Time series of annual Δ14C and δ13C in tree rings of Sequoiadendron giganteum, AD 998–1510, are similar in form. The Δ14C series completes, with data of Stuiver and Braziunas (1993), a 957-yr time-series. Discrete Fourier transformation of detrended Δ14C reveals periods of 126, 91, 56, 17.6, 13.6, 10.4, and 7.1 yr. Non-random differences exist between decadal averages of the Sequoiadendron Δ14C data and data of Stuiver and Becker (1993). Periods of 7–17 yr may correspond to Schwabe or related climatic cycles; these have 10–17-yr periods and amplitudes < 6‰ (AD 1100–1250), and periods near 7 yr with amplitudes up to 10‰ (AD 1380–1420). Abrupt increases in Δ14C are mainly less than 5‰, and do not constitute convincing evidence of increased 14C production from supernovae or solar proton events. The δ13C time-series is likely to reflect climate change, and for centennial periodicity lags behind Δ14C by 20–40 yr (centennial time-scale) and 25–50 yr (millennial). Phase-shifts between solar luminosity and surface Δ14C are 125–175 yr and 20 yr for millennial and centennial cycles, respectively. The study suggests that strongest climate effects may therefore follow peak luminosity by 125–175 yr for millennial cycles and 20–40 yr for centennial cycles.

This paper presents radiocarbon (14C) variations in the atmosphere from Ramnicu Valcea, Romania. The samples were collected in the vicinity of the Experimental Pilot Plant for Tritium and Deuterium Separation (PESTD) from the Institute of the Cryogenics and Isotopic Technologies (ICSI) placed about 10 km south from the Ramnicu Valcea city (Romania), in the Govora industrial area. This facility is an experimental project in the national nuclear energy research program, which has the aim of developing technologies for tritium separation from heavy water. It should be noted that in the Govora industrial area operates a 315 MW coal-fired thermoelectric power plant and two chemical plants. In order to determine radiocarbon activity in the atmosphere, samples were collected monthly by absorption of CO2 into sodium hydroxide (NaOH) at Ramnicu Valcea. In addition, control materials (tree leaves, wild vegetation, and grapes), known activity standards, and process blanks (marble) were analyzed. Radiocarbon measurements were performed using the direct absorption method and liquid scintillation counting. The measured Δ14C levels varied between –57‰ and 61‰. The results have a decreasing trend, but due to local influence caused by the continuous production of fossil CO2, we cannot observe Δ14C seasonal variations.

In this study, we examined how land use and urbanization changes in adjacent areas affected biological productivity and carbon cycling in a lake ecosystem over 100 years and how these changes are reflected in carbon isotope variations. We performed radiocarbon (14C) activity and stable carbon isotope ratio analysis in two organic fractions: humin and humic acids of lake sediment. Additionally, we performed pigment and diatom analysis and determined the carbonate and organic matter (OM) content in sediments. Over the last century, the estimated 14C reservoir age in both sediment organic fractions varied from 1136 ± 112 yr to 5733 ± 122 yr. The increase in the reservoir age by 1175 ± 111 yr was related with higher inputs of pre-aged organic carbon and 14C depleted hard water due to the opening of the channel connecting two lakes. Nuclear weapons tests caused an increase in the reservoir age of up to 5421 ± 135 yr and 5733 ± 122 yr in humin and humic acids, respectively. 13C values in the humic acid fraction showed a tendency to decrease, depending on the content of autochthonous versus allochthonous OM in sediments, while changes in the sources of OM had a minor impact on the stable carbon isotope composition in the humin fraction.

The question under discussion is whether the dates of the Late Bronze (LBIIB)-LBIII (Iron IA) transitions in three sites in the southern Levant, namely Megiddo, Tell es-Safi/Gath and Qubur el-Walaydah occur at the same time, as has been proposed by Israel Finkelstein in his article in 2016 in Egypt and Levant. Here we respond to Finkelstein’s comments. We add some new data, clarify the issues that were raised, and conclude that the Late Bronze (LBIIB)-LBIII (Iron IA) transitions occurred at different times in northern and southern Israel.

