A large collection of maize macro-specimens has been gathered from archaeological sites across the American continent, but only a few have been directly dated by accelerator mass spectrometry (AMS). We recently conducted two new excavations in several rock shelters of Tehuacán valley (San Marcos, Coxcatlán, and Purrón) and uncovered 132 non-manipulated macro-specimens of maize suitable for morphological and paleogenomic analysis, including many complete cobs, stalks, internodes, and leaves. Direct AMS dates for 43 samples found in San Marcos or Coxcatlán confirm the previously reported chronologies for these sites. By contrast, a cob found in Purrón was dated to 3060±30 before present (3360–3180 cal BP) (2σ), demonstrating that maize was present at that site at least 1500 calendar years earlier than previously expected, and suggesting that other specimens of similar age are still likely to be found in the southeastern region of the Tehuacán valley. A global comparison of macro-specimen chronology across the continent shows that the current archaebotanical record does not yet reflect the chronology of dispersal from central Mexico to northern or southern regions, opening the possibility for finding the missing links in subsequent expeditions within Mexico and Central America.

Two archaeologically unexplored mounds were studied in the area of the central Great Hungarian Plain. The age of the construction of the mounds was clarified on the basis of radiocarbon (14C) age determination of buried soil layers. Different, later-building phases of the mounds were detected by pedological and geo-electric analyses of the human-made layers. The age of the buried soils was corrected for the reservoir age of the recent soils found in the surroundings of the mounds. Radiocarbon ages of the carbon extracted from the soils at temperatures 400 and 800ºC were almost completely the same. Based on the calibrated ages of cal BP 4830–5270 (Szálka Mound) and cal BP 4880–5290 (Vajda Mound) of the buried soil layers, the identified kurgans were built by people of the Copper Age Yamnaya Culture. On the basis of the pedological and geophysical analysis of the layers, Szálka Mound and Vajda Mound were built in two and in three phases respectively from the chernozem-like humus-rich topsoil layers of the surrounding area. The former shallow quarry sites have been almost completely filled and cannot be identified at the foot of the mounds even using geodetic methods.

Soil CO2 flux measurement is a key method that can be used to monitor the hazards in an active volcanic area. In order to determine accurately the variations of the CO2 soil emission we propose an approach based on the radiocarbon (14C) deficiency recorded in the plants grown in and around the Solfatara (Naples, Italy). We twice sampled selected poaceae plants in 17 defined sites around the Solfatara volcano. 14C measurements by liquid scintillation counting (LSC) were achieved on the grass samples. The 14C deficiency determined in the sampled plants, compared to the atmosphere 14C activity, ranged from 6.6 to 51.6%. We then compared the proportion of magmatic CO2 inferred to the instantaneous measurements of CO2 fluxes from soil performed by the accumulation chamber CO2 degassing measurement at the moment of the sampling at each site. The results show a clear correlation (r=0.88) between soil CO2 fluxes and 14C activity. The determination of the plants 14C deficiency provides an estimate of the CO2 rate within a few square meters, integrating CO2 soil degassing variations and meteorological incidences over a few months. It can therefore become an efficient bio-sensor and can be used as a proxy to cartography of the soil CO2 and to determine its variations through time

The Eastern Black Sea region of the South Caucasus contains an extremely rich record of metallurgical remains that is poorly known outside of the former Soviet Union. Large numbers of relatively small smelting sites dot the foothill regions, forming a dispersed, yet large-scale metallurgical landscape. New fieldwork in the region has followed up on earlier Soviet period research, relocating and reanalyzing previously known sites and identifying new ones. This paper presents a series of 33 radiocarbon (14C) dates from copper and iron smelting sites in this region. Dates from copper smelting sites suggest that copper smelting occurred over a shorter and more intense period than previously thought, between about 1300 and 800 BC. Dates from newly discovered iron smelting sites place these activities in two episodes during the Classical-Hellenistic period (ca. 500–200 BC) and the High Medieval period (ca. AD 1050–1400). The dramatic expansion in bronze production immediately prior to the adoption of iron mirrors patterns in other regions of Europe and the Near East, and has implications for understanding the economic contexts in which iron emerged. While the new dates from iron smelting sites provide only an initial outline of the iron production chronology in the region, they represent an important step for resolving outstanding issues from previous investigations.

