Although the Chernobyl accident caused increased 14C levels in certain areas, it has been difficult to prove that it had any effect in two areas of Sweden and one on Svalbard (Spitsbergen), where the precipitation and wind conditions were such that the γ-active fall-out was negligible. Knowledge of the steady regional decrease and annual variations at high latitudes, where the pollution from fossil fuel is less than in central Europe, is essential for global studies of the CO2 cycle. The present 14C excess is a net effect of the 14C supply, mainly from tests of nuclear weapons, and dilution, by 14C-free, fossil-fuel consumption. In Sweden, at these northern latitudes, the 14C excess is steadily slightly higher than for “clean air” in central Europe. Annual variations are also smaller in Sweden and Svalbard than in central Europe. The normal 14C excess on Svalbard is slightly less than in Sweden. Detailed results, especially from autumn 1984 to autumn 1987, are given for atmospheric CO2 collected in northern Sweden (Abisko) and on Svalbard (Kapp Linné) and for some atmospheric samples and plant material collected ca 50km east of Uppsala, very close to heavily polluted areas.

The results of a 10-year survey of 14C content in tree leaves from the vicinity of Swiss nuclear installations are reported. The interpretation is based on the results from a reference station showing a systematic decrease from δ14C = +350 in 1977 to ca 4–190 in 1987. Excess activities of up to ca 100 are observed in the vicinity of nuclear power plants which are compatible with release rates and dilution calculations. A higher excess of up to 1400 is measured in the close vicinity of a small research plant which releases the activity on top of the roof. The determined decrease of the activity with distance can be described by a power law with ca −1.4 in the exponent. Additional doses of 14C to plants and population from excess 14C activities are estimated to be negligible compared to natural doses.

We present results of airborne 14C emission measurements from the Paks PWR nuclear power plant. Long-term release of 14C in the form of carbon dioxide or carbon monoxide and hydrocarbons were simultaneously measured. The results of internal gas-proportional and liquid scintillation counting agree well with theoretical assessments of 14C releases from pressurized water reactors. The mean value of the 14C concentration in discharged air is 130Bqm-3 and the normalized release is equal to 740GBq/GWe · yr. > 95% of 14C released is in the form of hydrocarbons, ca 4% is apportioned to CO2, and <1% to CO. Tree-ring measurements were also made and indicated a minute increase of 14C content in the vicinity of the nuclear power plant.

Detonation of the first fission bomb at White Sands, New Mexico, on July 16, 1945, produced a tremendous neutron flux capable of creating tritium and radiocarbon byproducts. We sampled a 115-year-old pinyon (Pinus edulis) 10km east of the Trinity test site to determine 14C evidence of this event. The most likely mechanism for this enrichment in the 1945 tree ring would be fixation of 14CO2 produced at the blast site and carried with the fallout cloud over the pinyon site. Analysis of cellulose of the 1944 and 1945 rings shows δ13C values of −19.9 and −19.5, respectively, and 14C activity (fraction of modern uncorrected for δ13C) as 0.991 ± .005 and 0.991 ± .006, respectively. It is likely that the duration and/or concentration of the 14CO2 exposure was not sufficient to increase 14C activity expected for that year.

Tree rings spanning the past three decades were collected from Picea spp trees grown in Matra, northern Hungary. Cellulose was prepared from the wood and samples were separately combusted for tritium and 14C analyses. Methane was synthesized from CO2 obtained by sample combustion via catalytic reaction with tritium-free hydrogen. 14C activity was measured by proportional counter. The exchangeable tritium was removed from cellulose samples used for tritium analysis. Water samples produced by combustion were measured by liquid scintillation counting. The distribution of tritium and 14C activities in tree rings are shown for years 1956–1986. Results are compared with published data on global-scale distribution of 14C and HTO. A comparison of tritium activity in precipitation and wine samples from the same region is presented.

