Peaks Of CO2 Research Articles

Quantification of organic and inorganic hydrogen in mudstones: a novel approach using the difference between organic-rich and organic-free mudstones during pyrolysis process

Whether mudstone is rich in or free of organic matter has a great influence on the occurrence of water. Comparing different types of water in organic-rich and organic-free mudstones is helpful for further understanding the role of water in hydrocarbon generation. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) combined with mass spectrometry (MS) afford the opportunity to identify the mass change, reactions and products of the sample in a real-time monitored heating process. This study compared the pyrolysis characteristics of an organic-rich mudstone (CN1) and an organic-free mudstone (CW1) by using the TGA/DTA-MS method to estimate the content of different types of H2O and CO2 in organic-rich mudstones. The results show that the mass changes in CN1 and CW1 can be divided into the three thermogravimetric (TG) stages of 0°C–200°C, 200°C–650°C, and 650°C–900°C, while the peak temperatures of H2O and CO2 obtained through MS are different for CN1 and CW1. The differences in mineral components and organic matter between CN1 and CW1 suggest that the MS peaks of H2O and CO2 in CW1 are mainly influenced by clay and carbonate minerals, and that those of CN1 are also influenced by organic matter. In addition, quantification equations for CO2 and H2O contents from both the organic and inorganic origin of the organic-rich mudstone can be established by using the MS peak area of CO2 and H2O, mass loss in TGA and the mineral composition of the organic-free mudstone. This work provides useful insights for further understanding the hydrocarbon generation mechanism, as well as quantifying different types of water in organic-rich mudstones.

Investigation of emission characteristics of a marine cargo ship in real-world conditions

Pollution caused by ship emissions will considerably impact coastal areas. A test system that matched the actual conditions of a ship was designed based on a portable emission measurement system (PEMS), and the emission characteristic of gaseous and particle emissions and the particle size distribution of the ship's main engine were investigated under real-world operating conditions. The results showed that the emission concentrations of the main pollutants fluctuated greatly under the departure, anchoring, and docking conditions, and the peaks of CO, CO2, and NOx emissions appeared under these transient conditions. The emission concentrations of CO2, hydrocarbons, particle number (PN), and particulate mass increased with the increase in speed. The PN-based particle size distribution of the engine presented a unimodal distribution under daily operating conditions. The maximum emission factor of NOx based on the engine power was 29.53 g/kWh at the engine speed of 66 r/min. The results of the study may contribute to supplementing the emission factors of this type of ship, and provide data support for monitoring and assessment of the marine environment.

Enhancement of iron‐based oxygen carriers through alloying with tungsten oxide for chemical looping applications including water splitting

AbstractChemical looping applications offer a variety of options to decarbonise different industrial sectors, such as iron and steel and hydrogen production. Chemical looping with water splitting (CLWS) is a chemical looping technology, which produces H2 while simultaneously capturing CO2. The selection of oxygen carriers (OCs) available to be used in CLWS is finite, due to the thermodynamic limitations of the oxidation with steam for different materials at the relevant process temperatures. Iron‐based materials are one of the most widely studied options for chemical looping combustion (CLC), touted for their relative abundance and low cost; likewise, for CLWS, iron is the most promising option. However, when the reduction of iron oxide (Fe2O3) is extended to wüstite (FeO) and iron (Fe), agglomeration and sintering problems are the main challenge for fluidisation.This work presents iron and tungsten mixed oxides as the OCs for a family of chemical looping applications. The OCs were produced via co‐precipitation; performance assessment was conducted in a thermogravimetric analyser and a lab‐scale fluidised bed reactor over continuous redox cycles. The use of tungsten combined with iron results in a solid solution of tungsten within the Fe2O3 matrix that produced a more mechanically stable material during operation, which performed well during multiple redox cycles with no apparent decrease in the oxygen transport capacity and showed no apparent agglomeration. Furthermore, materials containing tungsten showed a resistance to carbon deposition, whereas the reference Fe2O3 showed peaks of CO and CO2 during the oxidation period, thus indicating carbon deposition. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.

