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The Lawrence Livermore National Laboratory (LLNL) and the University of California (UC) now have in operation a large AMS spectrometer built as part of a new multiuser laboratory centered on an FN tandem. AMS measurements are expected to use half of the beam time of the accelerator. LLNL use of AMS is in research on consequences of energy usage. Examples include global warming, geophysical site characterization, radiation biology and dosimetry, and study of mutagenic and carcinogenic processes. UC research activities are in clinical applications, archaeology and anthropology, oceanography, and geophysical and geochemical research. Access is also possible for researchers outside the UC system. The technological focus of the laboratory is on achieving high rates of sample throughput, unattended operation, and advances in sample preparation methods. Because of the expected growth in the research programs and the other obligations of the present accelerator, we are designing a follow-on dedicated facility for only AMS and microprobe analysis that will contain at least two accelerators with multiple spectrometers.

The Simon Fraser AMS spectrometer operated at McMaster University for a period of about ten years. This instrument was unique in that the isotope beams of interest were injected into the accelerator simultaneously rather than sequentially, using an achromatic multimagnet injector. As well, our group has also been involved in the design and operation of the LLNL spectrometer, which uses a more conventional fast-pulsing sequential system. We compare our first-hand experience with the two systems and discuss the strengths and weaknesses of the different approaches.

The multi-user tandem laboratory at Lawrence Livermore is a new facility dedicated to AMS and a variety of other ion-beam analysis techniques. The AMS spectrometer design aims and implementation are presented here, and present performance and planned improvements are discussed.

THE eruption of Vesuvius in AD 79 (as described by Pliny) is the archetype1–4 of explosive 'plinian' eruptions which can cause recur-rent local destruction and which may affect global climate through aerosol emissions5–7. Studies of the past eruptions of such vol-canoes require accurate age determinations, especially if the erup-tions are to be correlated with distant events. Here we use materials from two plinian eruptions of Vesuvius, the AD 79 and the preceding Avelline1,8 event, to test the 14C methods that often provide these ages. Our 14C ages for charred samples and corrected soil reservoirs buried by the Avellino eruption averaged to 3,360 ±40 BP (1617–1703 cal BC), 200–500 years later than the original 14C ages of soil humic carbon9,10 and total organic carbon11. Furthermore, a re-evaluation of the 14C data for the Mount St Helens Yn and Aniakchak II eruptions suggests that these major plinian eruptions may also have occurred in the seventeenth century BC. The 14C ages for these three eruptions are identical, within uncertainties, to that of the 'Minoan’ eruption of Thera (Santorini), which has often been correlated with mid-seventeenth century BC disturb-ances recorded in tree-ring series12,13 and ice-core layers14. Addi-tional information is still required to distinguish which, if any, of the eruptions relate to these records.

“Post-maximum-bomb” 14C activities (1964 to the present) provide a natural isotopic signature to obtain information on biomass source age in contemporary food preparations. An analysis of the 14C content in frozen orange juice-containing products purchased in 1996 suggested, in one case, an inferred growth period between 1992 and 1994 for oranges used in the preparation of this commodity. In another case, the 14C analysis indicated an inferred average growth period of 1988−90 for the organics in a “frozen concentrated enriched citrus beverage”. The presence of significant amounts of chemical additives obtained or synthesized from fossil carbon sources can also be documented by measuring 14C content. Keywords: Radiocarbon; carbon isotopes; orange juice; component age

A new radiocarbon accelerator mass spectrometry (AMS) laboratory for carbon cycle studies has been established at the University of California, Irvine. The 0.5MV AMS system was installed in mid-2002 and has operated routinely since October of that year. This paper briefly describes the spectrometer and summarizes lessons learned during the first year of operation. In the process of setting up the system, we identified and largely suppressed a previously unreported 14C AMS background: charge exchange tails from 14N beams derived from nitrogen-containing molecular ions produced near the entrance of the accelerator.

