T03_02

New absorption-catalytic setup for graphitization of C-containing gases from water sources

Parkhomchuk E^1,2,3, Petrozhitskiy A^1,2,3, Ignatov M^1,3, Kuleshov D^1,3, Kalinkin P⁴, Novikov D⁵, Sabrekov A⁶, Parkhomchuk V^1,2

¹Novosibirsk State University, Novosibirsk, Russian Federation, ²Budker Institute of Nuclear Physics Siberian Branch Russian Academy of Sciences , Novosibirsk, Russian Federation, ³Institute of Archaeology and Ethnography Siberian Branch Russian Academy of Sciences , Novosibirsk, Russian Federation, ⁴Boreskov Institute of Catalysis Siberian Branch Russian Academy of Sciences , Novosibirsk, Russian Federation, ⁵Trofimuk Institute of Petroleum Geology and Geophysics Siberian Branch Russian Academy of Sciences , Novosibirsk, Russian Federation, ⁶Severtsov Institute of Ecology and Evolution Russian Academy of Sciences , Moscow, Russian Federation

The AMS Golden Valley laboratory is equipped with two accelerator mass spectrometers: BINP AMS facility and MICADAS-28, and two graphitization systems: AGE-3 and Absorption-catalytic setup, developed in Boreskov Institute of Catalysis (ACS BIC). The last one is designed for graphitization of labeled biomedical samples, dissolved organics and dissolved or gaseous carbon dioxide. Detailed description and characteristics of ACS BIC will be presented compared with that one’s of AGE-3 on the samples from Glasgow International Radiocarbon Inter-comparison (GIRI). A comparison of the results from two series of experiments with GIRI samples: AGE-3 + MICADAS-28 and ACS BIC + MICADAS-28 will be given. Some results on dating of methane seeps – cm-sized holes and craters with an active release of gas bubbles and water, found in Western Siberia, and dating of carbon dissolved in springs in Novosibirsk region, will be also presented. Novel technique for graphitization of CH₄ and CO₂, dissolved in water, was provided by ACS BIC.

T03_03

Radiocarbon dating correlated microlayers in engraved, oxalate-rich accretions: new archives of paleoenvironments and human activity from Australian rock art shelters

Green H¹, Gleadow A¹, Finch D¹, Myers C², McGovern J³, Levchencko V⁴, Heaney P⁵, Pickering R⁶, Balanggarra Aboriginal Corporation⁷

¹The University of Melbourne, Melbourne, Australia, ²Dunkeld Pastoral Company, Kununurra, Australia, ³The University of Queensland, Brisbane , Australia, ⁴Australian Nuclear Science and Technology Organisation, Lucas Heights, Australia, ⁵Lettuce Create, Brisbane, Australia, ⁶The University of Cape Town, Cape Town, South Africa, ⁷Balanggarra Aboriginal Corporation, Kununurra, Australia

Distinctive, dark coloured, glaze-like mineral accretions, often found in rock shelters around the world, offer important opportunities for radiocarbon dating of associated rock art. The mineralogy of these accretions is dominated by well-crystallised calcium oxalate and sulphate minerals, most commonly whewellite and gypsum, with significant occurrences of phosphates in some samples. The accretions are typically several millimetres thick and characterised by distinctive internal laminations and other apparently microbial features that support a microbiological origin for the oxalate component. Risks surrounding contamination and open system behaviour, previously limiting the application of radiocarbon dating to these accretions, are addressed by the well-crystallised nature of the oxalates and the preservation of fine laminar features within their internal stratigraphies. In a case study from the north Kimberley region of north-western Australia, we demonstrate the use of sample characterisation and chemical pre-treatment techniques to pre-screen for evidence of open system behaviour and address potential contamination. The results provide stratigraphically consistent sequences of radiocarbon dates in mm-scale laminated accretions, with correlations between distinctive patterns in the layer sequences visible in rock shelters up to 90 km apart. This demonstrates that pre-screened samples offer opportunities to reliably date rock art, particularly symbolic markings commonly engraved into these relatively soft deposits and suggests their synchronised formation is not entirely shelter specific but broadly controlled by variations in regional environmental conditions. Consequently, these accretions also offer potential as paleoenvironmental archives, with radiocarbon dating of layers in nine accretions indicating four, approximately synchronous growth intervals covering the last 43 ka.

T03_04

Refining the Bulk: Utilizing Complementary Pyrolysis-Gas Chromatography-Mass Spectrometry to Focus and Inform Ramped Pyrolysis Radiocarbon Analyses

Ginnane C¹, Turnbull J^1,2, Phillips A¹, Zondervan A¹, Naeher S¹

¹GNS Science, Lower Hutt, New Zealand, ²CIRES, University of Colorado at Boulder, Boulder, USA

Ramped pyrolysis oxidation-accelerator mass spectrometry (RPO-AMS) has been established at Rafter Radiocarbon Laboratory at GNS Science, NZ. RPO-AMS has a niche in Antarctic sediment chronology where traditional radiocarbon analyses are unsuitable. In this depositional environment, carbonates are not well-preserved, and autochthonous carbon is commingled with detrital carbon. RPO-AMS improves on bulk radiocarbon measurements for these challenging environments by partitioning the sedimentary organic carbon pool according to thermochemical stability. More labile, predominantly younger depositional carbon can be separated from older, refractory detrital carbon that skews the bulk radiocarbon measurement.

