• Energy Research

During COP 21 in Paris 2015, several states and organizations agreed on the "4/1000" initiative for food security and climate. This initiative aims to increase world's soil organic carbon (SOC) stocks by 4‰ annually. The influence of soil development status on SOC dynamics is very important but usually not considered in studies. We analyse SOC accumulation under forest, grassland and cropping systems along a soil age gradient (10-17,000years) to show the influence of soil development status on SOC increase. SOC stocks (0-40cm) and accumulation rates along a chronosequence in alluvial soils of the Danube River in the Marchfeld (eastern Austria) were analysed. The analysed Fluvisols and Chernozems have been used as forest, grassland and cropland for decades or hundreds of years. The results showed that there is a fast build-up of OC stocks (0-40cm) in young soils with accumulation of ~1.3tha-1a-1 OC in the first 100years and ~0.5tha-1a-1 OC between 100 and 350years almost independent of land use. Chernozems with a sediment deposition age older than 5.000years have an accumulation ratemodern" and "modern" carbon indicating a fast carbon cycling. Carbon in subsoil is less exposed to decomposition and OC can be stored at long-time scales in the subsoil (14C age of 3670±35 BP). In view of the '4/1000' initiative, soils with constant carbon input (forest & grassland) fulfil the intended 4‰ growth rate of SOC stocks only in the first 60years of soil development. We proclaim that under the present climate in Central Europe, the increase of SOC stocks in soil is strongly affected by the state of soil development.

Aerosols dispersed in the atmosphere represent important factors influencing not only the environment, but also human health. Carbonaceous aerosols are one of the main components of total atmospheric aerosols, and their sources are of great interest. Radiocarbon analysis provides an excellent way to determine the fraction of fossil and non-fossil aerosols in the atmosphere. Over the period of one year (June 2017-June 2018), we sampled atmospheric aerosols with size greater than 0.3 μm in Bratislava, Slovakia and used the exposed quartz filters for radiocarbon analysis of the elemental carbon (EC) aerosol fraction. The results show that on average the fossil fuel combustion is the dominant source of EC aerosol particles in Bratislava. In summer months, they represent more than half (65-80%) of the total EC aerosols. The relative amount of EC particles derived from biomass burning was 20-35% in summer, which increased to 40-55% in winter months. The dominance of fossil fraction is caused by high degree of industrialization and urbanization of the city. The increase of biomass fraction in winter is probably caused by domestic wood burning in areas surrounding the Bratislava city.

Recent improvements in isobaric suppression for medium-mass isotopes, e.g. Ca-41, offer new possibilities for tandem accelerators with terminal voltages of 3 MV or lower; i.e. when dealing with particle energies

Cedar (Cedrus sp.) wood from two archaeological contexts in Egypt – (i) the First Intermediate Period coffin of Ipi-ha-ishutef, (ii) a funerary boat at the pyramid of Middle Kingdom king Senusret (or Sesostris or Senwosret) III – form floating tree-ring sequences. Since one of the sample sets had been mounted with Elmer's glue products in core-mounts for dendrochronological examination, we investigate whether pretreatment can remove this potential contaminant before 14C dating. We find that even in (unrealistic) cases of extensive glue contamination this can be largely/successfully removed – making it likely that the samples in this study, where, moreover, only wood samples without traces of glue were employed, can provide accurate 14C dates. Dendro-14C-wiggle-matching was then employed to provide precise calendar dates for the two tree-ring sequences. The last extant ring of the Ipi-ha-ishutef coffin lies ca. 2081–2064 BC (95.4% probability), supporting, but refining, its assumed date. In the case of the Senusret III boat, we find a temporary, small, but important offset within the period ca. 2200–1900 BC in contemporary 14C ages between the Levant and central and northern Europe. It is suggested this is likely a result of exaggeration of normal seasonal variations in the uptake of 14C and its latitudinal distribution caused by climate change in the 2200–1900 BC/4200–3900 Cal BP (y2k) interval. A date for the last extant ring of the Senusret III boat is probably around 1898/95–1879/76 BC (95.4% probability) – more consistent with a high Middle Kingdom Egyptian chronology.

The increasing demand for measuring long-lived radionuclides with small AMS machines at energies below 1 MeV per nucleon raises the need for compact detectors which still have a decent energy resolution and allow for a clear identification of the incident particles. Based on a design by the AMS group at the ETH Zurich a compact gas ionization chamber was built and installed at the 3 MV tandem AMS facility VERA (Vienna Environmental Research Accelerator). The main challenge in AMS is the detection of rare isotope species in the presence of strong isotopic and isobaric interferences. The task of the ionization chamber is the suppression of the unwanted isobar by separating the ions via their different stopping powers. Measurements of 36Cl at VERA showed an achieved suppression of the unwanted stable isobar 36S of 3 × 10−4 and measurements of 10Be showed an achieved suppression of 10B of at least 3 × 10−6. Additional suppression of the isobaric ions can be achieved by a degrader foil technique applied to 10Be measurements by G.M. Raisbeck. In combination with the new ionization chamber the achieved suppression of 10B is at least 10−10. Measurements of blank samples at VERA show that the background for AMS with 10Be is below 2 × 10−15.