Long-term variation of 14C concentration in atmospheric CO2 in Japan from 1991 to 2000

The long-term variation of ¹⁴C concentrations in atmospheric CO₂ samples collected every 10 days was measured in the Ohkuwa area of Kanazawa, Ishikawa prefecture, Japan (36.3°N, 136.4°E), from April 1991 to December 2000. The ¹⁴C concentration decreased gradually by about 5‰ each year from 1991 to 2000, with a pronounced seasonal cycle which began to increase from spring and reached the maximum in late July or early August, followed by a decrease to the minimum from December to February. The appearance of large seasonal cycles and the extreme decrease of ¹⁴C concentration in winter seemed to be caused mainly by the air containing a large amount of ¹⁴C-free fossil fuel CO₂ transported across the Sea of Japan from the Asian continent, not by the influence of local fossil fuel consumption.     

Estimation of 14C in irradiated graphite using CO2 gasification method

To efficiently inhibit the diffusion of radioactive nuclides in soil that were left by nuclear emergency accidents, microwave sintering technology was used in this work to vitrify the simulated strontium contaminated soil. Four kinds of simulated strontium-contaminated soil could be successfully vitrified almost completely within 30 min without any additional components. Sr²⁺ cations are immobilized into aluminosilicate glass network structure. In addition, the solubility of SrSO₄ in different soil is related to the element contents of aluminum and silicon. This work reveals a demonstration that beta-radioactive contaminated soil could be treated by microwave vitrifying.

     

Study on the production of formaldehyde-14C by direct reduction of14CO2 with LiAlH4

A vial technique was developed for the synthesis of formaldehyde-¹⁴C from¹⁴CO₂ in an ether solution of lithium aluminium hydride. The yield of formaldehyde (40–50%) was achieved by optimization of the reaction parameters.     

Diffusion of14CO2 in Polyurethanes

Summary Diffusion coefficients and their temperature coefficients were obtained on a series of four polyurethanes believed to differ mainly in their molecular chain stiffness, and on one partially crystalline polyurethane of high molecular symmetry having flexible chains. The diffusion coefficients of CO₂ in these materials and their temperature dependence are f ound to be much lower than those of many other typical organic polymers, notably rubbers. The data are interpreted in terms of theH-bonds formed between neighbouring polymer chains which are thought to make for regions of high packing efficiency, interrupted at irregular intervals by more open regions of small size. The effect of molecular chain flexibility appears to be smaller than the influence of theH-bonding.

---

Zusammenfassung Diffusionskoeffizienten und ihre Temperaturkoeffizienten wurden an einer Serie von 4 Polyurethanen erhalten, von denen anzunehmen ist, daß sie sich hauptsächlich in ihrer Kettensteifheit unterscheiden, und ferner an einem partiell kristallinen Polyurethan hoher molekularer Symmetrie mit flexiblen Ketten. Die Diffusionskoeffizienten von CO₂ in diesen Materialien und ihre Temperaturabhängigkeit erwiesen sich als viel niedriger als die für viele andere typische organische Polymere, insbesondere für Gummis. Die Daten lassen sich aufgrund der H-Bindungen zwischen benachbarten Ketten deuten, durch die Bereiche höherer Packungsdichte, unterbrochen von irregulär geformten, mehr offenen Bereichen kleiner Ausdehnung, entstehen mögen. Die Effekte der Kettenbeweglichkeit scheinen kleiner als der Einfluß der Wasserstoff-Brückenbindung zu sein.

     

Accelerator mass spectrometry 14C determination in CO2 produced from laser decomposition of aragonite

The determination of (14)C in aragonite (CaCO(3)) decomposed thermally to CO(2) using an yttrium-aluminum-garnet doped neodymium laser is reported. Laser decomposition accelerator mass spectrometry (LD-AMS) measurements reproduce AMS determinations of (14)C from the conventional reaction of aragonite with concentrated phosphoric acid. The lack of significant differences between these sets of measurements indicates that LD-AMS radiocarbon dating can overcome the significant fractionation that has been observed during stable isotope (C and O) laser decomposition analysis of different carbonate minerals. The laser regularly converted nearly 30% of material removed into CO(2) despite it being optimized for ablation, where laser energy breaks material apart rather than chemically altering it. These results illustrate promise for using laser decomposition on the front-end of AMS systems that directly measure CO(2) gas. The feasibility of such measurements depends on (1) the improvement of material removal and/or CO(2) generation efficiency of the laser decomposition system and (2) the ionization efficiency of AMS systems measuring continuously flowing CO(2).     

