bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiocarbon Dating in the Arctic Region
Authors: Olsson Ingrid U
Published: July 2016

The Landnám of Iceland is usually dated too early by the 14C dating method, at least to judge from the tradition according to the Landnámabók. Various sources of error are considered. One, the use of driftwood, can be excluded in many cases, since birch is often selected for dating purposes. Second, the settlers may have brought wood with them. A third obvious source of uncertainty is the age of a tree before felling. It is difficult to explain the seemingly too early results by secular global variations of 14C content. A regional low level of 14C may result from volcanic activity or the small size of the land areas in the Arctic region.
A System for Studying Carbon Allocation in Plants Using 11C-Labeled Carbon Dioxide
Authors: Fares Youhanna , Goeschl J D , Magnuson C E , Nelson C E , Strain B R , Jaeger C H , Bilpuch E G
Published: July 2016

The effects of environmental factors such as water stress, elevated CO2, or temperature on carbon assimilation and allocation in plants have been studied extensively (Gifford and Evans, 1981; Loomis, Rabbinge, and Ng, 1979; Neales and Incoll, 1968). However, the interactions of these processes are not well understood and cannot be predicted with any degree of confidence. Continuous and simultaneous measurements of photosynthesis, transport, and sink activity have never been made during the short- and long-term responses of live, intact plants to step changes in environmental factors. Thus, direct environmental effects and adaptive responses of plants are generally not distinguished. This results in part from limitation in experimental techniques and protocol used in past studies and the lack of experimental validation of hypotheses and models (eg, Goeschl et al, 1976; Magnuson et al, 1979; Smith et al, 1970) dealing with these problems. This paper describes in detail the components of an integrated technique for studying carbon assimilation, transportation and allocation in intact live plants under any set of environmental conditions, using continuously produced 11CO2.
Measurement of Carbon Fixation and Allocation Using 11C-Labeled Carbon Dioxide
Authors: Strain Boyd R , Goeschl John D , Jaeger Charles H , Fares Youhanna , Magnuson Charles E , Nelson Charles E
Published: July 2016

The real-time measurement of net photosynthesis and dark respiration of plants has been possible since the development of the infra-red analyzer and its application in the 1940's. This technique has allowed intensive investigations of the mechanisms and dynamics of carbon dioxide assimilation by green plants (Sestak, Catsky, and Jarvis, 1971). As a result, physiologic and ecologic aspects of net carbon dioxide exchange are the subject of much research (eg, Osmond, Bjorkman and Anderson, 1980).
Evaluation of Direct-Precipitation and Gas-Evolution Methods for Radiocarbon Dating of Ground Water
Authors: Yang In Che
Published: July 2016

The extraction of dissolved carbonate species for age dating from a 100L water sample by the direct-precipitation method (DPM) and by the gas-evolution method (GEM) has been investigated. Stable carbon-isotope fractionation between initial and final carbon dioxide evolved was ca 11‰ by GEM and 1‰ by DPM. GEM will produce isotopically lighter carbon dioxide compared with DPM if carbonate recovery is low. Extraction efficiency of > 95% can be achieved by GEM in 3 hours using nitrogen gas at a sweeping rate of 2000cc per minute. DPM requires precipitates to settle overnight to assure > 95% recovery. GEM is little affected by a high concentration of sulfate ions, whereas DPM is greatly affected by sulfate resulting in less yield.
A Multiple Proportional 14C Counter System for Milligram-Sized Samples
Authors: Hut Gert , Keyser Jan , Wijma Stef
Published: July 2016

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.
Possibilities in the Dating of Writing Materials and Textiles
Authors: Burleigh Richard , Baynes-Cope A D
Published: July 2016

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.
Tandem Accelerator Measurements of 10Be Deposition Rates
Authors: Nelson DE , Korteling R G , Southon J R , Vogel J S , Nowikow I , Ku T L , Kusakabe Masashi , Reyss J L
Published: July 2016

A Tandem Van de Graaff accelerator has been modified for use in the direct measurement of natural abundances of 10Be and 14C. A description of the system is given and some 10Be results on oceanographic samples are discussed.
Production of C− Directly from CO2 Using the ANIS Sputter Source
Authors: Heinemeier Jan , Andersen Hans Henrik
Published: July 2016

Micro-ampere beams of C– have been produced with the Aarhus negative-ion source, operated on CO2 gas. The efficiency of the source and memory effects have been measured, using 13C-enriched CO2, in order to evaluate the applicability of the source to 14C dating by accelerator mass spectroscopy.
Detection of the 36Cl Radioisotope at the Rehovot 14UD Pelletron Accelerator
Authors: Paul Michael , Meirav Oded , Henning Walter , Kutschera Walter , Kaim Robert , Goldberg Mark B , Gerber Jean , Hering William , Kaufman Aaron , Magaritz Mordeckai
Published: July 2016

A program of accelerator mass spectrometry has been started at the Rehovot 14UD Pelletron Accelerator Laboratory. Part of the initial emphasis has been directed to the detection of the 36Cl radioisotope. We report here on the present status of our work and describe our experimental system. Preliminary results are presented, showing that 36Cl/Cl concentrations ranging down to 1×10−14 could be measured with our system.
International Agreements and the Use of the New Oxalic Acid Standard
Authors: Stuiver Minze
Published: July 2016

