Radiocarbon dates on charred plant remains are often used to define the chronology of archives such as lake cores and fluvial sequences. However, charcoal is often older than its depositional context because old-wood can be burnt and a range of transport and storage stages exist between the woodland and stream or lake bed (“inherited age”). In 1978, Blong and Gillespie dated four size fractions of charcoal found floating or saltating in the Macdonald River, Australia. They found larger fragments gave younger age estimates, raising the possibility that taphonomic modifications could help identify the youngest fragments. In 1978 each date required 1000s charcoal fragments. This study returns to a sample from the Macdonald River to date individual charcoal fragments and finds the inherited age may be more than 1700 years (mode 250 years) older than the collection date. Taphonomic factors, e.g., size, shape or fungal infestation cannot identify the youngest fragments. Only two fragments on short-lived materials correctly estimated the date of collection. In SE Australia, this study suggests that wood charcoal will overestimate the age of deposition, taphonomic modifications cannot be used to identify which are youngest, and multiple short-lived materials are required to accurately estimate the deposition age.

Accelerator mass spectrometry (AMS) radiocarbon (14C) dating is central to the development of robust chronologies in archaeological and paleoenvironmental contexts spanning the last 50,000 years. For dates to be accurate, samples must be free of exogenous carbon contamination. At the Oxford Radiocarbon Accelerator Unit (ORAU), considerable advancements in the dating of bone collagen have been made through the development of a high performance liquid chromatography (HPLC) method for the dating of the amino acid hydroxyproline, which can mitigate the effects of carbon contamination. However, recent changes in ligand manufacturing methods for the mixed-mode column used in the ORAU protocol (Primesep A, SIELC Technologies; IL, USA) have resulted in unacceptably high analytical backgrounds. Prior to the manufacturing change, backgrounds of > 50k BP were achievable. Since the manufacturing change, a mean background of 32.5k BP has been measured. Due to column bleed, the Primesep A is therefore no longer suitable for 14C measurement of hydroxyproline from older material. Here, we present background data and the chromatography conditions used to isolate hydroxyproline using an alternative column, a preparative-scale Newcrom AH, which shows promising potential as an alternative for the routine isolation and AMS dating of hydroxyproline—especially approaching the age and mass limits of the method.

We present case studies on three objects of high importance for cultural heritage in southern Poland, dated in years 2018–2022 at the Gliwice 14C and Mass Spectrometry Laboratory with radiocarbon (14C) and dendrochronology methods. The first was a richly ornamented wooden cane, discovered during excavations on the market in Bytom city. The cane can be associated with medieval court proceedings. The archaeological context indicates the 13th century AD, and the 14C result corresponds perfectly with this time, confirming that it is the oldest object of this type in Poland. The second was a 4-m-tall oak column from St. Leonard Church in Lipnica Murowana, a UNESCO heritage site. The local story said it was previously devoted to Światowid, a pagan deity. Our analysis excluded the pre-Christian age, as the tree was felled no earlier than the late 15th century, which is in agreement with historical records. The third was a wooden Saint Lawrence Church in Bobrowniki. The presbytery was covered with up to five layers of polychromic paintings, some of high artistic value. We dated three samples from the original wooden board, and by wiggle-matching, the calibrated age interval was narrowed to 1731–1754 cal AD.

The Early Iron Age hillfort in Chotyniec (SE Poland) is the westernmost permanent settlement of the Scythian cultural circle. Recognizing the construction of the fortified settlement’s ramparts and their chronology was considered one of the priorities of the systematic research conducted since 2016. Based on 18 radiocarbon dated samples from different parts of the rampart, a chronological model of its functioning was made. It indicates that the construction of this monumental fortifications protecting the settlement in Chotyniec should be dated to between 651–595 or 531–409 BC. This dating synchronizes well with the chronology of the most important ritual and ceremonial object within the Chotyniec settlement—the so-called zolnik and other Scythian settlements from the East European forest-steppe zone.