14CO2 and CO2 Transport in polycarbonate: Measurement of the time lag and permeability

Transport of CO₂ across polycarbonate films has been studied using a diffusion cell technique employing a radioactively labelled tracer (¹⁴CO₂). Because the ¹⁴CO₂ driving force could be established independently of the unlabelled CO₂ driving force, several classes of experiments not possible with conventional techniques were performed. These different classes of experiments showed measurably different time lags. Formally, these experiments all are limiting cases of the more general mixed-gas permeation problem; however, simplifying assumptions in the dual sorption theory are possible because the tracer concentration approaches zero and because the two species in this special mixed-gas problem exhibit the same dual sorption parameters. These simplifications allow derivation of analytical expressions for the time lag for both the unlabelled and labelled gas species. The experimental measurements are in good agreement with the dual sorption model formulated for the mixed-gas tracer diffusion problem.     

The enzymatic hydrolysis of pretreated agricultural residues and the fermentation of the liberated sugars to ethanol

Agricultural residues were pretreated by steam explosion and the cellulosic component of these substrates were converted to ethanol using a combined enzymatic hydrolysis and fermentation (CHF) process. The enzymatic hydrolysis was carried out using culture filtrates ofTrichoderma harzianum E58 while the liberated sugars were fermented to ethanol byS. cerevisiae. Initially, pretreatment conditions were optimized to ensure that the substrates were readily hydrolyzed and fermented. The agricultural residues were steamed for various times between 30 and 120 s at approximately 240‡C prior to rapid decompression (explosion) in a small masonite-type gun. The various substrates were selectively extracted by water and alkali to see whether the enzymatic hydrolysis and fermentability of the substrates were enhanced. A comparison between the overall conversion of wheat and barley straw was made since these are the two most readily available agricultural residues in Canada. Steam explosion did not affect the hexosan content of the residues, although the pentosan content of the substrates decreased with increasing duration of steaming. The hexosan (cellulose) content of wheat straw was 50.7% of the total substrate while a slightly higher 52.9% cellulose content was detected in the barley straw. Wheat straw was more efficiently hydrolyzed after it had been steamed for 90 s while optimum hydrolysis of the barley straw was detected after 60 s. Steam exploded wheat and barley straw that was subsequently extracted with water was readily hydrolyzed to their component sugars.S. cerevisiae could almost quantitatively convert these sugars to ethanol. This indicated that water washing not only enhanced the enzymatic hydrolysis of the steam exploded substrates, it also removed inhibitory material that restricted the growth of S.cerevisiae. Maximum hydrolysis (78.5%) and ethanol yields (10 mg/mL) were obtained when wheat straw was steamed for 90 s. Slightly lower hydrolysis (76.0%) and ethanol yields (9.5 mg/mL) were obtained with barley straw that had been steamed for 120 s.     

Diode laser spectroscopy of the fundamental bands of 12C14N, 13C14N, 12C15N, 13C15N free radicals in the ground 2 Sigma+ electronic state

Rotationally resolved spectra of the fundamental band of the CN free radical in four isotopic forms have been measured using tunable diode laser absorption spectroscopy. The source of the radical was a microwave discharge in a mixture of isotopically selected methane and nitrogen diluted with argon. The lines were measured to an accuracy of 5 x 10(-4) cm(-1) and fitted to the formula for the vibration rotation spectrum of a diatomic molecule, including quartic distortion constants. The band origins of each of the isotopomers from the five parameter fits were found to be 12C14N: 2042.42115(38) cm(-1), 13C14N: 2000.08479(23) cm(-1), 12C15N: 2011.25594(25) cm(-1), 13C15N: 1968.22093(33) cm(-1) with one standard deviation from the fit given in parenthesis. Some of the lines showed a resolved splitting due to the spin rotation interaction. This was averaged for fitting purposes. The average equilibrium internuclear distance derived from the upsilon = 0 and 1 rotational constants of the four isotopomers is 1.171800(6) A which is in good agreement with the value determined from microwave spectroscopy.     