The international radiocarbon community met on June 25, 1982. Two reports were presented, and several measures related to radiocarbon dating discussed and adopted.
14C Variations from Tasmanian Trees—Preliminary Results
Authors: McPhail Steve , Barbetti Mike , Francey Roger , Bird Trevor , Dolezal Jiri
Published: July 2016

Huon pine is endemic to Tasmania. It has well-defined annual rings, may live for over 2000 years, and is particularly resistant to decay. Celery-top pine has similar characteristics and may live for 800 years. As part of a multi-disciplinary study of these trees and their habitat, a simple wood pretreatment method for isotope analysis is described. The solvent-acid-alkali-acid sequence yields a value of Δ14C = −16 ± 6‰ for AD 1941–45 Huon pine heartwood; Δ14C for extracts containing various proportions of post-AD 1955 carbon are also presented. Δ14C measurements on super-canopy and sub-canopy leaves from Celery-top pines are compared and used to place an upper limit of 10% on the amount of sub-canopy CO2 assimilated by sapling leaves, originating from decaying litter-mass. 14C ages from well-preserved logs illustrate the potential for a continuous Holocene chronology from 7400 years BP to the present. A 12,000-year-old Celery-top log has also been found.
Institut Royal du Patrimoine Artistique Radiocarbon Dates IX
Authors: Dauchot-Dehon Michèle , Van Strydonck Mark , Heylen Jos
Published: July 2016

This list contains the results of 14C age determinations obtained at the laboratory in 1981–1982. Samples are analyzed in three new proportional counters which are described in R, 1980, v 22, p 442. Our installation differs from that of Heidelberg in that our filling gas is methane.
Radiocarbon Dating in the Southern Levant
Authors: Weinstein James M
Published: July 2016

Radiocarbon dating provides the principal chronometric data for the Middle and Upper Palaeolithic, Epipalaeolithic, and Chalcolithic periods in the southern Levant. It is a secondary source of dating evidence for the Early Bronze age, when archaeological correlations with Syria and especially Egypt become available. For the Middle and Late Bronze age, Iron age, Persian, Hellenistic, Roman, and Byzantine periods,14C dating has only limited value because the technique is less precise than the normally available archaeologic and historic materials.
University of Lund Radiocarbon Dates XVII
Authors: Håkansson Sören
Published: July 2016

Most of the14C measurements reported here were made between October 1982 and October 1983. Equipment, measurement, and treatment of samples are as reported previously (R, 1968, v 10, p 36–37; 1976, v 18, p 290; 1980, v 22, p 1045).

Age calculations are based on a contemporary value equal to 95% of the activity of NBS oxalic acid standard (No. 4990A) and on the conventional half-life for14C of 5568 yr. Results are reported in years before 1950 (years bp). Errors quoted with the dates are based on counting statistics alone and are equivalent to ± 1 standard deviation (±σ).
Queens College Radiocarbon Measurements IV
Authors: Pardi Richard R , Tomecek Lynn , Newman Walter S
Published: July 2016

The following list includes radiocarbon analyses of samples related to studies of Holocene sea levels completed since the publication of the last list (R, 1980, v 22, p 1073–1083). Sample preparation and counting for liquid scintillation samples remain the same. However, an additional gas-proportional facility was added in 1981 to handle the analyses of small samples, some of which are included in this list. The new system consists of two 660cc OFHC copper counters built at Queens College. Samples are counted over at least two 2800 minute intervals alternating with backgrounds and standards counted over 1400 minute intervals. Ages are based on the Libby half-life of 5568 years and include 1σ standard deviations of sample, standard, and background activities.
Measurement of 14C Directly from CO2 Using a Tandetron Accelerator Mass Spectrometer Facility
Authors: Raisbeck G M , Yiou Françoise , Arnold Maurice , Duplessy J C
Published: July 2016

Tests have been carried out on the measurement of 14C directly from CO2, using a source designed by Middleton, and a Tandetron accelerator mass spectrometer system. These tests were very promising from the point of view of minimum quantity of carbon necessary (<50μg), but suffered from a background (apparently not memory effect) giving an equivalent age of ∼25,000 years. As a demonstration of the technique, a single thread from the mummy wrapping of the Egyptian king Ramses II was dated.
Accelerator Radiocarbon Dating at SFU
Authors: Nelson D E , Vogel J S , Southon J R , Brown T A
Published: July 2016

The Simon Fraser University accelerator mass spectrometry (AMS) facility has now been in semi-routine use since the beginning of 1985. The advantages and limitations for 14C dating are described.
Laser Resonance Ionization Mass Spectrometry for Krypton-81 Analysis
Authors: Lehmann B E , Loosli H H , Oeschger Hans , Rauber Dominique , Hurst G S , Allman S L , Chen C H , Kramer S D , Thonnard Norbert , Willis R D
Published: July 2016

A new laser-based analytical technique is described for isotope selective noble gas atom counting. The method has been used to detect 81Kr atoms in a groundwater sample.
The ETH/SIN Dating Facility: A Status Report
Authors: Bonani Georges , Hofmann Hans-Jakob , Morenzoni Elvezio , Nessi Marzio , Suter Martin , Wölfli Willy
Published: July 2016

