A 22 m sediment core was collected from the unsaturated zone (USZ) in the dunes south of Ashdod, Israel, in a low rainfall year, following an even lower-rainfall year. The mineralogy of was quartz with some clay and carbonate. The local climate is semi-arid. The roots of the sparse vegetation can reach ~8 m. The porosity was ~40–55%. The DIC ranged from 2 to 13 mmole C/L. Large variability is noted in the soil moisture, with a maximum at the high clay region at ~8 m. Oxygen isotopes enter the USZ with rain falling on the surface. There is 18O enrichment in the top of the section due to evaporation during the summer. Below this depth δ18O values of ~ –5‰ prevail as in the local aquifer. CO2 and the carbon isotopes enter the USZ laterally by exhalation from roots. The δ13C varies from –5‰ to –23‰, representing stages in carbon isotopic fractionation: CO2gas becomes dissolved CO2aqueous which then forms carbonic acid and HCO3– . The high δ13C, Δ14C, and DIC are found at the 8 m depth. These values along with high humidity are replicated at ~22m depth. They most probably represent recharge water from the previous rainy season at 8 m depth subsequently pushed down 12.8±0.8 m during the last winter.

This date list consists of some of the samples measuredsince summer 1965. For the routine measurements thesame technique and equipment as described earlierwas used (Bern IV).

The recent progress in radiocarbon dating of the prehistoric cultural complexes in the Russian Far East is discussed against the background of ancient chronologies for greater East Asia. Since 1997, the wide use of accelerator mass spectrometry (AMS) radiocarbon dating along with the continuation of conventional dating has allowed us to establish the age of several key Paleolithic, Neolithic, and Paleometal sites. It has also contributed to advancing a deeper understanding of the timing for the beginning of pottery production, maritime adaptation, and agriculture, and several other important issues in prehistoric chronology for the studied region. Reservoir age correction values for the Japan and Okhotsk seas are now used to adjust the age for samples of marine origin. Some of the cultural-chronological models for prehistoric far eastern Russian complexes put forward in the last 10 yr lack a solid basis, and are critically evaluated herein.

We implement a Bayesian statistical analysis of the chronology of Canímar Abajo in Cuba in order to estimate two episodes of burial activity and the period of time corresponding to the hiatus between them. We show that by using simple Bayesian modeling, conclusions can easily be reached by the analysis of the marginal posterior distribution of each parameter of the model. However, we also suggest and describe new statistical tools that exploit the joint posterior distribution of collections of dates. These new tools give complementary information regarding the chronology of human activity.

We follow the same method of radiocarbon dating used in the Gif-Sur-Yvette dating laboratory. Samples are inspected and foreign material removed. Wood and charcoal samples are treated with 0.1N ammonium hydroxide and 0.1N hydrochloric acid. Shells are treated with 10% hydrochloric acid to eliminate surface contamination. Bone samples are treated with 0.1N ammonium hydroxide to remove humic acids and 10% HCl to remove inorganic carbonate and retain collagen for radiocarbon measurements. Sample CO2 is produced by combustion in oxygen. The stream of gases passes over CuO at 600°C to insure complete oxidation of C to CO2 and through traps containing, respectively, silver nitrate and sulfuric chromic acid solution for purification; barium carbonate is precipited from barium hydroxide bubblers. After filtering and drying, CO2 is liberated from barium carbonate by sulfuric acid. The CO2 is used to fill a 1.2L steel proportional counter at 740mm Hg. Age calculations are based on a 14C half-life of 5568 ± yr and 0.95 of activity of the NBS oxalic acid standard; ages are quoted in yr before 1950. Finite ages are quoted with 1σ criterion corresponding to the standard deviation based only on counting errors; the maximum age is quoted with 4 σ criterion above background.

We have developed a technique using a single apparatus to recover the inorganic and organic carbon from a small (few milligrams) aliquot of dried marine material for radiocarbon analysis. The main advantages of using a single apparatus are: 1) less sample is required, 2) decreased handling reduces contamination, and 3) less time and materials are used. Blank values of ∼5 μg and 19–44 μg are obtained for the inorganic and organic carbon extractions, respectively. δ14C results from sinking particulate organic and inorganic carbon are presented for samples collected in deep-sea sediment traps deployed for 10–30 day periods at 650 and 100 m above bottom (mab) in the northeast Pacific Ocean.

Measurements have continued with the same proportional counter system, sample pretreatment procedure, methane preparation and measurement, and calculation using a half-life of 5568 ± 30 yr as described previously (R., 1970, v. 12, p. 298-318). Uncertainties quoted are single standard deviations originating from standard, sample, background counting rates and half-life. No C13/C12 ratios were measured.

