Ppmv CO2 Research Articles

Studies of breakeven prices and electricity supply potentials of nuclear fusion by a long-term world energy and environment model

In response to social demand, this paper investigates the breakeven price (BP) and potential electricity supply of nuclear fusion energy in the 21st century by means of a world energy and environment model. We set the following objectives in this paper: (i) to reveal the economics of the introduction conditions of nuclear fusion; (ii) to know when tokamak-type nuclear fusion reactors are expected to be introduced cost-effectively into future energy systems; (iii) to estimate the share in 2100 of electricity produced by the presently designed reactors that could be economically selected in the year. The model can give in detail the energy and environment technologies and price-induced energy saving, and can illustrate optimal energy supply structures by minimizing the costs of total discounted energy systems at a discount rate of 5%. The following parameters of nuclear fusion were considered: cost of electricity (COE) in the nuclear fusion introduction year, annual COE reduction rates, regional introduction year, and regional nuclear fusion capacity projection. The investigations are carried out for three nuclear fusion projections one of which includes tritium breeding constraints, four future CO2 concentration constraints, and technological assumptions on fossil fuels, nuclear fission, CO2 sequestration, and anonymous innovative technologies. It is concluded that: (1) the BPs are from 65 to 125 mill kW−1 h−1 depending on the introduction year of nuclear fusion under the 550 ppmv CO2 concentration constraints; those of a business-as-usual (BAU) case are from 51 to 68 mill kW−1h−1. Uncertainties resulting from the CO2 concentration constraints and the technological options influenced the BPs by plus/minus some 10–30 mill kW−1h−1, (2) tokamak-type nuclear fusion reactors (as presently designed, with a COE range around 70–130 mill kW−1h−1) would be favourably introduced into energy systems after 2060 based on the economic criteria under the 450 and 550 ppmv CO2 concentration constraint, but not selected under the BAU case and 650 ppmv CO2 concentration constraint, and (3) the share of electricity in 2100 produced by the presently designed tokamak-type nuclear fusion reactors (introduced after 2060) is well below 30%. It should be noted that these conclusions are based upon varieties of uncertainties in scenarios and data assumptions on nuclear fusion as well as technological options.

Nitrogen dynamics in paddy field as influenced by free-air CO2 enrichment (FACE) at three levels of nitrogen fertilization

As part of a FACE (free-air CO2 enrichment) experiment in a rice paddy field in Shizukuishi (Iwate Prefecture, Japan), studies were conducted to determine the effects of elevated CO2 on N dynamics at three levels of N application. Rice plants were grown under ambient CO2 or ambient + 200 ppmV CO2 conditions throughout the growing season in an Andosol soil with each treatment having 4 replicated plots. Three levels of N fertilizer (high, standard and low; 15, 9 and 4 gN m−2, respectively) were applied to examine different N availability under both CO2 conditions. Soil samples were collected at 4 different times from upper and lower soil layers (0–1 cm and 1–10 cm soil depths, respectively) and analyzed for microbial biomass N (BN), mineralizable N (Min. N) and NH4+-N in soil. Plant sampling was also done at 3 different times during the growing season to determine the N uptake by plant. Elevated CO2 significantly increased BN and Min. N in the upper soil layer at harvest by 25–42% and 18–24%, respectively, compared to ambient CO2, regardless of N application rate. In low N soil, these significant increases were also observed at the ripening stage. In addition, elevated CO2 only significantly increased the NH4+-N in the upper soil layer at harvest in low N soil compared to ambient CO2. The N uptake was not significantly affected by CO2 treatment. These results indicate that elevated CO2 had significant positive influence on BN and Min. N in the upper soil layer in paddy soil at the later period of the cropping season at all levels of N application rates, but only at low levels of application rate on NH4+-N.

Effect of free-air CO2 enrichment (FACE) on microbial biomass in paddy field soil

To determine the effect of free-air CO2 enrichment (FACE)on microbial biomass in paddy soil, a field experiment was conducted in an Andosol field in Shizukuishi (Iwate Prefecture, Japan). Rice plants were grown under ambient CO2 or FACE (ambient +200 ppmv CO2 ) during the growing season in 1998 and 1999. Soil samples were collected at 5 different times from the upper (0–1 cm) and lower (1–10 cm) layers and analyzed for the amounts of microbial biomass C (B c) and N (B N) and mineralizable N (Min. N). The amount of chlorophylltype compounds (ChIs), an index of algal growth, in the upper soil layers was also measured. During the first growing season (1998), FACE treatment did not cause any significant difference in the above-measured parameters except for B C at harvest, compared to the ambient CO2 treatment. However in 1999, FACE caused a significant increase in the amounts of B N, Min. N, and ChIs in the upper soil layers at harvest, compared to ambient CO2. Furthermore, FACE significantly increased the amount of Be in both soil layers, from mid-plant growth until harvest. From early plant growth until harvest, the upper soil layers subjected to both FACE and ambient CO2 treatments exhibited significantly higher values for B C, B N and Min. N than those in the lower soil layers. The amount of ChIs in the FACE treatment increased compared to that in the ambient CO2 treatment, especially at harvest. These findings suggest that FACE exerted a positively significant effect on the amounts of B C and B N, Min. N, and ChIs in paddy soil, particularly in the surface soil layers.