In order to radiocarbon (14C) date a building, several components of the mortar could be used, such as the mortar binder, the lime lumps, the charcoal particles and shell fragments eventually present among the aggregates. In particular, the mortar binder requires a purification treatment in order to separate it from other sources of carbon, which could change the 14C signature of the binder invalidating the dating process. Here, we present the application of the Cryo2Sonic method to 14C dating of the ancient building structures unearthed during excavation at the Padua Cathedral complex. The dated samples were pretreated by using Cryo2Sonic method and the improved Cryo2Sonic version 2.0, recently developed by introducing additional steps such as centrifugation of the mortar suspension and gravimetric sedimentation of the binder fractions. The Cryo2Sonic version 2.0 relies heavily on the characterization of the mortar and of the purified binder fractions, allowing the isolation of a reliable 14C datable mortar fraction. Through this new method, the 14C dating of different ancient structures excavated next to the Padua Cathedral allow to identify the first religious complex of the city of Padua (3rd–4th centuries AD).

Areas affected by routine radiocarbon (14C) discharges from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) and accidental releases in March 2011 were investigated by analysis of cores from Japanese cypress and cedar trees growing at sites 9 and 24 km northwest of the plant. 14C concentrations in tree rings from 2008–2014 (before and after the accident) were determined by accelerator mass spectrometry, with 14C activities in the range 231–256 Bq kg−1 C. Activities during the period 2012–2014, after FDNPP shutdown, represent background levels, while the significantly higher levels recorded during 2008–2010, before the accident, indicate uptake of 14C from routine FDNPP operations. The mean excess 14C activity for the pre-accident period at the sites 9 and 24 km northwest of the plant were 21 and 12 Bq kg−1 C, respectively, indicating that the area of influence during routine FDNPP operations extended at least 24 km northwest. The mean excess tree-ring 14C activities in 2011 were 10 and 5.8 Bq kg−1 C at 9 and 24 km northwest, respectively, documenting possible impact of the FDNPP accident on 14C levels in trees.

In practice, obtaining radiocarbon (14C) composition of organic matter (OM) in sediments requires first removing inorganic carbon (IC) by acid-treatment. Two common treatments are acid rinsing and fumigation. Resulting 14C content obtained by different methods can differ, but underlying causes of these differences remain elusive. To assess the influence of different acid-treatments on 14C content of sedimentary OM, we examine the variability in 14C content for a range of marine and river sediments. By comparing results for unacidified and acidified sediments [HCl rinsing (RinseHCl) and HCl fumigation (FumeHCl)], we demonstrate that the two acid-treatments can affect 14C content differentially. Our findings suggest that, for low-carbonate samples, RinseHCl affects the Fm values due to loss of young labile organic carbon (OC). FumeHCl makes the Fm values for labile OC decrease, leaving the residual OC older. High-carbonate samples can lose relatively old organic components during RinseHCl, causing the Fm values of remaining OC to increase. FumeHCl can remove thermally labile, usually young, OC and reduce the Fm values. We suggest three factors should be taken into account when using acid to remove carbonate from sediments: IC abundance, proportions of labile and refractory OC, and environmental matrix.

Alpine glaciers are valuable archives for the reconstruction of human impact on the environment. Besides dating purposes, measurement of radiocarbon (14C) content provides a powerful tool for long-term source apportionment studies on the carbonaceous aerosols incorporated in ice cores. In this work, we present an extraction system for 14C analyses of dissolved organic carbon (DOC) in ice cores. The setup can process ice samples of up to 350 g mass and offers ultra-clean working conditions for all extraction steps. A photo-oxidation method is applied by means of external UV irradiation of the sample. For an irradiation time of 30 min with catalyzation by addition of Fe2+ and H2O2, we achieve an efficiency of 96 ± 6% on average. Inert gas working conditions and stringent decontamination procedures enable a low overall blank of 1.9 ± 1.6 μg C with a F14C value of 0.68 ± 0.13. This makes it possible to analyze the DOC in ice samples with a carbon content of as low as 25 μg C kg−1 ice. For a first validation, the new method was applied to ice core samples from the Swiss Alps. The average DOC concentration and F14C values for the Fiescherhorn ice core samples show good agreement with previously reported data for the investigated period of 1925–1936 AD.

