Abundance Of Carbon Monoxide Research Articles

Absolute measurement of the abundance of atmospheric carbon monoxide

The main aspects of an absolute method for measurement of the mixing ratio of atmospheric carbon monoxide (CO) are presented. The method is based on cryogenic extraction of CO from air after oxidation to CO2 followed by accurate volumetric determination. Gravimetric measurement is used to determine the quantity of sample air processed. In routine operation the overall error can be kept below 1%. Furthermore, the results of a laboratory intercomparison are analyzed. It is shown how offsets in the commonly applied analytical methods can occur and how these can seriously affect results obtained at the low concentration end (<100 nmole/mole).

Solubility, speciation and dissolution mechanisms for CO 2 in melts on the NaAlO 2–SiO 2 join

CO 2 solubility and speciation in melts along the NaAlO 2–SiO 2 join from Ne (NaAlSiO 4) to a model rhyolite (Ry) composition (NaAlSi 6O 14), have been investigated as a function of pressure (10 to 25 kb) and temperature (1450 to 1700°C). Quenched glasses have been analysed using LECO bulk carbon analysis in conjunction with Fourier transform infrared (FTIR), Raman, and 13C Magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopic measurements. In agreement with previous studies, the CO 2 solubility was found to increase as a function of total pressure for the Ne, Jd (NaAlSi 2O 6), Ab (NaAlSi 3O 8), and “Eu” (NaAlSi 4O 10) compositions. The temperature dependence of the CO 2 solubility was also investigated. For the Ne (15 kbar) composition, a slight increase in solubility was noted with increasing temperature, whereas a broad minimum in solubility was noted for the Jd composition (15 and 20 kbar) in the 1550 to 1650°C range. No obvious dependence of the solubility on run temperature was noted for the high silica compositions Eu to Ry at 15 kbar. Infrared (IR) and NMR spectra of the quenched glasses show that the type and relative amounts of carbon-bearing species change systematically as a function of composition. The relative and absolute abundance of carbonate (CO 3 2−) groups increases rapidly with decreasing Si/(Na + Al) ratio, whereas the relative and absolute abundance of molecular CO 2 decreases. The result is that, for a given pressure and temperature, the CO 2 solubility remains approximately constant or decreases slightly with decreasing Si/(Na + Al) ratio between Ry and Jd compositions, but increases rapidly between Jd and Ne compositions, at 15 kbar and 1600°C. In the most silica-rich compositions nearly all the dissolved CO 2 is in the form of molecular CO 2. The IR and Raman spectra of dissolved molecular CO 2 indicate some interaction with the silicate melt structure, which changes over the compositional range studied. Four different types of dissolved carbonate groups with differing degrees of distortion have been identified by NMR spectroscopy, the relative proportions changing systematically with glass composition. Two of these carbonate groups are dominant in silica-poor, carbonate-rich compositions and correlate with distinguishable features in the IR spectra. The structural changes in both the carbonate and the molecular CO 2 species as a function of bulk composition along the join, result in changes in the IR extinction coefficients for these species. The degree to which the observed quenched glass species reflect the situation in the melt at run conditions are discussed. Dissolved carbon monoxide (CO) has been identified from the NMR and FTIR spectra of glasses for experiments carried out under (unintentionally) reducing conditions. The experimental results indicate that considerable caution is required in preparing nominally “CO 2 -saturated” glasses. The absence of CO-related spectral features can be used to ensure that the experimental P CO 2 is in fact equal to P tot.

Highly elevated carbon monoxide concentrations in the upper troposphere and lowermost stratosphere at northern midlatitudes during the STREAM II summer campaign in 1994

During the second Stratosphere Troposphere Experiment by Aircraft Measurements (STREAM II) five flights up to 12 km altitude were performed over the North Sea, Great Britain, The Netherlands, and Germany, with a Cessna Citation II twin jet aircraft during the period 20–29 July 1994. Carbon monoxide (CO) concentrations in the lowermost stratosphere, which were measured by tunable diode laser absorption spectroscopy, varied between typical background values around 40 parts per billion by volume (ppbv) and highly elevated levels of up to 300 ppbv. The high CO concentrations were observed before a cold front passed over western Europe. The enhanced CO abundance was most probably caused by boreal fires in Canada in connection with convective mixing and subsequent horizontal advection over the North Atlantic Ocean.

Identification of two sources of carbon monoxide in comet Hale-Bopp.

