Radiocarbon dates (n = 18) from three archaeological sites on Adak Island, Alaska, were analyzed to understand the marine reservoir offset. Samples of marine and terrestrial origins recovered from the same archaeological context were compiled in nine pairs. The mean ΔR value calculated for them totaled 545 ± 10 yr. This value can be regarded as a sound estimate of the marine reservoir offset in the central Aleutians.

Radiocarbon results from houses, pits, and burials at the SunWatch site, Dayton, Ohio, are presented within an interpretative Bayesian statistical framework. The primary model incorporates dates from archaeological features in an unordered phase and uses charcoal outlier modeling (Bronk Ramsey 2009b) to account for issues of wood charcoal 14C dates predating their context. The results of the primary model estimate occupation lasted for 1–245 yr (95% probability), starting in cal AD 1175–1385 (95% probability) and ending in cal AD 1330–1470 (95% probability). An alternative model was created by placing the 14C dates into two unordered phases corresponding with horizontal stratigraphic relationships or distinct groups of artifacts thought to be temporally diagnostic. The results of the alternative model further suggest that there is some temporal separation between Group 1 and Group 2, which seems more likely in the event of a multicomponent occupation. Overall, the modeling results provide chronology estimates for SunWatch that are more accurate and precise than that provided in earlier studies. While it is difficult to determine with certainty if SunWatch had a single-component or multicomponent occupation, it is clear that SunWatch's occupation lasted until the second half of the AD 1300s.

Foodcrusts, the charred surface deposits on pottery vessel surfaces, provide a rich source of data regarding container function. This article reviews recent applications focusing on the detection of aquatic resources (marine and freshwater) in pottery vessels using a range of analytical approaches including bulk isotope measurements of carbon and nitrogen, lipid biomarker analysis, and compound-specific carbon isotope determinations. Such data can help to evaluate the presence of reservoir effects when undertaking radiocarbon dating of foodcrust samples. In particular, molecular and isotopic analysis can aid in the selection of suitable candidates for 14C where it can be demonstrated that aquatic resources are unlikely to contribute to the residue. Prospects for compound-specific 14C analysis of lipids in foodcrusts and ceramic-absorbed residues are also discussed.

The Jomon culture is an ancient Japanese society that existed during approximately 14,000 to 400 BC and which is characterized by Jomon (cord pattern) pottery. To investigate the paleodiet of the people of northeastern Tohoku in Japan during the Final Jomon period (about 1000–400 BC), we studied three sites in Aomori Prefecture, the center of the Kamegaoka culture. The Fubinashi site is on the coast and was supported by a rich fishing culture. Imazu was a coastal salt-making site. Sugisawa is a mountainous inland site on the banks of a river. We determined the 14C ages of the interior and exterior surfaces of carbonized material on potsherds and compared the data with pottery typology and age to study the marine reservoir effect. We also analyzed the bulk carbon and nitrogen stable isotopes and C:N ratios to determine the presence of aquatic foodstuffs. The organic residues from pottery typology corresponding to the described analyses provided a general perspective of differences in the ancient diets at each site. When we recovered sufficient lipids, we analyzed compound-specific stable isotopes of fatty acids to obtain a multilateral view of those diets. Our findings indicate that the diets of inhabitants of both Fubinashi and Imazu consisted primarily of marine products and some terrestrial foodstuffs, whereas people from Sugisawa processed mainly C3 plants and some terrestrial animals and aquatic commodities.

The flame-sealed tube zinc reduction graphitization method has been successfully adapted and optimized for radiocarbon measurements on EnvironMICADAS in the Institute for Nuclear Research of the Hungarian Academy of Sciences, Hertelendi Laboratory of Environmental Studies (ATOMKI HLES). To reduce the cost and treatment time of producing graphite targets from samples of about 1 mg carbon content, we have omitted the titanium hydride (TiH2) reagent and used a decreased amount of zinc as the sole reductant in our new method. These changes have also helped to eliminate methane formation during the graphitization processes as well as to recover higher ion current at the same background level. These conditions have led to improved efficiency in the 14C measurements; furthermore, the instrument background level remained sufficiently low (<49,000 yr BP). After determining the optimum parameters of the new Zn graphitization method (2.5 mg Fe powder, 15.0 mg Zn powder, 10 hr graphitization at 550°C in heating block, reaction cells with reagent pretreated at 300°C for 1 hr), verification of the accuracy was carried out by the preparation and measurement of IAEA standard samples (C2, C6, C7, C8) with known 14C activity. The sensitivity of the method for gas contamination was tested and determined by comparing the results to measurements of reserved portions of previously processed real samples.

