Varga Tamás
@atomki.hu
Research fellow
Institute for Nuclear Research
RESEARCH, TEACHING, or OTHER INTERESTS
Multidisciplinary, Environmental Science, Atmospheric Science, Food Science
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Tamás Varga, Mihály Molnár, Anita Molnár, A.J. Timothy Jull, László Palcsu, and Elemér László
Elsevier BV
Tamás Varga, Irka Hajdas, Lucio Calcagnile, Gianluca Quarta, István Major, A J Timothy Jull, Anita Molnár, and Mihály Molnár
Cambridge University Press (CUP)
ABSTRACTThe method of determining the biobased carbon content in liquid fuel samples is standardized, but different laboratories use different protocols during sample preparation and perform the measurements using different machines. The accelerator mass spectrometry (AMS) laboratories use different combustion, preparation, and graphitization methods for the graphite production for the spectrometric measurements. As a result, the intercomparison between the laboratories is inevitable to prove precision and accuracy and to demonstrate that the results are comparable. In this study, we present the results of an intercomparison campaign involving three 14C accelerator mass spectrometry laboratories. Five samples were used in the measurement campaign, including two biocomponents (fatty acid methyl ester, hydrotreated vegetable oil), one fossil component (fossil diesel), and two blends (mixtures of fossil and biocomponent with 90–10% mixing ratio) in the laboratories of CEDAD (Italy), ETH (Switzerland), and INTERACT (Hungary). The results presented by the laboratories are comparable, and all three laboratories could determine the biobased carbon content of the samples within 1% relative uncertainty, which is acceptable in the scientific, economic, and industrial fields for biocomponent determination.
Tamás Varga, Dóra Szejke, Zoltán Nemes, A J Timothy Jull, and Mihály Molnár
Cambridge University Press (CUP)
ABSTRACT Biobased content analysis is a well-established, analytically independent, standardized method to determine the biobased content of fuels and plastics, based on differences of the specific radiocarbon (14C) activity of fossil and recent biogenic compounds. This biogenic content analysis can be useful for the producers as a quality assurance tool, for the customers as feedback about the truly biobased products and for the control organizations as an independent analytical tool to prove the biological origin. More than 100 commercially available foods, cosmetics, and drug samples have been used for biobased carbon content analysis by accelerator mass spectrometry (AMS) 14C measurement to demonstrate the potential of this technique. Our results show that this measurement technique is a unique tool for the determination of biocontent in foodstuff and medical products. Most of the tested materials were nearly or completely biobased (≥ 98 pMC), and no completely fossil-based final product was detected. The lowest biogenic compound was measured in a vanilla aroma flavor. In 45 of the 102 samples selected a wide range (2–98%) presented fossil-based carbon content. The method can be applied for monitoring raw materials and final products for biobased content in the industry and consumer protection as well.
Irina Panyushkina, Valerie Livina, Mihály Molnár, Tamas Varga, and A J Timothy Jull
Cambridge University Press (CUP)
ABSTRACTA signal of rapid changes in 14C production is logged in annual series of 14C derived from tree rings, which can be associated with diverse effects of cosmic-ray fluxes, including solar burst and supernova events. These 14C signatures may vary in time and space. The intensity and structure of the 14C signal is multifaced, which complicates understanding of the forcing and attribution of the underlying astrophysical events. It was suggested that Δ14C in 1052/53 CE and 1054/55 CE signatures at a 4‰–6‰ range over two years could be caused by the Crab Nebula supernova (SN1054) or/and solar perturbation. The temporal incoherence of the signals in published 14C series is investigated with dynamic time warping (DTW), novel approach for matching time-behavioral patterns in multiple 14C datasets. DTW analysis of four 14C signatures from tree rings of California, Finland and England suggests that 14C spikes between 1052 CE and 1055 CE can be caused by a single event. The flickering fingerprint may result from cross-dating inconformity. Cross-checking of tree-ring records from distant locations is impossible sometimes due to large difference in environmental conditions limiting tree growth. The methodology helps to align the signals and can be applied to other 14C datasets.