A series of radiocarbon (14C) dates of peat and other materials, containing organic matter, were obtained from Belyi Island. We have identified a large group of dates associates with MIS 1, as well as a significant group of dates associated with the Kargin (MIS 3) period (40–31 ka cal BP). A large number of dates from the Late Glacial period and from the Early Holocene (MIS 1—ca. 14–9 ka cal BP) point to this time interval being associated with warm climate conditions (the Holocene thermal maximum). The climate cooled off significantly during the Middle and Late Holocene, and the intensity of peat accumulation declined. The dates from the MIS 2 period are missing, due to the conditions of this period being extremely unfavorable for the accumulation of peat, as well as of other materials suitable for 14C dating.

We applied the high temperature pyrolysis-combustion technique to partition the total soil organic carbon (SOC) into labile and inert carbon pools for accelerator mass spectrometry radiocarbon (AMS 14C) dating and stable carbon isotope (δ13C), SOC, and carbonate carbon (CC) content analyses to examine SOC variability at a Critical Zone Observatory site in Illinois, USA. The AMS 14C dates of labile and inert carbon in the top 1.55 m overlap except in the Bt horizon. Below 1.55 m the labile carbon is younger by 8000–14,800 years. The SOC content decreases from 3.61% to 0.12% and CC content increases from 0% to 19.16% at this depth. Results indicate that SOC production exceeds its loss in the weathering zone causing a continuous turnover of both SOC pools. A small amount of modern SOC infiltrates into deeper sediment below 1.55 m, making the labile carbon pool much younger. Their difference of AMS 14C contents, ΔF14C, reveals 3−5% more modern carbon in the labile SOC pools except in the Bt horizon, further quantifying that <3−5% modern carbon with potential pollutants is translocated into the unweathered sediments. The δ13C reveals the sources for SOC cycling dynamics in both carbon pools at this site.

Terrestrial plant remains in the sediments of lakes from semi-arid and arid regions are rare and therefore the establishment of a sediment chronology depends on accurate assessment of the reservoir effect of the lake water. In a study of Genggahai Lake in the Gonghe Basin, northeastern Qinghai-Tibetan Plateau, we used accelerator mass spectrometry radiocarbon (AMS 14C) dating to determine the age of (1) dissolved inorganic carbon in the water (DICLW), (2) macrophyte remains in the uppermost samples of core sediments, (3) living P. pectinatus in the lake, and (4) dissolved inorganic carbon of spring water in the catchment. The results show that the ages of the DICLW (910 14C yr BP on average) were much younger than the ages of the groundwater (6330 14C yr BP on average), which may result mainly from CO2 exchange between the lake water and the atmosphere. In addition, the 14C ages of DICLW and macrophyte remains in the uppermost core sediments varied from site to site within the lake, which we ascribe to the different photosynthesis rates of Chara spp. and vascular plants. The higher photosynthesis rate of Chara spp. decreases lake-water pCO2, which leads to more atmospheric CO2 being absorbed by the lake water, and thereby greatly reducing the age of carbon species in areas dominated by Chara spp. Although Genggahai Lake is well mixed, the differences between the apparent ages of the lake water are significantly modulated by the photosynthesis intensity of submerged plants.

In this paper, we compile recent 14C dates related to the Neolithic transition in Mediterranean Iberia and present a Bayesian chronological approach for testing the dual model, a mixed model proposed to explain the spread of farming and husbandry processes in eastern Iberia. The dual model postulates the coexistence of agricultural pioneers and indigenous Mesolithic foraging groups in the Middle Holocene. We test this general model with more regional models of four geographical areas (Northeast, Upper, and Middle Ebro Valley, and Eastern and South/Southeastern regions) and present a filtered summed probability of all 14C dates known in the region in order to compare socioecological dynamics over a long period. Finally, we discuss the results and analyze how certain specific characteristics of sites and their chronologies can serve for timing the Neolithic expansion in Mediterranean Iberia.

