Macrofossils of terrestrial plants have been picked from a sediment core taken in Lake Lobsigen, a small lake on the Western Swiss Plateau. The sediments were previously analyzed for pollen composition, plant and animal macrofossils, and stable isotopes. Plant macrofossils were selected near pollen zone boundaries in Late Glacial and early Postglacial sediment for 14C dating by AMS. In the same lake carbonate and gyttja (aquatic plant) samples were dated by decay counting. The dates on terrestrial material are generally younger than those on carbonate and gyttja, ie, material reflecting the 14C/C ratio of dissolved bicarbonate in lake water. This is probably due to a contribution of dissolved limestone carbonate and thus a somewhat reduced 14C/C ratio in the lake's water (hard water effect).

A more developed and modern technology replaced the old radiocarbon measuring methods in Hungary, based on isotope separation by accelerator mass spectrometry (AMS) and not on activity measurements. In summer 2011, the EnvironMICADAS was successfully installed in the Laboratory of HEKAL, Debrecen, Hungary. In this project, a multipurpose gas-handling system was developed for the gas ion source of EnvironMICADAS at ETH Zürich, designed for the measurement of small environmental origin samples (<50 μg carbon) with moderate precision requirements. The ultimate aim is an automated device for high sample throughput. Since its final installation and first year of operation, over 2000 graphite targets were analyzed. Long-term stability of the instrument is confirmed through measurements of the Ox-II standard and processed blank targets during the first half of 2012.

This paper describes all the major procedures adopted by the Scottish Universities Environmental Research Centre (SUERC) Radiocarbon Dating Laboratory. This includes sample pretreatment, graphite production, accelerator mass spectrometry (AMS) measurement, associated stable isotope measurements, data handling, and age calculations, but with the main emphasis being on the chemical pretreatment methods. All of the above enable the laboratory to provide a complete analytical service comprising advice on sample selection, preparation and analysis of samples, and Bayesian analysis of resulting 14C (and other) data. This applies to both our research and commercial activities. The pretreatment methods that we mainly focus on are used to remove contaminant carbon from a range of sample types or to isolate a particular chemical fraction from a sample prior to combustion/hydrolysis, graphitization, and subsequent AMS 14C measurement. The methods described are for bone (collagen extraction, with and without ultrafiltration), cremated bone, tooth enamel, charcoal, grain, carbon residues, shell, wood (including alpha-cellulose isolation), peat, sediments, textiles, fuel/biofuel, and forensic samples.

Accelerator mass spectrometry (AMS) radiocarbon dating of ostracod and gastropod shells from the southwestern Black Sea cores combined with tephrochronology provides the basis for studying reservoir age changes in the late-glacial Black Sea. The comparison of our data with records from the northwestern Black Sea shows that an apparent reservoir age of ∼1450 14C yr found in the glacial is characteristic of a homogenized water column. This apparent reservoir age is most likely due to the hardwater effect. Though data indicate that a reservoir age of ∼1450 14C yr may have persisted until the Bølling-Allerød warm period, a comparison with the GISP2 ice-core record suggests a gradual reduction of the reservoir age to ∼1000 14C yr, which might have been caused by dilution effects of inflowing meltwater. During the Bølling-Allerød warm period, soil development and increased vegetation cover in the catchment area of the Black Sea could have hampered erosion of carbonate bedrock, and hence diminished contamination by “old” carbon brought to the Black Sea basin by rivers. A further reduction of the reservoir age most probably occurred contemporary to the precipitation of inorganic carbonates triggered by increased phytoplankton activity, and was confined to the upper water column. Intensified deep water formation subsequently enhanced the mixing/convection and renewal of intermediate water. During the Younger Dryas, the age of the upper water column was close to 0 yr, while the intermediate water was ∼900 14C yr older. The first inflow of saline Mediterranean water, at ∼8300 14C yr BP, shifted the surface water age towards the recent value of ∼400 14C yr.