G Quarta, I Hajdas, M Molnár, T Varga, L Calcagnile, M D’Elia, A Molnar, J F Dias, and A J T Jull
Cambridge University Press (CUP)
ABSTRACTIn the frame of the IAEA-CRP (Coordinated Research Projects): Enhancing Nuclear Analytical Techniques to Meet the Needs of Forensic Sciences, an intercomparison exercise was organized between three AMS laboratories. Aim of the program is to promote the use of nuclear and accelerator-based techniques in routine forensics practice. In this view, one of the key points is the assessment of the precision and accuracy levels achievable on material of forensic interest. We review the general structure and status of the project, with emphasis on results obtained in the analysis of wines of different grape varieties and grounded coffee beans from different locations such as Brazil, Spain, and Italy. The three laboratories processed the samples according to different chemical protocols and performed the 14C measurements using different systems: MICADAS in Zurich and Debrecen and a HVEE 4130HC 3 MV Tandetron in Lecce. Within the quoted uncertainty, the results showed good reproducibility, indicating that uncertainty level of the order of 0.3% are achieved by AMS on a single sample while multiple sample analyses results in precision down to 0.1–0.2%. The measured 14C concentrations on coffee and wine samples resulted to be consistent with atmospheric 14C levels in the growing years.
Irka Hajdas, Lucio Calcagnile, Mihaly Molnár, Tamás Varga, and Gianluca Quarta
Elsevier BV
István Major, Mihály Molnár, István Futó, Virág Gergely, Sándor Bán, Attila Machon, Imre Salma, and Tamás Varga
MDPI AG
The aim of this study was to estimate and refine the potential sources of carbon in the atmospheric PM2.5 fraction aerosol at three sampling sites in Hungary. Quantification of total, organic and elemental carbon (TC, OC and EC, respectively), as well as radiocarbon (14C) and stable carbon isotope analyses were performed on exposed filters collected at an urban background site, a suburban background site of the capital of Hungary, Budapest from October 2017 to July 2018. Results were also collected from the rural regional background site of K-puszta. Compared to TC concentrations from other regions of Europe, the ratio of the lowest and highest values at all sites in Hungary are lower than these European locations, probably due to the specific meteorological conditions prevailing in the Carpathian Basin over the observation period. The concentration of OC was constantly higher than that of EC and a seasonal variation with higher values in the heating period (October–March) and lower values in the non-heating vegetation period (April–September) could be observed for both EC and OC fractions. Using 14C, the seasonal mean fraction of contemporary carbon (fC) within the TC varied between 0.50 and 0.78 at the sites, suggesting that modern sources were remarkable during the year, regardless of the heating or vegetation period. At the two urban sites, assuming constant industrial emission during the year, the fossil fuel combustion sources were responsible for the seasonal variation of EC, while modern carbon emissions from biomass-burning and biogenic sources influenced the OC concentration. The higher EC/TC ratios at these sites were associated with lower fC and δ13C values, which can be explained by soot emission from transportation. The notably high EC/TC ratios in the spring were likely caused by the reduced concentration of OC instead of increased EC concentrations. This could probably be caused by the ending of winter biomass burning, which emits a huge amount of OC into the atmosphere. On the contrary, the rural K-puszta site showed some differences relative to the sites in Budapest. No correlation could be revealed between the EC/TC ratio, fC and δ13C results, suggesting that the structure of sources was very stagnant and balanced in each season. In autumn, however, some less depleted values were observed, and agricultural corn-stalk burning after harvesting in the southern and eastern directions from Hungary can be suggested as the main source.