Leaching tests were carried out in aerobic and anaerobic conditions to assess the 14C released from TRIGA irradiated graphite. Both total 14C and inorganic and organic fractions in the leachant solutions were measured. The experimental results obtained from the leaching tests confirm the low 14C release rate in alkaline environment. Less than 2% of the total 14C inventory in the specimens subject to the leaching tests was released as dissolved species. Both inorganic and organic 14C species are released in alkaline conditions, with more inorganic 14C release under aerobic conditions (around 68% of the total 14C released was released as inorganic dissolved species), and more organic 14C species in anaerobic conditions (around 65% of the total 14C released was released as organic dissolved species). Both for anaerobic and aerobic conditions, the leaching rates are high in the first days of immersion and decrease after that, indicating a two stage process: an initial quick release (less than 9 × 10–02 % of inventory/day for the first 48 days) followed by a slower release rate (around 4 × 10–03 % of inventory/day).

Temporal changes in soils of forest landscapes of the forest-steppe zone—Haplic Luvisols and Greyzemic Phaeozems—under the impact of Holocene climate changes (natural factor) and long-term cultivation (anthropogenic factor) were studied on level interfluves of the Central Russian Upland. These soils were developed from covering loesslike loam of varying thickness. To study soil evolution under the impact of climate changes, soil chronosequences of archaeological sites—paleosols buried under ramparts of ancient settlements and background surface soils of adjacent areas—were analyzed. The time of the soil burying was determined via the 14C dating of charcoal from thin twigs sampled in the material of ramparts immediately above the surface of buried soils. According to 14C dates, the paleosols were buried in the interval from 2450±40 to 1150±110 BP. Before the Subatlantic period, these paleosols developed under grassland (steppe), which is proved by their properties typical of steppe soils and by the presence of paleokrotovinas—the features created by the burrowing activity of steppe animals (mole rats)—in the studied profiles. The 14C dates of the total organic carbon of humus in the dark gray filling of a paleokrotovina from a Phaeozem buried at the depth of 140–150 cm under the rampart of 1150±110 BP in age ranged from 6080±150 to 2810±60 BP. The evolution of steppe Chernozems into forest Phaeozems and Luvisols took place in the Late Holocene. The anthropogenic evolution of forest Luvisols and Phaeozems under the impact of long-term (more than 150–230 years) plowing was analyzed in the soil agrochronosequences that included background soils under native forest vegetation and their arable analogs with different durations of cultivation. It was concluded that this evolution is directed towards Chernozemic pedogenesis, i.e., it proceeds in the direction opposite to the natural trend of pedogenesis in the Late Holocene. This process takes place despite the traditional practice of limited application of organic fertilizers in arable farming in the studied region. A decrease in the mean residence time (MRT) of total organic carbon (TOC) in the old-arable soils is considered a consequence of the formation and accumulation of fresh humus material in the profiles of cultivated soils—one of the major processes in the transformation of arable forest soils into Chernozems. The accumulation of carbonates and an increase in their 14C age take place in the arable soils in comparison with their forest analogs. In the agrochronosequence from the Polyana site, the 14C age of carbonates at the depth of 170–180 cm reaches 8000±100, 8270±150, and 9150±100 BP under the forest, 100-year-old plowland, and 150-year-old plowland, respectively. This can be explained by the ascending migration of ancient carbonates from the parent material in suspensions. In the analogous Samarino agrochronosequence, the 14C age of carbonates from the depth of 90–100 cm comprised 6500±90, 7150±100, and 12,360±230 BP, respectively. Thus, the studied forest-steppe soils have a polygenetic nature specified by a complicated history of pedogenesis under the impact of both natural (climate-driven forest invasion into steppe) and anthropogenic (deforestation and land plowing) factors.

We implement a Bayesian statistical analysis of the chronology of Canímar Abajo in Cuba in order to estimate two episodes of burial activity and the period of time corresponding to the hiatus between them. We show that by using simple Bayesian modeling, conclusions can easily be reached by the analysis of the marginal posterior distribution of each parameter of the model. However, we also suggest and describe new statistical tools that exploit the joint posterior distribution of collections of dates. These new tools give complementary information regarding the chronology of human activity.

Substantial amounts of annual radiocarbon (14C) data have recently been produced with the purpose of increasing the time resolution of 14C records used for constructing the calibration curve and for studying the occurrence of abrupt cosmic-ray events. In this study, we investigate if it is possible to resolve sub-annual scale changes in the atmospheric 14C content by measuring radiocarbon in early-wood and late-wood fractions from Danish oak. The tree-ring samples span the period 1954–1970 CE, hereby covering the peak of the bomb pulse. A least squares test comparing the atmospheric 14C content and the new sub-annual 14C record from Danish tree rings reveals that by measuring early-wood and late-wood fractions, it may be possible to resolve sub-annual variations in past atmospheric 14C levels.

