CO2 In Region Research Articles

Sources and sinks of CO2 in the west coast of Bay of Bengal

Observations at high spatial resolution (100×50 km2) in the western continental shelf of Bay of Bengal during southwest monsoon, when peak discharge occurs into the Bay through major rivers of the Indian subcontinent, revealed that freshwater discharge exerts dominant control on the inorganic carbon components in surface waters. Lower than present atmospheric pCO2 levels were found in the northwestern (NW) than southwestern (SW) coastal Bay of Bengal. The pCO2 levels in the peninsular rivers were an order of magnitude higher (5000–17000 µatm) than that of atmospheric levels and glacial river Ganges (∼500 µatm). The discharge from the peninsular rivers has a stronger influence in the SW region, whereas the Ganges river discharge has a stronger influences in the NW region. Source or sink of CO2 in the shelf region depends on the discharged river characteristics and the East India Coastal Current that distributes discharged water along the coast. Although during northeast monsoon, the situation is briefly reversed and the region acts as a sink, and on annual scale, the western Bay of Bengal acts as a source for atmospheric CO2 than hitherto hypothesised.

Uptake mechanism of anthropogenic CO2 in the Kuroshio Extension region in an ocean general circulation model

The uptake mechanism of anthropogenic CO2 in the Kuroshio Extension is examined by a Lagrangian approach using a biogeochemical model embedded in an ocean general circulation model. It is found that the uptake of anthropogenic CO2 is caused mainly by the increase of pCO2 dependency of seawater on temperature, which is caused by greater dissolved inorganic carbon concentration in the modern state than in the pre-industrial state. In contrast with the view of previous studies, the effect of the vertical entrainment, which brings waters that last contacted the atmosphere with the past lower CO2 concentration, is comparatively small. Winter uptake of anthropogenic CO2 increases with the rise of the atmospheric CO2 level, while summer uptake is relatively stable, resulting in a larger seasonal cycle of the uptake. This increase is significant, especially in the Kuroshio Extension region. It is newly suggested that this increase in the Kuroshio Extension region is largely caused by the combined effects of the increased pCO2 dependency of the sea water on the temperature and the seasonal difference in cooling.

Trimellitate complexes of divalent transition metals with hydrazinium cation

New dihydrazinium divalent transition metal trimellitate hydrates of empirical formula (N2H5)2M(Html)2·nH2O, where n = 1 for M = Co or Ni, and n = 2 for M = Mn, Zn, or Cd (H3tml = trimellitic acid), and monohydrazinium cadmium trimellitate, [(N2H5)Cd(Html)1.5·2H2O] have been prepared and characterized by physico-chemical methods. Electronic spectroscopic, and magnetic moment data suggest that Co and Ni complexes adopt an octahedral geometry. The IR spectra confirm the presence of monodentate carboxylate anion (Δν = νasy(COO−) − νsym(COO−) > 190 cm−1) and coordinated N2H5+ ion (νN–N 1015 − 990 cm−1) in all the complexes. All the complexes undergo endothermic decomposition eliminating CO2 in the temperature region 200–250 °C, followed by exothermic decomposition (in the range of 500–570 °C) of organic moiety to give the respective metal carbonate as the end products except nickel and cobalt complexes, which leave respective metal oxides. X-ray powder diffraction patterns reveal that Ni and Co complexes are isomorphous as are those of, Zn(II) and Cd(II) of the type, (N2H5)2M(Html)2·2H2O.

Seasonal variations of CO2 near the tropopause observed by commercial aircraft

We present variations of CO2 in the tropopause region obtained by frequent in situ measurements aboard commercial aircraft. The data were obtained from a total of 373 flights between Japan and Europe during the period November 2005 to September 2007. The local phase and amplitude of the CO2 seasonal cycle varied with distance from the tropopause. In the upper troposphere and in the region just above the dynamical tropopause, a strong seasonal cycle with a springtime maximum and a relatively sharp minimum in July was observed. In the region bounded by potential temperatures 10 K to 30 K above the extratropical tropopause, no significant seasonal cycles were found. In the region greater than 30 K from the tropopause (i.e., at higher altitudes), sharp CO2 increases in summer followed by gradual decreases were found, resulting in a slightly increasing seasonal cycle amplitude with distance from the tropopause. The observed CO2 distributions also showed that CO2 isopleths followed the tropopause during the winter and spring, whereas in the summer they tracked potential temperature surfaces crossing the tropopause. The observed seasonal variation in CO2 suggests that the lowermost stratospheric region is influenced by a combination of (1) fast meridional transport of high CO2 from the tropical troposphere in the summer, (2) active subsidence of low CO2 from higher altitudes in the spring, and (3) relatively weak vertical mixing near the tropopause.

