The cycle of atmospheric CO

Oceanic source strength of carbon monoxide on the basis of basin-wide observations in the Atlantic

We measured the carbon monoxide (CO) concentrations in the marine boundary layer and the surface waters of the Atlantic Ocean from 50°N to 50°S during the UK Atlantic Meridional Transect expedition (AMT-7) in October 1998, covering the open ocean and coastal regions. Throughout the cruise track, atmospheric CO concentrations continually decreased southwards in the northern hemisphere with sporadic low and high concentrations encountered. South of the intertropical convergence zone (ITCZ) atmospheric CO was enhanced by ∼10 ppb compared to north of the ITCZ due likely to biomass burning emissions prevailing in the tropical continents. The remainder of the southern hemisphere remains nearly invariable except for the vicinity of Rio de la Plata. The surface seawater was supersaturated everywhere along the track and its saturation anomaly oscillated up to 90, exhibiting a typical diurnal cycle. The maximal dissolved CO concentration in the diurnal cycle appeared 2-5 hours behind the local maximum of solar insolation in the open ocean and the time lag further increased in the coastal region. The global ocean flux of CO to the atmosphere was estimated to be 14 Tg(CO) a(-1) within the range of 4-24 Tg(CO) a(-1). This is within uncertainty almost identical to what was estimated on the basis of the basin-wide observations in the Pacific and the Atlantic, but more than ∼4 times lower than the values appeared in the Intergovernmental Panel on Climate Change (IPCC) reports.

Tropospheric CO observed with the NAST-I retrieval methodology, analyses, and first results

High-resolution infrared spectra from aircraft and space-based observations contain information about tropospheric carbon monoxide (CO) as well as other trace species. A methodology for retrieving tropospheric CO from such remotely sensed spectral data has been developed for the National Polar-Orbiting Operational Environmental Satellite System's Airborne Sounder Testbed-Interferometer (NAST-I). CO profiles of the troposphere, together with its thermodynamic properties, are determined by use of a three-stage retrieval approach that combines the algorithms of physically based statistical eigenvector regression, simultaneous and iterative matrix inversion, and single-variable error-minimization CO profile matrix inverse retrieval. The NAST-I is collecting data while it is aboard high-altitude aircraft throughout many field campaigns. Detailed retrieval analyses based on the NAST-I instrument system along with retrieval results from several recent field campaigns are presented to demonstrate NAST-I CO retrieval capability.

Streptomyces thermoautotrophicus sp. nov., a Thermophilic CO- and H 2 -Oxidizing Obligate Chemolithoautotroph

The novel thermophilic CO- and H 2 -oxidizing bacterium UBT1 has been isolated from the covering soil of a burning charcoal pile. The isolate is gram positive and obligately chemolithoautotrophic and has been named Streptomyces thermoautotrophicus on the basis of G+C content (70.6 ± 0.19 mol%), a phospholipid pattern of type II, MK-9(H 4 ) as the major quinone, and other chemotaxonomic and morphological properties. S. thermoautotrophicus could grow with CO ( t d = 8 h), H 2 plus CO 2 ( t d = 6 h), car exhaust, or gas produced by the incomplete combustion of wood. Complex media or heterotrophic substrates such as sugars, organic acids, amino acids, and alcohols did not support growth. Molybdenum was required for CO-autotrophic growth. For growth with H 2 , nickel was not necessary. The optimum growth temperature was 65°C; no growth was observed below 40°C. However, CO-grown cells were able to oxidize CO at temperatures of 10 to 70°C. Temperature profiles of burning charcoal piles revealed that, up to a depth of about 10 to 25 cm, the entire covering soil provides a suitable habitat for S. thermoautotrophicus . The K m was 88 μl of CO liter −1 and V max was 20.2 μl of CO h −1 mg of protein −1 . The threshold value of S. thermoautotrophicus of 0.2 μl of CO liter −1 was similar to those of various soils. The specific CO-oxidizing activity in extracts with phenazinemethosulfate plus 2,6-dichlorophenolindophenol as electron acceptors was 246 μmol min −1 mg of protein −1 . In exception to other carboxydotrophic bacteria, S. thermoautotrophicus CO dehydrogenase was able to reduce low potential electron acceptors such as methyl and benzyl viologens.