Studies on14CO2 exchange reaction with p-fluorophenyl acetic acid and microsynthesis of carboxyl-14C labelled p-fluorophenyl acetic acid

The exchange reaction between¹⁴CO₂ and sodium salt of p-fluorophenyl acetic acid was found to proceed with greater than 50% isotope incorporation when salt to CO₂ ratio was 61. The carboxyl-C-14 labelled p-fluorophenyl acetic acid was isolated in a pure form using small chemical concentrations of radioactive¹⁴CO₂ of high specific activity /30 mCi/mmol/.     

Determination of14C in environmental materials: Combination of CO2 absorbent and a large-volume low-background liquid-scintillation counter

Commerically available CO₂ absorbent and its scintillator were used to determine¹⁴C in environmental materials. Absorption of CO₂ by the CO₂ absorbent was quantitative, and strong and stable fixation was confirmed by no release of CO₂ from the CO₂ absorbent for a long period after absorption. The¹⁴C activity was measured by a large-volume low-background liquid-scintillation counter and the counts were quite stable for two weeks. Counting efficiency and background counts varied with the amounts of CO₂ absorbed, indicating a change of quenching level with absorption of CO₂. The different quenching levels were, however, normalized with external standard channel ratio (ESCR). Specific activity of¹⁴C in the present shell was evaluated for samples with different amounts of CO₂ absorbed and were consistent with each other within the counting error, suggesting validity of the present method. Contemporary¹⁴C level in the environmental materials, 95% CO₂ saturated sample, could be measured with 4% counting error (2) by 1000 min counting time.     

放射性气体中~(14)CO_2吸收方法研究

本文针对核电厂废树脂存储厂房空气中存在大量14CO2,设计了实验室规模的CO2吸收装置,研究了液态和固体吸收剂对气体中CO2的吸收效果及溶液夹带等问题。由不同条件下吸收效果和适用性的对比结果可知,氢氧化钠溶液吸收法具有吸收效率高、易于操作等优点,为工程装置设计及操作工艺提供了技术依据。     

毛细管离子电泳法定量监测丙酮丁醇梭菌发酵过程中产生的有机酸的浓度变化

建立了一种用于监测丙酮丁醇梭菌发酵过程中产生的3种有机酸(乳酸、乙酸、正丁酸)浓度变化的毛细管离子电泳方法。该方法以对甲氧基苯甲酸为电泳缓冲液,以十六烷基三甲基氯化铵(CTAC)为电渗流改性剂,采用间接紫外检测方式测定发酵过程中产生的有机酸。发酵液经过简单的离心处理后,上清液稀释后直接进样分析。考察了电泳操作条件对分离的影响,对实验条件进行了优化。优化后的分离条件为10 mmol/L对甲氧基苯甲酸（pH 5.8）、0.15 mmol/L CTAC。该方法测定乳酸、乙酸和正丁酸的定量限分别为1.22,0.38和0.58 mg/L;完成一次分析只需要5 min,并具有良好的重现性。该方法已成功地用于丙酮丁醇梭菌的代谢流量分析。     

Vibration-rotation infrared spectra and molecular force field of 14C labelled acetylene, 14C2H2

Infrared spectrum of ¹⁴C₂H₂ was examined under medium resolution. Rotational structures of the ν₃, ν₄¹ + ν₅¹ and ν₅ were analysed to yield values of ν₀, B′, B″ and D.Literature values of vibrational frequencies of seven isotopic species of acetylene including ¹⁴C₂H₂ were used to determine the harmonic force constants.     

