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In 2010 more than 600 radiocarbon samples were measured with the gas ion source at the MIni CArbon DAting System (MICADAS) at ETH Zurich and the number of measurements is rising quickly. While most samples contain less than 50 mu g C at present, the gas ion source is attractive as well for larger samples because the time-consuming graphitization is omitted. Additionally, modern samples are now measured down to 5 per-mill counting statistics in less than 30 min with the recently improved gas ion source. In the versatile gas handling system, a stepping-motor-driven syringe presses a mixture of helium and sample CO2 into the gas ion source, allowing continuous and stable measurements of different kinds of samples. CO2 can be provided in four different ways to the versatile gas interface. As a primary method. CO2 is delivered in glass or quartz ampoules. In this case, the CO2 is released in an automated ampoule cracker with 8 positions for individual samples. Secondly, OX-1 and blank gas in helium can be provided to the syringe by directly connecting gas bottles to the gas interface at the stage of the cracker. Thirdly, solid samples can be combusted in an elemental analyzer or in a thermo-optical OC/EC aerosol analyzer where the produced CO2 is transferred to the syringe via a zeolite trap for gas concentration. As a fourth method, CO2 is released from carbonates with phosphoric acid in septum-sealed vials and loaded onto the same trap used for the elemental analyzer. All four methods allow complete automation of the measurement, even though minor user input is presently still required. Details on the setup, versatility and applications of the gas handling system are given. (C) 2012 Elsevier B.V. All rights reserved.

Measurements of 14C in the organic carbon (OC) and elemental carbon (EC) fractions, respectively, of fine aerosol particles bear the potential to apportion anthropogenic and biogenic emission sources. For this purpose, the system THEODORE (two-step heating system for the EC/OC determination of radiocarbon in the environment) was developed. In this device, OC and EC are transformed into carbon dioxide in a stream of oxygen at 340 and 650 �C, respectively, and reduced to filamentous carbon. This is the target material for subsequent accelerator mass spectrometry (AMS) 14C measurements, which were performed on sub-milligram carbon samples at the PSI/ETH compact 500 kV AMS system. Quality assurance measurements of SRM 1649a, Urban Dust, yielded a fraction of modern fM in total carbon (TC) of 0.522 ±0.018 (n ¼ 5, 95% confidence level) in agreement with reported values. The results for OC and EC are 0.70± 0.05 (n ¼ 3) and 0.066 ± 0.020 (n ¼ 4), respectively.

Ranking among the largest volcanic eruptions of the Common Era (CE), the ‘Millennium Eruption’ of Changbaishan produced a widely-dispersed tephra layer (known as the B-Tm ash), which represents an important tie point for palaeoenvironmental studies in East Asia. Hitherto, there has been no consensus on its age, with estimates spanning at least the tenth century CE. Here, we identify the cosmogenic radiocarbon signal of 775 CE in a subfossil larch engulfed and killed by pyroclastic currents emplaced during the initial rhyolitic phase of the explosive eruption. Combined with glaciochemical evidence from Greenland, this enables us to date the eruption to late 946 CE. This secure date rules out the possibility that the Millennium Eruption contributed to the collapse of the Bohai Kingdom (Manchuria/Korea) in 926 CE, as has previously been hypothesised. Further, despite the magnitude of the eruption, we do not see a consequent cooling signal in tree-ring-based reconstructions of Northern Hemisphere summer temperatures. A tightly-constrained date for the Millennium Eruption improves the prospect for further investigations of historical sources that may shed light on the eruption's impacts, and enhances the value of the B-Tm ash as a chronostratigraphic marker.

Pteropods are holoplanktonic molluscs presently endangered because their fragile aragonitic shell is very sensitive to ocean acidification. The preservation of pteropods, and in particular of the mesopelagic Heliconoides (Limacina) inflatus, has been used to assess aragonite saturation state in Quaternary sediments (Limacina Dissolution Index, LDX) as an inferred proxy for climatic changes. Three deep-sea cores retrieved in 2016 during the EUROFLEETS2 SEMSEEP cruise offshore Israel are investigated to assess the preservation degree of H. inflatus (d'Orbigny, 1835) in representative environments across the base of the southeastern Mediterranean margin (cold water coral, active seepage pockmark and deep sea channel areas). In some core intervals, yellowish, recrystallized internal molds of this species are present. They have been previously observed in the Eastern Mediterranean, but the nature and origin of their colour was never explained. Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Electron Backscatter Diffraction (EBSD) revealed that the recrystallized molds of the H. inflatus shells are formed by aragonite needles and high-Mg calcite crystals. The formation and preservation of these internal molds is induced by advective methane emissions, typically precipitating aragonite and High-Mg calcite phases close to the sediment–water interface. These molds were never used in previous applications of the LDX or in any existing ranking of pteropod preservation. Therefore, we have categorized these peculiar features combining previous pteropod ranking descriptions with the new observations to develop a modified biotic index (Heliconoides Modified Dissolution Index-HMDI). High values of the HMDI at the base of the pockmark core correspond to the interval where also active seepage-related features – e.g., bubble emissions, low-oxygen benthic foraminifera, chemosymbiotic molluscs, small fragments of authigenic carbonate crusts and slightly depleted δ13C values – occur, showing the applicability of the HMDI to methane seeps environments., Ecological Indicators, 152, ISSN:1470-160X, ISSN:1872-7034