RPO-AMS presents a step change in radiocarbon measurement, providing an intermediate technique between bulk and compound-specific radiocarbon analysis (CSRA). More accurate information is obtained relative to bulk sediment dating without the cost and major technical challenges associated with CSRA. By combining pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) with RPO-AMS, a chemical fingerprint is determined for each RPO split partitioned along the thermal gradient, informing the composition of the carbon source. Aliquots containing carbon compounds indicative of deposition can be identified prior to selecting samples for radiocarbon analysis. Focused analyses shorten run times and reduce measurement costs to achieve more accurate and comprehensive chronologies. In addition to targeted sample selection, the Py-GC-MS fingerprints can be used to interpret detrital depositional environments and sedimentary processes in tandem with RPO-AMS data.

T03_06

Radiocarbon in dissolved organic carbon by UV oxidation: an update of procedures and blank characterization at NOSAMS

Xu L¹, Roberts M¹, Elder K¹, Hansman R¹, Gagnon A¹, Kurz M¹

¹Woods Hole Oceanographic Institution, Woods Hole, United States

Radiocarbon measurements of dissolved organic carbon (DOC) in aquatic systems provide key insights into the age and biogeochemical cycling of this large and reactive carbon reservoir. At the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility, we have worked extensively to reduce the procedural blank of DO¹⁴C to 3.3 ± 0.8 µg C with Fm of 0.35 ± 0.15, down from 22.0 ± 6.0 µg C in 2018. This was achieved through modifications of sample processing that included elimination of higher blank organic carbon reagents and improved sample and reactor handling intended to reduce exposure to laboratory air (which may contribute to the DOC blank via volatile organic compounds). Sample throughput has been improved three-fold to three samples per day by increasing the size of the UV oxidation chamber to allow for three reactors.

T03_07

Eruption History of Mt. Fuji Further Constrained Through Radiocarbon Dating of Fossil Pollen Automatically Extracted from Lake Motosu Sediments

Ota K^1,2, Yokoyama Y^1,2,3,4,5, Miyairi Y², Obrochta S⁶, Yamamoto S⁷, Aurelia H⁸, V.M.A. H^9,10, M. De B¹⁰, Fujiwara O¹¹

¹University of Tokyo, Kashiwa, Japan, ²Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Japan, ³Graduate Program on Environmental Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Bunkyoku, Japan, ⁴Biogeochemistry Program, Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan, ⁵Research School of Physics, The Australian National University, Canberra, Australia, ⁶Graduate School of International Resource Science, Akita University, Akita, Japan, ⁷Yamanashi Prefectural Government Mount Fuji Research Institute, Yamanashi, Japan, ⁸niversity of Liege Department of Geography, Belgium, Belgium, ⁹Geological Survey of Belgium, Royal Belgian Institute of Natural Sciences, Belgium, Belgium, ¹⁰Ghent University Department of Geology, Belgium, Belgium, ¹¹Geological Survey of Japan, AIST, Tsukuba, Japan

Lake sediments continuously record paleoenvironmental changes and/or the history of volcanic eruptions, and the construction of highly accurate age models is important for paleoclimatic studies. Organic fossils such as leaves, which have been widely used for dating, are useful because they directly record atmospheric radiocarbon(¹⁴C) and are deposited quickly, but they are only rarely found in sediments, limiting high time-resolution studies. Pollen fossils, on the other hand, not only directly reflect atmospheric ¹⁴C, but also are not easily degraded and are commonly contained within sediments, making them valuable for high temporal resolution and high precision dating of any desired layer. However, manually collecting the requisite number of grains is prohibitively time consuming.

Therefore, in this study, we applied flow cytometry to separate pollen grains for radiocarbon measurement of the sediments of Lake Motosu, at the northern part of Mt. Fuji, Japan. The ¹⁴C measurements were made using single-stage accelerator mass spectrometer (AMS) at the Atmosphere and Ocean Research Institute, University of Tokyo.

As a result, multiple age values were obtained from the sediments of Motosu Lake. The pollen ¹⁴C age agrees leaf fossils within the analytical uncertainty. Compared to the ¹⁴C age of bulk sediments, ¹⁴C age of pollen fossils are 300 to 350 years younger. Since several thin tephra layers in the sediments of Lake Motosu have been reported possibly to record small-scale eruptions of Mt. Fuji, pollen ¹⁴C dating will be applied above and below each tephra layer to further constrain the timing of Mt. Fuji eruptions.

T03_08

Lifespan of fishes and LA-AMS – Investigations of maximum age for grouper and alligator gar

Andrews A¹, Welte C^2,3, Wertnik M^2,3, Sanchez P⁴, Rooker J⁴, Daugherty D⁵, Smith N⁵

¹Age and Longevity Research Lab, Honolulu, United States, ²Laboratory of Ion Beam Physics, ETH Zürich, Zürich, Switzerland, ³Geological Institute, ETH Zürich, Zürich, Switzerland, ⁴Texas A&M University at Galveston, Department of Marine Biology, Galveston, USA, ⁵Texas Parks and Wildlife Department, Heart of the Hills Fisheries Science Center, Mountain Home, USA

The longevity of fishes is an important consideration for a proper understanding of population dynamics, survivorship strategies, and consequently management policy. Bomb radiocarbon dating of otoliths (ear stones) has validated lifespans that exceed 50-60 years for long-lived alligator gar and deep-water grouper in North America and the Gulf of Mexico (GoM). However, low variability in radiocarbon concentrations prior to the bomb-produced rise sets a limit for this technique to carbonates deposited after the mid-1950s.

