Constraining radiocarbon (14C) reservoir age offsets is critical to deriving accurate calendar-age chronologies from 14C dating of materials which did not draw carbon directly from the atmosphere. The application of 14C dating to such materials is severely limited in hydrologically sensitive environments like the Black Sea because of the difficulty to quantify reservoir age offsets, which can vary quickly and significantly through time, due to the dynamics of the biogeochemical cycling of carbon. Here we reconstruct 14C reservoir age offsets (Rshell-atm) of Holocene bivalve shells from the coastal Black Sea relatively to their contemporaneous atmosphere. We show that the 14C reservoir age offset and the stable carbon isotope composition of bivalve shells are linearly correlated in this region. From a biogeochemical standpoint, this suggests that inorganic stable carbon isotope and 14C compositions of Black Sea coastal waters are controlled by the balance between autochthonous primary productivity and heterotrophic respiration of allochthonous pre-aged terrestrial organic matter supplied by rivers. This provided an important implication for Black Sea geochronology as the reservoir age offset of 14C-dated bivalve shell can be inferred from its stable carbon isotope composition. Our results provide a fundamental and inexpensive geochemical tool which will considerably improve the accuracy of Holocene calendar age chronologies in the Black Sea.

Combined dendrochronology and accelerator mass spectrometry radiocarbon (AMS 14C) dating analyses were used in order to date an old living tree named Italus, growing in the Pollino massif in Southern Italy. Wiggle match AMS 14C dating analysis was performed on a 320-yr-long floating chronology obtained by cross-dating four wood cores extracted from the exposed roots of the tree. Following this approach, an age for the tree of ≈1230 yr was estimated. This age makes Italus the oldest living tree in Europe. High-resolution 14C dating analyses performed on single rings extracted from the tree stem allowed us to identify the 993–994 CE large excursion in atmospheric 14C concentration (Miyake event) revealing for the first time its presence in the Mediterranean basin.

Miyake et al. (2012, 2013, 2014) described a sudden increase of radiocarbon (14C) concentration in annual tree rings of Japanese cedar (Cryptomeria japonica) and Hinoki cypress (Chamaecyparis obtusa) between AD 774 and 775 and between AD 993 and 994. In both analyzed periods, the sudden increase was observed almost in a single year. The increase in the 14C content was about 12‰ in the period AD 774–775 (Miyake et al. 2012) and about 11.3‰ in the period AD 993–994 (Miyake et al. 2013, 2014; Fogtmann-Schultz et al. 2017; Rakowski et al. 2018). A similar increase was observed in 660 BC, with a peak height of about 10‰ (Park et al. 2017). Single-year samples of dendrochronologically dated tree rings of deciduous oak (Quercus robur) from Grabie, a village near Krakow (SE Poland), spanning the years 670–652 BC, were collected and their 14C content was measured using an AMS technique. The results clearly show a rapid increase in the 14C concentration in tree rings around 660 BC similar to this observed in Park et al. (2017).

Graphitization of 0.5–1.5 mg C, and of smaller samples to a lesser extent, is routinely done at our Facility by reduction over zinc. The method yields low background, good accuracy but offers a limited throughput, requires dedicated equipment and considerable operator time. Sealed-tube graphitization is faster, easier and cost-efficient producing as many graphites as CO2 can be purified in one day with low background, good accuracy and precision, provided precise measurements of δ13C values can be attained by accelerator mass spectrometry (AMS) to correct for isotope fractionation (Xu et al. 2007). We tested sealed-tube graphitization on 0.1 to 1.0 mg C samples and found that while we were able to obtain low backgrounds of >57,000 ±1000 yr BP for ∼1.7 mg C and 41,230 ± 430 yr BP for ∼0.09 mg C (0.0008 ± 0.0001 and 0.0059 ± 0.0003 Fraction Modern, respectively), results were variable for sample sizes <0.5 mg C. Measurements of FIRI Belfast Cellulose and TIRI Barleymash showed 0.3–0.6% precision and 1% accuracy for most sample sizes. We found better results in our laboratory by introducing the following modifications: (1) shorter inner tube (2 cm long), (2) short flame-seal length (∼7–8 cm) and (3) keeping the inner tube with iron separate from the outer tube containing zinc and titanium hydride during cleaning.

