The total 14C content and its partition between inorganic and organic species were measured on irradiated Zy-4 samples from a CANDU spent fuel rod transferred from Cernavoda Nuclear Power Plant (NPP). Long-term leaching tests and accelerated corrosion tests were carried out to measure the 14C release and corrosion rate, respectively, in chemical conditions relevant to cementitious environment. Experimentally measured 14C inventory was compared to the theoretically one predicted based on the irradiation history and impurity content of Zy-4 by means of ORIGEN computations. CANDU SF claddings have a 14C content of around 2 × 104 Bq/g of Zy-4, mainly as organic compounds (more than 99%). The total 14C content measured by acid dissolution/wet oxidation method is in good agreement with the value estimated by ORIGEN simulations for an average burn-up of 7 MWd/kgU. The total 14C released as dissolved species after 18 days and 18 months of Zy-4 immersing in alkaline solution are similar, indicating that a small amount of 14C was available as instant release fraction (0.05% from the initial 14C content) followed by a very low release rate that could not be measured by liquid scintillation counting. In alkaline conditions, 14C is released predominantly (∼70%) as soluble species, but also inorganic 14C was measured as gaseous species. From the soluble 14C released during leaching test, more than 60% was found to be as organic species. Generally, corrosion rates values ranging between 46 and 130 nm/yr were measured by the linear polarization resistance method. In addition, defects and cracks were observed on the oxide layer by scanning electron microscopy (SEM) investigation.

In 373 bc a catastrophic earthquake and seismic sea wave destroyed Helike, a Greek city near Aigion on the southern shore of the Gulf of Corinth. The ruins were buried by sediments of unknown depth, leaving no trace of the city. We here discuss the radiocarbon dating of organic sediment samples recovered from seven boreholes drilled on the coastal plain in the area where ancient sources located Helike. Most of the samples apparently acquired a substantial addition of older carbon from natural sources, and hence their apparent ages are older than the true ages of sedimentation. However, if we assume that the addition is systematic, we can use the apparent ages to show that the sedimentation rate was initially rapid (about 1 cm yr-1) for the strata between 40 and 10 m below the surface, and then decreased by an order of magnitude about 6500 yr ago. A related change in the sediment deposition at about the same time has been found in many other marine deltas throughout the world, probably due to the deceleration of the global sea-level rise. We conclude that in the boreholes sampled by the present data, the horizon corresponding to ancient Helike is less than 8 m deep.

My path to the invention of accelerator mass spectrometry—now just called AMS—was quirky and extraordinary, and it is a saga worth telling, particularly for young people who may have an oversimplified image of how progress in science is actually made. It was an adventurous journey, and like many adventures, it was often uncomfortable, haphazard, and frequently characterized by a feeling of being lost. In retrospect, the only reason I set out on this journey was my belief that I didn't know much about finding my path in physics, and that the best I could do was to follow the lead of the great physicist Luis Alvarez. He had an incredible ability to create new and ingenious projects that led in new directions, and I wanted to understand how he did that. So I had decided that I would work with him on any new idea he came up with, even if it inconvenienced the rest of my life. And true to my expectations, while working with Luie (that's what he wanted everyone to call him), I often felt like Odysseus, tossed between distant shores by capricious gods.

The late Pleistocene to early Holocene Champlain Sea provides a unique opportunity to study the development of marine ecosystems in a context of global climatic change. This study presents radiocarbon (14C) dates and stable isotope analyses on 15 vertebrate specimens from Champlain Sea sediments, including the Charlotte Whale, which is Vermont’s State marine fossil. Data are used in an attempt to investigate the timing of colonization and ecological dynamics in this newly formed sea. Using the average marine correction, 14C dates on four specimens likely calibrate prior to or possibly synchronous with the accepted origination date for the Champlain Sea, implying larger marine reservoir effects than the average marine correction in the vertebrate tissues. Without knowing the specific marine reservoir offsets, it is not possible to calculate the timing of colonization or its relation to concurrent climatic change. Observed lower δ13C and δ15N values in walruses, a fin whale, and a right whale support consumption of prey from lower trophic levels such as bivalve mollusks, krill, and copepods. Higher isotopic values in beluga whales and a bird, the thick-billed murre, support consuming fish, such as cod and capelin. These isotopic data show comparable values and relationships as observed in modern arctic marine ecosystems.