The ETH/SIN AMS dating facility is routinely used for 10Be, 14C, 26Al, and 36Cl measurements. The present status and performance of this facility are reviewed and some of its major applications summarized.
Radiocarbon Activity Variation in Dated Tree Rings Grown in Mackenzie Delta
Authors: Fan C Y , Tie-Mei Chen , Si-Xun Yun , Kai-Mei Dai
Published: July 2016

We measured the Δ14C values in 57 rings (from AD 1824 to 1880) of a white spruce grown in Mackenzie Delta (68°N, 130°W), as part of our continuing study of the Δ14C variation related to solar activities. The values exhibit a 10‰ fluctuation with an 11-year periodicity anti-correlated with the solar activity cycle. We also measured the Δ14C values in 6 rings (from AD 1940 to 1945). The abnormally high value in the 1943 ring may be due to two large solar flares occurring in 1942.
Uptake of Anthropogenic Co2by Lateral Transport Models of the Ocean Based on the Distribution of Bomb-Produced14C
Authors: Peng Tsung-Hung
Published: July 2016

The pattern of global water column inventories of bomb-produced14C suggests that a sizeable portion of bomb14C that entered the Antarctic, northern Pacific, and tropical oceans has been transported to adjacent temperate regions. Models of lateral transport of surface water in the Atlantic, Indian, and Pacific Oceans are based on this distribution pattern. Upwelling of bomb-14C-free water from below takes place in the Antarctic, northern Pacific, and tropical regions; downwelling of surface water occurs in the temperate oceans and northern Atlantic. Uptake of excess CO2by these models is calculated using the observed Mauna Loa pCO2record as an input function. Results indicate that 35% of fossil fuel CO2is taken up by these model oceans during the period 1958–1980. Considering the observed airborne fraction of 0.55, it appears that ca 10% of the global fossil fuel CO2is still missing.
14C Dating of Plant Macrofossils in Lake Sediment
Authors: Andree Michael , Oeschger Hans , Siegenthaler Ulrich , Riesen Trudi , Moell Markus , Ammann Brigitta , Tobolski Kazimierz
Published: July 2016

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 for14C 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 the14C/C ratio of dissolved bicarbonate in lake water. This is probably due to a contribution of dissolved limestone carbonate and thus a somewhat reduced14C/C ratio in the lake's water (hard water effect).
Dating Polar Ice by14C Accelerator Mass Spectrometry
Authors: Andree Michael , Beer Juerg , Loetscher H P , Moor Ernst , Oeschger Hans , Bonani Georges , Hofmann H J , Morenzoni Elvezio , Nessi Marzio , Suter Martin , Wölfli Willy
Published: July 2016

Results of14C/12C ratio measurements on CO2extracted from air bubbles in polar ice are presented. The samples investigated originate from the Dye 3, South Greenland, deep ice core and span approximately the last 10,000 years. The results are calibrated with tree-ring records. The14C ages are compared with information obtained from seasonal variations of ice-core parameters and rheologic model calculation.
Routine AMS Dating of Bone and Shell Proteins
Authors: Gillespie Richard , Hedges R E M , Humm M J
Published: July 2016

14C dating of bone has been unreliable in comparison with more stable materials such as wood or charcoal. Attempts have been made to use various components or fractions isolated from the raw bone sample; these include dilute acid soluble, dilute acid insoluble, collagen, and gelatin, as well as alkali soluble and insoluble fractions of burned bone, and carbonate or apatite fractions of organic-poor bone. All of these fractions have yielded useful data in some cases, but no single method has proven suitable in all situations. The work reported here describes the isolation and purification of amino acids from the dilute acid insoluble fraction of bone collagen and parchment, with some preliminary experiments on amino acids from shell conchiolin.
Anomalous High 14C Activity Found in Recent Corals from the Philippines
Authors: Willkomm Horst
Published: July 2016

The carbonate skeletons of small living corals collected in Spring 1981 from Cebu Island, the Philippines, had 14C activities up to 147% of recent standard. Similarly high values were found in the carbonate structure of three large coral heads, where the 14C content of six penetrating cores was measured. In these corals the activity of the outer parts grown since 1960 reached values as high as 155% (corrected for δ13C = − 25‰) while the inner part grown from 1860 to 1950 had values of 106 to 110%. The 14C content of corals should be ca 116% due to the atomic bomb effect and 95% before 1955. The samples were taken from the shore, exposed to tidal waters, so that local contamination is improbable. Organic samples collected from the same region showed normal 14C activity.
14C Electronic Measurement System with a Microcomputer
Authors: Walanus Adam
Published: July 2016

Even though the reliability of equipment has improved, the quality of measurement should still be checked. This task may be performed by a microcomputer with the physicist's intervention only when an error in measurement is detected.
Urban Atmospheric 14CO and 14CH4 Measurements by Accelerator Mass Spectrometry
Authors: Klouda G A , Currie L A , Donahue D J , Jull A J T , Naylor M H
Published: July 2016