The emergence of separate cemeteries for disposal of the dead represents a profound shift in mortuary practice in the Late Neolithic of southeast Europe, with a new emphasis on the repeated use of a specific space distinct from, though still often close to, settlements. To help to time this shift more precisely, this paper presents 25 dates from 21 burials in the large cemetery at Cernica, in the Lower Danube valley in southern Romania, which are used to formally model the start, duration of use and end of the cemetery. A further six dates were obtained from four contexts for the nearby settlement. Careful consideration is given to the possibility of environmental and dietary offsets. The preferred model, without freshwater reservoir offsets, suggests that use of the Cernica cemetery probably began in 5355–5220 cal BC (95% probability) and ended in 5190–5080 cal BC (28% probability) or 5070–4940 (67% probability). The implications of this result are discussed, including with reference to other cemeteries of similar age in the region, the nature of social relations being projected through mortuary ritual, and the incorporation of older, Mesolithic, ways of doing things into Late Neolithic mortuary practice.

This study characterized cremated bone to better understand isotope exchanges during burial, using archeological samples. The cremated bones of Jokei, a Buddhist monk (AD 1155–1213), found in an urn from the Jisho-in Temple, Nara Prefecture, Japan, were used for the analysis. 14C dates were determined for eight of Jokei bone fragments of different colors (black, gray, and white). The white fragments had the highest x-ray diffractometry (XRD) crystallinity index (CI) values (0.89–1.05), Fourier-transform infrared spectroscopy (FTIR) splitting factor values (IRSF) of 5.3–7.1, and the lowest Ba concentrations. The calibrated date of the white bone fragments is 1152–1216 cal AD, consistent with Jokei’s lifespan, showing these fragments yield reliable 14C ages. Meanwhile, the black and gray fragments, which probably experienced lower temperatures during cremation, had lower CI and IRSF values of 0.25–0.46 and 4.2–4.9, respectively, and higher Ba concentrations. The black and gray fragments tended to show unreliable younger 14C dates and higher 87Sr/86Sr values close to the soil value due to soil contamination. The results in this study indicate that it is important to check crystallinity of apatite and soil contamination using chemical indexing methods such as Ba capture, to clarify the reliability of 14C dates for cremated bone samples.

We present a comparative study on a 700-yr sequence of dendrochronologically ordered tree-rings of Pinus cembra originating from Eastern Carpathians for the period AD 1009–1709. This period covers the solar minima of the Little Ice Age. The aim of this study was to assess the accuracy of our radiocarbon (14C) determinations interpreted on the IntCal13 calibration data and to observe any apparent offsets. The 14C measurements on single and double tree-rings were “wiggle-matched” to secure the dendrochronology cross-matching of all the Pinus cembra wood pieces. The results showed a very good agreement between the age datasets for four out of five wood trunks. However, for one of them a new cross-matching was performed after a quality assurance test, establishing an earlier 48-yr position, recommended by wiggle-matching Bayesian statistics and dendrochronological analysis. Following this adjustment, the quantification of the 14C level variability with respect to the IntCal13 calibration curve was obtained by calculating Δ14C for all tree-ring samples. As a final conclusion, an insignificant 14C concentration offset of –0.63 ± 3.76‰ was found for the Romanian samples.