The radiocarbon (14C) content of simultaneously deposited substrates in lacustrine archives may differ due to reservoir and detrital effects, complicating the development of age models and interpretation of proxy records. Multi-substrate 14C studies quantifying these effects remain rare, however, particularly for large, terminal lake systems, which are excellent recorders of regional hydroclimate change. We report 14C ages of carbonates, brine shrimp cysts, algal mat biomass, total organic carbon (TOC), terrestrial macrofossils, and n-alkane biomarkers from Holocene sediments of the Great Salt Lake (GSL), Utah. 14C ages for co-deposited aquatic organic substrates are generally consistent, with small offsets that may reflect variable terrestrial organic matter inputs to the system. Carbonates and long-chain n-alkanes derived from vascular plants, however, are ∼1000–4000 14C years older than other substrates, reflecting deposition of pre-aged detrital materials. All lacustrine substrates are 14C-depleted compared to terrestrial macrofossils, suggesting that the reservoir age of the GSL was > 1200 years throughout most of the Holocene, far greater than the modern reservoir age of the lake (∼300 years). These results suggest good potential for multi-substrate paleoenvironmental reconstruction from Holocene GSL sediments but point to limitations including reservoir-induced uncertainty in 14C chronologies and attenuation and time-shifting of some proxy signals due to detrital effects.

The development of chronologies relies on integrating information from a number of different sources. In addition to direct dating evidence, such as radiocarbon dates, researchers will have contextual information which might be an environmental sequence or the context in an archaeological site. This information can be combined through Bayesian or other types of age-model. Once a chronology has been developed, this information can be used to estimate, for example, chronological uncertainties, rates of change, or the age of material which has not been directly dated.

Dealing with the information associated with chronology building is complicated and re-evaluation of chronologies often requires structured information which is hard to access. Although there are many databases with primary dating information, these often do not contain all of the information needed for a chronology. The Chronological Query Language (CQL) developed for OxCal was intended to be a convenient way of pulling such information together for Bayesian analysis. However, even this does not include much of the associated information required for reusing data in other analyses.

The IntChron initiative builds on the framework set up for the INTIMATE (Integrating Ice core, Marine and Terrestrial Records) chronological database (Bronk Ramsey et al. 2014) and is primarily an information exchange format and data visualization tool which enables users to pull together the types of information needed for chronological analysis. It is intended for use with multiple dating methodologies and while it will be integrated with OxCal, is intended to be an open format suitable for use with other software tools. The file format is JSON which is easily readable in software such as R, Python and MatLab. IntChron is not primarily intended to be a data depository but rather an index of sites where information is stored in the relevant format. As an initial step, databases of radiocarbon dates from the Oxford Radiocarbon Accelerator Unit (including those for the NERC radiocarbon facility), the RESET tephra database, the INTIMATE chronological database and regional radiocarbon databases for Egypt and Southern Africa are all linked. The intention is that users of OxCal will also be able to make published data accessible to others and to store working data, visible only to the user, to be used with the associated analysis tools. The IntChron site allows data from third party sources to be accessed through a representational state transfer (REST) application programming interface (API) in a number of different formats (JSON, csv, txt, oxcal) and associated bibliographic information in BibTeX format.