Atmospheric gas samples (0.1m3) were collected at ground level during January/February 1984 in Las Vegas, Nevada for 14C/13C accelerator mass spectrometry and total abundance measurements of CO and CH4. During winter months in this locale, CO concentrations can occur at 10 to 100 times background, occasionally exceeding the National Ambient Air Quality Standard (NAAQS). Methane concentrations show a slight enhancement (∼24%) above the background (non-urban troposphere) level. A comparison of CO and CH4 concentrations shows a good linear correlation which may indicate a common source. Preliminary 14C/13C results of the two species suggest that fossil emissions are the predominant source of excess CO and CH4 in the samples taken. Estimates of anthropogenic CO and CH4 are important for source apportionment of combustion emissions. In addition, this information is valuable for understanding the global CO and CH4 cycles and, therefore, human impact on climate and the stratospheric ozone layer.
δ13C and Diet: Analysis of Norwegian Human Skeletons
Authors: Johansen Olav Sverre , Gulliksen Steinar , Nydal Reidar
Published: July 2016

The relationship between 13C content of human bone and the marine fraction in the individual diet is well established. In the present investigation human skeletons from inland and coastal areas in Norway were analyzed. Both regional and chronologic differences are revealed, and larger variability than expected at specific sites indicate more complex cultural adaptations than earlier recognized. Extremely high δ13C values, comparable with those obtained from Eskimo sites, are found for material from Early Stone Age fishing/hunting communities.
Birmingham University Radiocarbon Dates IV
Authors: Shotton F. W. , Blundell D. J. , Williams R. E. G.
Published: July 2016

Measurements have continued with both the 1 L and 6 L counters. Results are not corrected for C13 fractionation. Errors quoted refer only to the standard deviation calculated from a statistical analysis of sample and background count rates and the Libby half-life of 5570 ± 30 yr. Pretreatment has been continued as described previously (Shotton, Blundell, and Williams, 1969).
Glasgow University Radiocarbon Measurements II
Authors: Ergin M. , Harkness D. D. , Walton A.
Published: July 2016

A third radiocarbon counting system has been established in the Chemistry Department, University of Glasgow, since April, 1968. Operating conditions for the previous systems have remained essentially as described by Baxter et al. (1969).
Illinois State Geological Survey Radiocarbon Dates II
Authors: Kim Stephen M.
Published: July 2016

The following date list includes samples processed by the Illinois State Geological Survey Radiocarbon Dating Laboratory from September 1968 through November 1969. Detailed descriptions of sample methods are published elsewhere (Kim and Ruch, 1969; Kim, Ruch, and Kempton, 1969).
British Museum Natural Radiocarbon Measurements VII
Authors: Barker Harold , Burleigh Richard , Meeks Nigel
Published: July 2016

Dates listed below are based on measurements made from June 1968 to May 1970 by the liquid scintillation technique using benzene. In general, the experimental procedure is as described previously (Barker, Burleigh, and Meeks, 1969a) with a few changes in detail. Data are now processed by computer using a comprehensive Algol program written by Andrew Barker, King's College, Univ. of London. There is no need to standardize on any particular sample weight and, as the benzene synthesizer can also deal with samples in the range up to the equivalent of 9 gm of carbon in a single synthesis, the amount of sample available is now less critical. However, for older material, a minimum of 1 gm of carbon is required. Another factor contributing to efficiency of operation is the “bomb” technique for sample combustion (Barker, Burleigh, and Meeks, 1969b), also mentioned in the previous date list. Finally, during 1969, an MS20 double collection mass spectrometer was acquired and all dates (but not all those in this list) are now corrected for isotopic fractionation.
GIF Natural Radiocarbon Measurements VI
Authors: Delibrias G. , Guillier M. T. , Labeyrie J.
Published: July 2016

This list consists mainly of dates obtained from analysis during 1967 and 1968 of archaeologic and geologic samples. The last section deals essentially with climatic, palynologic, and sea level variation problems. All measurements of atmospheric CO2 made periodically from 1962 until end of 1970 are also published here. In agreement with international convention, all dates have been calculated on the basis of the C14 half-life of 5568 years and 95% of NBS oxalic acid as the modern reference year.
Geological Survey of Canada Radiocarbon Dates XI
Authors: Lowdon J. A. , Robertson I. M. , Blake W.
Published: July 2016

During the past year, 1969-1970, both the 2-L (Dyck and Fyles, 1962) and 5-L (Dycket al., 1965) counters were routinely operated. A 1-L counter was finally constructed with acceptable characteristics (see description below) and was operated in July in place of the 5-L counter. The 2-L counter was operated exclusively at 2 atm. The 5-L counter was operated at 1 atm, except for October and November, 1969, when it was operated at 4 atm. The 1-L counter was operated at 1 atm.
University of Lund Radiocarbon Dates IV
Authors: Håkansson Sören
Published: July 2016

The C14 measurements reported here were made in this laboratory between October 1969 and September 1970. The measuring technique and equipment, and the treatment of samples are the same as reported previously (R., 1968, v. 10, p. 36-37; R., 1970, v. 12, p. 534).
Birmingham University Radiocarbon Dates VII
Authors: Shotton F. W. , Williams R. E. G.
Published: July 2016

The following list of dates contains all measurements made during 1972,i.e., since our last list. Counting equipment, operating procedures and sample pretreatment are the same as previously described (R., 1969, v. 11, p. 263). Age calculations are based on 95% activity of the NBS oxalic acid standard computed from the Libby half-life of 5570 ± 30 yr. Background samples are synthesized from Welsh anthracite. Errors quoted refer only to the standard deviation (1σ) calculated from a statistical analysis of sample, background and standard count rates.
Florence Radiocarbon Dates I
Authors: Azzi C. M. , Bigliocca L. , Piovan E.
Published: July 2016