Transformation of 14C‐Labeled Graphene to 14CO2 in the Shoots of a Rice Plant

This study focused on using carbon‐14‐labeled few‐layer graphene (FLG) to determine its uptake, distribution, transformation, and depuration in rice plants. After 7 d hydroponic exposure to FLG suspension at 250 μg L^?1, roots accumulated 694.8 mg kg^?1 graphene and shoots had 53.7 mg kg^?1 graphene from intra‐plant translocation. FLG could likely pass through the cell wall and membrane and enter the chloroplast in the shoots. After 14 days of depuration, only about 15 % of the accumulated FLG were eliminated into the depuration solution with about 70 % of graphene retained in the plants. About 9 % of the accumulated FLG was degraded to ¹⁴CO₂ and proposed that reaction with OH^. in the leaves may likely contribute to the degradation of FLG, which had structural defects. These findings have an important impact on the long‐term environmental fate of graphene‐related materials in soil–plant systems.     

Influences of the (NH2)2CO concentration on magnetic photocatalytic composites

Magnetic photocatalytic Fe₃O₄@TiO₂ composites have been fabricated by changing the concentration of (NH₂)₂CO. Samples were named as low (NH₂)₂CO concentration group which the (NH₂)₂CO concentration in the synthesis process was below 2.25 mol/L and high (NH₂)₂CO concentration group which the (NH₂)₂CO concentration was above 2.5 mol/L. Photocatalytic degradation experiments of methyl orange showed that the final degradation rates of low (NH₂)₂CO concentration group samples were higher than that of high (NH₂)₂CO concentration group, even better than P25 at the same test conditions. And it was interesting that samples of low (NH₂)₂CO concentration group had smaller values of BET surface areas than that of high (NH₂)₂CO concentration group. It indicated that the improvement of photocatalytic activity which was effected by BET surface areas was not obvious. There were two main factors enhancing the photocatalytic property of low (NH₂)₂CO concentration group: First, diffusing reflection spectra showed that the low (NH₂)₂CO concentration group samples had lower reflectivity, this suggested that the structure improved the efficiency of light absorption; Second, NH₄⁺ would take up the active sites on the surface of the TiO₂ particles, the FT-IR test results showed that the samples of the low (NH₂)₂CO concentration group samples bonded less NH₄⁺, thus leading to the higher photocatalytic activity. It had enlightenment role for optimizing the performance of photocatalytic materials.     

The influence of the brewing process on the formation of biogenic amines in beers

Biogenic amines, as dabsyl derivatives, were determined in beer samples, intermediate products, and raw materials (malt and maize) by HPLC. A procedure for the extraction of the amines from malt and maize with diluted hydrochloric acid was optimised by combining a Response Surface Methodology with a Simultaneous Decision Making Approach. The results of the analysis indicate that, in brewing, technology and hygiene are the decisive factors that determine the amine concentrations in the final product.     

[C14MIM]Br离子液体对聚丙烯超临界CO2发泡性能的影响

本文对PP/[C₁₄MIM]Br体系的熔融过程和对CO₂的吸收, 以及[C₁₄MIM]Br在PP基体中的分散状态进行了研究, 并初步考察了[C₁₄MIM]Br对PP发泡性能的影响.     

Isotope exchange in ionised CO2/CO mixtures: the role of asymmetrical C2O3+ ions

A hitherto unknown, atmospherically relevant, isotope-exchange reaction was studied in ionised gaseous mixtures containing carbon dioxide and monoxide. The mechanism of the O exchange, proceeding over a double-minimum potential-energy surface, was positively established by mass spectrometric and theoretical methods that also allowed the identification and characterisation of the C2O3+ intermediate. The increase of internal energy displaces the observed reactivity towards an endothermic reaction path that involves only CO2 and represents an indirect route to the dissociation of carbon dioxide.     

A study on immobilization of 14CO2 using inorganic materials

Journal of Radioanalytical and Nuclear Chemistry - Activated carbon wastes from the air cleaning system in a nuclear facility contain a long half-life value of 14C (5700 years). This 14C...