Development of an improved ramped pyrolysis method for radiocarbon dating and application to Antarctic sediments

<p>Archives of the retreat history of the Antarctic Ice Sheet since the Last Glacial Maximum (~20,000 years ago) are preserved in marine sediment cores from around the margins of Antarctica, but accurate dating methods remain elusive in many areas. Radiocarbon dating of key lithofacies transitions indicative of grounding-line retreat is problematic due to pervasive reworking issues in glacimarine sediments. Bulk sediment material can be radiocarbon dated but yields ages which are not indicative of the time of sedimentation due to the presence of reworked carbon material from pre-Last Glacial Maximum times. Consequently, development of methods to date only the autochthonous carbon component of these sediments are required to date the retreat of the Last Glacial Maximum ice sheet in Antarctica. A new radiocarbon dating capability has been developed at Rafter Radiocarbon Laboratory (RRL), National Isotope Centre, GNS Science, Lower Hutt, in the course of this study. This has entailed designing, building and testing a ramped pyrolysis (RP) system, in which sedimentary material is heated from ambient to ~1000oC in the absence of oxygen (pyrolysed), with the carbon liberated during pyrolysis being combined with oxygen at a temperature of ~800oC to produce CO2. The amount of CO2 produced is measured by a gas analyser and the CO2 is captured in a vacuum line. The method exploits the thermochemical behaviour of degraded organic carbon. Organic carbon which has been least degraded with time breaks down earliest under pyrolysis, so CO2 captured from this fraction most closely approximates the time of deposition of the sediment. CO2 captured at higher temperatures represents more degraded carbon-containing fractions and yields older ages. The RP system includes a gas delivery system to deliver ultra-high purity He (carrier gas) and O2, a furnace system in which to pyrolyse sample material and oxidise the liberated carbon, a CO2 detection system to measure the CO2 produced and a vacuum line system to enable simultaneous collection and processing of CO2. The RRL system was based on the design developed by Dr Brad Rosenheim (University of South Florida (USF)), the originator of the first RP system at the National Ocean Sciences AMS Facility (Woods Hole Oceanographic Institution, Massachusetts, USA), who also provided guidance in this thesis. As part of the study, a visit to USF was undertaken, with sediment samples from Crystal Sound, Antarctic Peninsula being processed in the USF RP system. CO2 collected from RP processing was radiocarbon dated at RRL. The scope of this thesis was to develop and build the RRL RP system, and numerous tests were conducted during this process and are presented in this thesis. As part of this, sediment samples from Crystal Sound were also processed on the RRL RP system, and an interlaboratory comparison was conducted on the same materials processed independently through both the USF and RRL RP systems. In the development and testing of the RRL system, numerous issues were identified and a set of operating protocols developed. Due to time constraints and the scope of this thesis, interlaboratory comparisons were limited in number, but initial results show good reproducibility, and that ramped pyrolysis captured significantly younger carbon populations in both the USF and RRL RP systems than methods using bulk sediment dating alone. Within uncertainties, the ages of the youngest and oldest splits from RP processing of the same material on both systems were indistinguishable.</p>

Development of an improved ramped pyrolysis method for radiocarbon dating and application to Antarctic sediments