Adsorption of CO2 on Terrace, Step, and Defect Sites on Pt Surfaces: A Combined TPD, XPS, and DFT Study

The interactions of CO2 with terrace, step, and defect or kink sites on Pt surfaces were investigated using temperature-programmed desorption, X-ray photoelectron spectroscopy, and density functional theory calculations. Desorption peaks of CO2 on Pt(997) were observed at ∼79, 88–89, ∼92 , and ∼103 K and were respectively assigned to desorption of CO2 from multilayer CO2 (amorphous CO2), CO2 from terrace, CO2 from step, and CO2 from defect sites. The defect sites, step sites, and terrace sites were saturated in that order before multilayer adsorption occurred. The adsorption energies of CO2 on the terrace, step, and defect sites were estimated to be around −0.23, −0.28, and −0.34 eV, respectively. The experimentally measured adsorption energies of CO2 on Pt were successfully reproduced using the optB86b-vdW, rev-vdW-DF2, and PBE-D2 functionals, and the actual adsorption energies were found to be between those calculated with rev-vdW-DF2 and optB86b-vdW. Additionally, it was found that CO2 adsorption is energetically more stable at higher CO2 coverage than at lower coverage because of CO2–CO2 lateral attractive interactions.

Bridging the Pressure Gap in CO Oxidation.

Performing fundamental operando catalysis studies under realistic conditions is a key to further develop and increase the efficiency of industrial catalysts. Operando X-ray photoelectron spectroscopy (XPS) experiments have been limited to pressures, and the relevance for industrial applications has been questioned. Herein, we report on the CO oxidation experiment on Pd(100) performed at a total pressure of 1 bar using XPS. We investigate the light-off regime and the surface chemical composition at the atomistic level in the highly active phase. Furthermore, the observed gas-phase photoemission peaks of CO2, CO, and O2 indicate that the kinetics of the reaction during the light-off regime can be followed operando, and by studying the reaction rate of the reaction, the activation energy is calculated. The reaction was preceded by an in situ oxidation study in 7% O2 in He and a total pressure of 70 mbar to confirm the surface sensitivity and assignment of the oxygen-induced photoemission peaks. However, oxygen-induced photoemission peaks were not observed during the reaction studies, but instead, a metallic Pd phase is present in the highly active regime under the conditions applied. The novel XPS setup utilizes hard X-rays to enable high-pressure studies, combined with a grazing incident angle to increase the surface sensitivity of the measurement. Our findings demonstrate the possibilities of achieving chemical information of the catalyst, operando, on an atomistic level, under industrially relevant conditions.

Study on the mechanical activation of malachite and the leaching of complex copper ore in the Luanshya mining area, Zambia

Mechanical activation (MA) of malachite was carried out by dry planetary grinding (DPG) and wet Isa grinding (WIG) methods. When the rotational speed was increased to 400 r/min in DPG, the specific surface area of malachite reached the maximum and the particle size reached the minimum of 0.7–100 µm. Agglomeration occurred between mineral particles when the rotational speed was increased to 580 r/min in DPG. However, no agglomeration was observed among particles with sizes 0.4–3 µm in WIG. X-ray diffraction analysis showed that, at a 580 r/min rotational speed in DPG, the amorphization degree of malachite was 53.12%, whereas that in WIG was 71.40%, indicating that MA led to amorphization and distortion of crystal structures. In addition, in the Fourier transform infrared (FT-IR) spectra of activated malachite, the bands associated with −OH, CO 3 2− and metal lattice vibrations of Cu-O and Cu-OH were weakened, and a new H-O-H bending mode and peaks of gaseous CO2 appeared, indicating that MA decreased the band energy, enhanced dihydroxylation, and increased the chemical reactivity of the malachite. Furthermore, the leaching behavior of copper ore was greatly improved by MA.

