Controlled feeding experiments demonstrate that the 14C content of the carbonate fraction of fossil avian eggshell should reliably reflect the 14C activity of feed and contemporary atmospheric CO2 regardless of amounts of 14C depleted scratch injested. Consideration of biochemical pathways and exchange rates across lung membranes leads to the possibility that the carbonate fraction may, in some instances, be slightly 14C depleted. 14C dates on eggshell carbonate should require little or no correction. As with marine shell carbonate, normal soil-forming processes may alter the surficial carbon isotopes in eggshell carbonate. 14C dates on the protein fraction should be even more reliable than those on the carbonate fraction, but only if special precautions or separation techniques exclude non-indigenous carbon from the sample. Original protein contents are likely to be too low for conventional 14C dating techniques.

The preparation and calibration of a secondary standard for the INGEIS Radiocarbon Dating Laboratory are presented. This standard is barium carbonate with a specific activity almost twice that of NBS oxalic acid. It was prepared from BaCO3 with high specific activity and commercial potassium carbonate by an isotopic dilution technique. The advantages of this standard are: 1) the preparation is simple and can be achieved with ordinary labware; 2) the production of CO2 by acid attack from this carbonate shows minimum isotopic fractionation. At least, it has less fractionation than wet oxidation of oxalic acid, the problems of which are described in the literature. This standard ensures better reproducibility in activity measurements; 3) despite some problems of activity exchange with atmospheric CO2 concerning carbonates, measurements of activity over a period of about two years have shown no significant deviation from the mean value. A tentative explanation of this phenomenon is also given. The activity ratio between BaCO3 and NBS oxalic acid is given with its error, and the statistical tests used in the calibration are briefly explained. Finally, a control chart for the activity of the standard over a long period is drawn, showing non-significant deviation and supporting the usefulness of this standard.

A system of 10 proportional 14C counters has been designed. The counters have a volume of 35ml and are operated with CO2 at a pressure of 1 bar and a voltage of 3300V. The amplified signals of the counters are fed through an analog multiplexer to the inputs of three discriminators. The Geiger signal is fed to a separate discriminator. A logic circuit selects from these discriminators the alpha, beta, muon, and purity counts which are then stored in a microcomputer (ITT 2020 with 48K RAM), where the necessary calculations are also performed. The purity of the gas sample is monitored by counting a part of the muon spectrum. The alpha and beta pulses are stored during 95% of the measuring period; the remaining 5% is used for registration of the muon and purity pulses. The overall accuracy of the system for modern carbon samples is 2% after a counting period of 6 days.

When 14C signals approach background levels, the validity of assumptions concerning Poisson counting statistics and measurement system stability becomes crucial in interpreting the resultant low-level counting observations. This has been demonstrated in our previous work on detection limits for non-Poisson error and it is critical in our current studies of carbonaceous pollutants, where the 14C signal from just 5 mg C is comparable to that of the background for our miniature gas proportional counters. To assure data quality, our multi-detector system is designed for the on-line monitoring of critical parameters that reflect both the (statistical) nature of the non-Poisson errors and the underlying (physical) causes. It sends >60 bits of information/pulse to a microprocessor which automatically generates, for each counting period, two-dimensional spectra and multiparameter correlation and control charts. To evaluate the validity of long-term counting of 1–10 mg C we use robust (statistical) estimators, optimal counting interval subdivision, and time series analysis of the individual pulses. New opportunities for selective sampling and chemical fractionation which come with the small sample measurement capability have led us to give special attention also to higher control levels, involving e g, isotonic heterogeneity and representative standard materials.

The Harwell system for measuring milligram size samples using Brookhaven miniature gas counters is fully operative. It comprises 12 counters of different sizes which operate simultaneously within a single NaI crystal (300mm diameter × 300mm long) acting as an anti-coincidence guard counter. Brief details are given of the construction and commissioning of the system, including counter assembly, shield design, electronics, data capture, data analysis, and chemical processing and filling procedures. The performance of the system and an overall view of the fields of application for which the counters have important applications are discussed.

A mini-gas-proportional counter prototype of 10ml capacity (at NTP) was constructed of oxygen-free Finnish copper. The counter tube will be one of 16 equivalent tubes of a small-sample gas counting system, which is equipped with passive graded shield made of lead, cadmium, and copper and a dual active anticoincidence shield, consisting of an external cosmic gas-proportional and an internal plastic scintillation guard. The aim of this study was to evaluate the parameters leading to the design of a cost-effective and compact shielding package for mini-counters.