Solubility of CO2 in solid-state PET measured by pressure-decay method

The solubility of CO2 in solid-state PET was measured using a pressure-decay method. In order to calculate the solubility of CO2 in the amorphous region of PET, the crystallinity of solid state PET dissolved in CO2 at different pressures and temperatures was measured by differential scanning calorimetry (DSC). The solubility increases with increasing pressure and it follows a linear relationship and obeys Henry’s law when the pressure is below 8 MPa. The effect of temperature on solubility is weak and the solubilities at different temperatures are almost the same under low pressures. At higher pressure, the solubility decreases with an increase in temperature. The solubility of CO2 in the amorphous region of PET at 373.15 K, 398.15 K and 423.15 K was correlated with the Sanchez-Lacombe equation of state with a maximal correlation error of 6.69%.

Catalytic properties of aluminum/nickel-, copper-containing oxide film compositions

The possibility of the single-step formation of nickel- and copper-containing thin-film oxide systems on aluminum by plasma electrolytic oxidation was demonstrated. The resulting structures were found to be active in the reaction of CO oxidation to CO2 in the temperature region 300–500°C. However, the resulting structures exhibited stable catalytic activity only in the simultaneous presence of nickel and copper compounds. The films were studied using X-ray diffraction, X-ray spectroscopic analysis, X-ray photoelectron spectroscopy, and electron microscopy. The resulting films exhibited an essentially inhomogeneous composition through the thickness. Electrolyte elements such as nickel, copper, sodium, and phosphorus were concentrated at the surface. Nickel occurred as Ni2+, and copper occurred as Cu+ and Cu2+. The surface contained carbon in detectable amounts.

Influence of vent air valve opening on combustion characteristics of a down-fired pulverized-coal 300 MWe utility boiler

Abstract Industrial experiments have been performed on a down-fired pulverized-coal 300 MWe utility boiler with vent air valve opening of 100% and 40%. The gas temperature distribution along the primary air and coal mixture flow, gas temperature distribution in the furnace, and gas components such as O2, CO, CO2 and NOx in the near-wall region were measured for the first time. The influence of vent air valve opening on coal combustion in the furnace was determined. The results indicate that ignition of the primary air and pulverized-coal mixture is delayed. The position of the gas temperature peak is above the arches. Emission of NOx is up to 2101 mg/m3 (at 6% O2 dry) with vent valve opening of 40%.

Temporal variations of atmospheric carbon dioxide in the southernmost part of Japan

We present analysis of the temporal variation of atmospheric CO2 in the subtropical region of East Asia, obtained aboard a ferry between Ishigaki Island and Hateruma Island, Japan for the period June 1993–April 2005. The annual mean CO2 concentration increases from 360.1 ppmv in 1994 to 378.4 ppmv in 2004, showing an average growth rate of 1.8 ppmv yr-1. The growth rate shows interannual variations with high values duringENSOevents. The average seasonal CO2 cycle reaches the maximum in early April and the minimum in mid-September, with a peak-to-peak amplitude of 8.5 ppmv. Numerical simulations using a three-dimensional atmospheric transport model show interannual variations of the CO2 growth rate similar to the observation, but the amplitude of the seasonal cycle is larger, with maximum concentration appearing earlier than the observation by 1 month. Low CO2 values observed during the spring of 1998 are likely associated with the 1997/1998 ENSO event. A backward trajectory analysis suggests that they were due to changes in atmospheric transport whereby maritime air masses from the Pacific Ocean dominated over polluted air masses from the Asian Continent. Extreme values (either high or low) of CO2 are also occasionally observed. A comparison of backward trajectories of air parcels with CO2 concentration fields calculated using the atmospheric transport model shows that these unusual CO2 concentrations result from the transport of air affected not only by anthropogenic CO2 emissions but also by terrestrial biospheric activities mainly in China.