In 1989 an ancient burial consisting of a skeleton and a few objects was discovered at the Monte dei Cappuccini Monastery, in Torino (Italy). Anthropological analysis of the skeleton revealed that it belonged to a young man, and the archaeometric characterization of the objects suggested that most of them are compatible with the Medieval period. As a proper archeological survey was not conducted at the time of the finding, due to the religious nature of the site, a high-precision radiocarbon (14C) dating has been performed. The samples were processed with three different methods: besides the ultrafiltration (UF) treatment, we applied the “collagen” (COL) and the Longin-base (LB) methods. While UF and COL treatments provided compatible results, LB method returned ages older with respect the UF one, with significant disagreements in some cases and this evidence is supported by several measurements on the same individual. Thanks to the reduction of the uncertainty with the high number of measured samples and the availability of historical evidence, the possible age of the burial has been limited to the time interval 1464–1515 cal AD.

The object of our investigation was to study a mechanism of water formation in the Surdulica geothermal system (recharge area, age and homogeneity of the waters). We collected 56 samples to determine the chemical, stable isotope, 14C and tritium content of the waters. We found large stable isotope variations in precipitation collected at different altitudes, whereas the geothermal waters are largely homogeneous and seasonally independent. Data on springs and rivers, the local meteoric water line and recharge area were obtained. Three groups of groundwater were identified by age – modern from natural springs, old from mines and very old from the Vranjska Banja. Because the initial 14C activity of infiltrated waters from the recharge area is unknown, the age of thermal waters can only be inferred, from HCO3 −, 14C and 3H content, to be 10,000 to 28,000 years old.

Speleothem organic matter can be a powerful tracer for past environmental conditions and karst processes. Carbon isotope measurements (δ13C and 14C) in particular can provide crucial information on the provenance and age of speleothem organic matter, but are challenging due to low concentrations of organic matter in stalagmites. Here, we present a method development study on extraction and isotopic characterization of speleothem organic matter using a rapid procedure with low laboratory contamination risk. An extensive blank assessment allowed us to quantify possible sources of contamination through the entire method. Although blank contamination is consistently low (1.7 ± 0.34 – 4.3 ± 0.86 μg C for the entire procedure), incomplete sample decarbonation poses a still unresolved problem of the method, but can be detected when considering both δ13C and 14C values. We test the method on five stalagmites, showing reproducible results on samples as small as 7 μg C for δ13C and 20 μg C for 14C. Furthermore, we find consistently lower non-purgeable organic carbon (NPOC) 14C values compared to the carbonate 14C over the bomb spike interval in two stalagmites from Yok Balum Cave, Belize, suggesting overprint of a pre-aged or even fossil source of carbon on the organic fraction incorporated by these stalagmites.

Moss et al. (2006) provided comments and criticisms of our recent paper in this journal (Hall et al. 2005). We can appreciate the need for promoting vigorous dialogue among those interested in the research of early sites along the New World Pacific Margin and thus welcome their intervention; however, we are compelled to respond because they raise several points that require clarification and introduce a critical error that must be corrected.

For the first time, a series of 14C dates has been obtained for samples from the archaeological excavations in Red Square, the historical center of Moscow. The remains of burned dwellings from the bottom of the cultural layer were dated as well as dispersed charcoal from the underlying plough soil. The results correspond to a 200-yr time interval and prove that arable activity at the site began as early as the late 11th century ad. The field belonged to Moscow itself or to rural settlements nearby. The oldest dwelling was built ca. the late 12th–early 13th century ad.

This date list consists of some of the samples measuredsince summer 1965. For the routine measurements thesame technique and equipment as described earlierwas used (Bern IV).