Carbon and nitrogen recycling from microbial necromass to cope with C:N stoichiometric imbalance by priming

The impact of increasing amounts of labile C input on priming effects (PE) on soil organic matter (SOM) mineralization remains unclear, particularly under anoxic conditions and under high C input common in microbial hotspots. PE and their mechanisms were investigated by a 60-day incubation of three flooded paddy soils amended with13C-labeled glucose equivalent to 50–500% of microbial biomass C (MBC). PE (14–55% of unamended soil) peaked at moderate glucose addition rates (i.e., 50–300% of MBC). Glucose addition above 300% of MBC suppressed SOM mineralization but intensified microbial N acquisition, which contradicted the common PE mechanism of accelerating SOM decomposition for N-supply (frequently termed as “N mining”). Particularly at glucose input rate higher than 3 g kg−1 (i.e., 300–500% of MBC), mineral N content dropped on day 2 close to zero (1.1–2.5 mg N kg−1) because of microbial N immobilization. To cope with the N limitation, microorganisms greatly increased N-acetyl glucosaminidase and leucine aminopeptidase activities, while SOM decomposition decreased. Several discrete peaks of glucose-derived CO2 (contributing >80% to total CO2) were observed between days 13–30 under high glucose input (300–500% of MBC), concurrently with CH4 peaks. Such CO2 dynamics was distinct from the common exponential decay pattern, implicating the recycling and mineralization of 13C-enriched microbial necromass driven by glucose addition. Therefore, N recycling from necromass was hypothesized as a major mechanism to alleviate microbial N deficiency without SOM priming under excess labile C input. Compound-specific 13C-PLFA confirmed the redistribution of glucose-derived C among microbial groups, i.e., necromass recycling. Following glucose input, more than 4/5 of total 13C-PLFA was in the gram-negative and some non-specific bacteria, suggesting these microorganisms as r-strategists capable of rapidly utilizing the most labile C. However, their 13C-PLFA content decreased by 70% after 60 days, probably as a result of death of these r-strategists. On the contrary, the 13C-PLFA in gram-positive bacteria, actinomycetes and fungi (K-strategists) was initially minimal but increased by 0.5–5 folds between days 2 and 60. Consequently, the necromass of dead r-strategists provided a high-quality C–N source to the K-strategists. We conclude that under severe C excess, N recycling from necromass is a much more efficient microbial strategy to cover the acute N demand than N acquisition from the recalcitrant SOM.

Raman spectra of gas mixtures in fluid inclusions: Effect of quartz birefringence on composition measurement

AbstractThe molar composition of gas mixtures in fluid inclusions is one of the most important properties to reconstruct the Pressure, molar Volume, Temperature Composition properties of geofluids. Raman spectroscopy is a powerful tool for quantitative analysis of the composition of fluids trapped in inclusions as the peak area of each species is directly linked to concentration by its Raman scattering cross section. Previous studies proved the effect of host mineral birefringence on the shape of the stretching vibration band of liquid water, and hence on the quantitative determination of salinity, but the influence on gas‐mixture inclusions was never evaluated. In this study, the Raman signals of coexisting CO2, CH4, and N2 in two natural fluid inclusions in quartz were collected with sample rotation on the microscope stage. Peak area ratios (CO2+/CH4, CO2+/N2, and N2/CH4) showed sinusoidal variations with a period of 45°. On the contrary, the area ratio of the two peaks of CO2 (CO2+/CO2−) and the Fermi diad splitting remained constant with sample rotation. This effect is most probably due to a combination of polarization effects as previously observed for liquid water: depolarization ratios of each gas species, birefringence of the host mineral, and polarization response curve of the spectrometer. It can be canceled by placing the sample at crystal extinction position.

In Situ Study of Self-sustained Oscillations in Propane Oxidation and Propane Steam Reforming with Oxygen Over Nickel

Self-sustained reaction rate oscillations in the oxidation of propane and in the propane steam reforming with oxygen over nickel foil have been studied in situ by near-ambient pressure X-ray photoelectron spectroscopy and mass-spectrometry. It was found that regular relaxation-type oscillations in both reactions proceed under similar conditions. In the former case, the peaks of CO, CO2, H2, and H2O were detected by mass-spectrometry as gas-phase products. In contrast, in the latter case, after addition of water to the reaction feed, the mass-spectrometric signal of water decreased simultaneously with the signals of O2 and C3H8, whereas the signals of CO, CO2, and H2 increased. It means that in the presence of water in the reaction feed, the propane steam reforming proceeds with a significant rate. In both cases, the oscillations arise due to spontaneous oxidation and reduction of the catalyst. According to the Ni2p and O1s core-level spectra measured in situ, the high-active catalyst surface is represented by nickel in the metallic state, and the transition to the low-active state is accompanied by the growth of a NiO film on the catalyst surface. The oscillations in the gas phase are accompanied by oscillations in the catalyst temperature, which reflects proceeding endothermic and exothermic processes. An oscillatory mechanism, which can be common for oxidative catalytic reactions over transitional metals, is discussed.