Applying radiocarbon (14C) dating using accelerator mass spectrometry (AMS) to the skeleton of a mammoth and the associated plant remains have been dated. The fossil of Zhalai Nur mammoth was dated to 43,500 +1000/–900 14C yr BP. The results of optically stimulated luminescence (OSL) dating, which show that a fluvially deposited gravel layer, from that the mammoth fossils were excavated, formed between 51,300±2100 and 26,600±1200 yr BP, place the new AMS 14C dates in a well-developed chronological framework. Through this study, it can be summarized that, firstly, using suitable sample material, it is possible to obtain reliable AMS 14C results, even when the ages of the target materials approach the upper limits of the method. Second, it reveals that a depositional hiatus exists during the Late Pleistocene, between ca. 26,000 yr BP and ca. 13,000 yr BP. Finally, large rivers and widely distributed areas of alluvial-fluvial deposits existed in this present-day desert area between ca. 51,000 and 26,000 yr BP. These results may shed new light on the study of the Mammuthus-Colelodonta-Bubalus fauna, the most important and fully developed fauna during the Late Pleistocene in northeastern China. They also deepen our understanding about the eco-environments of the region.

Documenting leads and lags in terrestrial records of past climate change is critical to understanding the behavior of Earth’s natural climate system and making reliable predictions of future climate conditions. However, uncertainties of several hundred years in age models make it difficult to distinguish synchronicity and feedbacks in paleo archives. In lakes this is often due to the lack of terrestrial macrofossils in climate-sensitive locations, such as high alpine or dryland settings. The potential of radiocarbon (14C) dating of pollen has long been recognized, but the difficulty of cleanly separating pollen from other kinds of organic carbon has limited its usefulness. Here we report 14C ages on pollen separated by flow cytometry, from a set of closely spaced samples from Mono Lake, California. The accuracy of the pollen ages is tested using well-dated bracketing tephras, the South Mono and North Mono-Inyo tephras. In spite of the purity of the sorted samples, the pollen dates are older than the bounding tephras by ~400 yr, similar to some other pollen-dating studies. While improvements in sample preparation protocols are planned, understanding the geological processes involved in the production, preservation, and deposition of pollen at each site will be critical to developing robust high-resolution age models.

The CO2 absorption and liquid scintillation counting (LSC) are methods used in radioactivity monitoring programs of nuclear facilities for 14C measurements due to high number of samples and relatively high expected level of 14C concentration. The paper describes the chemical sample preparation applied to a quality control material (IAEA-C3 Cellulose), in order to evaluate the reproducibility of CO2 absorption method for this type of material. Consequently, in the experiments we used two home-made scintillation cocktails, containing two amines, 2-methoxyethylamine (MEA) and 3-methoxypropyl amine (MPA), which detained CO2 as carbamates. Due to the fact that the material used in the dedicated experiments is cellulose (contained in all vegetable materials), the method can be considered as appropriate for 14C determination from biological and vegetable materials.

Lead carbonates were used as cosmetic and pigment since Antiquity. The pigment, known as lead white, was generally composed of cerussite and hydrocerussite. Unlike most ancient pigments, lead white was obtained by a synthetic route involving metallic lead, vinegar and organic matter. Fermentation of organic matter produces heat and CO2 emission, leading to the formation of carbonates. As lead white is formed by trapping CO2, radiocarbon (14C) dating can thus be considered. We have developed a protocol to prepare lead white. We selected modern pigments for the experiment implementation and ancient cosmetic and paintings for dating. After characterization of the samples by XRD, thermal decomposition of cerussite at various temperatures was explored in order to select the appropriate conditions for painting samples. CO2 extraction yield, SEM and XPS were used to characterize the process. Thermal decomposition at 400°C was successfully applied to mixtures of lead white with other paint components (oil as binder, calcite as filler/extender) and to historical samples. We obtained radiocarbon measurements in agreement with the expected dates, demonstrating that thermal decomposition at 400°C is efficient for a selective decomposition of lead white and that paintings can be directly 14C-dated by dating lead white pigment.

