135Cs with a half-life of T1/2=2.3×106 yr is an important nuclide in studies of the dispersal of nuclear material in the environment. Preliminary measurements using 133Cs as a proxy for the long-lived 135Cs, with accelerator mass spectrometry (AMS) have been developed at the China Institute of Atomic Energy (CIAE). In order to improve the sensitivity of 135Cs AMS measurement, a new conducting material, Fe powder, was used in the experiment. According to the present results, the background level that can be obtained with blanks was 135Ba/Cs~1.83×10–10 with the CIAE-AMS system. These measurements showed that the Fe was an inferior conducting medium because the interference of 135Ba in Fe powder is 10 times higher than that in Ag powder.

In 2003, flooding occurred in the Ciudadela (Citadel) of Teotihuacan and saltpeter began to damage the Temple of the Feathered Serpent. Work done to solve this problem led to one of the most important archaeological discoveries made in this site in recent years: an intact tunnel sealed for more than a thousand years. The project created to study the tunnel was named Tlalocan or Path to the Underworld. More than 60,000 objects have been recovered after years of exploration and removing huge amounts of soil and stones. This paper presents the first results of accelerator mass spectrometry (AMS) radiocarbon dating performed on some of those materials recovered from the tunnel. With these findings, in combination with the archaeological data, based on stratigraphy and ceramic typology, a chronology of several events is proposed concerning the construction phases and ceremonial use, as well as partial and definitive closures of the tunnel. Every closure was accompanied by a deliberate and structured deposition of offerings and ritual refuse along the tunnel. The range of ages that covers the Bayesian calibration of samples collected along the tunnel is around 115 yr, from AD 125 to 240. Material collected at the surface of the chamber located at the end of the tunnel and under the pyramid gave ages in the interval between AD 400 and 534. All samples analyzed fall within the interval of time that covers the period of occupation of Teotihuacan.

Radiocarbon (14C) is a radionuclide generated mainly through neutron-induced reactions in all types of nuclear reactors. Since most of the 14C released into the environment is in the form of gaseous emissions (CO2 and hydrocarbons), terrestrial plants are the primary indicators of increased 14C levels near nuclear power plants (NPPs). In 2013–2014, we collected samples of silver grasses (including common reed) and pine needles within 3 km of four South Korean NPP centers and measured 14C activities using accelerator mass spectrometry (AMS) at Seoul National University. The highest 14C activities were observed, respectively, in Wolsong>Hanul>Kori>Hanbit [220, 143, 127, and 123% modern carbon (pMC)].

In a case study to assess the possibilities and limitations of determining the exact age of paper, we measured radiocarbon (14C) concentrations in bulk-paper cellulose and starch extracts from 20 known-age paper samples of the last 65 yr. As expected, 14C concentrations in single-seasonal grown starch extracts are in reasonably good agreement with post-bomb atmospheric 14C. In contrast, 14C concentrations in bulk-paper cellulose indicate apparent admixtures of tree-ring fibers spanning up to >50 yr. In a forensic investigation, combining 14C results from single-seasonal components like starch with those from long-lived fibers, could potentially enhance the precision of paper production-date estimates for samples made after 1955.

The looting of archaeological and ethnographic objects from emerging countries and areas of conflict has prospered due to the high prices that these objects can achieve on the art market. This commercial value now almost necessarily requires proof of authenticity by the object’s age. To do so, absolute dating has been conducted since the end of the 1970s on terra cotta art objects using the thermoluminescence method, a practice that has since been condemned. It is only more recently, since the 2000s, that art dealers and collectors have begun to use the accelerator mass spectrometry (AMS) method to date different kinds of objects made of organic materials. Compared to conventional radiocarbon dating, the AMS technique requires only very small samples, thus depreciating neither the aesthetics nor commercial value of the object. As a result, the use of absolute dating has become widespread, accompanying the increase in looting of the cultural heritage of countries destabilized by political overthrows and armed conflicts, especially in the Near East and Africa. The present article condemns the practice of AMS dating of looted art objects and encourages the creation of a code of deontology for 14C dating laboratories in order to enhance an ethical approach in this sensitive field facing the current challenges.

Among other zooarchaeological remains, terrestrial snails’ shells from the Thaumastus and Megalobulimus genera are found in some Brazilian shellmounds, presenting a potential substitute for charcoal in radiocarbon dating analyses, as reliable representatives of the atmospheric carbon isotopic ratio. In this paper, we present statistically similar results of both charcoal and land snails samples from the same archaeological contexts in three settlements on the coast of Rio de Janeiro. The Manitiba I shellmound results range from 4.2 to 3.7 ka cal BP (95.4%), contemporary with the Saquarema shellmound, occupied during the period from 4.3 to 3.6 ka cal BP (95.4%). For the Usiminas shellmound, two groups of samples revealed different periods of time for two occupational layers from 2.3 to 2.1 ka cal BP (95.4%) and from 1.6 and 1.3 ka cal BP (95.4%). A model constraining each group of samples to within a single phase has a general agreement of 97% with only two outliers out of 22 dates, yielding minimum individual agreement of 74% and 7% posterior outlier probability for Saquarema shells. These are good examples of sites in which the occupation chronology can be successfully obtained by the radiocarbon dating of land snails.