Laser ablation accelerator mass spectrometry (LA-AMS) provides a novel approach through a high-resolution analysis that can locate the rise of bomb-produced radiocarbon within the growth zone structure, away from the otolith core or nucleus (birth year material) typically sampled with a micromilling machine. In this study, we expand on previous results from red snapper in the GoM (Andrews et al. 2019) by applying the technique to three large-bodied grouper species of the GoM and to three specimens of large and likely very old alligator gar from tributaries to the GoM.

Eight otolith thin sections were analyzed with scanning velocities between 5 and 10 µm/s. Each laser scan was approximately 10 minutes and was unique with regard to the radiocarbon signal. The rise of the bomb peak was identified for each specimen and linked to a location on the sample allowing assignment of a calendar year to that growth zone layer. Overall, ages for each species were validated as being older than a single core extraction could resolve, thus extending longevity estimates for each species.

T03_09

Going with the flow: rapid pollen sorting for radiocarbon analysis

Nakajima K^1,2, Heusser C^1,2, Welte C^1,2, Wacker L², Eglinton T¹

¹Geological Institute, ETH Zürich, Zürich, Switzerland, ²Laboratory of Ion Beam Physics, ETH Zürich, Zürich, Switzerland

Pollen grains have long been suggested ideal targets for radiocarbon (¹⁴C) dating of terrestrial sediment records. They are ubiquitously abundant in lacustrine sediments and represent atmospheric ¹⁴C concentrations as they form each year. Because pollen are established markers for terrestrial ecosystem variability, pollen-based ¹⁴C data provide the ideal, proxy-specific chronology for palynological research. Traditional approaches for pollen separation from sedimentary matrices have proven difficult due to a trade-off between purity, processing time, and yield. In recent years, a growing number of studies have demonstrated the suitability of flow cytometry cell sorters, in combination with physical and chemical processing, for the rapid separation of pollen grains from terrestrial sediments at high purity, e.g., [1]. With a dedicated flow cytometer (BD Influx Cell Sorter, BD Biosciences, US), we examine the robustness of this novel approach to isolate pollen grains for ¹⁴C analysis. We will provide the relevant parameters for reliable sorting and a detailed assessment of sorting efficiencies. First ¹⁴C results with elemental-analyzer-accelerator-mass-spectrometry of blank assessments at different preparation stages of the pollen separation and finally of natural sediment samples show that our protocol is suitable for microscale (< 20 µg C) pollen-¹⁴C dating. This will enable the dating of sediments previously limited by the lack of suitable material. With an established protocol and a dedicated instrument paving the way for routine application, pollen-¹⁴C dating will provide a versatile alternative to traditional dating approaches for terrestrial records.

[1] R. K. Tennant et al. (2013), JQS 28(3), 229-236.

T03_10

Data Reduction for Rapid, Continuous Radiocarbon Measurements by Laser Ablation

Wertnik M¹, Wacker L¹, Christl M¹, Synal H¹, Welte C¹

¹ETH Zurich, Zurich, Switzerland

The unique Laser Ablation (LA) setup coupled to a MICADAS Accelerator Mass Spectrometer (AMS) at ETH allows for the rapid measurement of continuous radiocarbon records on carbonate archives (e.g. speleothems, corals, otoliths). Using LA-AMS, ¹⁴C/¹²C ratios in such archives have been successfully analysed at spatial resolutions of up to 100 µm.

To ensure stable measurement conditions in the AMS, a continuous carbon flow of approximately 2.5 µg/min needs to be produced by the laser. Accordingly, CaCO₃ is ablated at comparably high repetition rates of 200 Hz, which in turn requires a continuous movement of the sample relative to the laser beam through a positioning system (typical velocities: 5 – 20 µm/s). Single data points are produced at 10 sec intervals resulting in a dense dataset with well localised relative coordinates.

As LA-AMS provides a transient signal , special care needs to be taken in basic data processing and the proper assignment of the measured signal to the sampling location. Important to consider are especially signal extraction and noise reduction as well as mixing and washout effects. Here, we show the current status of data processing and report on improvements in data processing.

T03_11

Radiocarbon dating and differentiation of tsunami deposits from the Isumi River lowland, Eastern Boso Peninsula, Japan

Soichiro O¹, Obrochta S¹, Fujiwara O², Yokoyama Y³, Miyairi Y³, Hatakeyama Y¹

¹Akita University, Akita, Japan, ²National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan, ³University of Tokyo, Kashiwa, Japan

We use high-density radiocarbon dating to assess the age of – and duration between – coarse overwash deposits that punctuate lagoonal to lacustrine sediments in a core recovered from the Eastern Boso Peninsula, Japan. The region has experienced seismic uplift, is now located several meters above sea level, and is prone to both tsunami and typhoon inundation. Several of the overwash beds appear stacked with a fining and thinning upward structure, which is characteristic of deposition by a tsunami “wave train” resulting from a single seismic event. However, without evidence of co-seismic uplift or run-up immediately followed by backwash, it is difficult to rule out a storm origin. We use the age modeling routine undatable to account for radiocarbon age uncertainty, sediment sample thickness, and dating material quality. Age model results indicate that the apparent groups of overwash beds lower in the core are separated by up to decades and therefore represent multiple washover events, and are therefore inconsistent with a tsunami “wave train”. The sediment accumulation rate then increased drastically, exceeding 1000 cm/ky at ~2500 cal. BP, after which, many of the grouped overwash beds appear to have accumulated geologically instantaneously, which is consistent with a seismic origin, though further study is needed to identify whether uplift events occured simultaneously to overwash bed deposition. Carbon, nitrogen, and sulfur concentrations further provide information on environmental changes caused by the washover events.