The Florence Radiocarbon Dating Laboratory was built in 1970 under the direction of Consiglio Nazionale delle Ricerche at the Istituto di Antropologia, Università di Firenze.
University of Lund Radiocarbon Dates VI
Authors: Håkansson Sören
Published: July 2016

Most of the C14 measurements reported here were made between October 1971 and October 1972. Equipment, measurement, and treatment of samples are the same as reported previously (R., 1968, v. 10, p. 36-37; 1970, v. 12, p. 534).
University of Cambridge Natural Radiocarbon Measurements XII
Authors: Switsur V. R. , West R. G.
Published: July 2016

The dates presented here comprise results obtained since our last list (R., 1973, v. 15, p. 156-164). Pure carbon dioxide prepared from the samples is used to fill copper proportional counters at two atmospheres pressure. The detectors are protected from environmental radiation by a massive lead shield inside which, and completely surrounding the proportional counters, is a high efficiency plastic scintillation anticoincidence screen (Switsur, Hall, and West, 1970). Modern sample gas is obtained from combustion of a.d. 1845 to 1855 rings of an oak tree grown near Cambridge, felled in 1950. Background samples are prepared from Welsh anthracite or Connemara limestone. The contemporary standard is compared frequently with the activity of NBS oxalic acid international standard. Age calculations are based on the14C half-life of 5568 years and the uncertainty stated as one standard deviation calculated from the statistical analysis of sample and standard counting rates.
Sydney University Natural Radiocarbon Measurements II
Authors: Gillespie R. , Temple R. B.
Published: July 2016

This list describes samples dated in this laboratory from January to November, 1972. Operating principles are as previously reported (Gillespie et al. 1972) using synthesized benzene for liquid scintillation counting. Ages are calculated using 0.95 NBS oxalic acid standard with reference to a.d. 1950 using Libby 5570 year half-life.
Tallinn Radiocarbon Dates I
Authors: Punning J. M. , Kakum T. , Rajamäe R.
Published: July 2016

Preparations for determining absolute age by the radiocarbon method were started at the Institute of Geology, Academy of Sciences of the Estonian SSR in 1971. Dating of samples has been carried out since 1972.
Optimum Operating Conditions of14C-Methane Isotope Enrichment By Concentric Type Thermal Diffusion Columns for Use in Radiocarbon Dating
Authors: Erlenkeuser Helmut
Published: July 2016

The optimum operating conditions providing minimum run-time and running costs have been studied theoretically for a thermal diffusion plant to be used for the enrichment of the radiocarbon isotope from finite sample size.

The calculations are based on a simple approximate model of the enrichment process, regarding the isotope separation column as operating under quasi-stationary state conditions. The temporal variation of the isotope accumulation is given by a single exponential term. From comparison with the numerical solution of the separation tube equation, approximate models of this simple type appear hardly sufficient for analytical work but seem well suited for optimization calculations. For column operation not too close to the equilibrium state, the approximate run-times were found accurate within 0.2 d.

The approximate model has been applied to a column of the concentric type, operated on gaseous methane. Cross-section configuration and temperatures were not varied (hot and cold wall radii: 2.0 and 2.6cm, respectively; hot and cold wall temperatures: 400°C and 14°C, respectively). The column transport coefficients used were derived from measurements. Run-time was minimized by optimizing both the operating pressure and the sample collection mode for different total sample size (range studied: 24 to 100 g), mass of enriched sample (1.8, 2.4, and 3.0 g), enrichment factor (12, 15, and 20) and column length (8 to 18 m). Optimum working pressures are between 1 and 2 atm. Usually, about 90 percent of the enriched sample mass is extracted favorably from the column itself, the length of the sampling section being about 2.5 to 5 m. Typical runtimes are between 3 days and 2 weeks, and isotope yield may reach 90 percent.

Optimum operating conditions have also been calculated for other column configurations reported in literature and are compared with the experimental results.
ANU Radiocarbon Date List VI
Authors: Polach H A , Head M J , Gower J D
Published: July 2016

The following list contains most of the measurements made during 1974, since our last list (R, 1973, v 15, p 241-251). All measurements were performed on a Beckman LS-200 Liquid Scintillation Spectrometer following previously published setting up (Polach, 1974), automatic cycling (Polach, 1969) and benzene synthesis (Polach and Stipp, 1966; Polach et al, 1972) procedures.
Information on the CO2 Cycle from Ice Core Studies
Authors: Berner Werner , Oeschger Hans , Stauffer Bernhard
Published: July 2016

Information on the history of the atmospheric CO2 content and the 13C/12 and 14C/C ratios is recorded in natural ice. Measurements on samples from very cold accumulation regions show that CO2 is occluded not only in air bubbles, but also in the ice lattice. The two CO2 components are of similar size. It is very difficult to measure CO2 in the bubbles and CO2 in the ice lattice separately. By melting the samples and extracting the evolving gases in two fractions, it is possible to estimate CO2 concentration in the bubbles and the ice lattice. Enrichment or depletion of CO2 in the bubbles by exchange with the ice is difficult to estimate. Information about this effect is expected from 13C/12C analysis on the extracted CO2 fractions.