The aim of the IntChron initiative is to make it easy for users to provide data (in the single JSON format with limited minimum requirements) as well as to access data and tools, while promoting robust chronologies including realistic estimates of uncertainties. It is hoped that this will help to bring the chronological research communities to a point where data access is as easy as it is in some other fields. This is particularly important for Early Career Researchers and for those seeking to use large datasets in novel ways.

The Late Bronze Age to Iron Age transition in the Levant includes the appearance of new material culture that is similar in styles to the Aegean world. In the southern Levant, the distribution of early styles of Aegean-like pottery, locally produced, is limited to the coastal areas of Canaan, making synchronization with the rest of the region difficult. Radiocarbon (14C) dating provides a high-resolution absolute chronological framework for synchronizing ceramic phases. Here, absolute 14C chronologies of the Late Bronze to Iron Age transition in the sites Tel Beth Shean, Tel Rehov, Tel Lachish, and Tel Miqne-Ekron are determined. Results show that the ranges of transitions vary in an absolute time frame by 50–100 years between different sites and that the range of the Late Bronze Age to Iron Age transition in Canaan spans the 13th–11th centuries BC plateau. These chronologies, based on a site-by-site approach for dating, show that the change between early types of Aegean-like pottery (Monochrome) to developed types (Bichrome), occurred over 100 years in Canaan and that the transition occurred in southern sites prior to sites in the north. These ranges show that not only is the Late Bronze to Iron Age not contemporaneous, but also synchronization between sites based on their ceramic assemblages is problematic.

Radiocarbon (14C) dating has previously been applied to modern paintings on canvas from the 20th century to identify potential modern forgeries, and dates indicate a time lag of several years between the harvesting of plant fibers for making canvas, and completion of a painting. This study investigated both the length of this time lag and the potential of 14C dating to inform about an individual artist’s mode of working (for example long-term storage or reuse of canvases, or extended reworking on a single canvas) and/or to establish a chronology for a corpus of work. Two pre-bomb and 16 post-bomb artworks by 17 mid-20th-century Scandinavian artists were 14C dated. The majority of post-bomb samples indicated a time lag of 2–5 years between the harvesting of the plants and completion of a painting, but some samples recorded lags of up to 10 years, and others produced much earlier results, potentially indicating the use of much older canvases or challenges removing contamination prior to dating. The importance of thorough pre-screening of canvas samples for both synthetic fibers and contaminants prior to dating, and selection of the most suitable calibration curve, are highlighted.

The radiocarbon (14C) chronology of hunter-fisher-gatherers’ archaeological settlements along the Brazilian coast is usually based on mollusk shells, charcoal from hearths, and eventually human bones. However, fish otoliths are found in several archaeological contexts and may represent a reliable option as a chronological record. In this work, we compare the 14C dates of whitemouth croakers (Micropogonias furnieri) otoliths with dates obtained from other materials (shell and charcoal), collected from shellmounds on the coast of Rio de Janeiro, with the aim of improving the accuracy in the 14C dating of Brazilian shellmounds, strengthening the comprehension of the native populations’ occupational trends and the coeval palaeoceanographic context. Based on x-ray diffraction results for archaeological otoliths, their geochemical composition indicates minimal diagenesis effect over time even under burial conditions in the studied sites. The comparison between otolith dates and dates obtained from other proxies revealed similar results but with decreased deviations in otolith dates in all of the studied sites.

The modern antiquities market uses radiocarbon (14C) dating to screen for forged objects. Although this fact shows the potential and power of the method, the circumstances where it is applied can be questionable and call for our attention. Here we present an outline of a call to radiocarbon laboratories for due diligence and best practice approaches to the analysis of antique objects requested by non-research clients.

