate also varies locally depending on rainfall rate. The accumulation rate of 10 Be in sediments is further complicated by overprinting of the geomagnetic and precipitation signals by 10 Be attached to remobilized dust, which fell from the atmosphere at some time in the past. Here, we demonstrate that these signals can be deconvoluted to derive both geomagnetic field intensity and paleoprecipitation records of Asian Monsoon intensity in an 80,000-yr-long 10 Be record from Chinese loess. The strong similarity between our derived paleomagnetic intensity record and the SINT 200 (Guyodo and Valet 1996) and NAPIS 75 (Laj et al. 2002) stacked-marine records suggests that this method might be used to produce multimillion-yr-long records of paleomagnetic intensity from loess. This technique also reveals a new method for extracting quantitative paleoprecipitation records from continental interior regions. Our derived precipitation record is broadly similar to the speleothem δ 18 O-based records of paleo-Asian Monsoon intensity from Dongge (Yuan et al. 2004) and Hulu (Wang et al. 2001) caves, and suggests that the paleo-Asian Monsoon intensity may be responding to a combination of both Northern and Southern Hemisphere insolation forcing.

Pushing the precision limit of 14C AMS

High precision for radiocarbon cannot be reached without profound insight into the various sources of uncertainty which only can be obtained from systematic investigations. In this paper, we present a whole series of investigations where in some cases (super 16) O: (super 17) O: (super 18) O served as a substitute for (super 12) C: (super 13) C: (super 14) C. This circumvents the disadvantages of event counting, providing more precise results in a much shorter time. As expected, not a single effect but a combination of many effects of similar importance were found to be limiting the precision. We will discuss the influence of machine tuning and stability, isotope fractionation, beam current, space charge effects, sputter target geometry, and cratering. Refined measurement and data evaluation procedures allow one to overcome several of these limitations. Systematic measurements on FIRI-D wood show that a measurement precision of + or -20 (super 14) C yr (1 sigma ) can be achieved for single-sputter targets.

VERA: A new AMS facility in Vienna

Abstract The basic features of VERA, a new AMS facility based on a 3-MV Pelletron tandem accelerator installed at the University of Vienna, are presented.

First performance tests of VERA

VERA is a new 3-MV Pelletron tandem AMS facility in Vienna, which was installed during the last months of 1995. This report will discuss the performance characteristics of the facility established during the test operating phase and present first measurements of 14C standards.

Systematic Investigations of 14C Measurements at the Vienna Environmental Research Accelerator

A newly operating accelerator mass spectrometry (AMS) facility such as VERA has to go through an extensive testing phase in order to establish optimal conditions for (super 14) C measurements, especially in the field of archaeological samples where an overall precision of 0.5% is desirable. We discuss the results of our measurements at the milligram carbon level as they relate to long-term stability, reproducibility, precision and isotope fractionation.

Extension of the measuring capabilities at VERA

Our standard setup used for accelerator mass spectrometry (AMS) with 14C was modified for measuring various other radionuclides. The injection and detection systems were modified to suit the particular isotope investigated. 10B, the stable isobar of 10Be, is stopped in a gas absorber in front of a surface barrier detector. 26Al is measured similar to 14C, except for a modification of the timing for the sequential isotope injection. For 129I, a time-of-flight setup was built to separate 129I from 127I. For heavier rare radionuclides, the mass resolution of the injector system was improved. We also improved our capabilities in measuring carbon samples having very low mass. We describe two different methods to prepare and to measure sub-milligram 14C samples.

Precision and accuracy of 26Al measurements at VERA

Abstract An accurate determination of the 27 Al(n,2n) 26 Al excitation function near threshold was carried out. The detection of the produced 26 Al was performed with 26 Al/ 27 Al isotope ratio measurements via AMS with the Vienna Environmental Research Accelerator (VERA). To this end systematic investigations of Al-metal and Al-oxide samples were performed and several standards were systematically investigated. No difference in the AMS results were obtained using either Al-metal or Al 2 O 3 samples but inconsistencies of different Al standards were found. An independent Al standard was produced by irradiating Al-metal samples with a high neutron fluence measuring the 26 Al activity with a Ge-diode. The resulting 26 Al/ 27 Al ratio could then be directly compared with the results from an AMS measurement on the same material. A very good agreement between the activity and the AMS measurement was obtained, normalizing the AMS results with Al standards used at Purdue and Munich.