Continuous 14C data of 1 or 2 weekly samples of atmospheric CO2 are presented, collected near two nuclear power plants (NPP-Biblis and NPP-Philippsburg) located in the rather densely populated upper Rhine valley. Tree-leaf and tree-ring samples from the area of a boiling water reactor in northern Germany (NPP-Würgassen) are also presented and discussed. Additional atmospheric 14CO2 samples from two continental ‘clean-air’ stations in Germany and Austria were used as reference for the polluted areas. For January 1982, these samples yield a ‘clean-air’ 14C concentration in central Europe of Δ14C=255±5‰ (7.7pCi/gC = 1.45pCi/m3 air).

The Harwell Low Level measurements Laboratory has been measuring a variety of natural materials from locations close to United Kingdom nuclear installations since 1977. The measurements are made first, to establish the past effects of releases to the atmosphere of 14C as observed from individual tree rings and second, to establish dispersion contours averaged over extended periods. The main study area has been in Cumbria, around the BNFL nuclear installation at Sellafield. 14C, which can be measured to good precision even at values close to the normal natural levels, provides a powerful technique for the provision of practical experimental values much wanted for theoretical dispersion models.

During the past three years radiocarbon assay has emerged as a primary tool in the quantitative assignment of sources of urban and rural particulate pollution. Its use in several major field studies has come about because of its excellent (fossil/biogenic) discriminating power, because of advances in 14C measurements of small samples, and because of the increased significance of carbonaceous particles in the atmosphere. The problem is especially important in the cities, where increased concentrations of fine particles lead to pollution episodes characterized by poor visibility and changes in the radiation balance (absorption, scattering), and immediate and possibly long-term health effects. Efforts in source apportionment in such affected areas have been based on emissions inventories, dispersion modeling, and receptor modeling – ie, chemical and physical (and statistical) characterization of particles collected at designated receptor sites. It is in the last category that 14C has become quite effective in helping to resolve particle sources. Results are presented for studies carried out in Los Angeles, Denver, and Houston which incorporated 14C measurements, inorganic and organic chemical characterization, and receptor modeling. The 14C data indicated wide ranging contributions of biogenic and fossil carbon sources – eg, <10% to 60% contemporary (biogenic) in Houston – depending on meteorological, biological, and anthropological activity. The combined (chemical, isotopic, statistical) data point to sources such as vehicles, wood combustion, power plants, and vegetation.

In recent years in California, smog aerosols have been observed in metropolitan and rural areas. We wondered what the relative contribution is from sources such as fossil fuel combustion (eg, cars, factories) and emissions from trees and other plants. Pollution produced by fossil fuel combustion can be distinguished from biological sources using radioactive carbon. Carbon in fossil organic materials is radioactively dead whereas carbon in living plants contains 14C. Smog particles were collected on clean glass or quartz fiber paper and analyzed in a small volume CO2 proportional counter for 14C content. Results are given for sampling locations at UCLA, El Monte, Riverside, and Lake Tahoe showing the relative contributions of fossil and modern carbon sources ranging from 0 to 74% and 26 to 100% respectively.

An example of how man's contaminants are introduced, deposited, and retained in sediments giving a chronological record of events has been developed for Lake Washington, Seattle. Significant amounts of both inorganic and organic compounds in the environment originate from fossil fuel sources, such as power plants and motor vehicles. Many organic compounds are introduced also from contemporary biogenic materials. Through the combined carbon isotope analysis technique (CCIA), we can distinguish between fossil and contemporary carbon sources classes (using 14C), as well as sources within each class (using 13C). To establish the chronology of the organic carbon pollutant input to the lake sediment, the ages of the layers were determined using 210pb dating techniques. Sediment profiles of trace metals and a fallout radionuclide plutonium were also obtained and compared with the carbon isotope profiles. The results show that the total organic carbon (TOC) concentration correspond to 93% modern carbon before 1905. This 14C concentration in TOC decreased to ∼60% modern in the 1930's and now is between 95 and 80% modern. The lipid fraction is ca 30% modern and the total aromatic hydrocarbon fraction reached a minimum of 5% modern in 1954. The large decrease in 14C of TOC around 1930 is believed to be due to coal dust or fly ash. The trace metal concentration also increased substantially at this time. The pattern observed in the sediment thus reflects the change in the local energy consumption pattern from a predominately coal to an oil-based economy. From the plutonium profile we infer that mixing occurs for 3 or 4 years before the sediment layers are compacted.

Bomb-produced 14C is a valuable tool for studying rates of short-term processes involving carbon cycling. This study shows that bomb 14C is an excellent tracer of a biochemical process that takes place in the human body, namely the accretion of stones in the gallbladder. The methods developed for obtaining time histories of 14C/12C and 13C/12C in concentric layers from a large gallstone (30mm diameter) are reported. Formation times are assigned by matching the 14C/12C obtained from individual layers with those found for known-aged tree rings. Results show that the gallstone grew over a period of 10 years and seems to have lain dormant within the gallbladder for a period of 11 years. The average growth rate was 1.5mm/year.

