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Fire-derived, pyrogenic carbon (PyC), sometimes called black carbon (BC), is the carbonaceous solid residue of biomass and fossil fuel combustion, such as char and soot. PyC is ubiquitous in the environment due to its long persistence, and its abundance might even increase with the projected increase in global wildfire activity and the continued burning of fossil fuel. PyC is also increasingly produced from the industrial pyrolysis of organic wastes, which yields charred soil amendments (biochar). Moreover, the emergence of nanotechnology may also result in the release of PyC-like compounds to the environment. It is thus a high priority to reliably detect, characterize and quantify these charred materials in order to investigate their environmental properties and to understand their role in the carbon cycle. Here, we present the benzene polycarboxylic acid (BPCA) method, which allows the simultaneous assessment of PyC's characteristics, quantity and isotopic composition ((13)C and (14)C) on a molecular level. The method is applicable to a very wide range of environmental sample materials and detects PyC over a broad range of the combustion continuum, i.e., it is sensitive to slightly charred biomass as well as high temperature chars and soot. The BPCA protocol presented here is simple to employ, highly reproducible, as well as easily extendable and modifiable to specific requirements. It thus provides a versatile tool for the investigation of PyC in various disciplines, ranging from archeology and environmental forensics to biochar and carbon cycling research.

Radiocarbon dating of mortars is a method for absolute dating of historical mortared stone structures. Successful mortar dating studies have answered chronological questions, while other studies have revealed that mortar samples can have complications and contaminants. These can cause inconclusive results even with present state‐of‐the‐art techniques. Previous research shows that adequate and proper sampling of mortar samples is of fundamental importance for a conclusive radiocarbon analysis. Therefore, this article thoroughly reviews the processes and environmental factors that may cause problems for successful radiocarbon dating of mortar samples, and presents best‐practice sampling strategies for radiocarbon mortar dating. [ABSTRACT FROM AUTHOR]

We document chemical laboratory procedures and results on international comparison samples at the Hertelendi Laboratory of Environmental Studies, Debrecen, Hungary. We also show results using the new MICADAS system and compare these results to internationally recognized standards and blank materials. The newly developed sample preparation system in HEKAL can handle samples as 1) organic material, 2) cellulose fraction of plant, 3) bones, 4) carbonate and shell, and 5) dissolved inorganic carbon of groundwater. The results of radiocarbon measurements on intercomparison samples confirm the reliability of the sample preparation system at HEKAL Lab and also the good performance of the MICADAS 14C system. The blank levels for each type of sample of 1 mg C carbon content are well reproducible, ~0.3-0.5 pMC. [ABSTRACT FROM AUTHOR]

The impact of soil chemical parameters (pH and base saturation) and soil depth on fine root dynamics in six acidic European beech (Fagus sylvaticaL.) stands with low soil base saturation was examined. The results were compared with published data from other European forests. Fine roots were sampled by sequential coring down to 1 m depth. Production, mortality, turnover and estimated age were calculated, and the ages of fine roots from two stands were measured by radiocarbon. In all stands, fine root biomass, necromass, production and mortality decreased significantly with soil depth. No relationships were observed between any of the soil chemical parameters and the fine root biomass, necromass, production and mortality. A significant negative correlation was found between soil pH and fine root turnover when our data were combined with the published data. The ages of fine roots estimated with sequential coring ranged from 0.9 to 2.9 years, and with radiocarbon from 3 to 26 years. These divergent results indicate the occurrence of two different fine root pools. [ABSTRACT FROM PUBLISHER]

Radiocarbon ages of 87 samples made up of terrestrial macrofossils (mainly twigs of Salix sp.) were washed out from sediments sampled at Hauterive/Rouges-Terres, Lake Neuchâtel, Switzerland, and measured using the AMS dating technique. These radiocarbon ages, which range from 8000 to 14,500 BP, were used to construct an absolute chronology of the record. A model of a sequence with known calendar ages for the period between 9000 to 17,500 cal BP was used to calibrate the 14C ages. Three known calendar ages were set by pollen based dating (biozones) of palaeoclimatic events at 11,450 cal BP (Younger Dryas/Preboreal), 13,450 cal BP (Gerzensee Oscillation) and 14,650 cal BP (Oldest Dryas/Bølling; see figure). This study shows that high resolution radiocarbon dating combined with such a calibration approach provides a powerful tool for dating stratigraphic sections by minimizing effects such as inversions in calendar ages and large errors caused by wiggles and plateaus in the radiocarbon time-scale. [Copyright &y& Elsevier]