To investigate whether atmospheric CO2 content was different during the last glaciation than during the present one, sets of 16 and 20 samples distributed over the last 40,000 years from the two deep ice cores from Camp Century (North Greenland) and Byrd Station (West Antarctica) were measured. The time scales for the two cores are based on a rheological model. Results and conclusions are:

—

The data series from both cores show similar trends correlated to a certain degree to the δ18O profiles.

—

For both cores, the values for the CO2 concentration of the first fraction, considered to best represent the atmospheric composition, show lower values during glaciation than in the Holocene, with a minimum before the end of glaciation.

—

Low CO2 concentrations in the first fractions (200ppm) of certain samples are a strong indication that the atmospheric CO2 concentration during last glaciation was lower than during the postglacial. These low concentrations indicate that, at that time, CO2 concentration in the atmosphere could have been lower than today by a factor of 1.5. Possible explanations for such a change in atmospheric CO2 content as well as its influence on atmospheric 14C/C ratio and on the radiation balance is discussed.
The Concept of DC Gain in Modeling Secular Variations in Atmospheric14C
Authors: Lazear Gregory , Damon Paul E , Sternberg Robert
Published: July 2016

A constraint on radiocarbon reservoir models is that the DC gain of a system (system transfer function at zero frequency) should equal the equilibrium ratio of the atmospheric radiocarbon mass to the production rate. The simple one-box model is essentially a “black box” but the value of the single residence time is theoretically equal to the DC gain. Using a sunspot-production rate algorithm as the forcing function, predictions of the one-box model match the14C data from ad 1700 to 1900 better than the 3-box, 5-box and box-diffusion models. The more complex models tend to pile up14C in the atmosphere because their DC gains are too high, and they over-attenuate the de Vries “wiggles”. The DC gains can be reduced to more acceptable levels by adjusting model parameters, particularly the sizes of the ocean reservoirs. Better fits to the “wiggles” are also obtained by parameter adjustment. Water content of deep-sea sediments constitutes an extra reservoir for dead carbon, and should help reduce system DC gain.
Radiocarbon in Annual Coral Rings of Belize and Florida
Authors: Druffel Ellen M
Published: July 2016

Radiocarbon measurements on a 109-year-old (1868-1977) core ofMontastrea annulariscoral from Glover Reef, Belize, in the Gulf of Honduras, reveal uptake of fossil fuel CO2and bomb14C by surface ocean waters. The history of Δ14C values revealed by this Belize growth agree remarkably well with results for coral growth from the Florida Straits. It is concluded that these corals are reliable recorders of14C concentrations of dissolved inorganic carbon (DIOC) in surface waters representative of the Gulf Stream.
The Effect of Anthropogenic CO2 and 14C Sources on the Distribution of 14C in the Atmosphere
Authors: Levin Ingeborg , Münnich K O , Weiss Wolfgang
Published: July 2016

14C measurements on continuous weekly samples of atmospheric CO2 and hydrocarbons, collected in a rather densely populated area are presented. The deviation of the measured 14C data from the clean air level is primarily due to CO2 from the combustion of fossil fuels. This is confirmed by fossil fuel admixture estimates individually calculated with an atmospheric dispersion model. Up to 10 percent admixture is predicted by this model and observed from the 14C shift for weekly averages, particularly during the winter season. Natural CO2 admixture due to soil respiration, however, even in winter, is of the same order of magnitude, but much larger in the warm season: the considerable variations in CO2 concentration in summer are almost exclusively controlled by natural sources. Using tree leaf samples, we have been able to identify boiling water reactors (BWR) as weak sources of 14CO2. Atmospheric samples taken in the environment of the pressurized water reactors (PWR) Biblis show that the 14C release of these reactors is primarily in the form of hydrocarbon 14C. The source strength of the various power plants, calculated on the basis of our observations in their environment, ranges from 0.5 to 7Ci per year.
Contemporary 14C Levels and Their Significance to Sedimentary History of Bega Swamp, New South Wales
Authors: Polach Henry , Singh Gurdip
Published: July 2016

Atmospheric 14C variations in nature, as previously documented for the Southern Hemisphere by studies carried out in South Africa and New Zealand, were supplemented by 14C concentration measurements of wheat-grain samples collected in southeastern New South Wales. Our measurements cover the critical period of 1945/46 up to 1956/57, and span the transition of Suess and atom-bomb effects. The observed variations can be followed quite precisely in the peat deposits of the Bega Swamp, New South Wales, and indicate that vertical mixing of organic components within the peat is negligible. Pollen analytical data covering the last 400 years also show that the peats act as efficient traps; thus, time-precise zonations can be identified, and historically documented man-induced changes in pollen assemblages can be correlated with 14C ages in recent times.
An Analysis of Shielding Efficiency for 14C Counters
Authors: Nydal Reidar , Gulliksen Steinar , Lövseth Knut
Published: July 2016

The “shielding” efficiency of the guard counters has been a main scope of the present investigation. Our special guard counters consist of closed shells (ca 3cm thick) filled with propane at 1.2 atmospheres pressure. These guard counters are nearly 100 percent efficient against charged particles, and 1 to 2 percent against gamma and neutrons. The efficiency has now been studied more in detail in an arrangement with four guard shells around a 14C counter. For each extra guard shell, the cosmic fraction of the counter background was reduced by ca 13 percent. The reduction does not involve penetrating high energy charged particles, but is related to γ ray showers penetrating the guards. A thicker old lead shield between 14C counter and the guard counters also reduces the background and serves the same purpose. In order to approach underground conditions for the 1.5 liter counter background (0.32 ± 0.01 c/min), most of the shielding material has to be put inside guard shells. An ordinary guard counter combined with an extra guard on top of the iron shield is very efficient. A background of 0.48 ± 0.01 c/min has already been obtained.
Enrichment of 14C and Sample Preparation for Beta and Ion Counting
Authors: Grootes P M , Stuiver Minze , Farwell G W , Schaad T P , Schmidt F H
Published: July 2016