High‐obliquity simulations for the Archean Earth: Implications for climatic conditions on early Mars

Global climate model simulations using high‐obliquity (70°), higher CO2 and CH4 but reduced O3 concentrations produce warm climate conditions for Archean boundary conditions (reduced solar forcing). Solar radiation under high‐obliquity is distribution in such a way as to warm high latitudes and cool low‐latitudes. Global mean air temperatures of approximately 280°K are found with a 25% reduction in the solar forcing, 4760 ppmv CO2 and 25 ppmv CH4. High‐obliquity could also explain why polar oceans on Mars may have occurred in its history. A substantial increase in the amount of insolation is accounted for if Mars had an obliquity of 70°.

Effects of doubled atmospheric CO2 concentration on the growth and photosynthesis of Chlamydomonas reinhardtii (Volvocales, Chlorophyceae)

SUMMARY The freshwater microalga, Chlamydomonas reinhardtii Dangeard, was cultured under 350 and 700 ppmv CO2 to determine the impact of doubled atmospheric CO2 concentration on its growth and photosynthesis. No significant difference was observed in the specific growth rate, photosynthetic efficiency, maximal net photosynthetic rate and light-saturating point between the low and high CO2 cultures. Both the low- and highCO2-grown cells showed reduced light-dependent O2 evolution rate and photochemical efficiency (Fv/Fm) owing to photoinhibition when exposed to high photon flux density. However, high-CO2-grown cells were less photoinhibited, and showed better recovery in dim light or darkness during the initial period of the recovery process.

CO 2-scrubbing and methanation as purification system for PEFC

Hydrogen is usually produced by steam reforming of natural gas in large-scale processes. The reformate consists of hydrogen, carbon dioxide, carbon monoxide, and residues of hydrocarbons. Since the anode catalyst of a polymer electrolyte membrane fuel cell (PEFC) is usually based on platinum, which is easily poisoned by carbon monoxide, the conditioned feed gas should contain less than 100 ppmv CO, and preferably, less than 10 ppmv. Depending on the design and operating conditions of the hydrogen production process, the CO content of a typical reformate gas, even after the CO shift reactor may be in the range of 0.2–1.0 vol.%; this is far higher than a PEFC can tolerate. A CO management system is required to lower the CO concentration to acceptable levels. In many cases, the CO purification system consists of a combination of physical or chemical processes to achieve the necessary reduction in CO content. A promising alternative for hydrogen purification is a combined process consisting of a carbon dioxide scrubber with subsequent methanation to reduce the carbon monoxide content to an acceptable level of less than 10 ppmv.

Nectar Production and Floral Characteristics of Tropaeolum majus L. Grown in Ambient and Elevated Carbon Dioxide

Tropaeolum majus (nasturtiums) were grown from seed in growth cabinets, under 380 and 750 ppmv CO2. Elevated CO2significantly increased nectar secretion rate, both in flowers milked of nectar daily and in once sampled, 3-d-old flowers. Elevated CO2did not affect time to flowering, total number of flowers produced, pollen to ovule ratio, or the total or individual concentrations of nectar amino acids. The dry weight and longevity of individual flowers was also unchanged. Nectar sugar content was unchanged by elevated CO2in a subset of flowers used to assess the 3-d-old nectar volume. This subset did not show the same increase in nectar volume under elevated CO2as the full set, resulting in the concentration of sugars remaining unchanged. Overall, the quantity rather than the quality of the nectar changed under elevated CO2while flower characteristics remained constant, implying that the identity of pollinators may remain the same while foraging behaviour (e.g. number of visits per plant, distance travelled) may change in the future.

Fuel cell operation on landfill gas at Penrose Power Station

This demonstration test successfully demonstrated the operation of a commercial phosphoric acid fuel cell (FC) on landfill gas (LG) at the Penrose Power Station in Sun Valley, CA. Demonstration output included operation up to 137 kW; 37.1% efficiency at 120 kW; exceptionally low secondary emissions (dry gas, 15% O 2) of 0.77 ppmV CO, 0.12 ppmV NO x , and undetectable SO 2; no forced outages with an adjusted availability of 98.5%; and a total of 707 h of operation on LG. The LG pretreatment unit (GPU) operated for a total of 2297 h, including the 707 h with the FC, and documented total sulfur and halide removal to much lower than the specified <3 ppmV for the FC. The GPU flare safely disposed of the removed LG contaminants by achieving destruction efficiencies greater than 99%.