The notable sparseness of human skeletal remains is a characteristic trait of early American prehistory and, therefore, this aspect of the archaeological record is seldom considered in its discussion. In this context, the finding of remains from five individuals dated to the 9th millenium BP on the re-excavations at Bano Nuevo Cave (Andean Central Patagonia, Chile) is particularly interesting. They may not appear excessively old, but several radiocarbon dates (two of them done through AMS directly on the bone of one of the individuals) place them among the very few well-dated early human skeletons throughout the Americas. The small sample size militates against any interpretation of biological affiliation (to say nothing of population movements) and we can only affirm that these people belonged to a generalized “mongoloid stock”, different from historically known Patagonian populations. After a brief presentation of the skeletal evidence and the bone dating methods, we evaluate the relevance of this context with respect to the sparse osteological record of humans in the Americas on the Pleistocene/Holocene transition.

We have developed techniques and are commencing experiments using enriched {sup 41}Ca as a tracer in isolated rabbit heart preparations. The aims of the study are to measure calcium uptake and deposition in response to cardiac ischemia and reperfusion, and to investigate events and mechanism leading to irreversible myocyte injury.

Radiocarbon data from the Cariaco Basin provide calibration of the carbon-14 time scale across the period of deglaciation (15,000 to 10,000 years ago) with resolution available previously only from Holocene tree rings. Reconstructed changes in atmospheric carbon-14 are larger than previously thought, with the largest change occurring simultaneously with the sudden climatic cooling of the Younger Dryas event. Carbon-14 and published beryllium-10 data together suggest that concurrent climate and carbon-14 changes were predominantly the result of abrupt shifts in deep ocean ventilation.

WIDESPREAD seepage of petroleum and natural gas in the southern California continental borderland1–4 provides an opportunity to study the long-term fate and biogeochemical effects of hydrocarbons in nearshore sedimentary environments. The hydrocarbons that enrich seep sediments have been hypothesized to serve as a carbon and energy source for sediment metabolism and in-faunal populations5–9. Here we present 14C natural abundances in sediment total organic carbon (TOC), pore-water dissolved inorganic carbon (DIG) and infauna from in and around a hydrocarbon seep off southern California which were measured to help test this hypothesis. Concentrations of 14C in each pool reflect the admixture of fossil (14C-depleted) seep-derived carbon with carbon from the euphotic zone. The 14C depletion in TOC and DIC increased with proximity to the seepage zone and with sediment depth; 14C abundances differed between meiofauna and macrofauna, suggesting that the two groups incorporate fossil carbon in different ways. The results indicate that fossil carbon can indeed comprise a major component of these carbon pools in nearshore seep sediments.

Carbon isotopes (C-13 and C-14) and elemental composition (C and N) in two fractions of colloidal organic matter (COM) were measured to study the origin and cycling of dissolved organic matter (DOM) in the Middle Atlantic Eight (MAE). COM(1) (1 kDa-0.2 mu m) was 59% of the bulk DOM in surface Chesapeake Bay waters and decreased to 30-35% in waters of the MAB. COM(10) (10 kDa-0.2 mu m), which was the high-molecular-weight (HMW) component of COM(1), comprised 3-12% of the bulk DOM, with highest concentrations in Chesapeake Bay waters and the lowest in deep waters in the MAB. Delta(14)C values of COM(1) decreased from nearshore (-21 to +12 parts per thousand) to offshore and from surface (-166 to -85 parts per thousand) to bottom waters (-400 to -304 parts per thousand). Although Delta(14)C values of surface-water HMW COM(10) were generally high (-2 to -7 parts per thousand), values for bottom-water COM(10) were much lower (-129 to -709 parts per thousand). The high Delta(14)C values in the surface water suggest a particulate origin of pelagic COM, consistent with the contemporary Delta(14)C values of particulate organic matter (POM). The very low Delta(14)C values of bottom-water COM(10) imply that in addition to the pelagic origin, sedimentary organic C may serve as an important source for the benthic colloids in the bottom nepheloid layer. The general flow direction of organic carbon is from POM to HMW and to LMW DOM. Three colloidal end-members were identified in the MAB as well as in the Gulf of Mexico: estuarine colloids with high Delta(14)C values, high C:N ratios, and lower delta(13)C values; offshore surface water colloids with intermediate Delta(14)C values, lower C:N ratios, and higher delta(13)C values; and offshore deep-water colloids with low Delta(14)C values, intermediate C:N ratios, and variable delta(13)C values.