Abstract: In 2010 more than 600 radiocarbon samples were measured with the gas ion source at the MIni CArbon DAting System (MICADAS) at ETH Zurich and the number of measurements is rising quickly. While most samples contain less than 50μg C at present, the gas ion source is attractive as well for larger samples because the time-consuming graphitization is omitted. Additionally, modern samples are now measured down to 5 per-mill counting statistics in less than 30min with the recently improved gas ion source. In the versatile gas handling system, a stepping-motor-driven syringe presses a mixture of helium and sample CO2 into the gas ion source, allowing continuous and stable measurements of different kinds of samples. CO2 can be provided in four different ways to the versatile gas interface. As a primary method, CO2 is delivered in glass or quartz ampoules. In this case, the CO2 is released in an automated ampoule cracker with 8 positions for individual samples. Secondly, OX-1 and blank gas in helium can be provided to the syringe by directly connecting gas bottles to the gas interface at the stage of the cracker. Thirdly, solid samples can be combusted in an elemental analyzer or in a thermo-optical OC/EC aerosol analyzer where the produced CO2 is transferred to the syringe via a zeolite trap for gas concentration. As a fourth method, CO2 is released from carbonates with phosphoric acid in septum-sealed vials and loaded onto the same trap used for the elemental analyzer. All four methods allow complete automation of the measurement, even though minor user input is presently still required. Details on the setup, versatility and applications of the gas handling system are given. [Copyright &y& Elsevier]

Abstract: Most laboratories prepare carbonates samples for radiocarbon analysis by acid decomposition in evacuated glass tubes and subsequent reduction of the evolved CO2 to graphite in self-made reduction manifolds. This process is time consuming and labor intensive. In this work, we have tested a new approach for the preparation of carbonate samples, where any high-vacuum system is avoided and helium is used as a carrier gas. The liberation of CO2 from carbonates with phosphoric acid is performed in a similar way as it is often done in stable isotope ratio mass spectrometry where CO2 is released with acid in septum sealed tube under helium atmosphere. The formed CO2 is later flushed in a helium flow by means of a double-walled needle mounted from the tubes to the zeolite trap of the automated graphitization equipment (AGE). It essentially replaces the elemental analyzer normally used for the combustion of organic samples. The process can be fully automated from sampling the released CO2 in the septum-sealed tubes with a commercially available auto-sampler to the graphitization with the automated graphitization. The new method yields in low sample blanks of about 50000years. Results of processed reference materials (IAEA-C2, FIRI-C) are in agreement with their consensus values. [Copyright &y& Elsevier]

Abstract: Small 14C samples gain importance in environmental research and for dating purposes. However, throughput of such samples is limited by the preparation of graphite targets for accelerator mass spectrometry (AMS) measurements. In our approach, oxidation of samples with copper oxide in quartz tubes was applied to form CO2 which was measured directly with the gas ion source of the small AMS facility MICADAS. The presented method was designed to meet the requirements for fast and easy handling of small samples (<100μg carbon). As combustion byproducts are likely to interfere with ionisation processes in the gas ion source, we additionally investigated the effects of several gases on C− currents. [Copyright &y& Elsevier]

Abstract: The new AMS facility at the University of Cologne (CologneAMS), Germany, was established in 2010 with the delivery of the HVE 6MV Tandetron AMS, which will be used for 14C, 26Al, 36Cl, 41Ca, 129I, 239U and 244Pu analyses. Parallel to the AMS installation the radiocarbon group has started to set up and test sample preparation methods and instruments for different materials. We present first results of reference and standard materials that have been processed and graphitized in our lab and measured at the ETH and CologneAMS facilities. The graphitization blank and its influence on small samples sizes processed with an automated graphitization system have been determined. Work on isolation of individual organic compounds with a preparative gas chromatography system has been started. The focus of our future work will be on reducing process blank levels and sample sizes as well as on the application of compound-specific radiocarbon analyses in (paleo-) environmental research. [Copyright &y& Elsevier]

Measurements of 14C in the organic carbon (OC) and elemental carbon (EC) fractions, respectively, of fine aerosol particles bear the potential to apportion anthropogenic and biogenic emission sources. For this purpose, the system THEODORE (two-step heating system for the EC/OC determination of radiocarbon in the environment) was developed. In this device, OC and EC are transformed into carbon dioxide in a stream of oxygen at 340 and 650 °C, respectively, and reduced to filamentous carbon. This is the target material for subsequent accelerator mass spectrometry (AMS) 14C measurements, which were performed on sub-milligram carbon samples at the PSI/ETH compact 500 kV AMS system. Quality assurance measurements of SRM 1649a, Urban Dust, yielded a fraction of modern fM in total carbon (TC) of 0.522 ± 0.018 (n=5, 95% confidence level) in agreement with reported values. The results for OC and EC are 0.70 ± 0.05 (n=3) and 0.066 ± 0.020 (n=4), respectively. [Copyright &y& Elsevier]

A depth profile of a Goniopora coral reef at Leizhou Peninsula, South China Sea, was radiocarbon dated using liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS). The time of formation, during 6600–7400 cal BP, can be divided into nine stages, each terminated by abrupt growth cessation of Goniopora and appearance of Ostrea shells. The results show that, during the Holocene megathermal (8.2–3.3 ka BP), large climatic changes have occurred in the South China Sea area. [Copyright &y& Elsevier]