Aerobic carboxydobacteria

Bacterial consumption of CO, a major atmospheric pollutant, has been described in the literature long ago, but often with controversial data. Attempts were made, therefore, to isolate and study a broader spectrum of aerobic CO bacteria in order to better understand their ecology.About 100 samples from various locations in the USSR (water, mud, junkyard, or garden, soil etc.) were inoculated into mineral medium and incubated under 80% CO and 20% O2. Such enrichments yielded a large number of strains representing 5-6 different bacterial species. The highest number of CO utilizers came from fresh samples of polluted, moist soil or mud. Some mixed cultures were composed of vitamin-dependent bacteria living together in a state of protocooperation. Seven strains (previously already partially described) were studied in greater detail. They are regarded as "carboxydobacteria." Six carboxydobacteria also utilized hydrogen, but none of the 7 cultures grew with methane or formate. The optimal concentration of, and sensitivity to, CO varied with the strains. Reducedvs. oxidized spectra revealed in all cultures the presence ofb-, c-, anda-type cytochromes, indicating a functioning electron transport chain when grown under CO. Isotope experiments with(14)C indicated that CO was assimilated only after oxidation to CO2, the pathway being the normal Calvin cycle reaction sequence as observed in other chemolithotrophs. The key enzymes of this sequence were shown to be present and active.Organotrophic growth of carboxydobacteria was obtained with a number of compounds such as organic acids, primary alcohols, carbohydrates, and amino acids. A description of properties of the 7 test strains is given. Their ecological niche(s) seem to be where facultatively anaerobic bacteria produce organic intermediates as well as H2 and CO. Pellicle formation indicates their presence on the water surface (neuston layer). Relationships with hydrogen-oxidizing bacteria are discussed and explained on ecological grounds.

Carbon monoxide oxidation by methanogenic bacteria

Different species of methanogenic bacteria growing on CO(2) and H(2) were shown to remove CO added to the gas phase. Rates up to 0.2 mumol of CO depleted/min per 10 ml of culture containing approximately 7 mg of cells (wet weight) were observed. Methanobacterium thermoautotrophicum was selected for further study based on its ability to grow rapidly on a completely mineral medium. This species used CO as the sole energy source by disproportionating CO to CO(2) and CH(4) according to the following equation: 4CO + 2H(2)O --> 1CH(4) + 3CO(2). However, growth was slight, and the growth rate on CO was only 1% of that observed on H(2)/CO(2). Growth only occurred with CO concentrations in the gas phase of lower than 50%. Growth on CO agrees with the finding that cell-free extracts of M. thermoautotrophicum contained both an active factor 420 (F(420))-dependent hydrogenase (7.7 mumol/min per mg of protein at 35 degrees C) and a CO-dehydrogenating enzyme (0.2 mumol/min per mg of protein at 35 degrees C) that catalyzed the reduction of F(420) with CO. The properties of the CO-dehydrogenating enzyme are described. In addition to F(420), viologen dyes were effective electron acceptors for the enzyme. The apparent K(m) for CO was higher than 1 mM. The reaction rate increased with increasing pH and displayed an inflection point at pH 6.7. The temperature dependence of the reaction rate followed the Arrhenius equation with an activation energy (DeltaHdouble dagger) of 14.1 kcal/mol (59.0 kJ/mol). The CO dehydrogenase activity was reversibly inactivated by low concentrations of cyanide (2 muM) and was very sensitive to inactivation by oxygen. Carbon monoxide dehydrogenase of M. thermoautotrophicum exhibited several characteristic properties found for the enzyme of Clostridium pasteurianum but differed mainly in that the clostridial enzyme did not utilize F(420) as the electron acceptor.

[Atmospheric trace chemicals]

This paper deals with the important trace-materials in the natural and anthropogenetic influenced atmosphere. They exist as gases as well as solid and solid-fluid particles. They are significant for numerous physical processes in the atmosphere and have also a direct influence on our biological environment.