Zsófi Sajtos, Tamás Varga, Zita Gajdos, Petra Burik, Máté Csontos, Zsuzsa Lisztes-Szabó, A.J. Timothy Jull, Mihály Molnár, and Edina Baranyai
Elsevier BV
Botond Buró, Gábor Négyesi, Tamás Varga, György Sipos, Dávid Filyó, A J Timothy Jull, and Mihály Molnár
Cambridge University Press (CUP)
ABSTRACTThe most widely used dating techniques in quaternary research are the radiocarbon (14C) and optically stimulated luminescence (OSL) dating methods. In some environments, the investigated sediments do not contain enough material for 14C dating. In these cases, 14C dating of bulk sediment may be used as a last resort. The major aim of the present study was to determine the reliability and limitations of the different fractions of the soil organic carbon (SOC) 14C ages in the Nyírség blown-sand study area, in Hungary. Therefore, the low- and high-temperature combustions of SOC (LT-SOC and HT-SOC) 14C age of fossil soils were compared with the charcoal ages from the same fossil soil layer, and their (LT-SOC, HT-SOC, and charcoal) age reliability was verified independently by applying OSL to the quartz fraction of the sediment samples. The 14C data show variable agreement with OSL ages. Charcoal fragments were collected from some of the best material for 14C dating and their ages are in agreement with the LT and HT-SOC 14C ages and OSL data. The 14C age LT-SOC gives a reliable, credible ages, which were confirmed by independent OSL measurements. If buried soils do not contain any other macroscopic remnants for 14C dating, the LT-SOC 14C ages can be used, in the case of the Nyírség study area. The LT-SOC, which is the younger fraction of the soil organic carbon, may be considered to represent the burial time of the fossil soil layer. The HT-SOC 14C ages are sometimes unrealistically older than expected and cannot be considered to be reliable.
A. J. Timothy Jull, Irina P. Panyushkina, Mihály Molnár, Tamás Varga, Lukas Wacker, Nicolas Brehm, Elemér Laszló, Chris Baisan, Matthew W. Salzer, and Willy Tegel
Springer Science and Business Media LLC
A Correction to this paper has been published: https://doi.org/10.1038/s41467-021-21647-w
A. J. Timothy Jull, Irina P. Panyushkina, Mihály Molnár, Tamás Varga, Lukas Wacker, Nicolas Brehm, Elemér Laszló, Chris Baisan, Matthew W. Salzer, and Willy Tegel
Springer Science and Business Media LLC
Sabrina G K Kudsk, Jesper Olsen, Gregory W L Hodgins, Mihály Molnár, Todd E Lange, Jessica A Nordby, A J Timothy Jull, Tamás Varga, Christoffer Karoff, and Mads F Knudsen
Cambridge University Press (CUP)
ABSTRACTA laboratory intercomparison project was carried out on 20 annually resolved late-wood samples from the Danish oak record. The project included the following three laboratories: (1) the University of Arizona AMS Laboratory, University of Arizona, USA (AA); (2) HEKAL AMS Laboratory, MTA Atomki, Hungary (DeA); and (3) Aarhus AMS Centre (AARAMS), Aarhus University, Denmark (AAR). The large majority of individual data points (96%) lie within ±2σ of the weighted mean. Further assessment of the accuracy associated with the individual laboratories showed good agreement, indicating that consistent and reliable 14C measurements well in agreement with each other are produced at the three laboratories. However, the quoted analytical uncertainties appear to be underestimated when compared to the observed variance of differences from the geometric mean of the samples. This study provides a general quality check of the single-year tree-ring 14C measurements that are included in the new calibration curve.
Tamás Varga, István Major, Virág Gergely, András Lencsés, Tibor Bujtás, A.J. Timothy Jull, Mihály Veres, and Mihály Molnár
Elsevier BV
T. Varga, R. E. Fisher, J. L. France, L. Haszpra, A. J. T. Jull, D. Lowry, I. Major, M. Molnár, E. G. Nisbet, and E. László
American Geophysical Union (AGU)
István Major, Enikő Furu, Tamás Varga, Anikó Horváth, István Futó, Brigitta Gyökös, Gábor Somodi, Zsuzsa Lisztes-Szabó, A.J. Timothy Jull, Zsófia Kertész,et al.
Elsevier BV
Mihály Molnár, Marianna Mészáros, Róbert Janovics, István Major, Katalin Hubay, Botond Buró, Tamás Varga, Titanilla Kertész, Virág Gergely, Ádám Vas,et al.