<p>Archives of the retreat history of the Antarctic Ice Sheet since the Last Glacial Maximum (~20,000 years ago) are preserved in marine sediment cores from around the margins of Antarctica, but accurate dating methods remain elusive in many areas. Radiocarbon dating of key lithofacies transitions indicative of grounding-line retreat is problematic due to pervasive reworking issues in glacimarine sediments. Bulk sediment material can be radiocarbon dated but yields ages which are not indicative of the time of sedimentation due to the presence of reworked carbon material from pre-Last Glacial Maximum times. Consequently, development of methods to date only the autochthonous carbon component of these sediments are required to date the retreat of the Last Glacial Maximum ice sheet in Antarctica. A new radiocarbon dating capability has been developed at Rafter Radiocarbon Laboratory (RRL), National Isotope Centre, GNS Science, Lower Hutt, in the course of this study. This has entailed designing, building and testing a ramped pyrolysis (RP) system, in which sedimentary material is heated from ambient to ~1000oC in the absence of oxygen (pyrolysed), with the carbon liberated during pyrolysis being combined with oxygen at a temperature of ~800oC to produce CO2. The amount of CO2 produced is measured by a gas analyser and the CO2 is captured in a vacuum line. The method exploits the thermochemical behaviour of degraded organic carbon. Organic carbon which has been least degraded with time breaks down earliest under pyrolysis, so CO2 captured from this fraction most closely approximates the time of deposition of the sediment. CO2 captured at higher temperatures represents more degraded carbon-containing fractions and yields older ages. The RP system includes a gas delivery system to deliver ultra-high purity He (carrier gas) and O2, a furnace system in which to pyrolyse sample material and oxidise the liberated carbon, a CO2 detection system to measure the CO2 produced and a vacuum line system to enable simultaneous collection and processing of CO2. The RRL system was based on the design developed by Dr Brad Rosenheim (University of South Florida (USF)), the originator of the first RP system at the National Ocean Sciences AMS Facility (Woods Hole Oceanographic Institution, Massachusetts, USA), who also provided guidance in this thesis. As part of the study, a visit to USF was undertaken, with sediment samples from Crystal Sound, Antarctic Peninsula being processed in the USF RP system. CO2 collected from RP processing was radiocarbon dated at RRL. The scope of this thesis was to develop and build the RRL RP system, and numerous tests were conducted during this process and are presented in this thesis. As part of this, sediment samples from Crystal Sound were also processed on the RRL RP system, and an interlaboratory comparison was conducted on the same materials processed independently through both the USF and RRL RP systems. In the development and testing of the RRL system, numerous issues were identified and a set of operating protocols developed. Due to time constraints and the scope of this thesis, interlaboratory comparisons were limited in number, but initial results show good reproducibility, and that ramped pyrolysis captured significantly younger carbon populations in both the USF and RRL RP systems than methods using bulk sediment dating alone. Within uncertainties, the ages of the youngest and oldest splits from RP processing of the same material on both systems were indistinguishable.</p>

Reactions of MoCl5 with 4-Methylpyridine, 2-Methylpyridine and 1-Methylimidazole in Tetrahydrofuran

MoCl5 reactions with 4-methylpyridine/2-methylpyridine/1-methylimidazole in THF in 1:1/1:2 stoichiometric ratios, at room temperature were carried out. The following products were synthesized: MoO2Cl(C6H7N), 1;Mo2O2Cl5(C6H7N)2(C4H8O)2,2; Mo4O4Cl4(C6H7N)3(C4H8O)2, 3 and Mo2O4Cl4(C4H6N)2(C4H8O), 4. These compounds have been investigated by FT-IR (transmission mode), FT-1H NMR, FT -13C NMR, microbiological, LC-MS and elemental (C, H, N, Mo, Cl) studies. In view of the sensitivity of all the reactants and products towards oxidation/hydrolysis by air/moisture, all the reactions and products were handled using dry nitrogen atmosphere in vacuum line. LC-MS and elemental studies agree with the formulae of compounds.

Reactions of MoCl5 and MoO2Cl2 with Succinimide, 1, 4-Diaminobutane, 3-Methylpyridine, 1, 3-Diaminopropane, Pyrazole and 1- Methylpyrrolidine in Tetrahydrofuran

It has been reported that molybdenum may extract oxygen from oxygen containing ligands. Oxo complexes of above bases with transition metals show numerous applications and are biologically active. So to study the biological activity of molybdenum complexes and to study oxo abstraction reactions by molybdenum, reactions of succinimide/1, 4-diaminobutane/3-methylpyridine/1, 3-diaminopropane/pyrazole/1-methylpyrrolidine with MoCl5/MoO2Cl2 have been carried out, in THF medium using equimolar/bimolar quantities of the ligand, at normal temperature. The products thus obtained are: Mo2O3Cl5(C4H5NO2)2(C4H8O)2, [1]; Mo2O2Cl2(C4H5NO2)2(C4H8O)2, [2]; MoO2Cl2(H2NCH2CH2CH2CH2NH2)2, [3]; Mo3Cl8(C6H7N)4(C4H8O)2, [4]; Mo3Cl6(C6H7N)6(C4H8O)6, [5]; MoO2Cl3(H2NCH2CH2CH2NH2)2, [6]; Mo2O4Cl4(C3H4N2)4, [7] and Mo2O6Cl8(C5H11N)4, [8]. There is oxygen abstraction by molybdenum during the reaction from the oxygen containing solvent THF. Formulations of these compounds were made and their properties were studied with FTIR(transmission mode), 1H NMR/13C NMR, microbiological studies, elemental analysis(Mo, Cl, C, H, N) and LC-MS. All preparations, separations and isolations were executed in vacuum line and inert atmosphere (dry nitrogen) to eliminate any oxidation/hydrolysis of products by air/moisture. The formulations proposed have been supported by the above characterization studies.