T03_12

The comparison of four ¹⁴C pretreatment methods applied to archaeological shells from Vale Boi (Portugal).

Paleček D¹, Falini G¹, Wacker L², Bicho N³, Talamo S¹

¹Department of Chemistry G. Ciamician, Alma Mater Studiorum University of Bologna, Bologna, Italy, ²Laboratory of Ion Beam Physics, ETH, Zürich, Switzerland, ³Interdisciplinary Centre for Archaeology and the Evolution of Human Behavior, University of Algarve, Faro, Portugal

Mollusc shells are often found in archaeological sites, given their great preservation potential and high value as a multipurpose resource. Vale Boi (Algarve, Portugal) is a well-known Upper Paleolithic archaeological site representing the earliest recorded modern human occupation in southwestern Iberia, as attested by the Early Gravettian remains dated to c. 32 ka Cal BP. The continued use and importance of mollusc shells at this site is attested by their presence throughout the long stratigraphic sequence. Thus, it is especially important to determine their age and purpose at the site.

Radiocarbon (¹⁴C) dating is a field in constant improvement; sample pretreatment chemistry is addressed by laboratories across the world, with the continuous development of new and improved protocols. Nevertheless, the pretreatment method for mollusc shells has not changed since the first application and is still used in many laboratories, although a new protocol was introduced in 2010. In our new ¹⁴C lab (BRAVHO) at Bologna University, we tested and applied these two methods in order to compare them. Furthermore, we introduced two alternative methods to extract the organic matrix from the shell, as it is protected from the environment and should reveal the true age of the shell. Here, we compare the ¹⁴C dates obtained to determine the most reliable pretreatment method for mollusc shells. The results of this study will give us the possibility to construct precise chronologies for sites such as Vale Boi, where shells are abundant throughout the stratigraphic sequence.

T03_P01

Monitoring of biogenic carbon fraction of disposable packaging

Aziz Gill K¹, Michczyńska D¹, Michczyński A¹

¹Silesian University of Technology (Politechnika Śląska), Gliwice, Poland

Disposable packaging materials are typically single use items and commonly used for enclosing or protecting food products during storage, sale, delivery and for the regular use mainly at restaurants. Annually more than18 million tonnes of waste can be collected in Europe by adopting the best strategies, resulting in 13% reduction in greenhouse gas emitted by packaging wastes. Europe intends to increase the recovered and recycled packaging waste which is 73 million tonnes (Tallentire and Steubing 2020). Disposable packaging prepared from sugarcane or paper can be a source of valuable resources and can overcome the plastic problem. Sugarcane plates are made from renewable sugarcane pulp so the compositing takeaway packaging minimizes the greenhouse gas emissions and improves the soil quality (APSnet). New paper production from waste paper requires less energy and emits less emissions than producing the same amount of paper from virgin materials, thus the recycling of waste paper could be beneficial to the environment (Merrild et al. 2008).

Our research aims to examine the ¹⁴C isotope concentration in disposable waste materials to make sure if indeed the materials contain some concentration of biogenic carbon to cause green effect in recycling. We examine the disposable paper plates, cups, straws, baking paper, sugar cane and wheat materials. The results of the measurements of bio carbon made by LSC and AMS techniques at Radiocarbon Laboratory in Gliwice (Pazdur et al. 2003; Piotrowska 2013) will be presented.

T03_P02

A new online ramped oxidation (ORO) system for improved coupled thermal and radiocarbon dissection of complex natural organic matter

Bolandini M¹, Bröder L¹, De Maria D², Eglinton T¹, Wacker L²

¹D-ERDW - Biogeoscience Group, ETH, Zürich, Switzerland, ²D-PHYS - Laboratory for Ion Beam Physics (LIP), ETH, Zürich, Switzerland

The coupling of serial or ramped pyrolysis and oxidation to carbon isotope measurements provides insights into the relationships between thermal activation energies and age distributions of natural organic materials. It therefore helps to elucidate controls on organic matter reactivity. The conventional approach involves heating of a bulk sample with a defined temperature ramp, simultaneous oxidation of thermal decomposition products, and collection of the resulting to CO₂ for subsequent ¹⁴C analysis.

The newly developed online ramped oxidation (ORO) system has been designed to sequentially trap and release evolved CO₂ via a customized interface to a gas-accepting source of an accelerator mass spectrometer (AMS), facilitating higher thermal and isotopic resolution of organic constituents. This is achieved via a two-stage oven that regulates the decomposition and subsequent oxidation of carbonaceous compounds to CO₂ in a mixture of He and O₂. This is coupled with a double zeolite trap interface (DTI, De Maria et al. 2021) that modulates the collection and transfer of evolved CO₂ to the AMS system for ¹⁴C measurement.

A functioning prototype of the ORO system has been developed to perform initial combustion tests. To this end, blanks, standard material, and samples from complex matrices such as soils, river, lake, and marine sediments are being measured and results compared with reference data.