We measured carbon isotope abundances in the layered, proteinaceous skeleton of a zoanthid Gerardia collected from 620 m depth off the Little Bahama Bank (27°N, 79°W). The δ 14C values decreased from -76% in the outer growth edge to an average of -267% in the center of three portions of the skeleton. These δ 14C data suggest an age for this living organism of 1800 ± 300 years. The possibility that the large decrease in δ 14C reflects the gradual input of bomb 14C over the entire growth of the organism is inconsistent with the post-bomb δ 14C values obtained for the most recent growth tips. If the age estimate of two millennia is correct, it may be the longest-lived animal yet observed in the ocean. Gerardia may serve as a long-lived recorder of ocean chemistry, similar to the Bristlecone pine tree that has served as a millennial-timescale recorder for atmospheric 14CO2 (Suess, 1980) and climate. In particular, there is potential for Gerardia to serve as a millennial-scale integrator of upper ocean particle flux, and possibly reveal past changes in the productivity of the surface ocean. © 1995.

Calcium metabolism in biology may be better understood by the use of {sup 41}Ca labels, although detection by accelerator mass spectrometry (AMS) is required. Methodologies for preparation of urine samples and subsequent AMS measurement were investigated. Novel attempts at preparing CaH{sub 2} were unsuccessful, but CaF{sub 2} of sufficient purity could be produced by precipitation of calcium from urine as oxalate, followed by separation of calcium by cation exchange chromatography and washing the CaF{sub 2} precipitate. The presence of some remaining impurities could be compensated for by selecting the appropriate accelerated ion charge state for AMS. The use of projectile x rays for isobar discrimination was explored as an alternative to the conventional dE/dx device.

Accelerator mass spectrometry (AMS) is used to determine the amount of carcinogen covalently bound to mouse liver DNA (DNA adduct) following very low-level exposure to a 14C-labeled carcinogen. AMS is a highly sensitive method for counting long-lived but rare cosmogenic isotopes. While AMS is a tool of importance in the earth sciences, it has not been applied in biomedical research. The ability of AMS to assay rare isotope concentrations (10Be, 14C, 26Al, 41Ca, and 129I) in microgram amounts suggests that extension to the biomedical sciences is a natural and potentially powerful application of the technology. In this study, the relationship between exposure to low levels of 2-amino-3,8-dimethyl[2-14C]imidazo[4,5-f]quinoxaline and formation of DNA adducts is examined to establish the dynamic range of the technique and the potential sensitivity for biological measurements, as well as to evaluate the relationship between DNA adducts and low-dose carcinogen exposure. Instrument reproducibility in this study is 2%; sensitivity is 1 adduct per 10(11) nucleotides. Formation of adducts is linearly dependent on dose down to an exposure of 500 ng per kg of body weight. With the present measurements, we demonstrate at least 1 order of magnitude improvement over the best adduct detection sensitivity reported to date and 3-5 orders of magnitude improvement over other methods used for adduct measurement. An additional improvement of 2 orders of magnitude in sensitivity is suggested by preliminary experiments to develop bacterial hosts depleted in radiocarbon. Expanded applications involving human subjects, including clinical applications, are now expected because of the great detection sensitivity and small sample size requirements of AMS.