A SIMPLE CO2 EXTRACTION METHOD FOR RADIOCARBON ANALYSES OF DISSOLVED INORGANIC CARBON IN WATER SAMPLES WITHOUT A CARRIER GAS

ABSTRACT We developed a simple and cost-effective method for extracting carbon from dissolved inorganic carbon (DIC) in water samples without a carrier gas. This method only slightly modifies the existing vacuum line for CO2 purification in radiocarbon research laboratories by connecting several reservoirs and traps. The procedure consists of repeated cycles of CO2 extraction from water into the headspace of the reaction container, expansion of the extracted gas into the vacuum line, and cryogenic trapping of CO2. High CO2 yield (∼98%) was obtained from a variety of water samples with a wide range of DIC concentrations (0.4–100 mmol·L−1, in the case of 1.2 mgC). The δ13C fractionation depended on the CO2 yield, while the 14C concentration was constant within the error range, regardless of the CO2 yield. The average δ13C discrepancy between the results of this method and direct analyses made using the GC-IRMS was 0.02 ± 0.06‰. The standard deviations (1σ) in fraction of modern carbon (F14C) ranged from 0.0002 to 0.0004 for waters below 0.01 of F14C, and below 0.8% of F14C values for waters above 0.1. We conclude that this method is useful for effectively extracting CO2 from DIC in water and yields accurate 14C data.

Reactions of MoOCl4 and MoO2Cl2 with Heterocyclic Thioamides

MoOCl4/MoO2Cl2 were reacted with 2-mercaptopyridine (IUPAC: pyridine-2-thiol)/4-phenylimidazole-2-thiol (IUPAC: 4-phenyl-1, 3-dihydroimidazole-2-thione)/6-mercaptopurine (IUPAC: 1, 7-dihydro-purine-6-thione) in acetonitrile medium using equal/twice molar concentrations at normal temperature. The reactions yielded products: MoOCl3(C5H4NS-SNH4C5).2HCl, [1]; Mo3O3Cl12(C5H4NS-SNH4C5)(CH3CN)2, [2]; Mo2OCl6(C9H7N2S)4, [3] and Mo2O2Cl8(C5H4N4S)(CH3CN), [4]. The various techniques used for characterization of compounds are: Fourier transform infrared, proton nuclear magnetic resonance, 13C nuclear magnetic resonance, liquid/gas chromatography mass spectrometry and C, H, N, S, Mo, Cl analysis. The products are prone to oxidation/hydrolysis by air/moisture, so all procedures were executed in vacuum line using dry nitrogen atmosphere. Elemental analysis and fragments recorded in mass spectrometry are in tune with the formulae proposed.

GROUNDING PARAMETERS OF THE MILKING MACHINE PULLER

Проблема и цель. Теоретические исследования направлены на возможность расчета расхода воздуха и мощности пневмодвигателя съемника аппарата с вымени животного. Методология. Холостое доение доильным аппаратом весьма опасно для коров, так как помимо болевых ощущений на сосках вымени часто приводит к заболеваниям животных и их преждевременной выбраковке. Таким образом, важно не только полностью выдоить корову, но и вовремя отсоединить подвесную часть доильного аппарата от вымени животного. Для устранения холостого доения авторами предложена конструкция съемника, обеспечивающего отсоединение подвесной части доильного аппарата от вымени коровы по окончании доения автоматически. Он состоит из пневмодвигателя с редуктором и нити, намотанной на барабан. Результаты. При теоретическом рассмотрении работы съемника аппарата были выявлены аналитические зависимости расхода воздуха пневмодвигателя съемника от частоты вращения ротора пневмодвигателя, количества его лопаток и значения вакуума в вакуумпроводе. Выявлено, что с увеличением вышеуказанных параметров увеличивается и расход воздуха съемником. Авторами также проведены теоретические исследования, в результате которых определен ряд параметров пневмодвигателя: мощность и частота вращения барабана пневмодвигателя в зависимости от размеров барабана, расстояния размещения съемника от пола, угла наклона подвесной части и ее массы. Заключение. Результирующие формулы позволяют определить требуемую мощность на валу барабана и частоту его вращения для съема аппарата с вымени без падения на пол. Problem and purpose. Theoretical studies are aimed at the possibility of calculating the air consumption and the power of the pneumatic motor of the device puller from the udder of the animal. Methodology. Blank milking with a milking machine is very dangerous for cows, since in addition to painful sensations on the udder teats, it often leads to diseases of animals and their premature culling. Thus, it is important not only to milk the cow completely, but also to disconnect the hanging part of the milking machine from the udder of the animal in time. To eliminate blank milking, a puller is proposed that automatically disconnects the hanging part of the milking machine from the udder of the cow at the end of milking. It consists of a pneumatic motor with a gearbox and a thread wound on a drum. Results. When considering the operation of the puller, analytical dependences of the air fow rate of the puller pneumatic motor on the rotational speed of the air motor rotor, the number of its blades and the vacuum value in the vacuum line were revealed. It was found that with an increase in the above parameters, the air consumption of the stripper also increased. There were also studies, as a result of which a number of parameters of the pneumatic motor were determined. They included the power and rotational speed of the drum of the pneumatic motor depending on dimensions of the drum, the distance of the puller from the foor, the angle of inclination of the suspension part and its mass. Conclusion. The resulting formulas make it possible to determine the required power on the drum shaft and its rotation frequency for removing the apparatus from the udder without falling to the foor.