We present atmospheric radiocarbon concentrations in CO2 integrated samples taken between January 2019 and December 2021 in the Mexico City Metropolitan Area (MCMA) and explain the variations in terms of changes in emission sources associated with the COVID-19 lockdown restrictions imposed from March 2020. Δ14C values for samples collected during 2019 range between –44.15‰ and –13.17‰, with lower values during months with higher fossil fuels consumption and air stagnation, whereas higher values were found for periods with high number of fires around MCMA or wet months with higher contribution of heterotrophic respiration. For samples collected during 2020, Δ14C values range between –17.7‰ and 2.25‰, with an increasing trend immediately after the initial lockdown and higher values obtained for samples collected during lockdown phases 2 and 3 and the period of extremely high epidemic risk. This agrees with the 38% and 52% decrease in gasoline and diesel sales. Once essential activities gradually opened from July 2020, Δ14C follow a decreasing trend as vehicle traffic started to increase again. Δ14C values for samples collected during 2021 range from –32.89‰ to –10.27‰, with the higher value obtained during a period of extremely high epidemic risk with a 30% reduction in gasoline and diesel consumption. Despite the complexity of emission sources in MCMA, from Δ14C variations it was possible to identify changes in fossil CO2 emissions resulting from the significant reduction in vehicle traffic due to the COVID-19 lockdown and the restrictions imposed to control transmission of the disease.

A summary of the chronology for the key paleontological and archaeological site of Volchia Griva in the southern part of the West Siberian Plain is presented. Currently, 42 reliable 14C values have been generated on animal bones (37 14C dates) and charcoal (5 14C dates). Three stratigraphic levels of animal bones are established. The 14C ages of the fossils are as follows: the upper level—ca. 10,620–12,520 BP; the middle level—ca. 13,700–17,800 BP; and the lower level—ca. 18,230–19,790 BP. The majority of animal fossils and artifacts are associated with the lower level. Based on the results obtained, we suggest that Upper Paleolithic people occupied the Volchia Griva site during the second part of the Last Glacial Maximum (LGM), ca. 18,200–19,800 BP, and perhaps occasionally afterwards. It is obvious that these humans were well adapted to the cold and dry climate of the LGM, as well as numerous other populations in Siberia south of 58°N. It is noteworthy that the youngest 14C values on woolly mammoth are of ca. 10,620–11,815 BP, and this makes the Volchia Griva one of the latest mammoth refugia in northern Eurasia outside of the Arctic.

The rich architectural heritage of Cyprus from the period of Byzantine and Latin rule includes 10 churches inscribed in the UNESCO World Heritage list. Most of these monuments preserve wooden elements: whether structural, decorative or furnishings. Many preserve wall paintings that are considered among the best examples of Byzantine and Medieval art in the Eastern Mediterranean. The dating of these paintings as well as the church buildings themselves, has been based mainly on style, with occasional dedicatory inscriptions and related historical interpretation. We report early results from a project investigating the wooden cultural heritage of Cyprus and in particular the combined use of dendrochronology with radiocarbon via tree-ring sequenced 14C wiggle-matching to help place initial tree-ring sequences. This includes a floating 264-year Pinus brutia chronology from several monuments, which, with a ca. 5-year gap, suggests prospects for >700-years of P. brutia chronology for Cyprus, and, with one gap of several decades to fill, ca. 1100 years of Pinus nigra chronology for Cyprus. Several currently floating elements from the multi-phase UNESCO-listed Timios Stravros church at Pelendri, including a terminus post quem for the celebrated liturgical wooden cross, are approximately dated across the 11th to 16th centuries AD.

Microbial processing of soil organic matter is a significant driver of C cycling, yet we lack an understanding of what shapes the turnover of this large terrestrial pool. In part, this is due to limited options for accurately identifying the source of C assimilated by microbial communities. Laboratory incubations are the most common method for this; however, they can introduce artifacts due to sample disruption and processing and can take months to produce sufficient CO2 for analysis. We present a biomass extraction method which allows for the direct 14C analysis of microbial biomolecules and compare the results to laboratory incubations. In the upper 50 cm soil depths, the Δ14C from incubations was indistinguishable from that of extracted microbial biomass. Below 50 cm, the Δ14C of the biomass was more depleted than that of the incubations, either due to the stimulation of labile C decomposition in the incubations, the inclusion of biomolecules from non-living cells in the biomass extractions, or differences in C used for assimilation versus respiration. Our results suggest that measurement of Δ14C of microbial biomass extracts can be a useful alternative to soil incubations.