Cambridge University Press (CUP)
ABSTRACTA coupled accelerator mass spectrometer–gas interface system has been successfully operating at the Hertelendi Laboratory of Environmental Studies, Debrecen, Hungary, since 2013. Over the last 6 years more than 500 gas targets were measured below 100 µg carbon content for carbon isotopic composition. The system was tested with blanks, OxII, IAEA-C1, IAEA-C2, and IAEA-C7 standards. The performance of our instrumentation shows good agreement with other published gas-interface system data and also shows a quite good agreement with the nominal value of international standard samples. There is a measurable but quite small memory effect after modern samples, but this does not significantly affect the final results. Typical ion currents at the low energy side were between 10–15 µA with a 5% CO2 in He mixing ratio. The relative errors average ±6% for samples greater than or equal to 10 µgC sample with mean count rates of 300 counts per microgram C for OxII. The blank is comparable with other systems, which is 0.0050 ± 0.0018 F14C or 34,000–47,000 yr BP, which allows for the routine measurement of both of small environmental and archeological samples.
F Terrasi, F Marzaioli, R Buompane, I Passariello, G Porzio, M Capano, S Helama, M Oinonen, P Nöjd, J Uusitalo,et al.
Cambridge University Press (CUP)
ABSTRACTAnnually resolved radiocarbon (14C) measurements on tree rings led to the discovery of abrupt variations in 14C production attributed to large solar flares. We present new results of annual and subannual 14C fluctuations in tree rings from a middle-latitude sequoia (California) and a high-latitude pine (Finland), analyzed for the period 1030–1080 CE, to trace a possible impact of the Crab supernova explosion, occurring during the Oort minimum of solar activity. Our results indicate an increase of Δ14C around 1054/55 CE, which we estimate is higher in magnitude than the cyclic variability due to solar activity at a 2σ significance level. The net signal appears to be synchronized in the studied locations. Several sources of this event are possible including γ-rays from the Crab supernova, an unusually weak solar minimum or a solar energetic particle incident. More data are needed to provide more insight into the origin of this 14C event.
Tamás Varga, Zsófi Sajtos, Zita Gajdos, A.J. Timothy Jull, Mihály Molnár, and Edina Baranyai
Elsevier BV
Imre Salma, Anikó Vasanits-Zsigrai, Attila Machon, Tamás Varga, István Major, Virág Gergely, and Mihály Molnár
Copernicus GmbH
Abstract. Fine-fraction aerosol samples were collected, and air pollutants and meteorological properties were measured in situ in the regional background environment of the Carpathian Basin, a suburban area and central part of its largest city, Budapest, in each season for a 1-year-long time interval. The samples were analysed for PM2.5 mass, organic carbon (OC), elemental carbon (EC), water-soluble OC (WSOC), radiocarbon, levoglucosan (LVG) and its stereoisomers, and some chemical elements. Carbonaceous aerosol species made up 36 % of the PM2.5 mass, with a modest seasonal variation and with a slightly increasing tendency from the regional background to the city centre (from 32 % to 39 %). A coupled radiocarbon-LVG marker method was applied to apportion the total carbon (TC = OC + EC) into contributions of EC and OC from fossil fuel (FF) combustion (ECFF and OCFF, respectively), EC and OC from biomass burning (BB) (ECBB and OCBB, respectively), and OC from biogenic sources (OCBIO). Fossil fuel combustion showed rather constant daily or monthly mean contributions (of 35 %) to the TC in the whole year in all atmospheric environments, while the daily contributions of BB and biogenic sources changed radically (from <2 % up to 70 %–85 %) at all locations and over the years. In October, the three major sources contributed equally to the TC in all environments. In January, it was the BB that was the major source, with a share of 70 % at all sites. The contributions from biogenic sources in January were the smallest. In April, FF combustion and biogenic sources were the largest two contributors at all locations with typical shares of 45 %–50 % each. In July, biogenic sources became the major source type with a monotonically increasing tendency (from 56 % to 72 %) from the city centre to the regional background. The share of BB was hardly quantifiable in July. The ECFF made up more than 90 % of EC in April and July, while in October and January, the contributions of ECBB were considerable. Biomass burning in winter and autumn offers the largest and most considerable potential for improving the air quality in cities as well as in rural areas of the Carpathian Basin.