In the past 30 years many hundreds of archaeologic samples have been dated by radiocarbon laboratories. Yet, one cannot say that 14C dating is fully integrated into archaeology. For many archaeologists, a 14C date is an outside expertise, for which they are grateful, when it provides the answer to an otherwise insoluble chronologic problem and when it falls within the expected time range. But if a 14C date contradicts other chronologic evidence, they often find the ‘solution’ inexplicable. Some archaeologists are so impressed by the new method, that they neglect the other evidence; others simply reject problematic 14C dates as archaeologically unacceptable. Frequently, excavation reports are provided with an appendix listing the relevant 14C dates with little or no discussion of their implication. It is rare, indeed, to see in archaeologic reports a careful weighing of the various types of chronologic evidence. Yet, this is precisely what the archaeologist is accustomed to do with the evidence from his traditional methods for building up a chronology: typology and stratigraphy. Why should he not be able to include radiocarbon dates in the same way in his considerations?

14C dates of a medieval settlement with archaeologically well-dated strata are compared with the true ages of the respective layers. The 14C values indicate that each layer may contain older material reaching up to the beginning of settlement. Therefore, the 14C measurement of only a few wood or charcoal samples may lead to age estimations several hundred years too old.

Radiocarbon determinations, employing both decay and direct counting, were obtained on various organic fractions of four human skeletal samples previously assigned ages ranging from 28,000 to 70,000 years on the basis of their D/L aspartic acid racemization values. In all four cases, the 14C values require an order of magnitude reduction in age.

A small 200ml capacity CO2 proportional counting system has been developed which uses only 100mg of carbon for complete filling. Thus, with respect to the small quantities needed, it compares favorably to dedicated accelerators at significantly lower cost. The performance of this equipment is demonstrated using a variety of samples including some human bone fragments from La Jolla which had been estimated to be 28,000 years old by aspartic acid racemization analysis.

Computer storage and surveys of large sets of data should be an attractive technique for users of 14C dates. Our pilot project demonstrates the effectiveness of a text retrieval system, NOVA STATUS. A small database comprising ca 100 dates, selected from results of the Trondheim 14C laboratory, is generated. Data entry to the computer is made by feeding typewritten forms through a document reader capable of optical character recognition. A text retrieval system allows data input to be in a flexible format. Program systems for text retrieval are in common use and easily implemented for a 14C database.

An annotated card index of 14C dates directly relating to Old World cultural material of Palaeolithic and Mesolithic age (> 50,000 − ∼7000 BP) and New World material older than 7000 BP was compiled in 1972 to include all previously published dates. It is updated annually and currently correct to the end of 1981. The need for such an index to reduce duplication of research time spent in primary data acquisition has long been implicity recognized. Indeed, many such data files may already exist. We wish to discover the nature, scope, and intercompatibility of other lists both to improve our own system and to allow for an exchange of information without unnecessary duplication. Our sources include SCIENCE and NATURE but RADIOCARBON is the major source of information. The general scientific and archaeologic literature has not been systematically searched. Where possible, other published lists have been consulted and additional dates incorporated in our list.

This paper discusses the characteristics of the commoner classes of writing materials and textiles deriving from ancient and more recent historical sources and the problems they present for 14C dating. The materials under consideration are, firstly, paper in various forms, parchment, and vellum (ancient papyrus, which poses different kinds of dating problems, is not considered) and secondly, fabrics such as linen, cotton, and woolen textiles, to which, from the dating point of view, similar technical considerations apply. Our main concern is with problems associated with the dating of paper.

One of my former teachers in nuclear physics, H Morinaga, once pointed out to me that essentially all the fundamental discoveries in nuclear physics were done without the use of accelerators. At first, this statement seemed extremely exaggerated, but now I think there is much truth in it. Once we build an instrument to investigate a specific problem we have already realized the existence of the problem and do not need the instrument to discover it. It is almost inevitable that the most interesting discoveries with a new technique will be made in fields for which the technique was not invented. Accelerators, built for nuclear physics, produced a great amount of data on nuclear structure and forces but the most fundamental discoveries were made in elementary particle physics. In any case, for almost 40 years the sole purpose of accelerators was to deliver beams of ever increasing energy and versatility to perform experiments after the accelerator. The analytic properties of accelerators were almost completely ignored even after the very early use of the Lawrence cyclotron at Berkeley as a mass spectrometer to discover 3He in nature (Alvarez and Cornog, 1939 a; b). The enormous analytic power of accelerators is now fully recognized, but the joy of the revival is mixed with some disappointment that the great prospects for studying 14C problems (Muller, 1977; Bennet et al, 1977; Nelson, Korteling, and Stott, 1977) have not yet been fulfilled. Fortunately, some of the papers of this conference show that a big step forward has been taken. But in view of what I said before it is not surprising that most of the studies were actually done with other radioisotopes.