Precise manometric pressure, volume, and temperature (P-V-T) measurements of carbon in samples, standards, and blanks are critical for radiocarbon studies. While P and T uncertainties depend on instrument choice and environmental stability, V uncertainties depend on their method of measurement and are often overlooked. We used numerical simulations and error propagation to find optimum procedures for measuring “cold-finger” volumes equipped with capacitance diaphragm gauges (CDGs) by two common application of Boyle’s Law: cryogenic transfers and serial gas expansions with a reference flask of known volume. Minimum relative uncertainties of cold-finger volumes are comparable for these two methods (∼0.002), but the serial gas expansion method is preferred due to its convenience. Serial gas expansions can be performed to high precision by using dry air, an initial pressure ∼76% full-scale (e.g., 760 Torr), and a reference flask with an optimal volume based on preliminary estimates of cold-finger volumes and an empirical power function. The volumes of cold-fingers ≥ 12 cm3 can be determined with minimum achievable relative uncertainties of 0.0021 to 0.0023. This limit translates to minimum achievable relative uncertainties of 0.0026 to 0.0027 for P-V-T measurements of moles of gas simulated here.

Pyrolized carbon in biochar can sequester atmospheric CO2 into soil to reduce impacts of anthropogenic CO2 emissions. When estimating the stability of biochar, degradation of biochar carbon, mobility of degradation products, and ingress of carbon from other sources must all be considered. In a previous study we tracked degradation in biochars produced from radiocarbon-free wood and subjected to different physico-chemical treatments over three years in a rainforest soil. Following completion of the field trial, we report here a series of in-vitro incubations of the degraded biochars to determine CO2 efflux rates, 14C concentration and δ13C values in CO2 to quantify the contributions of biochar carbon and other sources of carbon to the CO2 efflux. The 14C concentration in CO2 showed that microbial degradation led to respiration of CO2 sourced from indigenous biochar carbon (≈0.5–1.4 μmoles CO2/g biochar C/day) along with a component of carbon closely associated with the biochars but derived from the local environment. Correlations between 14C concentration, δ13C values and Ca abundance indicated that Ca2+ availability was an important determinant of the loss of biochar carbon.

Cast iron objects recovered primarily in eastern Mongolia, spanning the Xiongnu through the Early Historic periods (ca. 3rd BC–AD 17th century), were examined for their radiocarbon (14C) concentration and microstructure. Most of the samples examined were found to have originated from charcoal-based smelting with a few exceptions that were made using a mineral coal-based technique. A comparison of 14C dates with dates derived from artifact typology allowed the charcoal-smelted objects to be classified into two groups, based on whether the radiometric and typological periodization are in agreement or not. In addition, those with differing 14C and typological dates can be divided into two subgroups with and without evidence for a melt treatment applied after original casting. These conflicting dating results are confusing and would seem to provoke skepticism about the use of 14C measurements for dating iron artifacts. We demonstrate however that 14C analysis, when combined with metallographic examination and other lines of chronological evidence, can clarify the history of a given iron object and its multiple users, often separated in time by more than a millennium.

The jungles of Linyun and Longlin Autonomous Prefecture, located in the heart of the southwestern Guangxi Zhuang Autonomous Region of China, are home to the oldest tea trees (Camellia sinensis) in the world. In the absence of regular annual rings, radiocarbon (14C) dating is one of the most powerful tools that can assist in the determination of the ages and growth rates of these plants. In this work, cores were extracted from large ancient tea trees in a central Longlin rain forest; extraction of carbon was performed with an automated sample preparation system. The 14C levels in the tree cores were measured using accelerator mass spectrometry (AMS) at the University of Tsukuba. These measurements indicated that contrary to conventional views, the ages of trees in these forests range up to ~700 years, and the growth rate of this species is notably slow, exhibiting a long-term radial growth rate of 0.039±0.006 cm/yr. It was demonstrated that 14C analyses provide accurate determination of ages and growth rates for subtropical wild tea trees.

We analyzed rare wooden Komainu found at Akagami Shrine in Akita prefecture, Japan. The formation of historical objects is often thoroughly recorded in documents, although the formation age of this particular Komainu sculpture is still unknown due to its antiquity. Thus, age determination exercises have been conducted using radiocarbon (14C)-wiggle-matching techniques. Although only a limited quantity was available for sampling, we have successfully measured 14C samples in the sculptures along with several sets of tree rings. We interpret the Komainu sculptures age considering the age of the trees and the result obtained from the wooden construction materials used for the Akagami shrine. The results obtained from Komainu show a range from 550 CE to 1020 CE, which is consistent with the dates of the shrine’s formation. Thus, the multiple 14C-wiggle-matching method can determine precise calendar ages of wood, as well as provide some supportive information for the periods when there are no reliable historical documents.