T03_P03

¹⁴C blank determination for compound-specific radiocarbon analysis of lignin phenols

Cao M¹, Hefter J¹, Grotheer H¹, Mollenhauer G^1,2

¹Alfred Wegener Institute For Polar And Marine Research, Bremerhaven, Germany, ²MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany

Compound-specific radiocarbon analysis (CSRA) is one technique commonly used to constrain the cycling of biomarkers, such as lignin, between reservoirs. However, purification procedures of lignin for CSRA are prone to introduce extraneous (blank) carbon into the samples. These blanks will potentially lead to erroneous interpretation of lignin CRSA results, making the assessment of procedural blanks an important prerequisite. We describe a revised method for purification of lignin from sediment and evaluate F¹⁴C and the mass of the associated procedural blank following the method of Sun et al. (2020). We used two commercially available lignin phenol standards with known age and validated the procedure with lignin extracted from a standard sediment using the method of Goñi and Montgomery (2000). We isolated lignin phenols by HLB SPE cartridges (Waters Oasis, 200 mg, 6 ml) followed by single compound collection using high pressure liquid chromatography. Ten lignin-derived compounds were purified with a Phenomenex Synergi Polar-RP column and three compounds were isolated by a ZORBAX Eclipse XDB-C18 column. Radiocarbon analyses of several different sized aliquots of the standard compounds were performed on the miniaturized radiocarbon dating system at Alfred Wegener Institute, Germany (Mollenhauer et al., 2021). Samples were transferred into tin cups and combusted using an elementar analyser coupled with the gas interface system. We report the current status of carbon blanks associated with our preparation protocol for radiocarbon analysis of lignin phenols.

T03_P04

Update of radiocarbon analyses on dissolved inorganic carbon of seawater at ETH-Zurich

Castrillejo M^1,2, Wacker L², Bollhalder S², Casacuberta N^2,3, Kündig K^2,3, Leist L³, Scacco G², Synal H², Wefing A^2,3

¹Department of Physics, Imperial College London, London, United Kingdom, ²Laboratory of Ion Beam Physics, ETH-Zurich, Zurich, Switzerland, ³Department of Environmental Systems Science, ETH-Zurich, Zurich, Switzerland

In recent years, the Laboratory of Ion Beam Physics (LIP) has been actively involved in oceanographic expeditions to collect samples and measure radiocarbon on dissolved inorganic carbon of seawater. This work has been possible thanks to a new analytical method developed through the collaboration between oceanographers and experts in radiocarbon analysis at LIP. The fully automated method coupling the CO₂ extraction and graphitisation steps in a single line allows for rapid and precise determination of the radiocarbon content using only 50 ml of seawater. The method performs simultaneously on 7 samples and allows the processing of 21 samples a day.

Over the past two years, we have gained experience in sample collection, storage and processing allowing us to provide a substantial update on the ETH-LIP method that was first published by Casacuberta et al., (2020). We have compiled data on blanks, coral sample used as reference material, seawater replicates and data from a first interlaboratory exercise. Based on these new data, we discuss aspects related to sample collection and storage, background correction, accuracy, reproducibility and data comparability.

Casacuberta N., Castrillejo M., Wefing A.M., Bollhalder S., Wacker L. 2020. High precision ¹⁴C analysis in small seawater samples. Radiocarbon 62(1):13–24.

T03_P05

Direct graphitization of CO₂ from atmospheric air

Gautschi P¹, Wacker L¹, Synal H¹

¹ETH Zurich, Zurich, Switzerland

The atmospheric concentration of carbon dioxide (CO₂) is increasing rapidly since the industrialization. Emission of ¹⁴C free CO₂ from the combustion of fossil fuels, such as coal, oil or gas, reduces the ¹⁴CO₂ to ¹²CO₂ ratio in the atmosphere. When the background ¹⁴CO₂ level is known, the local surplus of fossil CO₂ in ppm can be calculated using the measured CO₂ concentration and the ¹⁴CO₂ abundance at a given sampling site.

A simple and fast method to prepare whole-air samples for radiocarbon analysis of atmospheric CO₂ has been developed and tested at ETH Zurich. Atmospheric air is collected in sampling bags (5 L) and then transported back to the laboratory, where CO₂ is isolated using the molecular sieve trap implemented in the automated graphitization line AGE3. The trapped CO₂ is then graphitized and measured by accelerator mass spectrometry (AMS).

A programmable air loading box to automatically collect and graphitize up to seven air samples at a time was constructed for reliable and repeatable results. A major benefit of the presented method is the reduced labour needed for sampling and graphitization. In a pilot study, twelve air samples were automatically collected within 1.5 days near the city of Zurich and later graphitized within another day.

T03_P06

DOC radiocarbon measurements at the AWI-MICADAS facility, current method developments and improvements

Grotheer H^1,2, Gentz T¹, Höhn M¹, Kattein L¹, Schlagenhauff S¹, Hefter J¹, Mollenhauer G^1,2

¹Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany, ²University Bremen, Dept. of Geosciences and MARUM, Bremen, Germany

Reliable radiocarbon ages of dissolved organic carbon (DOC) are a perquisite to obtain improved understanding of current carbon cycle dynamics. Dissolved organic matter (DOM) is an extremely complex natural organic mixture consisting of tens of thousands of individual compounds with a large variety of chemical and physical properties. Because of this complexity and the presence of sea salt, radiocarbon sample preparation for marine DOC is very challenging as available methods for extraction and purification (SPE, or ultra-filtration) depend on either physical or chemical properties and thus only consider a fraction of the DOC pool amenable to the preparation method. Consequently, the sample preparation selectivity hampers our wholistic understanding of the DOC pool, its cycling and reactivity. Today the only method available considered to reliably report bulk DOC radiocarbon composition is ultraviolet oxidation (UVox), where irrespectively of chemical or physical properties DOC molecules are quantitatively oxidized to CO₂. However, UVox is only available at a few very specialized laboratories, is very time consuming and tedious.