Fast Cycling NOx Storage and Reduction: Identification of an Adsorbed Intermediate Pathway

An experimental study describes fast cycling NOx storage and reduction on a Pt/Rh/BaO/CeO2/Al2O3 monolith catalyst for emission control of lean burn vehicles. Comparison of the temporal dependence of the effluent composition when using H2 and C3H6 as reductants enables an assessment of the mechanism. Involvement of a surface N-containing oxygenate pathway is indicated by the appearance of peaks of N2O, N2, and CO2 during the rich to lean switch. Adsorbed intermediate reactivity measurements provide further evidence. m/e = 28 signal indicating thermal decomposition and oxidation of HC-intermediates under lean/rich/blank cycle of different durations.

Cobalt-Based Oxygen Evolution Electrocatalysts Biotemplated on DOPA-Displaying Viruses

The Oxygen evolution reaction (OER), which involves a more complex mechanism compared to hydrogen evolution reaction (HER), determines the whole cell efficiency for (photo)electrochemical water splitting. Lately, non-precious metal based oxygen evolution catalysts (OECs), such as transition metal oxides got attentions for OER under relatively benign conditions at low overpotentials. In this work, we report a filamentous bacteriophage fd displaying 3,4-dihydroxy-L-phenylanlanine (DOPA) onto the major coat protein and promoted the spontaneous deposition of cobalt oxide based oxygen evolution catalyst (Co-OEC) onto the phages. The virus successfully worked as a biotemplate to enable deposition of thin Co layer along wire-like bodies, and the catechol group of DOPA moiety stabilized Co2+ to accelerate Co-OEC deposition on virus and slightly enhanced OER activity. The Co-based catalysts adhered to DOPA-phages through electroless deposition (Co/DOPA-phages) showed cathodic shift of Co3+/2+ oxidation peak and this phenomenon could be explained from partial-charge transfer from cobalt to DOPA group, which is supported from X-ray photoelectron spectroscopy (XPS) that shows more distinct satellite peaks of Co2+ at ~786 eV compared to electrodeposited Co-OEC. It is widely accepted that partial charge transfer caused by dopant cations raise activity enhancement and change the OER mechanism. The pronounced OER activity under 10 mA cm-2 and long-term stability of Co/DOPA-phages suggest potential for further optimization via systematically ordered and denser array of catechol group for improved performance.

The Choiyoi magmatism in south western Gondwana: implications for the end-permian mass extinction - a review

The end of the Permian period is marked by global warming and the biggest known mass extinction on Earth. The crisis is commonly attributed to the formation of large igneous provinces because continental volcanic emissions have the potential to control atmospheric carbon dioxide (CO2) levels and climate change. We propose that in southwestern Gondwana the long-term hothouse Permian environmental conditions were associated with the development of the Choiyoi magmatism. This large igneous province was developed between the Cisuralian and the early Triassic. It covers an area estimated at 1,680,000 km2 with an average thickness of 700 m, so that the volume of effusive and consanguineous rocks is estimated at 1,260,000 km3. Towards the western sector of the study region, a major overlap exists between the regional development of the Choiyoi magmatism and the Carboniferous sedimentary basins, which include paralic and continental deposits with intercalations of peat and coal beds. Commonly, these upper Palaeozoic deposits accumulated on a thick substrate composed of Cambro-Ordovician carbonates and Ordovician to Devonian terrigenous sedimentary rocks characterised by a large proportion of dark organic-rich shales and turbidite successions. While extensive volcanism released large masses of carbon dioxide into the Permian atmosphere, the heating of Palaeozoic organic-rich shales, peat and carbonates by ascending magma led to CO2 and CH4 gas generation in sufficient volumes to amplify the major climatic change. The analysis of the almost continuous record of Permian redbeds in the Paganzo basin, where the Choiyoi magmatism is not recorded, allowed us to recognize two main pulses of strong environmental desiccation, one at the Cisuralian and the second around the end-Permian. These two drastic climatic crisis are attributed to peaks of CO2 and CH4 outbursts to the atmosphere and related collateral effects, such as acid rain, impoverishment of soils and increase in forest-fire frequency. We propose that the combination of these multiple mechanisms triggered the decline of biodiversity in southwestern Gondwana and caused the end-Permian extinction of most of the Glossopteridales.

