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Abstract: This article presents a detailed explanation of the analytical method used to monitor and quantify measurement uncertainties at the NSF-Arizona Accelerator Mass Spectrometry (AMS) Laboratory. The method is applicable to all of the isotopes measured at the facility, including 14C, 10Be, 129I and 26Al. It is used for a variety of analytical purposes, including: calculation of random machine error (rme), calculation of radiocarbon dates, and as an indicator of daily and long-term machine performance. An algorithm for a diagnostic program used to monitor rme is described in detail. The performance of the AMS machine as measured by rme calculations is given for the most recent six month period. The long-term accuracy of the machine is discussed in terms of blind sample analyses made under the Third (TIRI), Fourth (FIRI) and Fifth (VIRI) International Radiocarbon Intercomparisons. [Copyright &y& Elsevier]

Abstract: The accuracy of global eustatic sea level curves measured from raised Quaternary reefs, using radiometric ages of corals at known heights, may be limited by time-averaging, which affects the variation in coral age at a given height. Time-averaging was assessed in uplifted Holocene reef sequences from the Huon Peninsula, Papua New Guinea, using radiocarbon dating of coral skeletons in both horizontal transects and vertical sequences. Calibrated 2σ age ranges varied from 800 to 1060 years along horizontal transects, but weighted mean ages calculated from 15–18 dates per horizon were accurate to a resolution within 154–214 yr. Approximately 40% of the variability in age estimate resulted from internal variability inherent to 14C estimates, and 60% was due to time-averaging. The accuracy of age estimates of sea level change in studies using single dated corals as proxies for sea level is probably within 1000 yr of actual age, but can be resolved to ≤250 yr if supported by dates from analysis of a statistical population of corals at each stratigraphic interval. The range of time-averaging among reef corals was much less than that for shelly benthos. Ecological time-averaging dominated over sedimentological time averaging for reef corals, opposite to patterns reported from shelly benthos in siliciclastic environments. [Copyright &y& Elsevier]

Radiocarbon records from modern corals have long been recognized for their usefulness as a geochemical tracer of surface ocean waters and oceanic upwelling. Pacific corals are especially interesting because of their potential relevance to El Niño – Southern Oscillation (ENSO) events. At present, the Pacific Ocean is undersampled with respect to radiocarbon time series. This study establishes a 14C time series for a coral from the Solomon Islands, located near the center of the Western Pacific Warm Pool (WPWP). We present radiocarbon results from a Porites colony which grew in Marau Sound, on the east coast of Guadalcanal. A semiannual record of 14C was constructed from measurements of alternating bands which grew continuously from 1944 to 1994. The record reflects the uptake of atmospheric bomb-produced 14C since the late 1950s with superimposed subannual radiocarbon variations, presumably related to changes in ocean circulation. Although the coral radiocarbon is influenced by ENSO events, the record is not closely correlated with the Southern Oscillation Index (SOI) for the same period. [Copyright &y& Elsevier]

China is an important fossil fuel CO 2 (CO 2 ff) emitter and the international community is thus concerned with quantifying reductions in Chinese carbon emissions in the recent past. Compared to traditional statistical method, radiocarbon (14C) offers a different approach to quantify atmospheric CO 2 derived from fossil fuel emissions. Here, we carry out a multi-year (2011 – 2016) CO 2 ff tracing by 14C in Xi'an, and a three-year (2014 – 2016) CO 2 ff tracing in 15 Chinese cities. The Xi'an results show that average CO 2 ff concentrations fell 35.9 ± 6.6% from 2014– 2016, compared to 2011–2013, and the timing of this decrease coincides with the implementation of nationwide carbon reduction measures in China, known as the Action Plan on Prevention and Control of Air Pollution. A WRF-Chem forward modeling simulation reveals that the CO 2 ff in Xi'an is mainly derived from local sources, and a source apportionment combined stable-carbon isotope showed that the CO 2 ff in this city is dominated by coal combustion (72.6 ± 10.4%). Strong CO 2 ff differences are found between January and July in most Chinese cities. High CO 2 ff concentrations often correspond to severe haze episodes and there are generally positive correlations between CO 2 ff and fine particulate (PM 2.5) concentrations. Our study provides scientific data to understand the effects of CO 2 ff reduction strategies in China that can be applied to other countries as well. Unlabelled Image • China has dual problems-CO 2 emissions reductions and air pollution mitigation. • CO 2 ff in Xi'an dropped after implementation of a 2013 pollution prevention plan. • Case study showed that CO 2 ff in Xi'an was mainly from local coal combustion. • CO 2 ff in January was significantly higher than that in July in most cities. • Positive correlations were found between CO 2 ff and PM 2.5 in Chinese cities. [ABSTRACT FROM AUTHOR]