In 2008, the atmospheric CO2 measurements at the Hegyhátsál rural tower station were extended further by 14CO2 air sampling from two elevations (115 and 10 m a.g.l.), in cooperation with HEKAL (ICER). Since then, a complete six-year-long (2008–2014) dataset of atmospheric CO2, Δ14C, fossil, and modern CO2 excess (relative to Jungfraujoch) has been assembled and evaluated. Based on our results, the annual mean CO2 mole fraction rose at both elevations in this period. The annual mean Δ14CO2 values decreased with a similar average annual decline. Based on our comparison, planetary boundary layer height obtained by modeling has a larger influence on the variation of mole fraction of CO2 (relative to Jungfraujoch), than on its carbon isotopic composition, i.e. the boundary layer rather represents a physical constraint. Fossil fuel CO2 excess at both elevations can rather be observed in wintertime and mainly due to the increased anthropogenic emission of nearby cities in the region. The mean modern CO2 excess at both elevations was even larger in winter, but it drastically decreased at 115 m by summer, while it remained at the winter level at 10 m.

This paper presents first chronological results for a Holocene marshland system from the southern part of the Danube-Tisza Interfluve. Radiocarbon (14C) ages were used to build age-depth models relying of probabilistic tools. Four models have been built: a linear one using dates gained via simple calibration, a P_Sequence model, fitting a polynomial function to calibrated dates; a Gamma_Sequence considering priori given and posterior accumulation rates have been constructed. As there was no significant difference between the mean values of individual models all seem suitable for establishing a reliable chronology despite differences in 95% CI ranges. While P_Sequence models underestimated SR, values calculated from the polynomial model were not significantly different from those of the G_Sequence. Based on multiproxy geochemical, sedimentological, paleoecological data the evolution of the system was reconstructed, covering a timespan of ca. 13,000 years starting from 12,000 BC and lasting until 1300 AD. Highest accumulation rates are dated to the Early Middle Ages from the 11th century. Several climate changes could have been identified which are present in other Hungarian and Western European records too, such as the 5b IRD event at ca. 5800 BC, a humid phase around 1600 BC, and a cool humid phase around the 6th century AD.

The biocomponent ratio in liquid fuels as well as the usage of renewable resources for fuel consumption in the transport sector needs to be increased as a result of EU directive 2003/30/EC. Based on radiocarbon (14C) measurements, it should be relatively simple and fast to measure the weight percentage of the fossil and biological sources by accelerator mass spectrometry (AMS) as recommended in the ASTM D 6866-12 and EN 16640 standards. In this study, a relatively easy and fast sample preparation and measurement method based on AMS measurements was developed at the Hertelendi Laboratory of Environmental Studies (HEKAL) using reference samples from the Hungarian MOL Nyrt. oil company. Considering the recent EU regulation for mixing rates of liquid fuels in the transport sector (0.7–2% biofuel content) and the projected higher rates (2–10% biofuel content), the method is applicable to determine fatty acid methyl ester (FAME) and/or hydrotreated vegetable oil (HVO) derived proportions of fuel blends with a 1σ uncertainty better than±0.3% m/m.

The determination of the proportion between the biogenic and the fossil-derived fraction in carbon dioxide emissions from industrial stationary sources is a relevant aspect in the frame of the worldwide efforts to reduce greenhouse gas emissions into the atmosphere. In this field the 14C-based method has gained importance over the years and has been included in standard protocols accepted at both the national and international levels. The advantages of the method, based on the large difference in terms of 14C signature between fossil and biogenic carbon, are reviewed as well as some critical aspects related to its application. In particular the results of a study aimed at validating the method by analyzing synthetic gas mixtures produced in a dedicated plant and with a tuneable proportion between fossil and biogenic carbon dioxide are presented.

