Radiocarbon in modern carbon cycle research

<p>Atmospheric nuclear weapon testing in the 1950s and 1960s has been worrying, however, in many aspects it was extremely beneficial for environmental sciences. The artificial production of more than 6 x 10<sup>28</sup> atoms or about 0.6 tons of radiocarbon (<sup>14</sup>C), leading to a doubling of the <sup>14</sup>C/C ratio in tropospheric CO<sub>2</sub> of the Northern Hemisphere, has generated a prominent spike in 1963. This “bomb-spike” has been used as transient tracer in all compartments of the carbon cycle, but also to study atmospheric dynamics, such as inter-hemispheric and stratosphere-troposphere air mass exchange. Moreover, our attempt to accurately determine total bomb produced <sup>14</sup>C led to improved estimates of the atmosphere-ocean gas exchange rate and to a new constraint of the residence time of carbon in the terrestrial biosphere. Today, the transient bomb-radiocarbon signal has levelled off, and the anthropogenic input of radiocarbon-free fossil fuel CO<sub>2</sub> into the atmosphere has become the dominant driver of the <sup>14</sup>C/C ratio in global atmospheric CO<sub>2</sub>. The observed decreasing <sup>14</sup>C/C trend in atmospheric CO<sub>2</sub> may thus help scrutinising the total global release of fossil fuel CO<sub>2</sub> into the atmosphere. On the local and regional scale, atmospheric <sup>14</sup>C/C measurements are already routinely conducted to separate fossil fuel from biogenic CO<sub>2</sub> signals and to estimate trends of regional fossil fuel CO<sub>2</sub> emissions. Some prominent examples where the bomb <sup>14</sup>CO<sub>2</sub> disturbance has been successfully used to study dynamic processes in the carbon cycle are discussed as well as our current activities applying this unique isotope tracer for continental scale carbon cycle budgeting.</p>

Determination of Plutonium and Uranium Radionuclides in Glacier Ice Samples by MC-ICP-MS

A radiochemical procedure for the determination of plutonium (Pu) and uranium (U) radionuclides in ice samples by multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS) is presented. Pu and U radionuclides are preconcentrated by coprecipitation and then separated by extraction chromatography. The purified Pu and U fractions are analyzed by MC-ICP-MS. Detection limits of 2 × 10 –3 and 3 × 10–6 mBq kg–1 were achieved for 239Pu and 236U, respectively. Surface ice samples collected from the Gauli glacier (Switzerland) were analyzed by this method. The surface of the Gauli Glacier retains historical records of 239Pu, 240Pu and 236U from the nuclear weapon testing (NWT) period. Pu and U radionuclides were found to be consistent in terms of pattern, showing two peaks possibly related to the two main periods of the NWTs (1954–1958 and 1961–1963). 3H measurements, also released by the NWT, further confirmed the Pu and U results. The 240Pu/239Pu ratio ranged from 0.14 to 0.25, and 236U/ 239Pu ranged from 0.14 to 0.81. The Pu atom ratios ranged within the limits of global fallout in the most intensive period of NWT (1952 to 1962).

Radiocarbon in modern Carbon Cycle research

<p>Atmospheric nuclear weapon testing in the 1950s and 1960s has been worrying, however, in many aspects it was extremely beneficial for environmental sciences. The artificial production of more than 6 x 10<sup>28</sup> atoms or about 0.6 tons of <sup>14</sup>C, leading to a doubling of the <sup>14</sup>C/C ratio in tropospheric CO<sub>2</sub> of the Northern Hemisphere has generated a prominent <sup>14</sup>C spike in 1963. This “bomb-spike” has been used as transient tracer in all compartments of the carbon cycle, but also to study atmospheric dynamics, such as inter-hemispheric and stratosphere-troposphere air mass exchange. Moreover, our attempt to accurately determine total bomb produced <sup>14</sup>C led to improved estimates of the atmosphere-ocean gas exchange rate and to a new constraint of the residence time of carbon in the terrestrial biosphere. Today, the transient bomb-radiocarbon signal has levelled off, and the anthropogenic input of radiocarbon-free fossil fuel CO<sub>2</sub> into the atmosphere has become the dominant driver of the decreasing <sup>14</sup>C/C ratio in atmospheric CO<sub>2</sub>; the observed trend may thus help scrutinising the total global release of fossil fuel CO<sub>2</sub> into the atmosphere. Prominent examples where the bomb <sup>14</sup>C disturbance has been successfully used to study dynamic processes in the carbon cycle are discussed as well as our current activities applying this unique isotope tracer for continental scale carbon cycle budgeting.</p>

This Is Only a Test? Long-Run and Intergenerational Impacts of Prenatal Exposure to Radioactive Fallout

We examine the effect of radiation exposure in utero, resulting from nuclear weapon testing in the 1950s and early 1960s, on long-run outcomes of Norwegian children. Exposure to low-dose radiation, specifically during months 3 and 4 in utero, leads to lower IQ scores for men and lower education attainment and earnings among men and women. Children of persons affected in utero also have lower cognitive scores, suggesting a persistent intergenerational effect of the shock to endowments. Given the lack of awareness about nuclear testing in Norway at this time, our estimates are likely unaffected by avoidance behavior or stress effects.

Technetium Encapsulation by A Nanoporous Complex Oxide 12CaO•7Al2O3 (C12A7)

Technetium (99Tc) is an important long-lived radionuclide released from various activities including nuclear waste processing, nuclear accidents and atmospheric nuclear weapon testing. The removal of 99Tc from the environment is a challenging task, and chemical capture by stable ceramic host systems is an efficient strategy to minimise the hazard. Here we use density functional theory with dispersion correction (DFT+D) to examine the capability of the porous inorganic framework material C12A7 that can be used as a filter material in different places such as industries and nuclear power stations to encapsulate Tc in the form of atoms and dimers. The present study shows that both the stoichiometric and electride forms of C12A7 strongly encapsulate a single Tc atom. The electride form exhibits a significant enhancement in the encapsulation. Although the second Tc encapsulation is also energetically favourable in both forms, the two Tc atoms prefer to aggregate, forming a dimer.

Radioactive contamination mitigation in the Arctic region

This article discusses the most significant sources of large-scale radioactive contamination to which the Arctic has been exposed since the middle of the last century, which are identified as 1) radioactive fallout and deposition from nuclear weapon testing; 2) plum waste from the Sellafield radiochemical plant (United Kingdom) and Cap de la Ag (France) nuclear fleet operation; 3) radioisotope thermoelectric generators; and 4) submerged and sunken radioactive objects. The article assesses the comparative contribution and associated radioecological risks of these sources, and special attention is focused on the “nuclear legacy” of the USSR/Russian nuclear fleet and the search for solutions. The article describes the content and implementation results of the “Development of a Strategic Master Plan for Disposition of Decommissioned Russian Nuclear-Powered Fleet and Rehabilitation of Hazardously Radioactive Sites and Facilities of Its Support Infrastructure” which was developed with broad international cooperation. Attention is drawn to remaining environmental problems associated with submerged and sunken objects that contain spent nuclear fuel and radioactive waste in the Arctic, and the article presents generalized data on such objects and associated risks of water contamination as identified by analyses of model studies of possible accident consequences.