In-situ cosmogenic 10Be (and 26Al) concentrations in alluvial sediments provide a spatially averaged signal of the erosion rate of the catchment area. Catchmentwide erosion rates reflect the production rate of the entire basin, and their calculation requires knowledge of the complete production rate model. Available calculators determine production rates on a pixel-based approach and achieve computational efficiency by relying on a scaling method that ignores geomagnetic field strength variations. Here we introduce a new python-based tool that determines erosion rates based on the hypsometry of the catchment. The method relies on the fact that production rates are much more sensitive to changes in elevation than latitude. Our tool has two main advantages: (1) computation time is short (<30 seconds) and independent of the scaling method; there is no need to neglect magnetic field variations, and (2) because production rate scaling is performed by a widely used online calculator, the results are fully comparable to exposure ages or point-based erosion rates determined with the same calculator; future updates to production rate scaling are immediately effective for catchmentwide erosion rate calculation. We demonstrate in two case studies that (1) for similar scaling methods, our calculator reproduces pixel-based results within a few percent, and (2) erosion rates determined with different scaling methods may differ by >20%, differences can vary systematically with erosion rate, and using a time-constant scaling method may result in a bias in the interpretation of catchmentwide erosion rates.

A newly developed compact AMS, LEA (Low Energy Accelerator), is tested and compared with a state-of-the-art AMS system MICADAS (Mini Carbon Dating System), which has a precision performance of better than 1‰ for modern 14C. The main difference between these two systems is the acceleration voltage, which has been reduced from 200 kV with the MICADAS system to 50 kV with the LEA system. In order to execute the final performance tests, exactly same samples (2 sets consisting of 7 standards, 4 blanks, 26 wood samples) are measured on both systems successively. The results show that the LEA system is fully operational, and the performance is entirely comparable with that of the MICADAS system.

The article presents results of measurements of radiocarbon (14C) concentration in sub-annual dendrochronologically dated tree rings of English oak (Quercus robur L.) from Grabie village near Kraków (southern Poland). Samples of early wood (EW) and late wood (LW) spanning the years 664–658 BCE. α-cellulose was extracted from each sample and their radiocarbon content was measured at the ATOMKI laboratory in Debrecen, Hungary. The EW and LW data confirm a prolonged increase in Δ14C values around 665–663 as was observed by Park et al. (2017), Rakowski et al. (2019), or Sakurai et al. (2020). In addition, we found that this event may consist of two relatively small events, as was proposed by Sakurai et al. (2020). Based on obtained in this and previous study data we estimate that the occurrence of the two events were between 665 and 664 BCE (Rakowski et al. 2019), and in late spring of 663 BCE (May–June, before beginning of LW formation).

We present an alternative radiocarbon (14C) age-depth model using IntCal20 to calibrate new accelerator mass spectrometry (AMS) data applied to a Lake Baikal sediment core (VER99G12) in southern Siberia. 14C dating showed that the core extends to 31 ka. To take into account uncertainties in 14C age and sedimentation depth in the core, a new age-depth modeling routine, undatable, was used in this study. Undatable revealed that significant changes in sedimentation rate correspond to global climate events, either warm or cold, which periods are likely close to the timing of the occurrence of the Meltwater pulses (MWP) at 19 and 14 ka, and the Last glacial Maximum (LGM) at 21–20 ka. Since the Selenga River accounts for 50% of the total river inflow to Lake Baikal, we interpret that these changes in sedimentation rate could be signals of significant changes in Selenga River discharge to the lake, which is expected to be affected by global climate change. Based on pollen analysis, it is highly probable that the sudden influx of the Selenga River to Lake Baikal, particularly at 19 ka, was due to the thawing of permafrost water through the Selenga River, which had developed in the region. Total organic carbon content and mean grain size increases concurrent with sedimentation rate, suggesting river inflow increased available nutrients for biological activity. Our results indicate that hydrological changes corresponding to MWP events can be observed in continental areas of the Northern Hemisphere.