Parameterization of the absorption of the H2O continuum, CO2, O2, and other trace gases in the Fu-Liou solar radiation program

The absorption properties of the water vapor continuum and a number of weak bands for H2O, O2, CO2, CO, N2O, CH4, and O3 in the solar spectrum are incorporated into the Fu-Liou radiation parameterization program by using the correlatedk-distribution method (CKD) for the sorting of absorption lines. The overlap absorption of the H2O lines and the H2O continuum (2500–14500 cm−1) are treated by taking the two gases as a single-mixture gas in transmittance calculations. Furthermore, in order to optimize the computation efforts, CO2 and CH4 in the spectral region 2850–5250 cm−1 are taken as a new single-mixture gas as well. For overlap involving other absorption lines in the Fu-Liou spectral bands, the authors adopt the multiplication rule for transmittance computations under which the absorption spectra for two gases are assumed to be uncorrelated. Compared to the line-by-line (LBL) computation, it is shown that the errors in fluxes introduced by these two approaches within the context of the CKD method are small and less than 0.48% for the H2O line and continuum in the 2500–14500 cm−1solar spectral region, ∼1% for H2O (line)+H2O (continuum)+CO2+CH4 in the spectral region 2850–5250 cm−1,and ∼1.5% for H2O (line)+H2O (continuum)+O2 in the 7700–14500 cm−1 spectral region. Analysis also demonstrates that the multiplication rule over a spectral interval as wide as 6800 cm−1 can produce acceptable errors with a maximum percentage value of about 2% in reference to the LBL calculation. Addition of the preceding gases increases the absorption of solar radiation under all sky conditions. For clear sky, the increase in instantaneous solar absorption is about 9%–13% (∼12 W m−2) among which the H2O continuum produces the largest increase, while the contributions from O2 and CO2 rank second and third, respectively. In cloudy sky, the addition of absorption amounts to about 6–9 W m−2. The new, improved program with the incorporation of the preceding gases produces a smaller solar absorption in clouds due to the reduced solar flux reaching the cloud top.

Welding Colloidal Crystals with Carbon Dioxide

The effect of CO2 on the welding kinetics for a PS colloidal crystal was determined by in-situ measurement of Bragg diffraction and by ex-situ SEM microscopy. The welds grow tangentially from the points of contact of the spheres in all directions transforming the spheres into a continuous film. The dissolved CO2 provides the mobility for the polymer chains at the interface needed for welding, which removes the energetically unfavorable interfacial area between the polymer and CO2. At high pressures where CO2 is relatively incompressible, the relaxation time for welding increased by 6 orders of magnitude with an increase in thermal energy, and a glass transition temperature was observed. At constant temperature, an anomalous increase in the welding rate by 1−2 orders of magnitude with a decrease in pressure was observed in the region where CO2 is highly compressible. It is likely that this increase in welding dynamics is influenced by the excess CO2 in the interfacial region.

수평관내 초임계 영역의 Co2냉각 열전달 특성

The heat transfer coefficient and pressure drop during gas cooling process of carbon dioxide in a horizontal tube were investigated. The experiments were conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flowmeter, an evaporator, and a gas cooler(test section). The main components of the water loop consist of a variable-speed pump, an isothermal tank, and a flowmeter. The gas cooler is a counterflow heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. The test section consists of smooth, horizontal stainless steel tube of the outer diameter of 9.53 mm and of the inner diameter of 7.75 mm. The length of the test section is 6 m. The refrigerant mass fluxes were 200 ~ 300 kg/(m2 . s) and the inlet pressure of the gas cooler varied from 7.5 MPa to 8.5 MPa. The main results were summarized as follows: Pressure drop of CO2 increases with increasing gas cooler pressure. The friction factors of CO2 in a horizontal tube show a relatively good agreement with the correlation by Blasius. The heat transfer coefficient of CO2 in transcritical region increases with decreasing gas cooler pressure and decreasing mass flux of CO2. Most of correlations proposed in a transcritical region showed significant deviations with experimental data except for those predicted by Gnielinski.<br/>