We will report on ongoing method developments for processing marine DOC by utilizing a modified, commercially available Gräntzel thin-film flow-through reactor enabling fast sample processing. The offline UVox system is coupled via a custom-built zeolite trap to the existing GIS infrastructure of the MICADAS system. Technical details, reproducibility tests and current blank levels will be reported.

T03_P07

DIC radiocarbon measurements at the AWI-MICADAS facility, current method developments and improvements

Grotheer H^1,2, Gentz T¹, Hammes J³, Hefter J¹, Mollenhauer G^1,2

¹Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany, ²University Bremen, Dept. of Geosciences and MARUM, Bremen, Germany, ³University Bonn, Dept. of Geosciences, Bonn, Germany

Reliable radiocarbon ages of dissolved inorganic carbon (DIC) are a perquisite to obtain improved understanding of current carbon cycle dynamics. With the advance of small-scale radiocarbon measurements, it became possible to analyze samples in unprecedented spatial resolution and increasing precision obtained by replicate analysis. Small sample requirements allow reliable dating of DIC samples from even the most remote places on Earth, where access is challenging, and available material limited in quantities. Reliable high precision methodologies for these precious sample sizes are required, and due to the lack of accepted Δ¹⁴C DIC standard material a sample processing consensus must be developed within the community.

We will report on ongoing method improvements for processing marine dissolved inorganic carbon samples. Our developments utilize the standard MICADAS peripheral carbonate handling system (CHS) coupled via the gas interface system (GIS) to the AWI-MICADAS . We report on reproducible ¹⁴C dates measured on DIC samples as small as 2 mL sea water. We describe our method improvement pathway including testing of different acids for DIC outgassing, sampling duration and volume dependency on ¹⁴C replicability.

T03_P08

A new UV-Oxidation set up for AMS radiocarbon analysis for small dissolved organic carbon in marine and fresh water samples

Haghipour N^1,2, Lupker M¹, Wacker L², Eglinton T¹

¹Geological Institute, ETH Zurich, Zurich, Switzerland, ²Laboratory of Ion Beam Physics, ETH Zurich, Zurich, Switzerland

Radiocarbon measurements of dissolved organic carbon (DOC) can give us valuable information about origin and age of DOC, a major, yet little understood component in the global carbon cycle. One way to measure DOC in water is to remove dissolved inorganic carbon first, oxidize organic carbon with UV irradiation and ultimately analyses the formed inorganic CO₂ for ¹⁴C. The main challenge of UV-Oxidation (UVox) methods is to extract the typically low concentrations of DOC with low blanks required for relatively high precision ¹⁴C measurements. A disadvantage of currently used UVox methods is that only one sample can be oxidized in a laborious process at the same time. Here we present a UV-Oxidation system where up to 12 water samples can be oxidized simultaneously in 12 separate quartz reactors arranged around a single UV lamp in a compact setup. The simple setup further uses helium instead of vacuum typically used by conventional extraction lines to speed up the extraction of the formed CO₂ after oxidation. The key improvements of the new UVox setup are: 1) Reduced amount of water needed (30- 60 ml) as samples are measured for ¹⁴C with the Micadas gas ion source, 2) UV oxidation efficiency for standards is high (96%), 3) No KI trap is needed,4) Required time for sample preparation of up to 12 samples is 4-6 h. To test the oxidation efficiency, reproducibility and blank assessment we used different reference materials. Here we discuss the preliminary results from the performance of UVox extraction line.

T03_P09

One-pot processing of tree-ring samples for ¹⁴C analysis on cellulose

PHOUYBANHDYT B^1,4, DU BOISGUEHENEUC D^1,2,4, DAUX V¹, NOURY C¹, PIERRE M¹, STIEVENARD M¹, THIL F¹, HATTÉ C^1,3

¹Laboratoire des Sciences du Climat et de l'Environnement, Gif-sur-Yvette, France, ²Archéozoologie, Archéobotanique : Sociétés, Pratiques et Environnements, Paris, France, ³Silesian University of Technology, Gliwice, Poland, ⁴These authors contributed equally to this work, ,

Analyzing the radiocarbon fraction in tree rings is fundamental to the radiocarbon method in order to calibrate ¹⁴C years into calendar years. The increasing interest in measuring ¹⁴C at annual resolution implies an even larger number of tree-ring samples to be pretreated. And this, focusing on latewood cellulose to ensure that the carbon originates from only one year and has not been exchanged since formation.

To put ourselves on a battle footing for several projects we are involved in and that require large series of measurements, we confronted our protocol to others available in literature. We finally settled on an adaptation of the protocol used for stable isotopes measurements at LSCE that derives from the original protocol of Leavitt and Danzer (1993). We also considered some advice of Southon and Magana (2010) and added our own “touch”.