This paper is the third of a series detailing the general features of 14C distribution in the world oceans. In the preceding papers, we discussed the 14C activities of Atlantic and Pacific Ocean waters (Stuiver and Östlund, 1980; Östlund and Stuiver, 1980). We now give an outline of the 14C distribution of the Indian Ocean and profiles for one Mediterranean and three Red Sea stations.

The main methods applied to clean plant material for radiocarbon dating are not compound-specific and generally remove only the easily exchangeable components by an acid-base-acid sequence and additional optional steps like Soxhlet extraction to remove resins and oxidative bleaching with NaClO2. The products are normally clean enough for standard 14C measurement, but in some cases it is desirable to have pure cellulose, which remains unchanged and immobile over longer time ranges, better representing the original plant material. In this work, 2 more compound-specific but still simple methods were tested to separate the cellulose from wood. The viscose method is based on the xanthification process used in the textile industry, where the alkali-cellulose with CS2 forms a soluble cellulose xanthate, which is then extracted and cellulose is recovered. The second procedure is based on the wood/cellulose dissolution in ionic liquid 1-butyl-3-methylimidazolium chloride [BMIM]Cl, when the dissolved cellulose could be precipitated again by simply adding a water-acetone mixture. This process was recently reported, but still not used in sample preparation procedures for 14C dating.

We have studied environmental isotopes and noble gases in groundwater samples from various locations in the Great Hungarian Plain along two selected hydrogeological cross-sections of ca 100km. The 14C groundwater ages were corrected hydrochemically and compared with age information derived from excess helium due to 4He from α-decay of U and Th and their daughter nuclides within the aquifer and to He accumulation from the crustal (and mantle) He flux. In correcting the 14C groundwater ages, we considered carbonate dissolution under open and closed system conditions in the infiltration areas. Non-radioactive reduction of the 14C/12C isotope ratio also plays an important role due to the addition of “dead” carbon species to groundwater along its subsurface pathway. High (corrected) 14C ages, which fall into the last global cold period, are supported by significantly lower heavy stable isotope values as well as lower temperatures derived from the noble gases Ne, Ar, Kr and Xe.

In Groningen, all organic samples for accelerator mass spectrometry (AMS) are combusted in an automatic Elemental Analyzer, coupled to an Isotope Ratio Mass Spectrometer and Cryogenic Trapping System. The Gas Chromatographic (GC) column, part of the Elemental Analyzer system, appeared to be the main cause for memory effects. Therefore we modified the Elemental Analyzer, such that the trapped CO2 no longer passed the GC column. Our system modification reduced the memory effect significantly, as shown by lower radiocarbon concentration values for anthracite backgrounds, and a much smaller spread in these values. Our modified system can perform up to 40 combustions unattended in about 6 hr.

The occurrence of atmospheric 14C variations complicates calibration, ie, the translation of 14C ages into real calendar ages. The procedure of wiggle matching, however, allows very precise calibration, by matching known 14C variations with wiggles in the floating chronology. In principle, wiggle matching can also be applied to a series of 14C dates from organic (peat) deposits. Where, in general, 14C ages are required at short distances and on small samples, dating by 14C accelerator mass spectrometry (AMS) is required.

Non-hydraulic mortars contain datable binder carbonate with a direct relation to the time when it was used in a building, but they also contain contaminants that disturb radiocarbon dating attempts. The most relevant contaminants either have a geological provenance and age or they can be related to delayed carbonate formation or devitrification and recrystallization of the mortar. We studied the mortars using cathodoluminescence (CL), mass spectrometry (MS), and accelerator mass spectrometry (AMS) in order to identify, characterize, and date different generations of carbonates. The parameters—dissolution rate, 13C/12C and 18O/16O ratios, and 14C age—were measured or calculated from experiments where the mortars were dissolved in phosphoric acid and each successive CO2 increment was collected, analyzed, and dated. Consequently, mortar dating comprises a CL characterization of the sample and a CO2 evolution pressure curve, a 14C age, and stable isotope profiles from at least 5 successive dissolution increments representing nearly total dissolution. The data is used for modeling the interfering effects of the different carbonates on the binder carbonate age. The models help us to interpret the 14C age profiles and identify CO2 increments that are as uncontaminated as possible. The dating method was implemented on medieval and younger mortars from churches in the Åland Archipelago between Finland and Sweden. The results are used to develop the method for a more general and international use.