Seasonal Changes in Oceanic pCO2in the Oyashio Region from Winter to Spring

We observed the partial pressure of oceanic CO2, pCO2 sea, and related surface properties in the westernmost region of the subarctic North Pacific, seasonally from 1998 to 2001. The pCO2 sea in the Oyashio region showed a large decrease from winter to spring. In winter, pCO2 sea was higher than 400 μatm in the Oyashio region and this region was a source of atmospheric CO2. In spring, pCO2 sea decreased to extremely low values, less than 200 μatm (minimum, 139 μatm in 2001), around the Oyashio region with low surface salinity and this region turned out to be a strong sink. The spatial variations of pCO2 sea were especially large in spring in this region. The typical Oyashio water with minimal mixing with subtropical warm water was extracted based on the criterion of potential alkalinity. The contribution of main oceanic processes to the changes in pCO2 sea from winter to spring was estimated from the changes in the concentrations of dissolved inorganic carbon and nutrients, total alkalinity, temperature and salinity observed in surface waters in respective years. These quantifications indicated that photosynthesis made the largest contribution to the observed pCO2 sea decreases in all years and its magnitude was variable year by year. These year-to-year differences in spring biological contribution could be linked to those in the development of the density stratification due to the decrease in surface salinity. Thus, the changes in the surface physical structure could induce those in pCO2 sea in the Oyashio region in spring. Furthermore, it is suggested that the direction and magnitude of the air-sea CO2 flux during this season could be controlled significantly by the onset time of the spring bloom.

Enhanced climatic warming in the Tibetan Plateau due to doubling CO2: a model study

The National Center for Atmospheric Research (NCAR) regional climate model (RegCM2), together with initial conditions and time-dependent lateral boundary conditions provided by a 130-year transient increasing CO2 simulation of the NCAR Climate System Model (CSM), has been used to investigate the mechanism of ground warming over the Tibetan Plateau (TP). The model results show that when CO2 in the atmosphere is doubled, a strong ground warming occurs in the TP. Two regions within it with the largest warming are in the eastern TP (region I) and along the southwestern and western slopes (region II). Moreover, in region I the ground warming in the winter half year is stronger than that in the summer half year, but in region II the warming difference between the seasons becomes opposite to that in region I, i.e., the warming is strong in the summer half year and weak in the winter half year. There are indications that the summer monsoon enhances but the winter monsoon weakens when CO2 is doubled. A strong elevation dependency of ground warming is found in region I for the winter half year, and in region II for both winter and summer half years at elevations below 5 km. The simulated characteristics of ground warming in the TP are consistent with the observations. In region I, when CO2 is doubled, the cloud amount increases at lower elevations and decreases at higher elevation for the winter half year. As a consequence, at lower elevations the short wave solar radiation absorbed at the surface declines, and the downward long wave flux reaching the surface enhances; on the other hand, at higher elevations the surface solar radiation flux increases and the surface infrared radiation flux shows a more uniform increase. The net effect of the changes in both radiation fluxes is an enhanced surface warming at higher elevations, which is the primary cause of the elevation dependency in the surface warming. In the summer half year the cloud amount reduces as a result of doubling CO2 in region I for all elevations, and there is no elevation dependency detected in the ground warming. Furthermore, there is little snow existing in region I for both summer and winter half years, and the impact of snow-albedo feedback is not significant. In region II, although the changes in the cloud amount bear a resemblance to those in region I, the most significant factor affecting the surface energy budget is the depletion of the snow cover at higher elevations, which leads to a reduction of the surface albedo. This reduction in turn leads to an enhancement in the solar radiation absorbed in the surface. The snow-albedo feedback mechanism is the most essential cause of the elevation dependency in the surface warming for region II.

Direct Measurements of the Enthalpy of Solution of Solid Solute in Supercritical Fluids: Study on the CO2-Naphthalene System

A setup for a calorimeter for simultaneously measuring the solubility and the solution enthalpy of solid solutes in supercritical fluids (SCFs) has been established. The enthalpy of solution of naphthalene in supercritical CO2 was measured at 308.15 K in the pressure range from 8.0-11.0 MPa. It was found that the enthalpy of solution (deltaH) was negative in the pressure range from 8.0 to 9.5 MPa, and the absolute value decreased with increasing pressure. In this pressure range, the dissolution of the solute was enthalpy driven. However, the deltaH became positive at pressures higher than 9.5 MPa, and the dissolution was entropy driven. Monte Carlo simulation was performed to analyze the local structural environment of the solvated naphthalene molecules in supercritical CO2 under the experimental conditions for the calorimetric measurements. By combining the enthalpy data and the simulation results, it can be deduced that the energy level of CO2 in the high compressible region is higher than that at higher pressures, which results in the large negative enthalpy of solution and the larger degree of solvent-solute clustering in the high compressible region.