Thermal induced BCN nanosheets evolution and its usage as metal-free catalyst in ethylbenzene dehydrogenation

Compared with mushroomed progress in metal-free C-rich BCN catalysts, little is known about the BN-rich BCN or even BN ones. Its related study has drawn great interest recently but still in its infancy stage. In this study, three kinds of BCN nanosheets (NSs) with tuned surface carbon contents (5.5–14.3%), specific surface area (SSA, 82–290m2/g) and morphologies (ultrathin nanosheets, triangular plates) were fabricated through a solid state reaction by simply adjusting the reaction temperature, and those effects on the ethylbenzene dehydrogenation performances were studied in CO2 atmosphere. The morphology evolution of BCN NSs from ultrathin nanosheets to the triangular plates was observed and control experiments were carried out. The BCN nanosheets show relatively strong interaction with CO2 and distinct CO2 absorption properties. The CO2 temperature programmed desorption also indicates that the desorption peaks of CO2 are above 400°C, enabling them potential CO2 utilization catalysts. A weak association was found between the surface C contents and the catalytic performance as it normalized with SSA, and the B-O species could be taken as an active site in CO2 atmosphere. Though much progress still needed, it is convincing that the BCN catalyst could be a promising metal-free catalyst in dehydrogenation beyond carbocatalyst.

Passive in-vehicle driver breath alcohol detection using advanced sensor signal acquisition and fusion

ABSTRACTObjective: The research objective of the present investigation is to demonstrate the present status of passive in-vehicle driver breath alcohol detection and highlight the necessary conditions for large-scale implementation of such a system. Completely passive detection has remained a challenge mainly because of the requirements on signal resolution combined with the constraints of vehicle integration. The work is part of the Driver Alcohol Detection System for Safety (DADSS) program aiming at massive deployment of alcohol sensing systems that could potentially save thousands of American lives annually.Method: The work reported here builds on earlier investigations, in which it has been shown that detection of alcohol vapor in the proximity of a human subject may be traced to that subject by means of simultaneous recording of carbon dioxide (CO2) at the same location. Sensors based on infrared spectroscopy were developed to detect and quantify low concentrations of alcohol and CO2. In the present investigation, alcohol and CO2 were recorded at various locations in a vehicle cabin while human subjects were performing normal in-step procedures and driving preparations. A video camera directed to the driver position was recording images of the driver's upper body parts, including the face, and the images were analyzed with respect to features of significance to the breathing behavior and breath detection, such as mouth opening and head direction.Results: Improvement of the sensor system with respect to signal resolution including algorithm and software development, and fusion of the sensor and camera signals was successfully implemented and tested before starting the human study. In addition, experimental tests and simulations were performed with the purpose of connecting human subject data with repeatable experimental conditions. The results include occurrence statistics of detected breaths by signal peaks of CO2 and alcohol. From the statistical data, the accuracy of breath alcohol estimation and timing related to initial driver routines (door opening, taking a seat, door closure, buckling up, etc.) can be estimated.The investigation confirmed the feasibility of passive driver breath alcohol detection using our present system. Trade-offs between timing and sensor signal resolution requirements will become critical. Further improvement of sensor resolution and system ruggedness is required before the results can be industrialized.Conclusions: It is concluded that a further important step toward completely passive detection of driver breath alcohol has been taken. If required, the sniffer function with alcohol detection capability can be combined with a subsequent highly accurate breath test to confirm the driver's legal status using the same sensor device. The study is relevant to crash avoidance, in particular driver monitoring systems and driver–vehicle interface design.