As an extension of the Bratislava – Tbilisi collaboration, thermonuclear bomb-produced 14C variations in atmospheric CO2 of Bratislava (1967–1987) and in annually produced Georgian wines (1950–1987) are discussed. 14C produced in bomb tests performed in the atmosphere has considerably modified the natural 14C levels in the atmosphere and biosphere. Measurements of 14C in monthly samples of atmospheric CO2 show typical seasonal variations with maxima in summers and deep minima in winters. There is very good agreement between 14C measured in CO2 and in wine samples. Four maxima (1959, 1964, 1970 and 1978) were identified in the wine data. Our results confirm that wines prepared from annually grown grapes without any addition of other substances are good indicators of the 14C content of atmospheric CO2.

A simple and quick method for the determination of 14C in ethanol has been developed, using an ultra low-level liquid scintillation counter. I have studied factors influencing the lower limit of detection and have shown that liquor can be measured directly without pretreatment. Results of measurements on Austrian wines are presented and compared with results obtained from tritium measurements. The applicability and limitations of the results to age determination are discussed.

δ13C and 14C activity measurements were made on terrestrial, marsh and aquatic plants growing in their natural habitat of the Plitvice Lakes in northwest Yugoslavia. δ13C values were ca −47 for aquatic mosses, which indicate that the carbon source was dissolved inorganic carbon (DIC) from alkaline karst waters, following a C3 pathway, and ca −25 for marsh plants, indicating the carbon source was atmospheric CO2. 14C activity of true aquatic plants and submerged parts of helophytes was close to 14C activity of DIC, whereas that of emergent parts of helophytes and terrestrial plants was similar to atmospheric CO2 activity. Aquatic plants which use DIC in freshwater for their photosynthesis are not suitable for 14C dating, unless the initial activity of incorporated carbon is known. δ13C values of plant material also depend on the carbon source and cannot be used for 14C age correction.

The main purpose of this work is to reconstruct the atmospheric Δ 14C in the glacial-postglacial transition, 14,000 – 10,000 BP, a range not covered by the tree-ring calibration curve. We measured 14C/12C ratios on series of terrestrial macrofossils from sediments of two Swiss lakes. We selected exclusively plant remains of recognizable terrestrial origin that are not affected by hard water and thus reflect atmospheric 14C concentration. Due to the scarcity of such material, we used accelerator mass spectroscopy. Cores of two lakes were measured to eliminate local effects and to check the reproducibility of results. This required a reliable, 14C-independent correlation of the cores, obtained through local pollen zone boundaries 14C ages were obtained as a function of the depth in the cores. If sedimentation rates are known ages can be converted into Δ 14C values. We also attempted estimating sedimentation rates; calculations are based on the Swedish varve chronology. Results were combined to form an entire data set. The Δ 14C curve shows an increase with time during the Allerød and decreases during Preboreal and Bølling periods. Probabilities for these 14C variations are discussed.

A PC-based computer program for automatic calibration of 14C dates has been developed in Turbo-Pascal (version 4.0). It transforms the Gaussian 14C dating result on the 3σ level into a real calendar age distribution. It uses as a calibration curve a spline function, generated along the calibration data points as published in the Radiocarbon Calibration Issue. Special versions of the code can average several 14C dates into one calibrated result, generate smoothed curves by a moving average procedure and perform wiggle matching.

Two methods of assigning probability values to calendar years are compared by summing distributions for a large number of 14C ages derived from samples initially distributed uniformly in calendar years. The radiocarbon ages are calibrated with both a hypothetical calibration curve and the internationally accepted one. The effect of the calibration curve on an ideal and a random sample population is examined.

A set of computer procedures for probabilistic calibration of 14C dates was developed at the Gliwice Radiocarbon Laboratory for the IBM PC compatible microcomputer. The program comprises three main options: 1) calibration of a single 14C date, 2) calibration of a set of arbitrary dates, 3) calibration of a set of related dates. Results of calibration are presented in the form of graphs and numeric data, including tables of selected quantiles and inter-quantile ranges of resulting probability distribution of cal age. In this paper, we present the aims of the program, with a short description of its structure, show examples of working with output data in terms of expected archaeological application, and consider the possibility of standardization of calibration procedures.