Vibrational Branching Ratios and Asymmetry Parameters in the Photoionization of CO2 in the Region Between 650 Å and 840 Å.

The vibrational branching ratios and asymmetry parameters for CO2 have been determined in the wavelength region of 650 Å to near the ionization onset at about 840 Å. The study was performed using synchrotron radiation from the Daresbury storage ring that was dispersed with a 5 m grating monochomator that afforded resolution of 0.1 Å to 0.2 Å. This resolution allowed the study of the branching ratios and asymmetry parameters with enough detail to see the changes in the parameters within the pronounced autoionization structure in CO2 in this wavelength region. While the electron spectrometer resolution was not sufficient to resolve the spin orbit and Renner-Teller splitting in the photoelectron spectra, we are able to fit the data with a model that identifies the major structure in terms of the symmetric stretch and elements of the asymmetric stretch and bending modes. A calculation of the expected relative vibrational excitations based upon the Franck-Condon principle clearly showed non-Franck-Condon behavior in some of the vibrational-electronic transitions.

Direct covariance air‐sea CO2 fluxes

Direct covariance air‐sea CO2 flux measurements over the open ocean are reported. These measurements were performed during June 1998 in the North Atlantic within a significant CO2 sink. These direct estimates are in general agreement with the traditional geochemical isotope constraints. The covariance, or eddy correlation, technique directly measures the air‐sea CO2 flux over hour timescales by correlating the fluctuations of CO2 with the turbulent vertical velocity fluctuations in the atmospheric surface layer. These measurements quantify the transfer of CO2 between the atmosphere and ocean over a range of wind speeds and improve the understanding of the environmental factors controlling the flux. The relatively large flux of CO2 in the study region, together with improved analytical techniques, facilitated the measurements. The half‐hour mean wind speeds varied from 0.9 to 16.3 m s−1 over the month‐long experiment. The mean pCO2 during the study period was −85.8±16.0 μatm, and the mean covariance CO2 flux was estimated at 4.6 mol m−2 yr−1. The average observed wind speed was 7.7 m s−1. This is in close agreement with 3.9 mol m−2 yr−1, the approximate CO2 flux based on 14C parameterizations at this wind speed. At high winds, where the relationship between gas physical properties, surface processes, and air‐sea gas exchange is still elusive, direct CO2 flux measurements are crucial. The measurements for winds in excess of 11 m s−1 show a general enhancement of gas transfer velocity over previous indirect measurements, and it is believed that this enhancement can be explained by the fact that the indirect methods cannot discriminate surface process variability such as atmospheric stability, upper ocean mixing, wave age, wave breaking, or surface films.

In situ combustion measurements of CO_2 by use of a distributed-feedback diode-laser sensor near 20 µm

High-resolution absorption measurements of CO(2) were made in a heated static cell and in the combustion region above a flat-flame burner for the development of an in situ CO(2) combustion diagnostic based on a distributed-feedback diode laser operating near 2.0 mum. Calculated absorption spectra of high-temperature H(2)O and CO(2) were used to find candidate transitions for CO(2) detection, and the R(50) transition at 1.997 mum (the nu(1) + 2nu(2) + nu(3) band) was selected on the basis of its line strength and its isolation from interfering high-temperature water absorption. Measurements of spectroscopic parameters such as the line strength, the self-broadening coefficient, and the line position were made for the R(50) transition, and an improved value for the line strength is reported. The combustion-product populations of CO(2) in the combustion region above a flat-flame burner were determined in situ to verify the measured spectroscopic parameters and to demonstrate the feasibility of the diode-laser sensor.