Tamás Varga, Gergely Orsovszki, István Major, Mihály Veres, Tibor Bujtás, Gábor Végh, László Manga, A.J. Timothy Jull, László Palcsu, and Mihály Molnár
Elsevier BV
Tamás Varga, A J Timothy Jull, Zsuzsa Lisztes-Szabó, and Mihály Molnár
Cambridge University Press (CUP)
ABSTRACTThe increase of fossil-fuel-derived CO2 in the atmosphere has led to the dilution of the atmospheric radiocarbon concentration, but due to the costly instrumentation, the continuous atmospheric 14C/12C data is incomplete in developing countries, such as in Indonesia. These data give useful information about the level of local and regional fossil emissions. In this study, 14C AMS measurements of local vegetation and woody plant species samples have been used to estimate the rate of fossil-fuel-derived carbon in the plants, which fix the CO2 from the atmosphere by photosynthesis. Evergreen leaf samples were collected in September 2018 on the island of Bali in different, diverse districts in local and urban areas. The samples from the densely populated areas show observable fossil fuel emissions and show that the Δ14C level is close to zero ‰, similar to the natural level.
Tamás Varga, László Palcsu, Tomoko Ohta, Yasunori Mahara, A J Timothy Jull, and Mihály Molnár
Cambridge University Press (CUP)
ABSTRACTRadiocarbon (14C) analysis was performed on Japanese cedar (Cryptomeria japonica) tree rings from Koriyama, Fukushima prefecture. Our primary aim was to detect any 14C release from the Fukushima Dai-ichi nuclear power plant accident on 11 March 2011. We also completed and assessed the 14C level in Japanese tree rings for the period of 1990–2014 because of the lack of environmental 14C results in the Japanese island that time. For this reason, we used a trajectory model to investigate the air mass forward and backward trajectories at the area of the power plant and sampling site. The modeling data show that the air masses mainly moved to the Pacific Ocean, both during March 2011 and during the growing season (March–September). During the period 1990–2014 there was no significant 14C excess in any of the samples, but there was a detectable Suess effect in almost every tree ring sample. The average fossil contribution was 0.83 ± 0.01% and the calculated anthropogenic component ratio, the 14C excess varied between +0.5 and –1.6%. The Δ14C value decreased from 150.0‰ to 9.5‰ from 1990–2014, which follows the decline of the 14C bomb peak, in addition to any detectable Suess effect.
Tamás Varga, István Major, Róbert Janovics, Júlia Kurucz, Mihály Veres, A J Timothy Jull, Mónika Péter, and Mihály Molnár
Cambridge University Press (CUP)
ABSTRACTThe 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.
A J Timothy Jull, Irina Panyushkina, Fusa Miyake, Kimiaki Masuda, Toshio Nakamura, Takumi Mitsutani, Todd E Lange, Richard J Cruz, Chris Baisan, Robert Janovics,et al.
Cambridge University Press (CUP)
ABSTRACTTwo radiocarbon (14C) excursions are caused by an increase of incoming cosmic rays on a short time scale found in the Late Holocene (AD 774–775 and AD 993–994), which are widely explained as due to extreme solar proton events (SPE). In addition, a larger event has also been reported at 5480 BC (Miyake et al. 2017a), which is attributed to a special mode of a grand solar minimum, as well as another at 660 BC (Park et al. 2017). Clearly, other events must exist, but could have different causes. In order to detect more such possible events, we have identified periods when the 14C increase rate is rapid and large in the international radiocarbon calibration (IntCal) data (Reimer et al. 2013). In this paper, we follow on from previous studies and identify a possible excursion starting at 814–813 BC, which may be connected to the beginning of a grand solar minimum associated with the beginning of the Hallstatt period, which is characterized by relatively constant 14C ages in the period from 800–400 BC. We compare results of annual 14C measurements from tree rings of sequoia (California) and cedar (Japan), and compare these results to other identified excursions, as well as geomagnetic data. We note that the structure of the increase from 813 BC is similar to the increase at 5480 BC, suggesting a related origin. We also assess whether there are different kinds of events that may be observed and may be consistent with different types of solar phenomena, or other explanations.