We here report on two technical research projects of the Quaternary Isotope Laboratory (QL) vis, (1) the use of thermal diffusion isotopic enrichment to extend the technical range of 14C dating, (2) the preparation of samples for ion counting using a Van de Graaff tandem accelerator. The second project is carried out in cooperation with, and partly at, the Nuclear Physics Laboratory.

A gain in dating range of 3 to 4 half-lives can routinely be obtained with the QL and the Groningen enrichment systems. The same gain in age range can be obtained for ion counting with a simplified system that requires only 0.5 to 2g of carbon and 3 to 7 days enrichment time.

A method to convert CO2 quantitatively via CO into carbon is described. For short intervals the carbon deposit yields good 12C— beams. We also give a different procedure to make graphite-like carbon samples. The preparation of beryllium metal samples is given last.
The Behavior of 14C and 13C in Estuarine Water: Effects of In Situ CO2 Production and Atmospheric Exchange
Authors: Spiker Elliott C
Published: July 2016

The effects of nonconservative sources (inputs) and sinks (outputs) of carbon are indicated by the behavior of Δ14C and δ13C of the total dissolved inorganic carbon (ΣCO2) in San Francisco Bay and Chesapeake Bay. Isotopic distributions and model calculations indicate that in North San Francisco Bay the net CO2 flux to the atmosphere and carbon utilization in the water column are balanced by benthic production. Municipal waste appears to be a dominant source in South San Francisco Bav. In Chesapeake Bay, atmospheric exchange has increased the Δ14C and δ13C in the surface water. Decomposition of organic matter in the water column is indicated to be the dominant source of excess ΣCO2 in the deep water.
Content of14C in Marine Mammals from Northern Europe
Authors: Olsson Ingrid U
Published: July 2016

The reservoir effect of Scandinavian sea water has been determined by dating seals and whales killed well before man's impact on the natural14C concentration became significant. The samples were collected at different places along the Swedish coasts and in the Gulf of Finland. They derive from ad 1657 or 1658, 1868, 1875, 1894, and 1906. The EDTA treatment of bones was used to obtain collagen free from contaminants.

An elk, originating from ad 1881 was selected for comparison. A seal from ad 1899 from the Caspian Sea was also included in the investigation.

All results have been normalized to δ13C = —25‰ vs PDB. The determinations yield values of the reservoir effect in agreement with earlier results obtained from shells and mammals. The final results are discussed in light of previous variations of14C content in the atmosphere. Using a smoother curve, the reservoir effect is slightly smaller than was hitherto believed.

An event thought to be of cosmic origin caused the count rate of both proportional and Geiger counters to increase significantly around December 4, 1978. The correction for this has been studied. The statistics for background, oxalic acid, and unknown samples, measured repeatedly after this correction, were as good as usual.
The Use of Radiocarbon to Measure the Effects of Earthworms On Soil Development
Authors: Stout J D , Goh K M
Published: July 2016

Δ14C and δ13C values for organic matter in forest and grassland soils, in the presence or absence of earthworms, indicate that it should be possible to quantify the effects of earthworms on soil organic matter by this means. Without earthworms, both in forest and grassland soils, plant debris tends to accumulate on the surface of the mineral soil and little organic matter is incorporated into or is translocated down the soil profile. Where earthworms are present, there is much more marked incorporation of fresh plant debris in the mineral soil. This is shown especially by the pulse of ‘bomb’ carbon and also by the δ13C values.
Exploratory Analysis of the International Radiocarbon Cross-Calibration Data: Consensus Values and Interlaboratory Error Preliminary Note
Authors: Currie Lloyd A , Polach Henry A
Published: July 2016

A preliminary review is given of the evaluation of the International Cross-Calibration Radiocarbon Data. Consensus values and standard errors are D14C = 508.1 ± 2.0% (ANU Sucrose) and Δ = −2.5 ± 1.5% (1850 Wood). Reporting format follows recommendations of Stuiver and Polach (1977).
Workshop On 14C Data Reporting
Authors: Stuiver Minze
Published: July 2016

The purpose of the workshop was to clarify any possible confusion related to the reporting 14C data. Two areas of concern, the use of the new NBS oxalic acid standard (Cavallo and Mann, 1980), and the reporting of marine sample ages, were singled out for detailed discussions.
University of Michigan Radiocarbon Dates IX
Authors: Crane H. R. , Griffin James B.
Published: July 2016

The following is a list of dates obtained since the time of the compilation of List VIII in December 1962. The method is essentially the same as that used for the work described in the previous list. Two CO2-CS2 Geiger counter systems are used. The equipment and counting techniques have been described elsewhere (Crane, 1961a, 1961b). The dates and the estimates of error in this list follow the practice recommended by the International Radiocarbon Dating Conference of 1962, in that (a) dates are computed on the basis of the Libby half life, 5570 years, (b) a.d. 1950 is used as the zero of the age scale and (c) the errors quoted are the standard deviations obtained from the numbers of counts only. In previous Michigan date lists up to and including VII we have quoted errors at least twice as great as the statistical errors of counting, in order to take account of other errors in the over-all process. If the reader wishes to obtain a standard deviation figure which will allow ample room for the many other sources of error in the dating process, we suggest he double the figures that are given in this list. Where there is no comment, it is because the submitter of the sample had none to make.