Radiocarbon (14C) dating is widely used to determine the age of organic material in palaeoenvironmental research. Here we compare 14C dates (n=17) resulting from macro-charcoal (>250 μm), short-lived plant macrofossils and pollen-rich residues isolated from two mire environments in eastern Australia. In most samples we found that short-lived plant macrofossils were the youngest organic component, the charcoal samples most often fell into the middle and the pollen-rich residues consistently returned older dates than the other samples. Although pollen-rich residues have been widely used for 14C dating in Australasia we suggest some caution in their use, perhaps because in our fire-prone environments these samples often also contain fine charcoal and other oxidative resistant organic matter that is older than the surrounding sediment matrix. The macro-charcoal samples also often returned older calibrated ages compared to short-lived plant macrofossils from the same depth, although this difference was relatively small (<245 years). Our results demonstrate that 14C dating of short-lived plant macrofossils are likely to yield more accurate chronologies and we advocate their routine use in palaeoenvironmental research when they are available.

Observation of the ion source generated background has been an area of focus during our routine analytical work. It is noted that the results of very-low-ratio samples are dependent upon the particular procedures for measurement using the present-day Cs+ sputter ion sources. When measured without excessive Cs+ fluxes and without interleafing with other higher-ratio samples and references, the accelerator mass spectrometry (AMS) sensitivity can be somewhat improved. In some cases, it appears possible to assess old radiocarbon (14C) samples to beyond the long-standing 60 kyr limit. A number of observational studies are made for the sole purpose of minimizing the final contamination to the rare isotopes that is generated within the ion source.

To examine the implications of seasonality for the construction of a single-year calibration curve we obtained separate dates on earlywood and latewood fractions of tree rings originating from England and dendrochronologically dated between AD 1352 and AD 1442. These demonstrated that an average difference of 26±15 yr exists between earlywood and latewood and that this difference can be as high as 33±19 yr during periods of high radiocarbon (14C) production. It is argued that this difference is due to both changes in atmospheric 14C and the incorporation of stored carbohydrates into earlywood. Based on this, it was possible to separate an atmospheric and physiological contribution to this difference. Our modeling indicates that storage can produce a difference of up to 10 years between earlywood and latewood. This suggests that full-year tree rings from deciduous trees may be less appropriate for the construction of a single-year calibration curve and that specific atmospheric events can be more easily detected by measuring only latewood.

Little is known about the potential complications that may arise from the use of coastal foraminifera for radiocarbon (14C) dating. The aim of this study is to report the fortuitous finding of 14C-dated Haynesina germanica individuals picked from two sediment cores (Pertuis Charentais, France), which appeared 2500–2000 years older than their expected age of deposition. Stratigraphical and micropaleontogical evidence have ruled out the possible effect of reworking of calcareous tests from previous strata. Similar anomalous 14C ages were obtained on abundant lignocellulose debris recovered from the cores, which are supplied by rivers flowing into the study area. Given that H. germanica is an infaunal species, we hypothesize that in-situ living individuals acquired the 14C-depleted isotopic signature of lignocellulose debris within the sediment prior to definitive burial, following an unexplored pathway of carbon transfer between the two compartments. Based on the literature, we propose a plausible explanation, which involves bacterial communities living in the study area. This putative role of bacteria may have considerable importance for past and future studies of Holocene environmental changes in coastal environments. Further work is now needed to explore this hypothesis with more robust, direct evidence based on comprehensive geochemical, geochronological and microbiological studies.

The Abrolhos bank, in southern Bahia State (BA), is the largest coral reef system in the southwestern Atlantic. It is highly influenced by the Brazil Current (BC), since it is located in the continental shelf. By contrast, Todos os Santos Bay (TSB), in Salvador, capital of Bahia State (BA) has an important coral biodiversity, located in a bay inlet with restricted water circulation. Coral cores were collected in those sites and were analyzed for density band counting and by Th/U dating to estimate growth rates and age. In this work, we present 14C ages of some of these bands in order to evaluate the marine reservoir effect (MRE) to which the colonies were subjected during growth. It is the first study making use of coral skeleton samples for MRE determination for the Brazilian coast. ΔR was calculated to be –151±23 14C yr, while that for the TSB was –107±51 14C yr.