Although radiocarbon (14C) dating is commonly used for archeological music instruments, little research has been conducted on modern instruments (16th–19th centuries). New technology, based on the Mini Carbon Dating System (MICADAS), enables some of the recurring challenges (e.g. sampling size) to be circumvented and paves the way for a new field of investigation. We here address the Indian instrumentarium, about which very little is known. We investigate the making and the restoration phases of two vina, a kinnari vina (E.1444), and a rudra vina or bin (E.997.24.1). By comparing 14C measurements made on several samplings of elements of the instruments with museological information, we were able to specify a unique calibrated interval of ages [1666 AD–1690 AD] for the kinnari vina, with a restoration phase [1678 AD–1766 AD] for the upper nut. The bin is likely attributed to the [1650 AD–1683 AD] interval.

We present a new low-cost, high-throughput method for converting many types of organic carbon samples into graphite for radiocarbon (14C) measurements by accelerator mass spectrometry (AMS). The method combines sample combustion and reduction to graphite into a single procedure. In the Single Step method, solid samples are placed directly into Pyrex containing zinc, titanium hydride and iron catalyst. The tube is evacuated, flame sealed, and placed in a muffle furnace for 7 hr. A variety of organic samples have been tested including oxalic acid, sucrose, wood, peat, collagen, humic acid, and contamination swipe samples. The method significantly reduces the time required to produce a graphite sample for 14C measurement, with analytical precision and accuracy approaching that of traditional two-step combustion and hydrogen reduction methods. The details and applicability of the method are presented.

Surface radiocarbon (Δ14C) in the North Pacific has been monitored using a commercial volunteer observation ship since the early 2000s. Here we report the temporal and spatial variations in Δ14C in the summer surface water when the surface ocean is vertically stratified over a 13-yr period, 2004–2016. The long-term Δ14C decreasing trend after the late 1970s in the subtropical region has continued to the present and the rate of decrease of the Kuroshio and Kuroshio Extension, North Pacific and California current areas is calculated to be –3.3, –5.2 and –3.3 ‰/yr, respectively. After 2012 the Δ14C of the Kuroshio and Kuroshio Extension area, however, has remained at an approximately constant value of around 50‰. The result may indicate that subtropical surface Δ14C in the western North Pacific has reached an equilibrium with atmospheric Δ14CO2. The Δ14C in the subarctic region is markedly lower than values in the subtropical region and it seems that the decreasing tendency of surface Δ14C has changed to an increasing tendency after 2010. The results may indicate that bomb-produced 14C, which has accumulated below the mixed layer in the past few decades, has been entrained into the surface layer by deep convection.

Radiocarbon (14C) analysis of carbon dioxide (CO2) provides unique information on the age, turnover and source of this important greenhouse gas, raising the prospect of novel scientific investigations into a range of natural and anthropogenic processes. To achieve these measurements, cartridges containing zeolite molecular sieves are a reliable and convenient method for collecting CO2 samples. At the NERC Radiocarbon Facility (East Kilbride) we have been refining our molecular sieve methods for over twenty years to achieve high-quality, reproducible and precise measurements. At the same time, we have been developing novel field sampling methods to expand the possibilities in collecting gas from the atmosphere, soil respiration and aquatic environments. Here, we present our latest improvements to cartridge design and procedures. We provide the results of tests used to verify the methods using known 14C content standards, demonstrating reliability for sample volumes of 3 mL CO2 (STP; 1.6 mg C) collected in cartridges that had been prepared at least three months earlier. We also report the results of quality assurance standards processed over the last two years, with results for 22 out of 23 international 14C standards being within measurement uncertainty of consensus values. We describe our latest automated procedures for the preparation of cartridges prior to use.

In this paper, we present the first data from an alternative extraction method for atmospheric 14CO2 analysis, based on the direct trapping of whole air samples onto a molecular sieve zeolite (13X) trap, incorporated into a commercially available automated graphitization system. Results are presented for both inter-laboratory comparison samples and an in-house reference standard. The in-house reference was used to calculate the standard deviation of measurements (2.0‰). This newly developed method will facilitate faster sample processing and therefore lower cost per analysis, critical for scaling up such studies.