The chemistry is done in a 1.5 L Erlenmeyer flask in which the samples and standards are pooled, packed in an individual Teflon bag. The protocol is divided into three main steps: removal of water-soluble compounds, removal of lignin by a two-step oxidative delignification and removal of hemicellulose by alkaline extraction.

Our protocol allows the preparation of up to fifteen samples and five standards at the same time, without cross-contamination, saving thus time in handling and reducing chemical consumption. We present here the results we obtained on blanks and reference materials of different ages. They clearly indicate that this protocol allows to obtain results as accurate as with individual treatments.

T03_P10

Application of ¹⁴C dating of earthworm biospheroids to investigate paleosol formation

Kertész T^1,2, Gergely V¹, Buró B¹, Molnár M¹

¹Institute for Nuclear Research, Debrecen, Hungary, ²Doctoral School of Earth Sciences, University of Debrecen, Debrecen, Hungary

¹⁴C dating of paleosols is a challenging task as ordinary soil organic matter (SOM) does not give a realistic ¹⁴C age of a soil layer. If one could not find some macrofossil remains in the discovered soil horizon then the age determination is always a matter of debate. In this study we have investigated the earthworms produced biospheroids as a possible material for soil ¹⁴C dating. Recent studies suggested that earthworms consume preferably fresh organic matter during their life in the soil, which means the products of their digestion would contain rather recent organic carbon instead of the aged carbon from the SOM fraction.

Although biospheroids are rather small (diameter < 2 mm and mass < 5 mg) pure calcite granules, AMS technique gives the possibility of their radiocarbon dating.

We have investigated 8 different recent topsoil samples collected at 5 different localities in the Hajdúság area (Hungary). Results confirmed that contemporary biospheroids mostly contain young (max age 30 years) carbon, which gives realistic (zero) age. The method was applied on buried paleobiospheroids from the 10-50 krys old paleosol profile at Süttő (Hungary). ¹⁴C ages were compared with previous OSL data too. The ¹⁴C results (29), cover a 6.1 m long section, with 10 cm resolution, and show an very consistent picture with the previous OSL results and also some with ¹⁴C ages of conventional macrofossil from the same profile. Multiple repeated measurements were performed for reproducibility. Control samples may be present in the paleoenvironmental study of later Quaternary paleosols.

T03_P11

Simple method for analyses of total radiocarbon in water samples using wet chemical oxidation at HEKAL AMS Laboratory

Molnár A^1,2, Molnár M^1,3, Veres M², Czébely A², Rinyu L^2,3, Rozmanitz P⁴, Janovics R^2,3

¹University of Debrecen, Doctoral School of Physics, Debrecen, Hungary, ²Isotoptech Zrt., Debrecen, Hungary, ³INTERACT Centre, Institute for Nuclear Research, Debrecen, Hungary, ⁴Paks Nuclear Power Plant, Paks, Hungary

The ¹⁴C is the one of the most important radionuclides released from the nuclear facilities to the environment. Currently, the inorganic ¹⁴C is checked during regular environmental monitoring as part of the groundwater monitoring programme of the Paks Nuclear Power Plant.

One of disadvantages of the only inorganic carbon determination is that the DIC concentration has a significant dilution effect by the natural radiocarbon content of the groundwater on any discharged pollution surrounding the power plant.

For this reason, a wet oxidation method was developed for AMS ¹⁴C measurement technique to determine the ¹⁴C activity concentration of the total dissolved carbon content of water samples, coming from environmental monitoring wells. The typical ¹⁴C background is (1-2 pMC) obtained by preparation of blank samples, which allows a detection level of around 5·10-5 Bq L-1. The activity of the organic fraction can be calculated using the formula presented in the study. The method was applied for water samples deriving from environmental monitoring wells around Paks Nuclear Power Plant (pressurized-water reactors (PWR)). The results of our investigations over the 14 different water samples around the Paks NPP show that DO¹⁴C contribution to the total ¹⁴C activity concentration was between 5-25%.

The elaborated method may be useful mostly upon the environmental monitoring analyses of nuclear facilities and radioactive waste disposal facilities, as with the help of this method, the total radiocarbon activity of groundwater can be determined as easily, as the commonly applied DI¹⁴C analyses.

T03_P13

Radiocarbon dating putative homonin coprolites

Roberts M¹, Trowbridge N¹, Lardie Gaylord¹, Sistiaga A^2,3, Haws J⁴, Mojarro A³, Summons R³

¹Woods Hole Oceanographic Institution, Woods Hole, United States of America, ²Center for Evolutionary Hologenomics, University of Copenhagen, Copenhagen, Denmark, ³Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, United States of America, ⁴Dept. of Anthropology, University of Louisville, Louisville, United States of America

Several coprolites from a homonin habitation site on the Iberian Peninsula were recently submitted for radiocarbon analysis. Coprolites are proxies of the presence and diet of ancient animal populations. Based on chronostratigraphy, an average age of at least 40 kyr BC was expected. Bulk analysis of the organic fraction of the individual coprolites returned an average calibrated age of 28,000 (+/- 1000) (calBC). To better understand the conflict between the expected and measured ages, and to accommodate the very low total organic carbon of the samples, the organic fraction of a composite coprolite sample was further analyzed using the ramped pyrolysis and oxidation (RPO) system at Woods Hole. The sample was sequentially oxidized from room temperature to 1000 C at 5 °C/min and the evolved carbon dioxide was collected from five different temperature ranges or fractions. The first four temperature fractions returned calibrated ages all less than 31,000 (calBC). However, the highest temperature fraction (525-705 ˚C) returned a calibrated age of 39,900 (+/- 8,800) (calBC) in agreement with the chronostratigraphy. Analysis of the fractions using pyrolysis-GC-MS showed that only the high temperature faction released steroid biomarkers consistent with fecal matter. Phytosterols were detected in addition to trace amounts of coprostanol. Furthermore, a high temperature fraction between 525-600 ˚C pyrolyzed in the presence of a silylating reagent (MTBSTFA/DMF) enabled the identification of cholesterol and cholestanol. Utilizing the RPO system for coprolite radiocarbon analysis may provide a more representative age than bulk organic analysis. Sample preparation and measurement procedures will be presented.