Recent advancements in accelerator mass spectroscopic (AMS) radiocarbon (14C) analytical methods and instrumentation offer us reliable conventional 14C ages with highly reduced analytical uncertainty for archeological bone collagen. However, after calibration this may be still too high for archeologists in periods where archeochronology is capable of attaining a resolution of 25–30 yr. Furthermore, there are cases when wiggles in the calibration curve yield wider age ranges than initially expected. For the Avar Age in the Carpathian Basin (568 to early 9th century AD) reliable archeotypochronology is available for the 7th century AD alone. The date of Avar invasion (568 AD) is precisely known. Precise archeological dating for the late 6th and the 9th centuries is lacking, calling for other methods to be introduced. This paper reports the first 14C dates for an Early Avar Age cemetery, Makó-Mikócsa. According to archeotypochronology, the cemetery was in use for three generations until the mid-7th century AD. The imprecision in 14C chronology arising from wiggles in the IntCal13 curve was significantly reduced by relative stratigraphy-controlled Bayesian modeling. Introduction of further age constraints from archeotypochronology into the model reduces broad absolute age ranges providing more constraint ages.

An effective sealed tube combustion method was designed with an MnO2 oxidant for accelerator mass spectrometry radiocarbon (AMS 14C) measurements. Different types of materials (oxalic acid, cellulose, sucrose, wood, collagen, graphite, and humic acid) were used to test the method. A normal borosilicate glass tube was used instead of quartz and the combustion was done at 550ºC. The yield of the combustion is above 98% even in the case of the less combustible material such as graphite. The MnO2 reagent does not introduce detectable carbon contamination. The typical background is 0.29±0.20 pMC in the case of 200 µg carbon, measured as solid graphite target. With direct measurement of the CO2 by gas ion source AMS, the method is applicable up to 50 µg of carbon with an acceptable (~1 pMC) 14C background. A new type of tube cracker was developed for a quick chipless method of tube cracking and sample changing. In this way, the gas handling process takes only 5–6 min/sample.

In order to evaluate effects of three land uses on isotopic compositions of CO2 and O2 of soil air to 5 m soil depth, a field study was conducted in the Calhoun Critical Zone Observatory, located in the subtropical climate of the Southern Piedmont of South Carolina, USA. Soil gas reservoirs were installed in ecosystems with three different land uses, each replicated three times: (i) reference hardwood stands that were never cultivated; (ii) currently cultivated plots; (iii) pine stands, which had been used for growing cotton in 19th century but were abandoned in about the 1930s and 1940s when they were regenerated with pines that are today 70–80 yr old. In addition to soil CO2 and O2 concentration measurements, soil gas samples were analyzed for Δ14C, δ13C, and δ18O. Stable carbon isotopic composition becomes lighter with the depth in soils of all three land uses: in the cultivated site δ13C decreases from –18‰ at 0.5 m to –21‰ at 5 m, in pine site from –22 to –25‰, and in hardwood from –21.5 to –24.5‰, respectively. Δ14C increased with depth from 40 to 60‰ in the top 0.5 m to about 80–140‰ at 5 m depending on land use. While surficial soils had relatively similar Δ14C in CO2, between 40 to 60‰ at 0.5 m, at 3 and 5 m, cultivated soils had the highest Δ14C, hardwood the lowest, and pine in between, a pattern that emphasizes the importance of contemporary respired CO2 in hardwood stands. Oxygen isotopic composition of CO2 did not change with depth, whereas free O2 was greatly enriched in lower horizons of forest soils, which we attribute to strong fractionation by respiration.

This work focuses on building a high-resolution age-depth model for quantitative palaeoclimate study from the Mohos peat bog, East Carpathian mountains. The investigated core presents a continuous peat profile for the last 12 kyr. The chronology was based on 36 accelerator mass spectrometry radiocarbon (AMS 14C) analyses of the separated Sphagnum samples from different depths of the profile. Dry Sphagnum samples for AMS dating were prepared using the classic acid-base-acid (ABA) method followed with an oxidative bleaching step to get clean cellulose. Sphagnum cellulose samples were measured by AMS using the EnvironMICADAS at the ICER (Debrecen, Hungary). A high-resolution chronology was obtained with the use of Bayesian age-depth modeling. Peat accumulation rate has been calculated and the sections with variable accumulation rate values were observed along the profile.