The use of accelerator mass spectrometry (AMS) for age determinations of paintings is growing due to decreasing sample size requirements. However, as only the support material is usually dated, the validity of the results may be questioned. This work describes a novel sampling and preparation technique for dating the natural organic binder using radiocarbon (14C) AMS. In the particular case of oil paintings, the natural oil used has a high probability of being representative of the time of creation, hereby circumventing the problem of the originality of the support material. A multi-technique approach was developed for a detailed characterization of all paint components to identify the binder type as well as pigments and additives present in the sample. The technique was showcased on a painting of the 20th century. The results by 14C AMS dating show that both the canvas and binding medium predate the signed date by 4–5 yr. This could be the time span for keeping painting material in the atelier. The method developed provides, especially given the low amounts of material needed for analysis, a superior precision and accuracy in dating and has potential to become a standard method for oil painting dating.

Generally, 14C is produced in all types of reactors, mainly through neutron-induced reactions with isotopes of carbon, nitrogen, and oxygen. These isotopes are present in the fuel, fuel cladding, coolant, moderator, and structural materials of the reactor. Irradiated graphite contains a range of activation products but, from the point of view of geological disposal, another radionuclide which has to be taken into account is tritium (3H or T), produced through the neutron induced reaction Li(n,α)T. In this study we have investigated the release of 14C and 3H into the solution phase from two intact samples of irradiated graphite which have been cut from the thermal column disc located near the VVR-S reactor core. To evaluate 14C and 3H long-term release in solution the graphite samples were submerged in a solution of 0.1 M of sodium hydroxide. The experimental results regarding the release of 14C and 3H from VVR-S irradiated graphite to liquid phase show that a major fraction of the total release occurs in the first months and a slower release on a long time scale. However, these results should be applied cautiously for long time prediction.

In the sequences of landslide fen (mire) deposits of the Polish Western Carpathians, Late Glacial-Holocene paleoenvironmental changes were recorded. Downpours and/or continuous rains cyclically repeated during phases of climate humidity growth, causing supplies of mineral material to the minerogenic mires. In effect, illuvial or mineral horizons were formed in landslide fen deposits, as well as mineral covers overly fens in some sites. Sedimentological records reflect various, overlapping factors, as climatic changes, human activity (e.g. accelerating erosion), as well the specificity of the sedimentary environment in each studied landslide fens. The reconstruction and interpretation of the paleoenvironmental changes recorded in landslide fen sediments must be supported by multiproxy analysis of the sequences using pollen, lithological (loss on ignition, grain size and petrography) analyses of samples accurately dated by numerous radiocarbon (14C) dates.

The marine reservoir effect is the difference in radiocarbon (14C) between the atmosphere and the marine surface ocean. To overcome the dating errors induced, it is necessary to correct marine 14C ages for this effect. ΔR is the difference between the marine 14C age and the marine calibration curve based on an ocean-atmosphere box diffusion model, which accounts for the time delay in diffusion of carbon into the ocean from the atmosphere and biosphere. This global assessment, however, requires computation of a regional ∆R value for calibration to cater for studies based on a local scale. In this paper the marine reservoir effect is assessed for the southern and eastern coasts of South Africa using 14C dating on pre-1950 marine shells of known age. The resultant ∆R values enable a more complete understanding of the marine reservoir effect along the southern and eastern coastal zone of South Africa. 14C age determinations were conducted on 15 shell samples of known age and the results, combined with previously published values, were used to calculate regional marine reservoir correction values. The east coast has a weighted mean ∆R of 121±16 14C yr, while the south coast has a weighted mean ∆R of 187±18 14C yr.