Given the difficulty in obtaining robust chronologies from tree rings in tropical regions, the search for appropriate species is very important. Both dendrochronology and radiocarbon (14C) measurements are required to validate the use of any specific tree. Some species have proved to be reliable for representing atmospheric 14C concentration over time, such as Cedrela fissilis and Araucaria angustifolia. However, not only the species have to be validated, but also different climatic conditions may result in different growth patterns for the same species. In this work, we study the annual growth rings of Cedrela fissilis from a dry tropical forest patch typical of a highly seasonal climate in central Brazil. 14C accelerator mass spectrometry (AMS) was used to compare the isotopic ratios of tree rings with the 14C concentrations in the atmosphere during the nuclear tests based on curve Bomb13SH 1-2. Results are similar to the bomb peak curve within the period from 1958 to 1980 AD and serve as a crucial test for the cross-dating analyses using the skeleton plot technique.

When and where the process of state formation took place in the biblical kingdom of Judah is heavily debated. Our regional project in the southwestern part of Judah, carried out from 2007 to the present, includes the excavation of three Iron Age sites: Khirbet Qeiyafa, Tel Lachish, and Khirbet al-Ra’i. New cultural horizons and new fortification systems have been uncovered, and these discoveries have been dated by 59 radiometric determinations. The controversial question of when the kingdom was able to build a fortified city at Lachish, its foremost center after Jerusalem, is now resolved thanks to the excavation of a previously unknown city wall, dated by radiocarbon (14C) to the second half of the 10th century BCE.

Radiocarbon (14C) has become a unique and powerful tracer in source apportionment of atmospheric carbonaceous particles. In this study, the Asia Pacific Economic Cooperation summit (APEC) held in Beijing in 2014 was used as a demonstration to research the source apportionment of atmosphere PM2.5. We used a 200 kV single stage accelerator mass spectrometer recently completed at China Institute of Atomic Energy (CIAE). The PM2.5 samples related to above case were collected, and the characteristics of radiocarbon in organic carbon (OC) and elemental carbon (EC) in samples were analyzed using the AMS. The results show that the Before-APEC pollution emission mode is different from the During-APEC and After-APEC pollution emission modes. For Before-APEC, During-APEC and After-APEC, the average values of fossil carbon fraction of OC are 0.463, 0.431 and 0.615, respectively, and those of EC are 0.644, 0.561 and 0.687. The fossil source contributions of traffic activities using fossil fuels to OC and EC are 15.8 % and 21.9 %, respectively. The fossil source contributions of industrial activities to OC and EC are 38.0 % and 8.2 %, respectively. It is about 7–10 days that is needed to take to regenerate the PM2.5 pollution caused by human activities.

The half-life of radiocarbon (14C) is 5700 ± 30 yr, which makes it particularly useful for dating in archaeology. However, only an exceptional hindrance of the beta decay from 14C to 14N—a so-called Gamow-Teller ß-decay—makes this half-life so long. A normal strength would result in a half-life of only a few days, completely useless for archaeological dating. The unusual hindrance is based on the nuclear structure of the two nuclei, resulting in strongly destructive interferences of the nuclear transition matrix element. Nuclear model calculation with great computational efforts have been performed in the literature to reproduce the very low transition probability. Here, we will attempt to describe the nuclear physics behind this most unusual half-life.

Decommissioning of nuclear reactors requires determination of all remnant long-lived isotopes that were produced during their long functioning time of the respective facilities. Radiocarbon (14C) is such an isotope (T1/2 = 5730 yr), widely produced by neutron reactions in a thermal column of a nuclear reactor. Accelerator mass spectrometry (AMS) uses 14C for precise dating of up to 50,000 years old archaeological artifacts. This study presents a premier AMS measurement of high concentrated 14C samples that are strictly forbidden in laboratories dedicated to perform 14C dating. The determined 14C activities range from the natural level (isotopic ratio 14C/12C = 1.2 × 10–12) up to values of 10,000 times higher. 14C bulk and depth profile concentrations were measured in the thermal column disks of a decommissioned nuclear reactor. Results have shown that the 14C concentration in the thermal column, close the reactor core is about 75 kBq/g and decreases to 0.7 Bq/g and the end of the column. Such AMS measurements are applicable for decommissioning and waste management of nuclear reactors.