We have studied the limitations of conventional mass spectrometry and have examined accelerator based methods which could help circumvent these limitations. In particular, cyclotron-based accelerator mass spectrometric (AMS) techniques are discussed with an emphasis on evaluating performances of superconducting mini-cyclotrons designed for use as AMS instruments. We discussed the design of superconducting mini-cyclotrons dedicated to radioisotope dating research.

We consider one misconception of those who currently reject the general validity of radiocarbon (14C) age determinations older than, at most, 10,000 BP. There is an allegation that the presence of 14C reported by accelerator mass spectrometry (AMS) laboratories in their measurements of 14C infinite age (>100,000 years) organics used to define background levels, support their point of view. This article has been written for a general audience, primarily for those who have questions about the validity of these arguments. However, they may not be familiar with the literature relevant to providing a clear response to the claims of these individuals. We conclude that, in our view, of all of the possible explanations for the reports of the presence of 14C in these background samples, the least probable explanation has been advanced by those rejecting the validity of the 14C time scale in excess of, at most, 10,000 BP.

The Pleistocene history of the leopard (Panthera pardus) in Europe has been documented by the material obtained from 312 localities, with the last dated ∼1.1 Myr. The relatively small and gracile form of the leopard was very rare during the late Early and Middle Pleistocene. Only after the disappearance of the jaguar (Panthera gombaszoegensis) did P. pardus spread widely in Europe, increasing in size and ecologically substituting P. gombaszoegensis. The number of late Middle Pleistocene localities with leopard remains, younger than 300 kyr, increased considerably. The leopard reached the maximum extension of its geographical range in the Late Pleistocene. The Iberian Peninsula was the last European refuge for this cat. Six sites, the Naciekowa, Obok Wschodniej, Radochowska, and Wschodnia Caves from the Sudety Mountains and the Biśnik and Dziadowa Skała Caves from the Kraków-Częstochowa Upland, have documented the presence of the leopard in Poland between MIS 10/9 and MIS 3. These records are from rocky regions with rugged terrain and are located in the territory of Silesia (southern Poland). A newly obtained radiocarbon date (43–42 kyr) from the Radochowska Cave directly confirms the occurrence of P. pardus in the Sudety Mountains in the middle part of MIS 3.

A conventional 14C system with either a 15cm3 or a 100cm3 methane gas proportional counting tube, each constructed from high purity copper, has been used at the Washington State University 14C laboratory for three years (Sheppard, Hopper, Westberg, 1981). The electronic components of this system included highly stable (John Fluke) power supplies, modified pre-amplifiers (Canberra), and NIM amplifiers, single channel analyzers, scalers, timers, etc, (ORTEC). Modules were selected for a highly stable low-noise system. The system was designed to minimize problems generated by ground-loops, electromagnetic noise pick-up, and line noise. It operates in a copper-lined basement room of a four-story brick and concrete building along with a second and older gas proportional system which has three 500cm3 copper counting tubes operated at 2 or 3 atmospheres of methane. Analysis of the older system's background data indicates that the background counting rate of 0.8 counts per minute is virtually independent of atmospheric pressure. It has not been possible to determine the pressure dependence of the small counting tubes.

Air was sampled with 5L flasks at Kitt Peak (2100m elev) from 1983 through 1984 at approximately monthly intervals, occasionally supplemented with air samples from urban Tucson ca 75km away (760m elev). The Kitt Peak CO2 concentrations, represented by a yield measurement, fluctuated ca 25% over the monitoring period. The δ13C values (uncorrected for N2O) varied from ca −7.6 to −9.0, with high values (and low CO2 yields) in the late summer consistent with hemispheric seasonal biosphere effects. Tucson air has lower δ13C values and possibly greater CO2 yield suggesting a local fossil-fuel effect. 14C activity of four Kitt Peak samples range from 1.158±.007 to 1.223±.008 as uncorrected fraction of modern, below free air activity of ca 1.250 for 1984 even after correcting for fractionation. The slightly low 14C activity and δ13C values suggest the Kitt Peak air is not quite 100% clean and there may be a local/regional fossil-fuel contribution, but CO2 concentrations are similar to background atmospheric values.

An approximate randomization technique for comparing 14C histograms is described and illustrated with an example from Hawai'i. The technique determines intervals of significant difference in the histograms, rather than providing a single number summary.

Preliminary observations of changes of the background of three proportional counters during May and June, 1986, are presented. Some isotopes contributing to the rise of background were identified on the basis of their half-life determinations.