Luristan Iron Mask Swords have been recovered mostly from illegal diggings in the 1920s. The about 90 known objects are characterized by a disk-shaped pommel on the top of the handle with two mounted bearded heads on two sides. According to the similarity in form and radiocarbon (14C) measurements on two swords from museum collections, an overall short production period was assumed around 1000 BC (Moorey 1991; Rehder 1991). Here we present the results of metallurgical analysis and 14C measurements for three newly acquired Luristan swords, which were donated to the Royal Museums of Art & History, Brussels. Metallurgical analysis indicates an iron production via the bloomary furnace technique. Analyzed samples show large slag inclusions (Fayalite, Wüstite, glass) within a mostly ferritic and pearlitic iron. The carbon contents varied between 0.2 wt% to around 0.8 wt%). 14C measurements on thermally extracted carbon give 14C ages between 2800 BP–3360 BP (calibrated ∼1745 BC–900 BC). The reliability of the 14C measurements are discussed with respect to external (contamination during handling) and intrinsic contamination (e.g. fossil carbon sources during manufacture).

Proxy-based observations of solar activity in the past have revealed long-term variations, such as the Gleissberg cycle (~88 yr), de Vries cycle (~200 yr), and the Hallstatt cycle (~2000 yr). Such long-term variations of solar activity sometimes cause the disappearance of sunspots for several decades. Currently, solar activity is becoming weaker, and there is a possibility that another long-term sunspot minimum could occur. However, the detailed mechanism of the weakening in solar activity is unknown, and the prediction of solar activity is ambiguous. In this study, we investigate the transitions of solar cycle length before the onset of the Spoerer Minimum, the longest grand minimum in the past 2000 yr. We measured the 14C content in an asunaro tree (Thujopsis dolabrata) excavated at Shimokita Peninsula from 1368–1420 CE using the compact AMS system at Yamagata University. It is found that the solar cycle lengthened to be 14–16 yr from 2 cycles before the onset of the Spoerer Minimum.

We present 37 new radiocarbon (14C) measurements from mollusk shells fragments sampled along the Chilean continental margin and stored in museum collections with known calendar age. These measurements were used to estimate the modern pre-bomb regional marine 14C age deviations from the global ocean reservoir (∆R). Together with previously published data, we calculated regional mean ∆R values for five oceanographic macro regions along the coast plus one for a mid-latitude open ocean setting. In general, upwelling regions north of 42ºS show consistent although sometimes highly variable ∆R values with regional averages ranging from 141 to 196 14C yr, whereas the mid-latitude open ocean location of the Juan Fernández archipelago and the southern Patagonian region show minor, ∆R of 40±38 14C yr, and 52±47 14C yr respectively. We attribute the alongshore decreasing pattern toward higher latitudes to the main oceanographic features along the Chilean coast such as perennial coastal upwelling in northern zone, seasonally variable upwelling at the central part and the large freshwater influence upon the southern Patagonian channels.

In 2016, a burial chamber hewn into limestone was discovered at Khirbet Aqabet Al Qadi on the northwestern slope of Mount Ebal, 2km north of the city center of Nablus. The floor of the chamber is 3.15 × 2.9 m and the height averages 1.8 m. A movable closure at the entrance consists of a limestone slab. The burial chamber houses four sarcophagi. The aim of this case study is to give information not only on the burial chamber but also, for the first time in the region, on human remains. Stable isotope analysis of a human bone sample enabled us to obtain dietary information on one individual. Due to low collagen content, the sample did not allow precise dating but it can be placed between 50 BC and 50 AD. Systematic illegal excavation and looting at funerary sites in the Nablus area has caused material for potential information to be missing at the site. Nonetheless, the dietary information obtained supports other material finds indicating Mediterranean agricultural use of the land. Our evidence demonstrates that the site dates to between the 1st and 3rd centuries AD.

The very high temperature reactor (VHTR) is a development of the high-temperature gas-cooled reactors (HTGRs) and one of the six proposed Generation IV reactor concept candidates. The 10 MW high temperature gas-cooled reactor (HTR-10) is the first pebble-bed gas-cooled test reactor in China. A sampling system for the measurement of carbon-14 (14C) was established in the helium purification system of the HTR-10 primary loop, which could sample 14C from the coolant at three locations. The results showed that activity concentration of 14C in the HTR-10 primary coolant was 1.2(1) × 102 Bq/m3 (STP). The production mechanisms, distribution characteristics, reduction routes, and release types of 14C in HTR-10 were analyzed and discussed. A theoretical model was built to calculate the amount of 14C in the core of HTR-10 and its concentration in the primary coolant. The activation reaction of 13C has been identified to be the dominant 14C source in the core, whereas in the primary coolant, it is the activation of 14N. These results can supplement important information for the source term analysis of 14C in HTR-10 and promote the study of 14C in HTGRs.