This study tested whether accurate dating by accelerator mass spectrometry (AMS) radiocarbon wiggle-matching of short tree-ring series (~30 annual rings) in the Medieval period could be achieved. Scientific dating plays a central role in the conservation of historic buildings in England. Precise dating helps assess the significance of particular buildings or elements of their fabric, thus allowing us to make informed decisions about their repair and protection. Consequently, considerable weight, both financial and legal, can be attached to the precision and accuracy of this dating. Dendrochronology is the method of choice, but in a proportion of cases this is unable to provide calendar dates. Hence, we would like to be able to use 14C wiggle-matching to provide a comparable level of precision and reliability, particularly on shorter tree-ring sequences (~30 annual growth rings) that up until now would not routinely be sampled. We present the results of AMS wiggle-matching five oak tree-ring sequences, spanning the period covered by the vast majority of surviving Medieval buildings in England (about AD 1180–1540) when currently we have only decadal and bidecadal calibration data.

This study attempts to reconstruct food habits through carbon (C) and nitrogen (N) isotope analysis and C/N analysis of charred residues inside pottery from the Primorye in the Russian Far East (Luzanova Sopka 2, Sergeyevka 1, Boisman 2, and Vetka 2 sites). Dates were obtained that were from the later stages of the Rudnaya culture (6980–6485 BP, 7800–7400 cal BP), proto-Boisman type (6760–6330 BP, 7600–7300 cal BP), Boisman culture (6155–4720 BP, 7100–5400 cal BP), and Vetka culture (6030–5870 BP, 6900–6700 cal BP). There are major differences in the carbon and nitrogen isotope ratios between inland sites (δ13C –26.9 to –30.0‰, δ15N 7.6 to 9.3‰) and coastal sites (δ13C –18.1 to –24.2‰, δ15N 9.5 to 14.9‰). The results show that the diet of inland cultures consisted primarily of freshwater fish and terrestrial animals and plants, whereas that of coastal cultures consisted mainly of marine organisms.

Bone is frequently dated in archaeological studies and, especially for very old bones (more than 40,000 years old), it is critical to have an accurate and precise measure of the material-specific background value and its associated uncertainty. The SUERC Radiocarbon Laboratory has obtained a mammoth bone as a background bone standard and an appropriate number are now routinely prepared and measured in each AMS batch, resulting in the accumulation of a large number of background bone results over a two-year period. Additionally, information on which of the two accelerator mass spectrometry (AMS) instruments was used to make the radiocarbon (14C) measurements, and which sample pretreatment method (modified Longin or modified ultrafiltration) was used to extract and purify the collagen, is recorded for each sample. These data have been used to estimate the laboratory bone background (to be subtracted from each unknown bone sample prepared in the laboratory) and its associated analytical uncertainty. The statistical analysis of the bone results has made use of a linear mixed effects model to examine the variation, and to apportion the overall variation between and within batches on both AMS instruments, and the different pretreatment methods used at SUERC.

Radiocarbon (14C) in atmospheric CO2 for the Dakar (Senegal) urban area was measured using tree leaves collected by botanists from 1900 to 2003. The aim of our study was to compare the local Suess effect in Dakar to the global one during the 20th century. The ∆14C of atmospheric CO2 in this region decreased from 1900 to 1958 during the pre-bomb era (–2±5‰ to –22±4‰). From 1958 to 1964, nuclear bomb tests injected a large amount of artificial 14C into the atmosphere, reflected in the rise of ∆14C values. In the Dakar region, the atmospheric ∆14C reached 773±8‰ in 1964, but subsequently decreased to 80±5‰ by 2003, which is consistent with the global exponential decreasing trend. The ∆14C record presented here remains slightly lower than the global record. This result is attributed to the input of anthropogenic fossil carbon into the atmosphere. The amount of carbon input can be evaluated by comparing urban areas to those of clean air sites. The calculation of anthropogenic fossil carbon is deduced from a simple mathematical model.

Radiocarbon has been applied as a tracer to study carbon dynamics in different types of tropical soils, under paddy and non-paddy management on Java, Indonesia. The 14C concentrations were measured in samples of total organic carbon as well as in alkali-soluble humic acids, insoluble humin, and plant remains (roots, seeds, leaves) obtained from three sites with Andosols, Alisols, and Vertisols at different altitudes. In addition, the abundance and distribution of plant macrofossils in the soil column and organic δ13C values were determined. The results obtained so far are compared with those from a chronosequence of Cambisols in China. They indicate the input of fresh plant materials into the subsoil directly via roots and/or by soil cracks and bioturbation of aboveground litter. The total organic C and 14C concentrations show the usual decrease with increasing depth in paddy and non-paddy soils, reflecting the influence of direct input as well as the downward redistribution of organic material as particulates or dissolved organic carbon (DOC) depending on soil type (pedogenesis, plough-pan formation, drying cracks), crop type and management, and climatic factors. A disturbance of the Andosol around 0.4 m depth and a change in profile properties around 0.63 m in the Alisol limit the general conclusions.