Measurements of the radiocarbon (14C) and tritium (3H) activity in a 5.8-m-long ice core from the Saarhalle, Dachstein-Mammoth Cave allowed a substantial revision of previous opinions concerning the age of the ice block, and provide useful experience that may be applied to future 14C dating of cave ice deposits. The stepped combustion technique results in a remarkably older radiocarbon age for the 800°C than for the 400°C fractions of the carbonaceous matter from ice layer samples. The highest tritium activity (37.2±1.2 TU) can be linked to the period of anthropogenically increased tritium activity of atmospheric precipitation at the mid-1960s, providing a well-dated radiochemical reference horizon. Compared the 3H-based extrapolated ages of two shallow samples to the expected atmospheric signal an average 14C reservoir bias of ~1500 BP was obtained for the insoluble organic fraction combusted at 400°C. The conventional 14C age measured for the 400°C fraction of the deeper samples has been corrected with the average reservoir bias. The median calibrated age of the deepest analyzed sample of the ice profile is ~1830 cal BC and a linear extrapolation to the bottom ice layer gave 2590 cal BC, making the Saarhalle ice block among the oldest dated cave ice deposits known in the Alpine domain.

Organic material and a few tree trunks have been recovered from the shrinking ice deposits of Velebit Mountain, Croatia. Ten radiocarbon (14C) dates, seven new measurements and three recalibrated ones, from three cave ice deposits were evaluated. The new data argue for the preservation of a ~1000-yr-old deposit in the Kugina Ice Cave and a <500-yr-old accumulation in the Ledena Pit. A 14C age suggests that the ice in the lower section of Vukušić cave ice deposit is very likely older than 3500 yr. The work is in progress to verify this suggestion. Evaluation of the temporal distribution of the calibrated ages of the 14C-dated vegetal remains allowed constraining the accumulation and ablation history of cave ice in the northern and central Velebit. Periods lacking vegetal remains in these cave ice deposits (before the 11th century and in the 15th century) tend to match with similar patterns from other cave ice deposits from the Eastern Alps and the Swiss Jura Mountains, suggesting large-scale coherence regulating European cave ice mass balance changes over the past ~1200 yr.

Ecse Mound is a burial mound in the Hortobágy region of eastern Hungary. Built by prehistoric nomadic peoples from the east, it now stands on the border between two modern settlements. The construction of the mound was assumed to be related to representatives of the Pit Grave Culture populating the area between the Late Copper and Bronze Ages. This theory considered similarities in shape, orientation, and stratigraphy of this mound with other absolute-dated ones in the Hortobágy region alone. The mound comprises two construction layers as indicated by magnetic susceptibility and on-site stratigraphic observations. According to detailed sedimentological, geochemical analyses of samples taken from the bedrock, artificial stratigraphic horizons, and the overlying topsoil, there is a marked similarity between the soil forming the body of the mound in both artificial horizons and the underlying bedrock soil. In contrast the pedological, geological character of the modern topsoil is utterly different. According to our dating results, the uppermost stratigraphic horizon is coeval with the absolute-dated mounds in the region, assigning it to the period of the Pit Grave Culture. However, the lower anthropological horizon is older and dates to between the Early and Late Copper Ages.