The composition of ices in comets may reflect that of the molecular cloud in which the Sun formed, or it may show evidence of chemical processing in the pre-planetary accretion disk around the proto-Sun. As carbon monoxide (CO) is ubiquitous in molecular clouds, its abundance with respect to water could help to determine the degree to which pre-cometary material was processed, although variations in CO abundance may also be influenced by the distance from the Sun at which comets formed. Observations have not hitherto provided an unambiguous measure of CO in the cometary ice (native CO). Evidence for an extended source of CO associated with comet Halley was provided by the Giotto spacecraft, but alternative interpretations exist. Here we report observations of comet Hale-Bopp which show that about half of the CO in the comet comes directly from ice stored in the nucleus. The abundance of this CO with respect to water (12 per cent) is smaller than in quiescent regions of molecular clouds, but is consistent with that measured in proto-stellar envelopes, suggesting that the ices underwent some processing before their inclusion into Hale-Bopp. The remaining CO arises in the coma, probably through thermal destruction of more complex molecules.

The Structure of the Multi-Phase ISM in Low Surface Brightness Galaxies

AbstractThe multi-phase structure of the interstellar medium in low surface brightness galaxies is investigated and compared to observations. It is found that the ambient pressure and metallicity very strongly influence the abundances of molecular hydrogen and carbon monoxide. The emissivity of the latter is computed and found to agree naturally with the upper limits measured for low surface brightness galaxies. The implications for star formation efficiency and galaxy evolution are discussed.

Correlation between ISAMS and ATMOS measurements of co in the middle atmosphere

Measurements of IR emissions from CO at 4.6 μm in the middle atmosphere were recorded for nearly one year, from September 1991 to July 1992 by the Improved Stratospheric and Mesospheric Sounder (ISAMS) on board the Upper Atmosphere Research Satellite (UARS). These have been used to retrieve carbon monoxide abundances and study their distribution and variability in the middle atmosphere. Observations of carbon monoxide in this atmospheric region and from transitions of the same vibrational-rotational band were also carried out, using the solar occultation technique with fine altitude resolution, by the high resolution interferometer ATMOS during the ATLAS-1 mission (late March and early April 1992). Comparisons between these simultaneous emission and absorption experiments have been performed in order to improve and validate both data sets. Some of the first results and conclusions are presented and discussed.

Remote sensing of carbon monoxide over the continental United States on September 12–13, 1993

Tropospheric carbon monoxide (CO) column densities were retrieved from 491 nadir infrared spectra obtained by the University of Wisconsin's High‐Resolution Interferometer Sounder (HIS) during a cross‐country flight of a NASA ER‐2 on September 12–13, 1993 (UT). A classical, Fourier‐based signal‐processing technique was utilized to retrieve the CO column density from the 2135–2200 cm−1 portion of the CO 1–0 vibration‐rotation band. Error analysis indicates column CO retrieval uncertainties of approximately ±10%. Retrieved CO column densities over the western United States from this flight, ∼1.2×1018 cm−2, agree well with previous ground‐based CO column measurements over the western United States at the same season. Derived CO sensitivity functions for these measurements possess a broad peak centered in the 500–600 mbar region, thus implying the retrieved tropospheric CO mixing ratios are indicative of the mean free troposphere (mft). Across the United States, three spatial groupings of CO were observed: west, mft CO ∼76 parts per billion by volume (ppbv); midwest, mft CO ∼56 ppbv; and east, mft CO ∼71 ppbv. Weather map and back trajectory analyses indicate different source regions for the air parcels in each of these regions. The low CO amounts over the midwest most likely result from the mixing of rapidly subsiding air naturally low in CO with a low‐altitude inflow of similarly clean subtropical air off the Gulf of Mexico. These results demonstrate the utility of satellite infrared spectrometer observations to globally map tropospheric CO abundances and further reveal the impact of synoptic scale atmospheric circulations on CO abundances.

The Hybrid Rich-Burn/Lean-Burn Engine

This paper describes a new low-emissions engine concept called the hybrid rich-burn/lean-burn (HRBLB) engine. In this concept a portion of the cylinders of a multicylinder engine are fueled with a very rich natural gas-air mixture. The remaining cylinders are operated with a lean mixture of natural gas and air and supplemented with the rich combustion exhaust. The goal of this unique concept is the production of extremely low NOx (e.g., 5 ppm when corrected to 15 percent exhaust oxygen content). This is accomplished by operating outside the combustion limits where NOx is produced. In rich combustion an abundance of hydrogen and carbon monoxide is produced. Catalyst treatment of the rich exhaust can be employed to increase the hydrogen concentration and decrease the carbon monoxide concentration simultaneously. The hydrogen-enriched exhaust is used to supplement the lean mixture cylinders to extend the lean limit of combustion, and thus produces ultralow levels of NOx. Results to date have shown NOx levels as low as 8 ppm at 15 percent oxygen can be achieved with good combustion stability and thermal efficiency.