Differences in radiocarbon apparent ages between coexisting planktonic and benthic (B-P) foraminifers in the Santa Barbara Basin contain information about changes in the age (and thus the source) of water entering the basin. The Holocene sequence indicates a greater variability in circulation than previously detected. During the early Holocene, ca. 9 ka, B-P 1 4 C apparent age differences fluctuated between 220 and 560 1 4 C yr, similar to rapid variations seen during the Younger Dryas and the last glacial episode. During the relatively stable middle Holocene (8.5-2 ka), B-P 1 4 C apparent age differences averaged 440 1 4 C yr. After 2 ka, the average B-P 1 4 C apparent age difference increased to 620 1 4 C yr, which has persisted until the present. The shift in B-P 1 4 C apparent age differences likely represents a change in the strength or source of North Pacific Intermediate Water production and is concurrent with changes in regional climate patterns as well as with changes in temperature and accumulation rates measured in the Greenland Ice Sheet Project 2 ice core, suggesting large-scale changes in atmospheric circulation patterns.

The role of terrestrial ecosystems as sources or sinks for carbon to the atmosphere and their contribution to inter-annual variations in atmospheric CO2 remain hotly-debated topics. Carbon enters terrestrial ecosystems through a single process, photosynthesis, but it is returned to the atmosphere by the combined metabolic activity of plants, animals, and microbes (Figure l). The largest uncertainties in our understanding of terrestrial carbon cycling are in these return processes, especially how CO2 losses from ecosystems are divided among respiration by living plants—termed autotrophic respiration—versus microbial and faunal decomposition of plant residues—termed heterotrophic respiration (Figure 1); and how seasonal and climatic factors that change plant physiological status and soil conditions influence that partitioning.

Worldwide late Pleistocene terrestrial mammal faunas are characterized by stratigraphic associations of species that now have exclusive geographic ranges. These have been interpreted as either taphonomically mixed or representative of communities that no longer exist. Accelerator mass spectrometry {sup 14}C dates (n = 60) on single bones of stratigraphically associated fossil micromammals from two American and two Russian sites document for the first time that currently allopatric mammals occurred together between 12,000 and 22,000 yr B.P. on two continents. The existence of mammal communities without modern analogs demonstrates that Northern Hemisphere biological communities are ephemeral and that many modern biomes are younger than 12 ka. Future climate change may result in new nonanalog communities.

The News & Comment article “Kennewick Man's trials continue” by Virginia Morell (10 Apr., [p. 190][1]) reports the continuing legal and administrative conflicts over attempts by anthropologists and others to regain the ability to sample the Kennewick and other early North American skeletons to

Cores J-3-RGA, J-11-RGA (south and central part of the Japan Sea) were studied for δ^(18)O, palynological analyses, determination of carbonate and organic carbon content in sediments and dating by AMS methods. New AMS data on the J-11 core helped to identify the age of A-Tn volcanic ash as 25thousand years. The Synthesis of the obtained data and the data provided by other cores taken in the Japan Sea reveal the detailed carbonate stratigraphy of the Japan Sea sediments for the last 25Ky formed in the course of the paleoceonographic evolution of the basin. The carbonate horizons (CH) 1, 2, 3, are the result of the last glaciation event; they are related to the sea level regression and the semireduction condition of the bottom. The CH4 and CH5 horizons were formed during the transition period, and probably correlate with the cold events of Oldest and Younger Dryas. The CH6 and CH7 were accumulated in Holocene sediments, and they are related to insufficient changes in the Japan Sea environment.