Simulations of storage of anthropogenic carbon dioxide in the North Pacific using an ocean general circulation model

There is a large uncertainty of how much anthropogenic CO2 has been and will be taken up by the ocean. The North Pacific is normally considered a small sink of anthropogenic CO2. Recently, some researchers have proposed that the North Pacific may take up more anthropogenic CO2 than thought previously. Here we explore this issue with a basin-wide OGCM of the North Pacific. The sensitivities of ocean circulation and the redistribution of dissolved anthropogenic CO2 in the North Pacific to the values of some mixing parameters are examined. The increase of isopycnal diffusivity generally leads to improvement of distributions of water masses. Larger isopycnal diffusivity produces larger CO2 uptake in the subpolar region but smaller CO2 uptake in the tropical region. Increasing thickness diffusivity reduces CO2 uptake in both the subpolar and subtropical regions, and also reduces the inventory of CO2 in the western subtropical region. Both smaller isopycnal and thickness diffusivities result in a large net transport of CO2 from the North Pacific to the South Pacific. Simulated results show that the North Pacific has taken up about 23 GtC of excess carbon dioxide released by human activities between 1800 and 1997. The averaged uptake rate in the North Pacific during 1990–1997 is 0.40 GtC/year. Our model estimates the largest air–sea fluxes along the western boundary around 42°N, 150°E and in the equatorial Pacific. Our simulated inventories slightly overestimate data-based estimates in the eastern North Pacific, but exhibit less penetration of anthropogenic carbon dioxide in the western North Pacific.

The Contribution of Gas-Phase Reactions in the Pt-Catalyzed Conversion of Ethane–Oxygen Mixtures

This paper presents an analysis of the oxidative dehydrogenation of ethane on platinum-containing monoliths. The purpose of the work is to make a quantitative assessment of the extent to which homogeneous gas-phase reactions contribute to the overall conversion of the ethane. In making the analysis, extensive use is made of kinetic information obtained and compiled by A. M. Dean and associates for elementary homogeneous reaction steps and by L. D. Schmidt and associates for elementary surface reactions. A critical part of the analysis is concerned with accounting for the heat effects and for the reactor temperature gradient resulting therefrom. This is absolutely essential for meeting the objective of this investigation. The rise in temperature as the gases proceed through the reactor is responsible for a very substantial contribution of homogeneous gas-phase reactions in the chemical transformation occurring. One can view the process as a sequential one in which ethane is first oxidized on the platinum surface to CO, CO2, and H2O in the front region of the monolith. The formation of these products causes a substantial temperature increase that drives the dehydrogenation of ethane to ethylene (and acetylene) in the gas phase. The heat required to sustain these endothermic reactions in the tail end of the reaction zone is supplied by exothermic gas-phase oxidation reactions that form additional H2O and CO. Overall, the system can be viewed as one in which the catalyst initiates gas-phase chemistry through the acceleration of exothermic reactions at the front of the reactor which increase the downstream temperature to the point where gas-phase reactions occur readily.

Light-Scattering Study of Diblock Copolymers in Supercritical Carbon Dioxide: CO2 Density-Induced Micellization Transition

The behavior of polymeric surfactant polyvinyl acetate (PVAC)-b-poly(1,1,2,2-tetrahydroperfluorooctyl acrylate) (PTAN) in supercritical carbon dioxide (CO2) was investigated using static and dynamic light scattering. We observed three regions on the phase diagram of the copolymer in supercritical CO2: (i) two-phase region at low CO2 density; (ii) solutions of spherical micelles at intermediate CO2 densities; (iii) solutions of unimers (individual copolymer chains) at high CO2 densities. The aggregation number (the number of copolymer chains in a micelle) decreases with an increasing density of supercritical CO2 in region (ii). An increase of the CO2 density corresponds to the improvement of solvent quality for both blocks of the copolymer (PVAC and PTAN). The hydrodynamic radius of micelles and unimers was measured using dynamic light scattering in regions (ii) and (iii), respectively. This light-scattering study is the first one reporting a solvent density-induced transition between spherical micelles at lower supercritical CO2 density and unimers at higher CO2 density. The light-scattering technique appears to be a very powerful tool for the analysis of the carbon dioxide density-induced micellization transition. This phenomenon is unique to supercritical fluids and demonstrates a convenient control over the polymer solubility.