The Khayrgas Cave in Yakutia (eastern Siberia) is one of the most important Upper Paleolithic sites in northern Asia, and has been the subject of extensive 14C dating and study of mammal bones. The upper part of the cave sequence (Layers 2–4) dates to the Holocene (~4100–8200 BP), and the lower part (Layers 5–7) to the Late Pleistocene (~13,100–21,500 BP). In Layers 2–4, only extant animal species are known; ecologically they belong to a forest-type ecosystem. In Layers 5–7, several extinct species were identified, and the environment at that time corresponded to open and semi-open ecosystems. The Khayrgas Cave provides rare but reliable evidence of human occupation in the deep continental region of eastern Siberia at the Last Glacial Maximum, ~20,700–21,500 BP.

Radiocarbon (14C) dating is used widely in many projects as a basis for the creation and testing of chronological constructs. 14C measurements are by their nature complex and the degree of sample pretreatment varies considerably depending on the material. Within the United Kingdom and Europe, there are a number of well-established laboratories and increasingly, archaeologists are not just commissioning new dates, but also using statistical modelling of assemblages of dates, perhaps measured in different laboratories, to provide formal date estimates for their sites. The issue of comparability of measurements (and thus bias, accuracy and precision of measurement) from the diverse laboratories is one which has been the focus of some attention both within the 14C community and the wider user communities for some time. As a result of this but also as part of laboratory benchmarking and quality assurance, the 14C community has undertaken a wide-scale, far-reaching, and evolving program of intercomparisons, to the benefit of laboratories and users alike. This paper summarizes the most recent exercise, the Sixth International Radiocarbon Intercomparison (SIRI).

This paper presents the results of the first broad-scale study of modern freshwater reservoir effects (FREs) in various regions of the Eurasian Steppe, associated with archaeological sites. The aim of this work was not only to demonstrate the widespread variability of modern FREs in the region, but also to draw the attention of specialists working in the area to the necessity of taking into account this important and still not fully understood factor involving radiocarbon dating of human and some faunal remains from archaeological sites. To identify modern FREs, modern fish of different species from 10 regions of Siberia and Kazakhstan have been subjected to accelerator mass spectrometry radiocarbon (AMS 14C) dating and stable carbon and nitrogen isotope analysis, and the results are compared with the existing data from previous research. Freshwater reservoir offsets have been detected in all analyzed regions, with the exception of Kharga Lake (Buryatia, Russia) and Kyzylkoi River (central Kazakhstan), varying not only between, but also within regions depending on fish species. The most significant offset in this study has been recorded for the Chuya River basin (Altai Mountains, 1097±40 14C yr), though not as high as observed in previous research for the Caspian lowlands (1477±52 and 1037±52 14C yr) and Upper Lena River basin (Lake Baikal area, 1981±30 14C yr). Both δ13C and δ15N values have been measured with the majority of samples reflecting C3 ecology of local reservoirs and δ15N depending on the diet of particular species, with predatory species such as pike, perch, and burbot demonstrating the highest δ15N. No general relationship has been observed between freshwater reservoir offsets and either δ13C or δ15N values of the samples.

Due to an increasing number of nuclear reactors in operation, the radiocarbon (14C) released from nuclear power plants (NPPs) has become an important anthropogenic source of 14C. The examination of seasonal Δ14C and monthly Sr/Ca, Mg/Ca variations in a coral in Daya Bay (China) shows that NPPs located there have an impact on the Δ14C level and sea surface temperature (SST). The Mg/Ca variation was in good correlation with the Pacific Decadal Oscillation (PDO) before the operation of Ling’ao NPP in 2002, but this correlation became weak due to an abnormally higher SST after 2002. As illustrated by the Δ14C variation in the coral, there were two relative increases of Δ14C values in 1994 and 2002 when Daya Bay NPP and Ling’ao NPP began operations, respectively. The 14C released from NPPs, instead of oceanic circulation, is probably the primary factor on the Δ14C variation in Daya Bay during the NPPs’ operation. The relative increase in Δ14C value was ~80‰, which equals to ~18 Bq/kgC in specific activity. The seasonal variability in Δ14C value usually peaked in summer, the real reason of which was unknown. This study sheds light on how the NPPs influence the 14C content and SST in surrounding marine environment.

In 2013, one of Sweden’s largest archaeological excavations started in association with the building of the European Spallation Source (ESS) multidisciplinary research center in Lund. The 160 radiocarbon dates that were produced for the project represent the most exhaustive dating program for a Scandinavian site so far and provide evidence for the human impact and activities on the site from the Mesolithic to the Iron Age. This article presents the results within a Bayesian statistical framework for the 70 14C dates from the Early Neolithic settlement (object 1) and a burial site with dolmens and wooden façades. For the first time, a highly precise chronology provides deeper insight into the Neolithization processes and the early settlement strategies in southern Scandinavia from ~3800 cal BC onwards.