We wish to acknowledge the help of Patricia Dahlstrom in preparing chemical samples and Roscoe Wilmeth in preparing the descriptions. The descriptions and comments are essentially those of persons submitting the samples.
Geological Survey of Finland Radiocarbon Measurements III
Authors: Hyyppä E. , Toivonen A. V. P. , Isola A.
Published: July 2016

The following results represent measurements carried out since our second date list was prepared. The pretreatment of the samples and the production of pure CO2 followed the method described in Finland I.
Cambridge University Natural Radiocarbon Measurements VI
Authors: Godwin H. , Willis E. H.
Published: July 2016

The dates and activity measurements given below have been obtained during 1962 and 1963, and have been made with CO2 at 3 atm pressure in a proportional gas-counter very little modified from those described in previous contributions from this laboratory.
Tata Institute Radiocarbon Date List II
Authors: Agrawal D. P. , Kusumgar S. , Lal D. , Sarna R. P.
Published: July 2016

The C14 dates presented here have been obtained by counting acetylene, synthesised from the sample, in an Oeschger-Houtermans’ gas proportional counter. The chemical and counting procedures have been described in some detail (Kusumgar et al., 1963a).

Dates are based on the C14 half-life value of 5568 yr. For conversion of b.p. dates to a.d./b.c. scale, a.d. 1950 has been taken as the reference yr. Ninety-five % activity of NBS oxalic acid has been adopted as the value for the pre-1900 age-corrected wood.

All samples were treated with dilute HCl. Whenever NaOH pretreatment was possible, it has been mentioned in the date list. In the case of bones, only the inorganic fraction has been dated.
Trondheim Natural Radiocarbon Measurements IV
Authors: Nydal Reidar , Lӧvseth Knut , Skullerud Kari E. , Holm Marianne
Published: July 2016

This date list covers mainly the datings done in 1962 and 1963 and is therefore a continuation of our last date list (Trondheim III).
Groningen Radiocarbon Dates V
Authors: Vogel J. C. , Waterbolk H. T.
Published: July 2016

This date list mainly contains results obtained for archaeological samples which were measured in the Groningen laboratory in the course of the years and which have not hitherto been published in a similar form. As such it is an extension of the previous date list (Groningen IV) and reference is made to this publication for information on the method of presentation, the corrections applied, etc. Samples which are primarily of geological significance will be presented separately in next year's list.
ANU Radiocarbon Date List II
Authors: Polach H. A. , Golson J. , Lovering J. F. , Stipp J. J.
Published: July 2016

The C14 measurements reported here were carried out by the Radiocarbon Laboratory, Dept. of Geophysics and Geochemistry, A.N.U., between Jan. and Aug. 1967. Laboratory equipment consists of a Beckman methane gas-proportional unit (ANU I) supplemented in Dec. 1966 by an automatic 3-channel Beckman model LS-200 liquid scintillation spectrometer. Synthesis of methane and benzene is the same as used in ANU I and described by Polach and Stipp (1967). Treatment of samples remains a 2N hot acid (HCl) wash unless otherwise specified. Where applicable, fractional separation follows procedures reported by Olson (1963), Berger et al. (1964), Tamers and Pearson (1965), and Krueger (1966). In the treatment of bone samples, physical or mechanical cleaning could not completely remove sedimentary material often filling the structural pores. This material, if present, was retained with the fraction referred to as “collagen”. Since we are not dealing with pure collagen, we prefer to call it “acid-insoluble” bone fraction, a name describing the treatment. These dates are reported as equal to or greater than given age. Table 1 summarizes all dated fractions.
Copenhagen Radiocarbon Dates IX
Authors: Tauber Henrik
Published: July 2016

The following list comprises a selected number of measurements made up to October, 1967. Age calculations are based on 95% of the activity of the NBS oxalic-acid standard, and on a half-life for C14of 5570 yr. Results are reported in yr before 1950, and in the A.D./B.C. scale.

Errors quoted include standard deviations of the count rates for the unknown sample, contemporary value, and background. Because possible errors arising from isotopic fractionation in the plants, or from the de Vries effect, have not been included, calculated errors smaller than 100 yr have been increased by rounding to that figure as a minimum.

Sample descriptions have been prepared in collaboration with collectors and submitters.
University of Lund Radiocarbon Dates II
Authors: Håkansson Sören
Published: July 2016

The C14 measurements reported here were made in this laboratory between September 1967 and October 1968.
Uppsala Natural Radiocarbon Measurements IX
Authors: Olsson Ingrid U. , El-Gammal Shawky , Göksu Yeter
Published: July 2016

The following list covers some old measurements not included in previous lists and most of the samples measured at the Uppsala C14 laboratory since the last list (Radiocarbon, 1967, v. 9, p. 454-470); samples utilized for determining the increase of the C14/C12 ratio clue to explosion of nuclear devices are omitted