Carbon isotope measurements in soil CO2 are presented and discussed. Soil CO2 concentration and 13C profiles were measured using a new technique. A simple model describing the CO2 transport from the soil to the atmosphere is derived. The finding that CO2 in the soil is richer in 13C than the CO2 leaving the soil is attributed to isotopic fractionation in molecular diffusion.

Bayesian mathematics provides a tool for combining radiocarbon dating results on findings from an archaeological context with independent archaeological information such as the chronological order, which may be inferred from stratigraphy. The goal is to arrive at both a more precise and a more accurate date. However, by means of simulated measurements we will show that specific assumptions about prior probabilities—implemented in calibration programs and not evident to the user—may create artifacts. This may result in dates with higher precision but lower accuracy, and which are no longer in agreement with the true ages of the findings.

The reaction conditions for the graphitization of CO2 with hydrogen were optimized for a fast production of high-quality carbon samples for accelerator mass spectrometry (AMS) measurement. The iron catalyst in use is first oxidized by heating with air to remove possible carbon and other impurities and then after evacuation reduced back to iron with hydrogen in several flushing steps to remove any iron oxide. The optimum conditions for a fast graphitization reaction were experimentally determined by changing the reaction temperatures and the H2/CO2 ratio. The resulting graphite samples were measured by AMS to find the smallest isotopic changes (δ13C) at a minimum of molecular fragment formation (13CH current). The improvements are based on thermodynamic data and are explained with Baur-Glaessner diagrams.

Expensive and time-consuming preparation procedures for radiocarbon and stable isotope analyses can be conducted on archaeological bone samples even if no collagen is preserved. Such unsuccessful preparation can lead to the partial destruction of valuable archaeological material. Establishing a rapid prescreening method for evaluating the amount of bone collagen while minimizing the impact of sampling constitutes a challenge for the preservation of archaeological collections. This study proposes and discusses a new methodology to detect and quantify collagen content in archaeological bone samples by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. A total of 42 Pleistocene to modern bone samples were selected according to their nitrogen content measured using an elemental analyzer. Comparison of collagen content estimation using ATR-FTIR and mass spectrometry reveals that some of the studied samples are contaminated by a nitrogen source coming from the burial environment. Two different FTIR calibration approaches were tested on the uncontaminated samples: peak-to-peak ratio and multivariate regression (PLS). The two approaches yield similar results with a good correlation of ATR-FTIR analyses and N wt% from 0.7 to 4wt% (R²=0.97–0.99; standard error of estimation ±0.22 to 0.25wt%). While collagen content remains difficult to detect in poorly preserved bones (less than ~3wt%), ATR-FTIR analysis can be a fast alternative for sample screening to optimize the sampling strategy and avoid partial destruction of valuable samples that do not contain enough collagen for further analysis.

Infrared (IR) spectrophotometry and X-ray diffraction (XRD) were conducted on modern and fossil bone material from archaeological sites in the U S to determine post-mortem changes in bone apatite and to evaluate the effect of these changes on radiocarbon dating. IR absorption bands, XRD peak-broadening parameters, and XRD unit cell measurements indicated that during fossilization, bone apatite, a mineral similar to dahllite, was partially or completely recrystallized to francolite. Post-mortem changes involved then removal of some of the endogenous crystal carbonate both at surfaces and at internal OH-sites and introduction of exogenous carbonate into internal crystal PO4 sites. Increased fluorine content accompanied carbonate substitution.