The detection of enhanced carbon monoxide abundances in remotely sensed infrared spectra of a forest fire smoke plume

Nadir looking infrared spectra of a forest fire smoke plume off the south shore of Long Island, New York, were obtained from a NASA ER‐2 aircraft during two spatially coincident over‐flights on the morning of August 25, 1995. These spectra exhibit enhanced CO column densities at the same geographic locations over the smoke plume on both over‐flights with a peak CO column density ∼2.6 × 1018 cm−2, ∼6σ above the clear air background. Meteorological conditions suggest the smoke plume was confined to the planetary boundary layer (PBL), pressures ≥ 850 mb, and perhaps to a thin region near the top of the PBL. Constraining the excess CO to the PBL yields a CO mixing ratio ∼1,400 ppbv. Further constraining the CO to the model layer nearest the top of the PBL, 852–878 mb, yields‐4,300 ppbv. From the spatial overlap of the spectra, the estimated width of the CO rich portion of the plume is ≤ 2.8 km vs. a plume width of ∼5 km in GOES‐8 satellite visible images.

Validation of measurements of carbon monoxide from the improved stratospheric and mesospheric sounder

Carbon monoxide abundances in the middle atmosphere are retrieved from infrared measurements of the emission of this molecule at 4.6 μm taken by the improved stratospheric and mesospheric sounder (ISAMS) onboard the Upper Atmosphere Research Satellite. In addition to a limited signal‐to‐noise ratio, the measured radiances include significant contamination by other compounds in the stratosphere and show clear non‐local thermodynamic equilibrium effects in the mesosphere which also affect the stratospheric limb views. The application of the ISAMS retrieval method to these measurements and the particular method followed to deal with these difficulties are described. The actions carried out to understand and validate the obtained CO abundances are detailed. They include analysis of the radiances, sensitivity studies of the product to retrieval parameters, evaluation of the main sources of systematic and random errors, and comparisons with theoretical model predictions and with the few correlative measurements available. The gross features observed in the CO distribution present good agreement with dynamical‐chemical models of the middle atmosphere. The aspects of the retrieval that need further improvement are identified, and the global quality of the database and the expectations for its scientific use are discussed.

Chemical and thermal response of Jupiter's atmosphere following the impact of comet Shoemaker-Levy 9.

In July 1994, the collisions of the fragments of comet Shoemaker-Levy 9 with Jupiter resulted in dramatic changes in the planet's atmosphere. Observations of the events suggest that the composition and thermal properties of the atmosphere were considerably modified at the impact sites, with the changes persisting for times lasting from minutes to weeks (see, for example, refs 1-4). Here we report observations of the impact sites at millimetre wave-lengths, which reveal strong emission lines associated with carbon monoxide, carbonyl sulphide and carbon monosulphide. The abundance of carbon monoxide in the jovian atmosphere is normally very low; carbonyl sulphide and carbon monosulphide, on the other hand, have not hitherto been detected. We find that the largest fragments (G and K) each produced approximately 10(14) g of carbon monoxide, 3 x 10(12) g of carbonyl sulphide and 3 x 10(11) g of carbon monosulphide, most probably by shock-induced chemical reactions. Our observations also place firm constraints on the thermal response of Jupiter's stratosphere to the impacts.

Carbon monoxide and total ozone in Arctic and Antarctic regions: seasonal variations, long-term trends and relationships

Total column abundances of carbon monoxide (CO) were measured in Zvenigorod, near Moscow, and in the Russian Arctic (from Severnaya Zemlya to Wrangel Island, including the drifting station in the central part of the Arctic Basin). CO was found to decrease from early spring to summer, both in central Russia and in the Arctic; absolute mean CO abundances in both regions differed little. Vertically averaged CO mixing ratios over Zvenigorod were compared with those measured in the surface layer at Point Barrow, Alaska, between July 1988 and December 1990. Good agreement between them was observed in summer; in winter and early spring, however, the CO mixing ratios for Barrow were 40% greater than for Zvenigorod. This difference is most likely explained by CO becoming concentrated under the Arctic inversion layer in winter. The mean tropospheric mixing ratio over Zvenigorod increased at a rate of 0.7 ± 0.2% year−1 during the period between 1970 and 1993. This increase was not steady; during 1970–1982 it was larger, ∼ 1.5% year−1. Long-term variations in both sources and sinks of CO could be responsible for these phenomena.

Carbon monoxide budget in the northern hemisphere

To improve urban air quality the major industrialized nations of the West took steps during the 1970s and 1980s to reduce carbon monoxide (CO) emissions from automobiles and other industrial sources. Overall, CO/CO2 emission ratios from the mix of fossil fuel combustion sources have been reduced by about half during 1976–1990. Also, the tropospheric abundance of hydroxyl radical (OH), which is the main sink for CO, is proposed to have increased globally by about 1.0±0.8% yr−1 [Prinn et al., 1992]. We use a simple two‐box model to examine the impact of shrinking emissions and increasing OH on the global abundance of CO. We find that these factors contribute about equally in reducing CO levels in the Northern Hemisphere troposphere by about 1.8±0.8 ppb yr−1 on average.