Development of a new deep-sea hybrid Raman insertion probe and its application to the geochemistry of hydrothermal vent and cold seep fluids

Hydrothermal vent fluids, cold seep fluids, their associated chemosynthetic communities, and the biogeochemical anaerobic oxidation of methane (AOM) play very important roles in the biogeochemical sulfur and carbon cycles in the ocean. Based on our previous success developing and deploying a deep-sea sediment pore water Raman probe, we developed a new deep-sea hybrid Raman insertion probe (RiP) designed to operate at temperatures up to 450°C that can be inserted directly into high-temperature fluids emerging from hydrothermal vents. By routinely exchanging the various tips and optics of the probe, we can analyze the geochemistry of hydrothermal vent fluids, cold seep fluids, and sediment pore water profiles (0–60cm) in situ. The instrument ensemble also includes a new deep-sea laser Raman spectrometer in a custom-designed, 6000-m titanium pressure housing, which is powered, controlled and deployed by the remotely operated vehicle (ROV) Faxian down to a maximum water depth of 4500m. The new RiP was deployed at the Izena Hole hydrothermal area in the middle Okinawa Trough back-arc basin; the Papua–Australia–Canada–Manus (PACManus) hydrothermal vent area in the Manus back-arc basin, Papua New Guinea; and a cold seep field at Formosa Ridge in the northern South China Sea. The Raman peaks of CO2, CH4, H2S, HS-, SO42- and S8 were obtained in situ from high-temperature hydrothermal vents (290°C), low-temperature cold seep fluids (2°C) and the surrounding sediment pore water. Dissolved CH4 and S8 were identified for the first time in the fluids under the lush chemosynthetic communities of the cold seep. Several sediment pore water profiles collected near the cold seep were characterized by the loss of SO42- and increased CH4, H2S and HS- peaks. Additionally, the in situ pH range of the pore water profile was between 6.95 and 7.22. Thus, the RiP system provides a very useful tool for investigating the geochemistry of hydrothermal vent and cold seep fluids.

1s3p Resonant Inelastic X-ray Scattering of Cobalt Oxides and Sulfides

We are developing 1s3p resonant inelastic X-ray scattering (RIXS) as a versatile spectroscopic tool to probe active systems under working conditions. In order to establish detailed reference materials for cobalt-based systems, we have applied 1s X-ray absorption spectroscopy (XAS) and 1s3p RIXS to cobalt oxides (CoO, Co3O4) and sulfides (CoS and CoS2). We show that the Co3+ ions in Co3O4 contain a large nonlocal peak intensity in the pre-edge and that the resonant 3p final state of Co3O4 is dominated by the two exchange-split peaks of the tetrahedral Co2+ site. In contrast, the 3p final state of CoS and CoS2 shows a single asymmetric peak due to the large screening of the 3p-3d exchange interaction. While CoS has a single pre-edge peak, CoS2 contains an additional large nonlocal peak. This indicates that although CoS2 is often indicated as Co2+(S2)2–, it has a very strong sulfur-mediated cobalt–cobalt bonding, similar to the low-spin Co3+ sites in oxides. These electronic structure details reveal the significance of 1s3p RIXS spectroscopy for determining the symmetry, spin and covalence of transition metal compounds, information that is largely inaccessible in conventional K edge XAS. The experimental results are simulated with multiplet calculations that reveal the partial screening of the 3p3d exchange interaction and the presence of nonlocal transitions. We conclude that 1s3p RIXS combined with spectral simulations presents a valuable tool to unravel the electronic properties of functional materials under working conditions.

Exploring a suitable nitrogen fertilizer rate to reduce greenhouse gas emissions and ensure rice yields in paddy fields

The application rate of nitrogen fertilizer was believed to dramatically influence greenhouse gas (GHG) emissions from paddy fields. Thus, providing a suitable nitrogen fertilization rate to ensure rice yields, reducing GHG emissions and exploring emission behavior are important issues for field management. In this paper, a two year experiment with six rates (0, 75, 150, 225, 300, 375kgN/ha) of nitrogen fertilizer application was designed to examine GHG emissions by measuring carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) flux and their cumulative global warming potential (GWP) from paddy fields in Hangzhou, Zhejiang in 2013 and 2014. The results indicated that the GWP and rice yields increased with an increasing application rate of nitrogen fertilizer. Emission peaks of CH4 mainly appeared at the vegetative phase, and emission peaks of CO2, and N2O mainly appeared at reproductive phase of rice growth. The CO2 flux was significantly correlated with soil temperature, while the CH4 flux was influenced by logging water remaining period and N2O flux was significantly associated with nitrogen application rates. This study showed that 225kgN/ha was a suitable nitrogen fertilizer rate to minimize GHG emissions with low yield-scaled emissions of 3.69 (in 2013) and 2.23 (in 2014) kg CO2-eq/kg rice yield as well as to ensure rice yields remained at a relatively high level of 8.89t/ha in paddy fields.