Radiocarbon investigation of atmospheric PM2.5 aerosol synchronized with 14CO2 observations began in Debrecen in the winter of 2010. The aim of the study was to determine the contemporary and fossil carbon fractions in the aerosol and to set them against the fossil CO2 excess data referring to the same period. The mass of the collected PM2.5 mode on prebaked quartz filters was determined gravimetrically, while its total carbon mass was calculated from the pressure of CO2 gas produced after the combustion of the filters. As a result of the applied sampling and preparation method, the stable, nonvolatile carbon forms were principally studied. 14C measurements of the tiny aerosol bulk samples were performed using the EnvironMICADAS accelerator mass spectrometer at ATOMKI. The sample preparation method was tested using several blanks, standards, and real samples. Test results showed good reproducibility for the applied aerosol sample preparation and accelerator mass spectrometry (AMS) 14C analyses. Atmospheric fossil CO2 excess data were calculated according Levin et al. (2003), using the 14C results of collected CO2 samples measured by the gas proportional counting system at ATOMKI. Mass concentration of PM10 involving the PM2.5 mode in the city air exceeded the daily average of 50 μg/m3 (24-hr limit value in the EU) several times in 2011, mainly during the winter. The results showed that recently derived carbon most likely from domestic wood burning was causing the elevated carbon mass concentration of PM2.5 in Debrecen at the time. In the course of the 1-yr-long continuous and systematic comparison of fossil carbon mass concentration of PM2.5 mode and mole fraction of fossil excess of atmospheric CO2, similar and synchronous trends were observed during the studied period in Debrecen.

Aquatic macrophytes from a lacustrine environment are highly prone to a reservoir effect, resulting in an overestimation of age. This is often caused by the incorporation of dissolved carbon (CO2 and HCO3–) through photosynthesis from lake waters that have a different 14C activity than the atmosphere. The atmosphere-water disparity is often produced by a mixing of carbon between the water body and its terrestrial surroundings, a process highly prone to temporal variations. Thus, only a comprehensive understanding of the 14C budget over time enables a reliable chronology of lacustrine records. We studied lacustrine sediments from Lake Heihai on the northern Tibetan Plateau with a recent reservoir effect of 6465 ± 75 14C yr as estimated from accelerator mass spectrometry (AMS) dating of three living aquatic plants. Age inversions in a well-laminated composite core from the lake suggest that the reservoir effect markedly changed over the depositional period. In the lower part of the core, an excellent correlation was observed between the allochthonous input of dolomite and the inverse 14C ages, indicating the incorporation of dissolved 14C-dead carbon from a limestone catchment in the plant material. For the upper part of the core, sediment recycling of Holocene high-stand deposits may have further contributed to the reservoir effect. These findings give rise to a reliable process- and provenance-based chronology within a confidence interval supported by 137Cs measurements and magnetostratigraphic investigations. Our results highlight the need to identify the interactions of lakes with their surroundings to estimate reservoir-corrected ages in lacustrine settings.

Faial is one of the nine islands that form the Azores archipelago in the North Atlantic, characterized by a complex geodynamic setting dominated by the triple point where the North American, Eurasian, and African lithospheric plates meet (Figure 1).

The aim of this article is to bring to light a serious problem affecting radiocarbon dates produced at least from 2009 onwards by the AMS Leibniz laboratory at the Christian-Albrechts-Universität (Kiel, Germany). Archaeological observations and cross-checkings between several laboratories confirm that in a significant number of dates, clear deviations of the results from chronological schemes based on stratigraphical sequences and hundreds of measurements have occurred, which usually implies an aging of the 14C values.