Both the carbon isotopic composition and the amount of exogenous carbonate introduced into the apatite structure will affect the radiocarbon dating of bone apatite. Special sample pre-treatment may remove most of the substituted carbonate in some cases. Simulated experiments are suggested for a better understanding of the nature and mechanism of carbonate substitution in bone apatite for the removal of the exogenously substituted carbon and the improvement of radiocarbon dates.

Given the non-monotonic form of the radiocarbon calibration curve, the precision of single 14C dates on the calendar timescale will always be limited. One way around this limitation is through comparison of time-series, which should exhibit the same irregular patterning as the calibration curve. This approach can be employed most directly in the case of wood samples with many years growth present (but not able to be dated by dendrochronology), where the tree-ring series of unknown date can be compared against the similarly constructed 14C calibration curve built from known-age wood. This process of curve-fitting has come to be called “wiggle-matching.”

In this paper, we look at the requirements for getting good precision by this method: sequence length, sampling frequency, and measurement precision. We also look at 3 case studies: one a piece of wood which has been independently dendrochronologically dated, and two others of unknown age relating to archaeological activity at Silchester, UK (Roman) and Miletos, Anatolia (relating to the volcanic eruption at Thera).

Initially, radiocarbon dating by bomb 14C was used to check vintages of wine and whisky and to estimate the turnover times of carbon in various biological tissues. However, this technique has never been widely used for routine dating, although it has a wide field of application in geriatric medicine and forensic investigations. Fifteen years' experience in this field has shown the potential and limits of this technique. Taking into account the decisive biological factors, such as growth and aging, a complicated picture is obtained. Recent human bones cannot be dated with a constant precision. Despite an incomplete understanding of the process of incorporation of 14C into human bones, the present dating technique is still more precise than most estimates by geriatric experts, for conventional 14C dating follows that 14C dates of bone collagen represent the years of the termination of puberty rather than those of death.

Another application is the identification of furs of illegally hunted animals on the “Red List of threatened species” of the World Conservation Union (IUCN). For court cases, the year the animals were killed must be precisely determined. Due to the long and variable turnover time of more than one year of leather hair is the best dating material for animals.

This list contains most of the unpublished radiocarbon dates measured between 1961 and 1968. Analyses of the C14 content of groundwater are excluded and a number of geologic dates will be included in a later list. Certain earlier analyses performed by H. de Vries and H. de Waard are included, as well as a few results obtained since W. G. Mook assumed responsibility for the laboratory in 1969, to complete series. Descriptions and comments are mainly based on information supplied by the submitters or contained in the publications cited. However, our own interpretation is often given in the comments. Sections I A to D2, II B1, and B2 were mainly prepared by the first author and the rest by the second.

Oak and pine samples housed at the Institute of Botany, University of Hohenheim, are the backbone of the early Holocene part of the radiocarbon calibration curve, published in 1993 (Becker 1993; Kromer and Becker 1993; Stuiver and Becker 1993; Vogel et al. 1993). Since then the chronologies have been revised. The revisions include 1) the discovery of 41 missing years in the oak chronology and 2) a shift of 54 yr for the oldest part back into the past. The oak chronology was also extended with new samples as far back as 10,429 BP (8480 BC). In addition, the formerly tentatively dated pine chronology (Becker 1993) has been rebuilt and shifted to an earlier date. It is now positioned by 14C matching at 11,871-9900 BP (9922–7951 BC) with an uncertainty of ±20 yr (Kromer and Spurk 1998). With these new chronologies the 14C calibration curve can now be corrected, eliminating the discrepancy in the dating of the Younger Dryas/Preboreal transition between the proxy data of the GRIP and GISP ice cores (Johnsen et al. 1992; Taylor et al. 1993), the varve chronology of Lake Gościąż (Goslar et al. 1995) and the pine chronology (Becker, Kromer and Trimborn 1991).