Marine insertion indicators in the Vitoria estuary (ES) revealed relative variations in sea level during the Holocene in three sediment cores. Sedimentological, geochemical (C/N ratio), and paleontological (shells and palynomorphs) analysis and 14C dating associated five sedimentary facies to different estuarine deposits. A C/N ratio <10 at the core base indicated organic matter of marine origin. Moving up the cores to 110–150 cm, an abrupt increase in C/N to 26–63 in every core suggests the sudden entry of higher plants into the estuary, potentially the moment sea level retreated. High continental (10,743 palynomorphs/g) and low marine palynomorph concentrations (323 palynomorphs/g) suggest a primarily continental source even during transgression and at high sea level. Around 8973 cal BP, an open bay already existed in the region of Vitoria. Sea level potentially exceeded the current level around 7110 cal BP. The transgressive maximum was at 5567 cal BP. Marine insertion indicators, such as marine shells, low C/N ratios and foraminiferal linings, did not always respond directly to sea level oscillations. These discrepancies probably result from lateral variations in sedimentary deposits from transport patterns and from variations in organic matter and palynomorph preservation due to differences in river and obstacle proximity.

There are two units with RBMK-1500 type reactors at the Ignalina Nuclear Power Plant (Ignalina NPP) in Lithuania where graphite was used as a neutron moderator and reflector. These reactors are now being decommissioned, and Lithuania has to find a solution for safe irradiated graphite disposal. It cannot be disposed of in a near surface repository due to large amounts of 14C (radiocarbon, carbon-14); thus, a deep geological repository (DGR) is analyzed as an option. This study had the aim to evaluate 14C migration from the RBMK-1500 irradiated graphite disposed of in a potential DGR in crystalline rocks taking into account the outcomes of the research performed under the collaborative European project CAST (CArbon-14 Source Term) and to identify the potential to reduce the conservatism in the assumptions that was introduced in the lack of data and led in the overestimated 14C migration. The information gathered during the CAST project was used to model 14C transport in the near field by the water pathway and to perform uncertainty analysis. The study demonstrated that more realistic assumptions could reduce the estimated 14C flux from the near field by approximately one order of magnitude in comparison with the previous estimations based on very conservative assumptions.

A better understanding of the dynamics of different particulate organic matter (OM) pools in the coastal carbon budget is a key issue for quantifying the role of the coastal ocean in the global carbon cycle. To elucidate the benthic component of this carbon cycle at the land-sea interface, we investigated the carbon isotope signatures (δ13C and ∆14C) in the sediment pore waters dissolved inorganic carbon (DIC) in addition to the sediment OM to constrain the origin of the OM mineralized in sediments. The study site is located at the outlet of the Rhône River (Mediterranean Sea), which was chosen because this river is one of the most nuclearized rivers in Europe and nuclear 14C can serve as a tracer to follow the fate of the OM discharged by the river to the coastal sea. The ∆14C results found in the pore waters DIC show a general offset between buried and mineralized OM following a preferential mineralization model of young and fresh particles. For example, we found that the sediment OM has values with a mean ∆14C=–33‰ at sampling stations near the river mouth whereas enriched ∆14C values around +523‰ and +667‰ respectively were found for the pore waters DIC. This indicates complete mineralization of a riverine fraction of OM enriched in 14C in the river conduit during in-stream photosynthesis. In shelf sediments, the ∆14C of pore waters DIC is slightly enriched (+57‰) with sediment OM reaching –570‰. A mixing model shows that particles mineralized near the river mouth are certainly of riverine phytoplanktonic origin whereas OM mineralized on the shelf is of marine origin. This work highlights the fact that pore waters provide additional information compared to sediments alone and it seems essential to work on both pools to study the carbon budget in river prodelta.

The peat bog at Homoródszentpál Kerek-tó (Round Lake), situated in Homoród Hills of the Eastern Carpathians in Romania, provides a continuous record of paleoclimatic and paleoenvironmental changes from the Early Holocene. In this study, we present a 7500-year-long high-resolution record of past climatic changes and signs of human impact recorded in a peat bog via integrating sedimentological, paleoecological and geochemical proxies. The basin of Round Lake formed around the Pleistocene–Holocene border when the permafrost thawed. Ponded water accumulated in the catchment basin from the beginning of the Holocene but ca. 7500 cal BP years ago lacustrine sedimentation was exchanged for peat accumulation. The 570-cm-long core was subsampled at 2–4 cm intervals and subjected to grain-size, loss-on-ignition (LOI), pollen, and radiocarbon (14C) analyses. Our findings were correlated with and interpreted in the light of paleobotanical records deriving from archaeological sites and the newest bioclimatological models of the nearby areas. Sedimentological analysis document erosion and accumulation events which were influenced by more complex processes like climate change. Based on environmental historical and climatic data we aimed to reconstruct the environmental changes of forested areas in the Homoródi Hills.