We sampled individual growth rings from three ancient remnant bald cypress (Taxodium distichum) trees from a massive buried deposit at the mouth of the Altamaha River on the Georgia Coast to determine the best technique for radiocarbon (14C) dating pretreatment. The results of our comparison of traditional ABA pretreatment and holocellulose and α-cellulose fractions show no significant differences among the pretreatments (<1 sigma) thereby suggesting that ABA pretreatment will prove sufficient for the development of a high-resolution 14C tree-ring chronology based on these ancient bald cypresses which will indicate whether the U.S. Southeast is subject to a regional radiocarbon offset.

The Aqueduct is one of the city landmarks of Skopje, Republic of North Macedonia. It was part of a water-supply system, with a total original length of about 10 km, while its surface remains are about 385 m long. The age of the Aqueduct is not known—several hypotheses place it to periods between the 6th and 16th centuries. Six mortar samples from different positions of the eastern façade were taken for radiocarbon (14C) dating. In order to extract only the carbon associated to the time of building, three strategies for sample preparation were used: (1) mechanical separation of lime lumps formed during mortar hardening (2) selection on the basis of particle size and the ability to suspend in water induced by ultrasonic shock, and (3) collection of two gas CO2 fractions produced from the same bulk in reaction with acid. Characterization of fractions was performed by isotopic carbon composition and FTIR-ATR analyses. The most plausible results were obtained from lime lump fractions that were dated in the timeframe of 15th to 17th century.

This study combines radiocarbon (14C) analysis and sclerochronology research, an approach that to the best of our knowledge, has not yet been applied using bivalves from the Mediterranean Sea. We analyzed shells from the North Adriatic Sea: live- and dead-collected specimens of the infaunal bivalve Glycymeris pilosa and two dead-collected specimens of Glycymeris sp. According to crossdating results, growth increment time series obtained from acetate peels of the dead-collected G. pilosa (S3FP11) indicate the potential for creating longer chronologies from live and dead-collected specimens. The greatest longevity was seen in the dead-collected Glycymeris sp. specimen S3F3, estimated to be ~130 years (started growing AD 1678–1742 and died AD 1826–1860), indicating the potential to extend Glycymeris growth increment chronologies to past centuries. The highest ∆14C values obtained corresponded to the calendar year 1974. The 14C record obtained from G. pilosa correlates well with the modeled surface ocean (mixed-layer) bomb pulse curve (Reimer et al. 2009). Based on the results obtained from the shell growth increment assigned to AD 1950, the reservoir age and reservoir correction (ΔR) are 264±23 years and –6±32 years, respectively.

Sub-annual measurements, eight increments per year, of cellulose in a Scots pine tree growing in central Norway are presented as a proxy for tropospheric 14CO2 at biweekly to monthly resolution. The results are validated by comparison to direct atmospheric measurements in the years 1959–1965, and a new dataset is obtained for 1953–1958. In this period, our cellulose measurements deviate from the Bomb 13 NH1 calibration curve, which is derived from single-year measurements of tree rings. This is due to seasonal cycles in tropospheric radiocarbon (14C) concentrations, caused by the first series of atmospheric nuclear weapons tests.

The absolute chronology of Early Bronze Age in the Levant has been the object of a major revision (Regev et al. 2012a), which implied an increase of at least two centuries in respect of traditional chronology. Such a shift back was based upon two sites (Tel Yarmouth, Megiddo) which were the backbone of the “reform,” but actually do not offer complete sequences for the whole EBA. This was the weakest stone of the revision, together with a partial understanding of stratigraphy/contexts from where samples were taken. Tell es-Sultan/Jericho in Palestine was included in this study, as this prominent archaeological site provided well stratified 14C dates for EBA. Its stratigraphy, established by Kathleen M. Kenyon in the 1950s, was reappraised by the Sapienza University of Rome–Palestinian MOTA-DACH joint Expedition (1997–2018). Published 14C dates were reanalyzed along with new samples from carefully stratified and published archaeological contexts, measured by the CEDAD Laboratory (University of Salento, Lecce, Italy). They provided absolute dates connected with stratigraphy useful to double-check the proposed High Chronology. EBA stratigraphic periodization at Jericho suggests a more cautious approach and keeps a multi-based chronology more consistent with a comprehensive historical reconstruction of the Early Bronze Age in Syria-Palestine and Egypt.