The vertical distribution of soil organic carbon (SOC) with depth and its horizontal pattern is influenced by the topography and relief of the surface, due to lateral redistribution of soil material along slopes. Spatial and temproral variability of these changes is frequently due to human impacts on the landscape. In our study, the results of these processes were studied in detail in a small sub-catchment in a forested hillslope section using radiocarbon (14C) dating of SOC and embedded datable material (charcoal, artifacts) from soil profiles with colluvial accumulations. Events with accelerated material redistribution could be identified as an accumulation of a 40-cm-thick colluvial layer between cal BC 410–360 (2σ) and cal AD 430–580 (2σ). Later colluvial deposition resulted in thinner accumulations (cal AD 1120–1220 [2σ] 30 cm; cal AD 1810–1920 [2σ] 21 cm). As the earliest human impact, we found soil transformation from cal BC 1290–1130 (2σ). The depth-age model for SOC compiled according to the average SOC age and its depth showed different characteristics on middle-slope and down-slope position, with rates of 48.0 yr×cm–1 and 22.0 yr×cm–1 respectively, which indicates the importance of topographic position of soils in SOC redistribution processes.

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.

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.

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.

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.

We collected peat sediments (sediment core ADK13083002) from Haven Lake on the north side of Adak Island (central Aleutian Islands, Alaska) to determine whether the vegetation has changed. We confirmed the presence of six tephra layers, including Forty Years (0.3 cal ka BP), T2, YBO (3.3 cal ka BP), Intermediate (6.4 cal ka BP), Main (9.5 cal ka BP), and T6. We identified four major pollen assemblage zones (HL-1 to HL-4, in descending order) in the cored sediment. HL-1 was dominated by Ranunculaceae and Empetrum pollen; H-2 was dominated by Poaceae, Ranunculaceae, and Empetrum pollen; HL-3 was dominated by Poaceae and Empetrum pollen; and HL-4 was dominated by Poaceae, Cyperaceae, Lycopodiaceae, and Empetrum pollen. Small charcoal particles, likely transported from a distance, were found at low frequencies until 6.4 cal ka BP. The total cross-sectional area of charcoal particles increased to 1500 μm2 or more by 6.4 cal ka BP, implying that the large charcoal particles originated from nearby Aleut settlements, which were established around the same time.

Distributions of Δ14CTOC studied in bottom sediments collected during 2011–2016 in the Curonian Lagoon and in the open Baltic Sea indicated wide variations of Δ14CTOC values. Laboratory experiments on differential carbon utilization by Pseudomonas putida isolated from bottom sediments were carried out for better understanding of impacts of different sources on Δ14CTOC variations. Preferential glucose uptake (up to 80%) as a carbon source and a rather low (2–10%) inorganic carbon incorporation was found in media with diesel fuel. Pseudomonas putida a specific biomarker analyzed in biomass cultivated on the media with different carbon sources has been used to characterize microbial communities responsible for degradation of organic substances in bottom sediments. Large 14C depletions observed in sediments collected in the Gotland Deep of the Baltic Sea may indicate leakage from dumped chemical weapons.

Archaeological fieldwork at Hjarnø Sund in Horsens Fjord (eastern Jutland, Denmark) has explored an eroding Mesolithic shell midden. Its stratigraphy is characterized by two layers, containing marine mollusk taxa typically collected by Mesolithic hunter-gatherers for food. In the field, the lower layer appeared to be dominated by oysters (Ostrea edulis), while the upper one by cockles (Cerastoderma edule), which was confirmed by our zooarchaeological study. Accelerator mass spectrometry radiocarbon (AMS 14C) dating on shells and paired charcoal samples from the two layers indicate that these are chronologically consecutive (separated by as little as 0–163 yr [95.4%]) and that the oyster-to-cockle shift dated between ~5500–5300 and ~5300–5200 cal BC (around or just after the Kongemose/Ertebølle transition). The shell midden at Hjarnø Sund is, thus, one of the oldest-known in Denmark, demonstrating that intensive shellfish exploitation was a hallmark of the Ertebølle culture from its inception. Oyster-to-cockle shifts, thus, also occurred at times other than the Mesolithic–Neolithic Transition and may have been ultimately caused by local shoreline displacements, resulting from changes in sedimentation, possibly induced by drops in relative sea level.