Concentrations of 7Be and 210Pb in 2 years of weekly high-volume aerosol samples collected at Alert, Northwest Territories, Canada, showed pronounced seasonal variations. We observed a broad winter peak in 210Pb concentration and a spring peak in 7Be. These peaks were similar in magnitude and duration to previously reported results for a number of stations in the Arctic Basin. Beryllium 10 concentrations (determined only during the first year of this study) were well correlated with those of 7Be; the atom ratio 10Be/7Be was nearly constant at 2.2 throughout the year. This relatively high value of 10Be/7Be indicates that the stratosphere must constitute an important source of both Be isotopes in the Arctic troposphere throughout the year. A simple mixing model based on the small seasonal variations of 10Be/7Be indicates an approximately twofold increase of stratospheric influence in the free troposphere in late summer. The spring maxima in concentrations of both Be isotopes at the surface apparently reflect vertical mixing in rather than stratospheric injections into the troposphere. We have merged the results of the Be-based mixing model with weekly O3 soundings to assess Arctic stratospheric impact on the surface O3 budget at Alert. The resulting estimates indicate that stratospheric inputs can account for a maximum of 10–15% of the O3 at the surface in spring and for less during the rest of the year. These estimates are most uncertain during the winter. The combination of Be isotopic measurements and O3 vertical profiles could allow quantification of the contributions of O3 from the Arctic stratosphere and lower latitude regions to the O3 budget in the Arctic troposphere. Although at present the lack of a quantitative understanding of the temporal variation of O3 lifetime in the Arctic troposphere precludes making definitive calculations, qualitative examples of the power of this approach are given.

Average soil transport rates over a period of ∼3500 yr on a convex soil-mantled hillslope have been quantified using a mass-balance model that incorporates the soil concentration of the cosmogenic isotope 10 Be. The 10 Be model results support the assumption used in most geomorphic models that the soil creep rate is proportional to surface gradient. The predicted diffusion coefficient is 360 ±55 cm 3 ⋅ yr -1 ⋅ cm -1 contour length and the average rate of soil production is 0.026 ±0.007 cm/yr. Within the uncertainty of this technique, the data do not reject G. K. Gilbert9s hypothesis that some hillslopes may exist in a condition of dynamic equilibrium with a uniform soil production rate. However, the model does not require an assumption of dynamic equilibrium and may be an approach that uniquely allows the quantification of a local soil-production rate law.

Wc describe here the New Zealand kauri (Agathis australis) Younger Dryas (YD) research project, which aims to undertake Δ14C analysis of ∼140 decadal floating wood samples spanning the time interval ∼13.1–11.7 kyr cal BP. We report 14C intercomparison measurements being undertaken by the carbon dating laboratories at University of Waikato (Wk), University of California at Irvine (UCI), and University of Oxford (OxA). The Wk, UCI, and OxA laboratories show very good agreement with an interlaboratory comparison of 12 successive decadal kauri samples (average offsets from consensus values of –7 to +4 14C yr). A University of Waikato/University of Heidelberg (HD) intercomparison involving measurement of the YD-age Swiss larch tree Ollon505, shows a HD/Wk offset of ∼10–20 14C yr (HD younger), and strong evidence that the positioning of the Ollon505 series is incorrect, with a recommendation that the 14C analyses be removed from the IntCal calibration database.

Authors thank the National Natural Science Foundation of China grants NSFC 41888101 and NSFC 41731174, the 111 program of China (D19002), U.S. NSF Grant 1702816, and the Malcolm H. Wiener Foundation for support for research that contributed to the IntCal20 curve. The work on the Swiss and German YD trees was funded by the German Science foundation and the Swiss National Foundation (grant number: 200021L_157187). The operation in Aix-en-Provence is funded by the EQUIPEX ASTER-CEREGE, the Collège de France and the ANR project CARBOTRYDH (to EB). The work on the correlation of tree ring 14C with ice core 10Be was partially supported by the Swedish Research Council and the Knut and Alice Wallenberg foundation. M. Butzin is supported by the German Federal Ministry of Education and Research (BMBF) through the PalMod project (grant number: 01LP1505B). S. Talamo and M. Friedrich. are funded by the European Research Council under the European Union’s Horizon 2020 Research and Innovation Programme (grant agreement No. 803147-RESOLUTION, awarded to ST). C. Turney would like to acknowledge support of the Australian Research Council (FL100100195 and DP170104665). P. Reimer and W. Austin acknowledge the support of the UKRI Natural Environment Research Council (Grant NE/M004619/1). Radiocarbon (14C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals. Publisher PDF