Thirty-one samples of 5 tree rings from a single oak trunk with 300 tree rings were measured with improved precision to study natural 14C variations in the period from ca 9750 – 10,050 cal bp. Negative correlation was found between Δ 14C values and tree-ring indices. The pattern of 14C changes in the studied interval closely resembles the changes observed in several periodically spanned intervals within the limits of high-precision calibration data sets.

Radiocarbon variations in dated tree-ring samples represent an important tool for the study of the history of solar activity and sun-earth relationships. From this point of view, an investigation of the 11-year radiocarbon cycle is very important. Our cyclogram analysis of the Δ 14C record in tree-ring samples during the last century has confirmed previous results obtained by conventional harmonic analysis, eg, the average amplitude of 2, the phase shift of 3–5 yr for different 11-yr solar cycles, and the anticorrelation dependence of Δ 14C on Wolf sunspot numbers. The observed shorter periodicity (ca 9 yr for Δ 14C compared to 10.5 yr for sunspots), may be due to extra factors in sun-earth relationships.

Current calibration methods for single and replicate 14C dates are compared. Various forms of tabular and graphic output are discussed. Results from all the methods show reasonable agreement but further methodological development and improvements in computer output are required. Comparison of existing techniques for a series of non-contemporaneous dates showed less agreement amongst participants on this issue. We recommend that calibrated dates should be presented as a combination of graphs and ranges, in preference to mean and standard deviation.

This paper describes the organic carbon cycle of the recharge environment of a shallow, sandy aquifer, with an emphasis on the origin, flux and geochemical evolution of dissolved organic carbon using liquid chromatography, carbon isotopes and GC-MS techniques. The two components of DOC investigated are hydrophobic acids and C1-C10 hydrophilic compounds. The 14C activity of these components of the DOC was measured using TAMS.

14C analyses of DOC components may provide an additional tool for groundwater dating. The initial 14C activity of DOC in a recharge zone, however, depends mainly on the residence times and cycling of DOC sources in the recharge environment. Using 14C DOC to estimate groundwater residence times between sampling points along a flow path compares well with residence times estimated on the basis of hydraulic parameters and 14C DIC under closed system conditions.

An Accelerator Mass Spectrometry system has been developed using the 14UD tandem accelerator at the Australian National University. It has been used for 36Cl measurements on groundwater samples from the Murray Basin in southeastern Australia. Measurements of 14C have also been made on the same groundwaters. The information can be combined with stable isotope ratios and other data to illustrate the occurrence of processes such as radioactive decay and local recharge in different aquifers.

14C activity of dissolved inorganic carbon (DIC) in water and in recent tufa samples in several karst areas of Yugoslavia and Czechoslovakia was measured. Groundwater from 11 karst springs were measured for their isotopic content (14C, 3H, 13C), chemical composition (HCO3−, Ca2+, Mg2+) and physico-chemical properties (temperature, pH). Seasonal variations of the 14C activity of DIC in two karst springs in Plitvice Lakes area, Yugoslavia, were measured systematically from 1979 – 1987.14C activity of recent tufa samples from several locations downstream were also measured. The activity of DIC in karst spring water in both countries ranged from 63–87 pMC, which is attributed to differences in geologic structure of the recharge area, topsoil thickness and composition. Grouping of 14C activities of DIC ca (82±4)% is evident. Tritium activity at all the springs indicated short mean residence time (1–10 yr). Concentration of HCO3−, Ca2+ and Mg2+ in spring water varied with geomorphology. 14C activity of streamwater and recent tufa increased downstream from karst springs due to the exchange between atmospheric CO2 and DIC.

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.

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.