Dissolved inorganic carbon (DIC) in ocean water is a major sink of fossil fuel derived CO2. Carbon isotopes in DIC serve as tracers for oceanic water masses, biogeochemical processes, and air-sea gas exchange. We present a timeseries of surface DIC δ13C and Δ14C values from 2011 to 2022 from Newport Beach, California. This is a continuation of previous timeseries (Hinger et al. 2010; Santos et al. 2011) that together provide an 18-year record. These data show that DIC Δ14C values have declined by 42‰ and that DIC δ13C values have declined by 0.4‰ since 2004. By 2020, DIC Δ14C values were within analytical error of nearby clean atmospheric CO2 Δ14C values. These long-term trends are likely the result of significant fossil fuel derived CO2 in surface DIC from air-sea gas exchange. Seasonally, Δ14C values varied by 3.4‰ between 2011 and 2022, where seasonal δ13C values varied by 0.7‰. The seasonal variation in Δ14C values is likely driven by variations in upwelling, surface eddies, and mixed layer depth. The variation in δ13C values appears to be driven by isotopic fractionation from marine primary producers. The DIC δ13C and Δ14C values record the influence of the drought that began in 2012, and a major upwelling event in 2016.

Known as lead white, lead carbonates were used as white pigment or cosmetics from the 4th century BC to the 20th century AD. Lead white was produced by the corrosion of metallic lead by vinegar and horse manure up to the 19th c. In order to document the incorporation of carbon in the corrosion mechanism, lead carbonates were produced in the laboratory under monitored experimental conditions using materials with different isotope signatures in 14C and 13C. Six experimental setups were defined combining vinegar, acetic acid, horse manure and fossil CO2 gas. The corrosion products were characterized by X-ray diffraction. 14C content and δ13C values of the initial reactants and the final products were measured by accelerator and isotopic ratio mass spectrometry (AMS and IRSM). The reaction between lead and vinegar or acetic acid resulted in lead acetates with a carbon isotopic signature close to that of the corrosive reagent. In the presence of CO2, the carbonatation reaction occurred and the cerussite produced had a predominant 14C signature of the carbon dioxide source. These experiments demonstrate that the CO2 produced by horse manure fermentation is incorporated into the corrosion products, allowing the absolute dating of lead white by the radiocarbon method.

Over the course of one year (2021), we monitored the carbon isotope composition of atmospheric CO2 at three locations in Croatia: the Adriatic port city of Rijeka (Cfa climate) and at two rural sites: Gornje Jelenje (Cfb climate) in the vicinity of a main road and clean-air site Parg (Dfb climate). Carbon isotope composition at all sites shows seasonal variation, ranging from –41.3 to 25.2‰ for Δ14C and from –13.1 to –11.3‰ for δ13C. Rijeka systematically has the lowest and Parg the highest Δ14C, and δ13C at the sites are not statistically different one from another. The Δ14C of leaves of deciduous trees reflect the trend of atmospheric Δ14C. Based on the assumption that the investigated area is under the influence of two main sources of CO2: fossil and natural (sea exchange, biosphere, and undisturbed – clean air atmospheric component) the approximate share of fossil CO2 in total atmospheric CO2 has been estimated for Rijeka (2.1 ± 1.3%) and Gornje Jelenje (1.0 ± 0.9%). Comparison of our results with the data from European CO2 sampling stations indicates strong influence of CO2 from sea and biosphere. Backward trajectories indicate a possibility of Δ14CCO2 contribution from distant EU nuclear power plants, but movement of air masses should be considered in more detail to confirm this.