In SituRaman Analysis on the Dissociation Behavior of Mixed CH4–CO2Hydrates

Previous studies have indicated that CH4–CO2 hydrate replacement is closely related to the crystal dissociation and reformation processes. To further elucidate the replacement mechanism, the melting processes of mixed CH4–CO2 hydrates were characterized using in situ Raman spectroscopy and compared to that of pure CH4 and CO2 hydrates. Analysis results from powder X-ray diffraction showed that the crystalline structure of the mixed CH4–CO2 hydrates is strucutre I. The current study suggested that the hydrate crystal units collapse as an entity with no clear dependence upon gas distributions within the hydrate phase. The dissociation time was found to be stoichastic, consistent with the polycrystalline nature of the hydrate particles. Interestingly, for hydrates containing CH4, the Raman peaks of both CH4 and CO2 in the hydrate phase showed a temporary rise during the hydrate dissociation processes, suggesting the reformation of hydrates below the hydrate dissociation surface. A dissociation inside the hyd...

Raman spectroscopic study of CO2 in hydrate cages

The Raman spectra of CO2 molecules in hydrate cages was studied for structure I CO2 hydrate and structure II tetrahydrofuran (THF)+CO2 binary hydrate. The results obtained for sII hydrate indicated that the Fermi dyad peaks of CO2 in the small cage of THF–CO2 hydrate are located at 1274cm−1 and 1380cm−1. Numerical fitting of the sI CO2 hydrate Raman spectrum shows CO2 Fermi dyad peaks in the small cage are located at 1275cm−1 and 1382cm−1. The unperturbed frequencies of the symmetric stretching v1 and overtone bending v2 modes were calculated for CO2 in various states. It was found that the v1 frequency does not follow the loose cage–tight cage model for CO2 in hydrate cages. Explanations are given as to why such a relationship is not expected in terms of the incomplete sampling of the void space of the non-spherical cages by the linear guest molecule and the contribution of H-bonding to the guest–host interactions.

Effects of activated charcoal and tannin added to compost and to soil on carbon dioxide, nitrous oxide and ammonia volatilization

AbstractGiven high mineralization rates of soil organic matter addition of organic fertilizers such as compost and manure is a particularly important component of soil fertility management under irrigated subtropical conditions as in Oman. However, such applications are often accompanied by high leaching and volatilization losses of N. Two experiments were therefore conducted to quantify the effects of additions of activated charcoal and tannin either to compost in the field or directly to the soil. In the compost experiment, activated charcoal and tannins were added to compost made from goat manure and plant material at a rate of either 0.5 t activated charcoal ha−1, 0.8 t tannin extract ha−1, or 0.6 t activated charcoal and tannin ha−1 in a mixed application. Subsequently, emissions of CO2, N2O, and NH3 volatilization were determined for 69 d of composting. The results were verified in a 20‐d soil incubation experiment in which C and N emissions from a soil amended with goat manure (equivalent to 135 kg N ha−1) and additional amendments of either 3 t activated charcoal ha−1, or 2 t tannin extract ha−1, or the sum of both additives were determined. While activated charcoal failed to affect the measured parameters, both experiments showed that peaks of gaseous CO2 and N emission were reduced and/or occurred at different times when tannin was applied to compost and soil. Application of tannins to compost reduced cumulative gaseous C emissions by 40% and of N by 36% compared with the non‐amended compost. Tannins applied directly to the soil reduced emission of N2O by 17% and volatilization of NH3 by 51% compared to the control. However, emissions of all gases increased in compost amended with activated charcoal, and the organic C concentration of the activated charcoal amended soil increased significantly compared to the control. Based on these results, tannins appear to be a promising amendment to reduce gaseous emissions from composts, particularly under subtropical conditions.