Variations in the total column abundances of atmospheric carbon monoxide and methane in the polar regions

Atmospheric carbon monoxide and methane were studied spectroscopically in the Arctic and Antarctic. Seasonal variations of CO are evident in both polar regions, absolute values of abundance being three times larger in the Arctic than in the Antarctic. Increasing concentration trends were confirmed for both gases: 0.8% per year for Antarctic CO, 0.5% per year for Antarctic CH4 and 3.1% per year for Arctic CH4.

High-resolution absorption cross sections of carbon monoxide bands at 295 K between 91.7 and 100.4 nanometers

Theoretical descriptions of the abundance and excitation of carbon monoxide in interstellar clouds require accurate data on the vacuum-ultraviolet absorption spectrum of the molecule. The 6.65 m spectrometer at the Photon Factory synchrotron light source was used to measure photoabsorption cross sections of CO features between 91.2 and 100.4 nm. These data were recorded at a resolving power of 170,000, more than 20 times greater than that used in previous work.

Carbon monoxide frosts in the interstellar medium

The presence of solid carbon monoxide (CO) on interstellar grains was confirmed observationally in 1984 with the detection of infrared absorption at 4.67μm wavelength in several molecular clouds. Subsequent observations suggest that solid CO is ubiquitous in the quiescent molecular cloud environment. In some lines of sight, the degree of frosting on to grains is sufficient to reduce appreciably the abundance of CO remaining in the gas, a result of considerable astrophysical significance: in addition to its importance as a tracer of molecular material, CO is vital to the production of many polyatomic molecules by gas phase reaction schemes, and its depletion could have a dramatic effect on the abundances of more complex carbon-bearing molecules. The infrared spectrum of solid CO provides an important diagnostic of the chemical composition and thermal evolution of grain mantles, leading to the prediction that CO2 is also present in solid form.

The abundances of atomic carbon and carbon monoxide compared with visual extinction in the Ophiuchus molecular cloud complex

Emission from the 492 GHz lines of C I have been observed toward six positions in the Ophiuchus molecular cloud complex for which accurate visual extinctions are available. The column density of C I increases with A(V) to greater than 2 x 10 to the 17th/sq cm at 100 mag, the column-averaged fractional abundance reaches a peak of about 2.2 x 10 to the -5th for A(V) in the range 4-11 mag and the column-averaged abundance ratio of C I to CO decreases with A(V) from about 1 at 2 mag to greater that about 0.03 at 100 mag. These results imply that, while C I is not the primary reservoir of gaseous carbon even at cloud edges, its fractional abundance remains high for at least 10 mag into the cloud and may be significant at even greater depths.

Secular increase of the total vertical column abundance of carbon monoxide above central Europe since 1950

The secular increase of the total vertical column abundance of carbon monoxide has been derived from sets of infrared solar spectra recorded from an altitude of 3.58 km at the Jungfraujoch Station, Switzerland, in 1950–1951 and in 1985–1987. The results are based on equivalent width measurements of the R3 line of the 1‐0 vibration‐rotation band of 12C16O at 2159.30 cm−1. The set of 1985–1987 observations indicates a strong seasonal cycle in the total column abundance of CO, with a ±25% modulation between minimum values in late summer and the maximum values in late winter. Variability on shorter time scales is also present in both the old and recent data sets. The mean cumulative rate of increase of the total column abundance of CO above the Jungfraujoch is found to be (0.85 ± 0.20)%/yr between 1950–1951 and 1985–1987. The present findings are compared with trends reported in earlier studies.

Spectroscopic measurements of atmospheric carbon monoxide and methane. 2: Seasonal variations and long-term trends

A spectroscopic technique for measuring CO and CH4 contents is described and the latitudinal distributions of these gases are presented. Carbon monoxide abundance decreases southward, having two local maxima: in midlatitudes and in the tropics. The slope of latitude dependence varies according to the season of the year. The difference in CH4 content does not exceed the accuracy of the method (±8%).

Abundance of carbon monoxide in the stratosphere of Titan from millimeter heterodyne observations

We searched for the (1-0) rotation line of carbon monoxide on Titan with the IRAM 30-m radiotelescope on Pico-Veleta, Spain. Comparison of the results with previous near-infrared observations of Titan suggests that the stratospheric abundance of carbon monoxide is depleted with respect to the tropospheric value.