We constructed a laser ablation (LA) system using a diode laser for the accelerator mass spectrometry radiocarbon (AMS 14C) measurement of organic materials. The system could extract adequate CO2 to analyze small masses (0.1 mg C) at a resolution of 250 µm by a 5.5 W diode laser. The LA system was assessed using standard materials (IAEA-C1, IAEA-C2, IAEA-C3, IAEA-C6, and Ox II) and applied to natural tree ring samples. For the LA sampling of organic samples, which generally results in incomplete combustion, tungsten (VI) oxide was used as an oxidant to achieve complete burning. The results of the measurement of standard materials showed a low 14C background of F14C 0.0085 ± 0.0005 and reasonable reproduction of 14C values. Finally, we applied this system to a single-year analysis of tree-ringed spruce timber in Alaska. It was observed to have a detectable background for the 14C bomb peak.

El Japón is a 16th century hamlet site in the marshlands of the southern Basin of Mexico in central Mesoamerica. Radiocarbon (14C) dating and OxCal modeling of human bone collagen (n = 11) identifies a range of burials at El Japón cemetery from 1550–1650 cal. CE. The refined chronology identifies use of this rural settlement well after the onset of colonial government-sponsored relocation of Indigenous people to larger settlements (congregaciones). Historically documented information in this work supports chronological modeling beyond stand-alone calibration. Stable isotopic study of bone samples demonstrates similar sources of dietary protein and carbohydrates. The similarity of carbon sources for bone apatite (bioapatite) and collagen offers security that both bone fractions are viable 14C dating opportunities. Recent extension of this work examines bioapatite 14C dates (n = 5) from the same bone samples when quality parameters are met—atomic carbon-nitrogen ratios of 3.2–3.3 and collagen yield of 10–20%. No significant difference is found between collagen and bioapatite dates of the same individuals (p = 0.17, Mann-Whitney U test). 14C dates from human bone samples in this primarily terrestrial dietary context can be successfully acquired from either collagen or bioapatite fractions.

As there exists a growing demand for chronological research and tracer applications using radiocarbon (14C) analyses of samples smaller than 100 μg C, a compact micro-specific hydrogen graphitization method has been developed at the Xi’an Accelerator Mass Spectrometry (AMS) Center. This article describes the performance of the system and the mass of carbon background produced during ultra-small sample preparation. Furthermore, we discuss the results of contamination corrections and perform 14C analyses on small samples with known age or reference values. The results reveal that our 14C analysis of ultra-small samples of 10–100 μg C can obtain accurate and reliable results, and the micro-scale 14C-AMS analysis technique meets our research objectives for dating and tracer applications.

We have conducted radiocarbon (14C) dating of Japanese tree rings from 1053 to 921 BCE and 41 BCE to 130 CE. Dating was also performed using oxygen isotope dendrochronology to investigate subtle structures of the calibration curve corresponding to the beginning and the end of the Yayoi period in Japan. These two results followed IntCal20, which included the 14C ages of two Japan-sourced trees. The findings suggest that dating of specimens obtained from areas around the Japanese archipelago may be affected by periodic monsoons from the ocean, an effect that needs further examination.

GIRI (Glasgow International Radiocarbon Intercomparison) was designed to meet a number of objectives, including to provide an independent assessment of the analytical quality of the laboratory/measurement and an opportunity for a laboratory to participate and improve (if needed). The principles in the design of GIRI were to provide the following: (a) a series of unrelated individual samples, spanning the dating age range, (b) linked samples to earlier intercomparisons to allow traceability, (c) known age samples, to allow independent accuracy checks, (d) a small number of duplicates, to allow independent estimation of laboratory uncertainty, and (e) two categories of samples—bulk and individual—to support laboratory investigation of variability. All of the GIRI samples are natural (wood, peat, and grain), some are known age, and overall their age spans approx. >40,000 years BP to modern. The complete list of sample materials includes humic acid, whalebone, grain, single ring dendro-dated samples, dendro-dated wood samples spanning a number of rings (e.g., 10 rings), background and near background samples of bone and wood. We present an overview of the results received and preliminary consensus values for the samples supporting a more in-depth evaluation of laboratory performance and variability.