T03_P14

Palynological samples in marine cores: pollen extraction, dating, comparison with foraminiferal shells: a methodological challenge to investigate past reservoir ages

Tisnerat-laborde N¹, Coussin V², Thil F¹, Combrieu-Nebout N³, Fersi W², Eynaud F⁴, Toucanne S⁵, Babonneau N², Cattaneo A⁵, Penaud A²

¹LSCE/IPSL , Gif-sur-Yvette, France, ²LGO Univ Brest IUEM, Plouzané, France, ³HNHP/CNRS-MNHN-UPVD, Paris, France, ⁴EPOC-OASU, Univ.Bordeaux, Pessac, France, ⁵IFREMER, Geosciences Marines, Plouzané, France

The reconstruction of changes in marine reservoir age is a particularly challenging task but essential in paleo-oceanography to improve the chrono-stratigraphy of marine cores. In this work we have investigated the possibility of using continental material as monospecific pollen grains (Pinus) as well as palynological treatment residues (bulk or additionally treated with KOH to dissolve amorphous organic matter) and foraminifera collected in the same levels to study reservoir age variations over time (INSU EC2CO-LEFE project “DATAPOL”).

In a first step, we describe the methodology developed to extract pollen grains on cores MD04-2801 (Algerian Margin, Holocene) and MD13-3438 (northern Bay of Biscay, Heinrich Stadial 1) and the physico-chemical treatments of pollen carried out before ECHoMICADAS dating. The ¹⁴C results obtained between foraminifera, pollen, and palynological residues are here presented for the first time, highlighting a great variability of ages according to the nature of dated samples (organic matter vs. calcite). These first results raise questions about the effects reservoir ages of bottom water masses and potential diagenetic impacts on palynomorph membranes during organic matter fossilization. We also preliminary show that the use of palynological residues cannot be used to date marine cores. However, new methodological investigation is necessary to find solutions to sort pollen more efficiently to advance the ¹⁴C dating of monospecific pollen samples.

T03_P15

Radiocarbon based fossil component analysis of food products

Varga T¹, Molnár M¹

¹ELKH - Institute for Nuclear Research - INTERACT, Debrecen, Hungary

The accelerator mass spectrometry and radiocarbon based bio and fossil component ratio analysis is widely used for plastic and fuel materials, but it is not frequently used for food products. Several materials, what are generally used in the food industry, can contain fossil carbon like the food coloring, flavouring and sweetener materials, due to the cost effective production. In general, the molecular composition of these materials are the same compared to the biol-based ones. In this case, the radiocarbon based analysis is one of the best way to distinguish the biological and fossil sources in these products. In this study, we present our ¹⁴C based fossil component analysis results on commercial food products and raw materials. The results show that several food and drink can contain more than a few percent fossil carbon, but generally, most of the food products are 100 % bio-based. The highest fossil component ratio was determined in the food coloring materials.

T03_P16

Inorganic radiocarbon dating of a moraine profile – a case study in a LGM moraine in Tianshan Mountains

Yi C^1,4, Liu X², Liu K³, Yi R^1,3

¹Beijing Niandai(dating) Company, Beijing, China, ²Institute of Heavey Ion Physics, Peking University, Beijing, China, ³Zhijiudiance (Nuclide-electron dating) company at Suzhou, Suzhou, China, ⁴Institute of Tibetan Plateau Research, Chine Academy of Sciences, Beijing, China

Organic matter in glacial moraines in humid areas is used to date the burial ages of glaciations using radiocarbon. However, biomass is rare in glacial sediments in arid and semi-arid areas. Our results show that a moraine in the source area of the Urumqi River valley, Tianshan Mountains was dated to 20790+-140 yr cal using carbonate in fine, very similar to ¹⁰Be exposure dating age. The ages of the upper part of the profile were younger than the middle part and then younger than the lower part. The ages in coarse size fraction (250-125 μm) were younger than medium size fraction (125-63 μm) and then younger than fine size fraction (< 63μm). The carbonate deposits on a roche moutonnee in front of Glacier 1 and in the matrix of a modern till were dated to modern carbon. We suggest that inorganic carbon decomposed from calcium minerals dissolving in subglacial meltwater was exchanged sufficiently with atmospheric carbon. When a glacier melted, pressure in sediment decreased and carbonate precipitated on the surface of the particles. Vertical movement of ground water dominates in arid and semi-arid areas. The carbon in the upper part of the sediment was most likely exchanged with atmospheric carbon after post deposition. The fraction with large grain size has large voids which were easily let water pass through for carbon exchange and ¹⁴C age become younger. At a depth, exchange of carbon in fine matrix with atmosphere was weak and ¹⁴C can be used for dating glacial moraine.