Reactions of MoO2Cl2 and MoOCl4 with 2-Mercaptopyridine, 4-Phenylimidazole-2-thiol and 6-Mercaptopurine Monohydrate

MoO2Cl2/MoOCl4 have been reacted with 4-phenylimidazole-2-thiol/6-mercaptopurine monohydrate/2-mercaptopyridine in acetonitrile solvent in unimolar/bimolar proportions at room temperature. The products thus obtained are: MoOCl3(C9H8N2S), [1]; Mo2O3Cl6(C9H7N2S)(CH3CN)2, [2]; Mo2O3Cl8(C9H7N2S)2(CH3CN)2, [3] and Mo2O4Cl4(C5H4NS-SN4C5), [4]. These products were studied by various techniques: infrared, proton NMR, liquid/gas chromatography-mass spectrometry, elemental analyses. Owing to the sensitivity of the products to air and moisture, the reactions and work ups were performed in vacuum line purged with oxygen by flushing dry nitrogen in it. Ions observed in mass spectrum are concurrent with the depicted formulae.

Status of the AMS graphitization system in the dendrochronological laboratory at AGH-UST, Kraków

A new system for the preparation of graphite samples for radiocarbon (14C) measurement using an accelerator mass spectrometer (AMS) has been built in the Dendrochronological Laboratory at AGH-UST, Kraków. This system consists of three independent components. The first is the equipment for mechanical and chemical sample pre-treatment. The second is the vacuum line for sample sealing and the purification of CO2. The third and central part of this system is a graphitization line, where graphite is produced from CO2. In the first stage, chemical sample preparation was carried out to remove impurities. IAEA and NIST OxII standard materials were converted to CO2 without pre-treatment. In the next step, samples were combusted to CO2. The resulting CO2 was released under vacuum and cryogenically purified for subsequent graphitization. The performance of the system was tested with NIST OxII, IAEA standards (IAEA C5, C6 and C7) and background samples. The test confirms good reproducibility of results obtained for the samples prepared using this system. The results of the 49 samples of NIST Ox-II, IAEA standards and blank samples were presented in this article.

Reactions of MoCl5 and MoO2Cl2 with 4-Phenylimidazole-2-thiol and 2-Thiazoline-2-thiol

Reactions of MoCl5/MoO2Cl2 with 4-phenylimidazole-2-thiol/2-thiazoline-2-thiol in CH3CN solvent in 1:1/1:2 molar ratios have been carried out at room temperature. Products obtained MoCl3(C9H7N2S)(CH3CN),[1]; MoCl2(C9H7N2S)(CH3CN), [2]; Mo2OCl4(C9H8N2S)2, [3] and Mo4O2Cl12(C9H7N2S)4, [4]; MoO2Cl3(C3H5NS2)2, [5] and Mo2O4Cl3(C3H5NS2)2, [6] have been analyzed and characterized by elemental analysis, FTIR, 1H NMR and LC-MS techniques. Compounds being moisture and air sensitive, these have been prepared in inert atmosphere using vacuum line and liquid nitrogen cooled traps. Fragments obtained in LC-MS spectra support the formulae derived.