Radiocarbon dating of closely associated marine mollusk shells and terrestrial material (charred wood or bone) collected from archaeological contexts on Tenerife and Fuerteventura islands allowed us to quantify the marine 14C reservoir effect (ΔR) around the Canary Archipelago. Coastal Fuerteventura has a positive weighted mean ΔR value of +185 ± 30 14C yr, while for Tenerife a range of negative and positive values was obtained, resulting in a ΔR weighted mean value of 0 ± 35 14C yr. These values are in accordance with the hydrodynamic system present off the Canary Islands characterized by a coastal upwelling regime that affects the eastern islands (Fuerteventura and Lanzarote) but not the other islands of the archipelago, namely Tenerife. Because of this oceanographic pattern, we recommend the extrapolation of these results to the remaining islands of the archipelago, i.e. the first value must be used for the eastern islands, while for the central and western islands the acceptable ΔR value is 0 ± 35 14C yr.

Teotihuacan is one of the most studied archaeological sites in Mesoamerica because of its exceptional size and urban planning; however, its last years of occupation and abandonment are still under debate. We report a high-resolution chronology for the Xalla complex integrating archaeomagnetic dates, radiocarbon (14C) ages, and detailed archaeological information about sample type and context in a Bayesian model. The model includes 42 14C ages and 7 archaeomagnetic dates grouped in 6 phases, including samples from collapsed roofs with 14C ages earlier than expected, suggesting a problem of inbuilt age. The archaeomagnetic dates on lime plasters were classified in unburned samples, related to the time of construction, and burned samples, related to the Big Fire associated to the abandonment of Teotihuacan. The modeled 14C ages resulted in shorter intervals, with the possibility of differentiating the construction phases, confirming that big beams had inbuilt age. Further, combining the two dating methods and classifying lime plaster samples in burned and unburned, it was possible to date different events within the same archaeological context. It is concluded that by combining these two dating methods and understanding the moment that each sample is dating, it is possible to obtain solid and precise chronologies.

We have investigated the possibility of direct accelerator mass spectrometry radiocarbon (AMS 14C) measurement of carbonate samples at ANSTO using the STAR 2 MV tandem accelerator. Each carbonate sample was powdered, mixed with metal powder and pressed into an aluminum cathode for direct carbonate measurement by AMS 14C. Of the three high-purity metal powders (Fe, Nb, and Ag) used in our investigation, Nb was found to be the best metal, which delivered higher carbon beam currents and lower background. Beam currents for targets containing the optimal carbonate mass of 1.5–2.0 mg were ∼8% of those obtained from graphite targets of standard size (>0.5 mg C). Typical measured blank for Carrara marble (IAEA-C1) of ∼40 ka was obtained. Background-corrected 14C values of carbonate targets agreed well with their associated values obtained from high-precision analysis of graphite targets within 2σ uncertainties. Typical precision of this rapid AMS analysis was ∼1% for samples <8 ka. Despite lower precision for carbonate target ages (compared to standard graphite target ages), these ages are useful for palaeobiological applications where a large number of dates are required, such as time-averaging studies.

The Kostenki-Borshchevo site complex (Voronezh region, Russia) serves as the foundation of Eastern Europe’s Upper Paleolithic chronocultural framework. Here we present new radiocarbon dates for three Kostenki sites. Dates of ∼27.5–27 ka BP for Kostenki 15 suggest that its archaeological layer accumulated over a short period. These results help to confirm that the site is unrelated to Aurignacian assemblages. New dates for the Kostenki-Avdeevo Culture (KAC) Layer I of Kostenki 1 address the longstanding question of its chronology. Our results of ∼23.5–23 ka BP from different areas of the site are consistent with the layer’s accumulation over a short period. These results accord with recently obtained dates for Kostenki’s other KAC sites. Our younger results of ∼22.5–21 ka BP for different material from Layer III of Kostenki 21 are similarly consistent with a short chronological window for Kostenki’s KAC sites. Overall, this and other recent publications support the view that many Kostenki assemblages are chronologically distinct. This provides an important insight into the tempo of Upper Paleolithic cultural change.