Since 1977, the German Institute of Archaeology in Cairo has been reexamining the archaic Royal necropolis Umm el-Qaab at Abydos (ca. 500 km south of Cairo). The necropolis consists of the tomb complexes of six kings and one queen of Dynasty I as well as two kings of Dynasty II in the southern part, the cemetery with royal tombs from Dynasty 0 and early Dynasty I in the middle and the predynastic cemetery in the northern part. Although partly destroyed and deprived of most of their contents, the tombs and the remaining artifacts are a major source for the early dynastic period and are of utmost importance for the understanding of predynastic development during Naqada I–III and the chronology of the formation of Egyptian culture. Sixteen newly 14C-dated samples were mainly taken from remains of wooden roofs and coffins, or in the case of the earliest tombs from mattings. The dating results in general are in good accordance with the relative archaeological dating of the tombs, but 100–150 yr earlier than the so far established historical chronology.

Late Holocene relative sea-level reconstructions are commonly generated using proxies preserved in salt-marsh and mangrove sediment. These depositional environments provide abundant material for radiocarbon dating in the form of identifiable macrofossils (salt marshes) and bulk organic sediment (mangroves). We explore if single-step graphitization of these samples in preparation for radiocarbon dating can increase the number and temporal resolution of relative sea-level reconstructions without a corresponding increase in cost. Dating of salt-marsh macrofossils from the northeastern United States and bulk mangrove sediment from the Federated States of Micronesia indicates that single-step graphitization generates radiocarbon ages that are indistinguishable from replicates prepared using traditional graphitization, but with a modest increase in error (mean/maximum of 6.25/15 additional 14C yr for salt-marsh macrofossils). Low 12C currents measured on bulk mangrove sediment following single-step graphitization likely render them unreliable despite their apparent accuracy. Simulated chronologies for six salt-marsh cores indicate that having twice as many radiocarbon dates (since single-step graphitization costs ∼50% of traditional graphitization) results in narrower confidence intervals for sample age estimated by age-depth models when the additional error from the single-step method is less than ∼50 14C yr (∼30 14C yr if the chronology also utilizes historical age markers). Since these thresholds are greater than our empirical estimates of the additional error, we conclude that adopting single-step graphitization for radiocarbon measurements on plant macrofossils is likely to increase precision of age-depth models by more than 20/10% (without/with historical age markers). This improvement can be implemented without additional cost.

The following dates are samples measured since publication of Kiel III (Radiocarbon, v. 10, p. 328–332). Age calculations are based on 95% of the activity of NBS oxalic-acid standard as modern value of A.D. 1950. Results are calculated with Libby half-life and reported in yr before 1950. Error corresponds to 1σ variation of sample net counting rate as well as modern standard and background, but does not include the uncertainty in C14 half-life and in secular C14 variations. Dates are not corrected for isotopic fractionation.

Measurements of the radiocarbon abundance in 5 samples of bis(2–ethylhexyl) phthalate (DEHP) isolated from Stilton cheese were made by accelerator mass spectrometry (AMS) to determine the fraction of carbon originating from contemporary biogenic sources. DEHP is classified as a “priority hazardous substance” by the European Union, a probable human carcinogen by the United States Environmental Protection Agency, and is suspected to be a human endocrine disrupter. Measurement of its 14C abundance in a specific food indicates whether its presence is due to contamination from industrially synthesized DEHP or a naturally inherent component. A method was developed to determine the contemporary carbon fraction of DEHP in a fatty food matrix at concentrations of 0.14 mg/kg. Five 90–μg quantities of DEHP were extracted from 12 kg of Stilton cheese and isolated by silica gel, size exclusion, and high-performance liquid chromatography (HPLC). Masses of samples were determined by gas chromatography mass spectrometry (GC-MS) analyses prior to combustion and manometry afterwards. The purity of DEHP carbon mass in each isolate was determined by multivariate deconvolution of GCMS fragmentation spectra obtained from measurements of standards and isolates, and ranged from 88.0 ± 1.8% to 92.3 ± 1.1% (n = 5, 1σ). Concurrently processed isolation method blanks contained from 0.15 ± 0.04 to 1.52 ± 0.06 μg (n = 3, 1σ) DEHP per sample and significant quantities of pre- and post-chromatographic extraneous carbon contamination. The mean 14C-corrected contemporary carbon fraction of DEHP in the isolates was 0.235 ± 0.073 (1σ; and ± 0.091 at the 95% confidence level), revealing that the majority of DEHP in Stilton cheese results from anthropogenic sources, but with a significant naturally occurring component.