Along SE coast of Australia a variety of Holocene barriers composed of siliceous sand and shell detritus occur within bedrock-confined embayments. On basis of morphostratigraphy 4 barrier types are recognized: prograded, stationary, receded and episodic transgressive dunes. Several subtypes are also distinguished. Composite bay barriers involving partial eolian reworking of a prograded barrier constitute most complex examples of Holocene depositional sequences on this coast. The present list is a preliminary attempt at defining the age structure of a group of such barriers (excepting receded type). Ages are reported in conventional years bp. Text references to ages and age ranges are environmental effect corrected ages bp* and yr* (as recommended by Stuiver and Polach, 1977), using 450 ± 35 yr as postulated by Gillespie and Polach (in press) in order to relate Australian oceanic environment shells to terrestrial environment wood. δ13C errors, where based on measurement, are always ± 0.2% and are not shown in the text; when based on estimated values (Est) the error is given.

Preliminary observations of changes of the background of three proportional counters during May and June, 1986, are presented. Some isotopes contributing to the rise of background were identified on the basis of their half-life determinations.

We studied a suitable procedure for preparing of water samples used in radiocarbon intercomparisons involving dissolved inorganic carbon (DIC). The water samples must have inter-batch consistency and stable 14C concentrations and no sterilizing agent (e.g., HgCl2) should be added, in order to avoid the production of hazardous material. Six water samples, containing widely different amounts and types of salts, DIC, and 14C concentrations (1–100 pMC), were prepared in order to assess the procedure. Sample consistency was investigated through δ13C and chemical compositions; their low variabilities indicate that our procedure can be applied to radiocarbon intercomparison. A specific sample preparation protocol was developed for this kind of applications.

We consider one misconception of those who currently reject the general validity of radiocarbon (14C) age determinations older than, at most, 10,000 BP. There is an allegation that the presence of 14C reported by accelerator mass spectrometry (AMS) laboratories in their measurements of 14C infinite age (>100,000 years) organics used to define background levels, support their point of view. This article has been written for a general audience, primarily for those who have questions about the validity of these arguments. However, they may not be familiar with the literature relevant to providing a clear response to the claims of these individuals. We conclude that, in our view, of all of the possible explanations for the reports of the presence of 14C in these background samples, the least probable explanation has been advanced by those rejecting the validity of the 14C time scale in excess of, at most, 10,000 BP.

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.

Measurements of the radiocarbon abundance in 5 samples of bis(2–ethylhexyl) phthalate (DEHP) isolated from Stilton cheese were made by accelerator mass spectrometry (AMS) to determine the fraction of carbon originating from contemporary biogenic sources. DEHP is classified as a “priority hazardous substance” by the European Union, a probable human carcinogen by the United States Environmental Protection Agency, and is suspected to be a human endocrine disrupter. Measurement of its 14C abundance in a specific food indicates whether its presence is due to contamination from industrially synthesized DEHP or a naturally inherent component. A method was developed to determine the contemporary carbon fraction of DEHP in a fatty food matrix at concentrations of 0.14 mg/kg. Five 90–μg quantities of DEHP were extracted from 12 kg of Stilton cheese and isolated by silica gel, size exclusion, and high-performance liquid chromatography (HPLC). Masses of samples were determined by gas chromatography mass spectrometry (GC-MS) analyses prior to combustion and manometry afterwards. The purity of DEHP carbon mass in each isolate was determined by multivariate deconvolution of GCMS fragmentation spectra obtained from measurements of standards and isolates, and ranged from 88.0 ± 1.8% to 92.3 ± 1.1% (n = 5, 1σ). Concurrently processed isolation method blanks contained from 0.15 ± 0.04 to 1.52 ± 0.06 μg (n = 3, 1σ) DEHP per sample and significant quantities of pre- and post-chromatographic extraneous carbon contamination. The mean 14C-corrected contemporary carbon fraction of DEHP in the isolates was 0.235 ± 0.073 (1σ; and ± 0.091 at the 95% confidence level), revealing that the majority of DEHP in Stilton cheese results from anthropogenic sources, but with a significant naturally occurring component.