Effects of increased CO2 and N on CH4 efflux from a boreal mire: a growth chamber experiment.

Increases in the supply of atmospheric CO2 and N are expected to alter the carbon cycle, including CH4 emissions, in boreal peatlands. These effects were studied in a glasshouse experiment with peat monoliths cored from an oligotrophic pine fen. The cores with living plants were kept in 720 ppmv and 360 ppmv CO2 atmospheres for about 6 months under imitated natural temperature cycle. Fertilisation with NH4NO3 (3 g m-2 for 25 weeks) was applied to 18 of the 36 monoliths. The rate of CH4 flux was non-linearly dependent on the number of Eriophorum vaginatum shoots growing in the monoliths, probably due to the gas transport properties of the aerenchyma. The average CH4 efflux rate, standardised by the number of shoots, was increased by a maximum of 10-20% in response to the raised CO2 level. In the raised-NH4NO3 treatment, the increase in CH4 release was lower. The effect of combined CO2+NH4NO3 on CH4 release was negligible and even lower than in the single treatments. Both potential CH4 production and oxidation rates at 5, 15 and 25°C were higher near the surface than at the bottom of the core. As expected, the rates clearly depended on the incubation temperature, but the different treatments did not cause any consistent differences in either CH4 production or oxidation. The determination of potential CH4 production and oxidation in the laboratory is evidently too crude a method of differentiating substrate-induced differences in CH4 production and oxidation in vivo. These results indicate that an increase in atmospheric CO2 or N supply alone, at least in the short term, slightly enhances CH4 effluxes from boreal peatlands; but together their effect may even be restrictive.

Can a strong atmospheric CO2 rectifier effect be reconciled with a “reasonable” carbon budget?

Atmospheric CO2 accumulates near the Earth’s surface because of relatively deeper vertical mixing when photosynthesis is active than when it is not. Some models simulate an excess of more than 2.5 ppmv CO2 in the remote Northern Hemisphere due to this “rectification” of an annually balanced terrestrial carbon cycle. The covariance between CO2 flux and vertical mixing, and the resulting vertical structure of CO2 are generally consistent with field data at local scales, but it is difficult to reconcile such a strong rectifier signal with current ideas about the global carbon budget. A rectifier effect of 2.5 ppmv at northern flask sampling stations implies an unreasonably strong northern sink of atmospheric CO2, and a corresponding source in the tropics or Southern Hemisphere.

Linking a global terrestrial biogeochemical model and a 2-dimensional climate model: implications for the global carbon budget

We used the terrestrial ecosystem model (TEM, version 4.0) to estimate global responses of annual net primary production (NPP) and total carbon storage to changes in climate and atmospheric CO2, driven by the climate outputs from the 2-dimensional MIT L-O climate model and the 3-dimensional GISS and GFDL-q atmospheric general circulation models (GCMs). For contemporary climate with 315 ppmv CO2, TEM estimates that global NPP is 47.9 PgC/yr and global total carbon storage is 1658 PgC: 908 PgC of vegetation carbon and 750 PgC of reactive soil organic carbon. For climate change associated with a doubling of radiative forcing and an atmospheric level of 522 ppmv CO2, the responses of global NPP are + 17.8% for the MIT L-O climate, + 18.5% for the GFDL-q climate and + 20.6% for the GISS climate. The responses of global total carbon storage are + 6.9% for the MIT L-O climate, + 8.3% for GFDL-q climate and + 8.7% for the GISS climate. Among the three climate change predictions, the changes in latitudinal distributions of cumulative NPP and total carbon storage along 0.5° latitudinal bands vary slightly, except in high latitudes. There are generally minor differences in cumulative NPP and total carbon storage for most of the 18 biomes, except for the responses of total carbon storage in boreal biomes for the 2-D MIT L-O climate change. The results demonstrate that the linkage between the TEM and the 2-D climate model is useful for impact assessment and uncertainty analysis within an integrated assessment framework at the scales of the globe, economic regions and biomes, given the compromise between computational efficiency in the 2-D climate model and more detailed spatial representation of climate fields in 3-D GCMs.

CO2Effects on Phasic Development, Leaf Number and Rate of Leaf Appearance in Wheat

It has been predicted that the concentration of CO 2 in the air could double during the 21st century. Though it is recognized that CO 2 -doubling could increase yield through its effects on plant photosynthesis and stomatal behaviour, it is unclear whether CO 2 -doubling will change phasic development in wheat. A phytotron study was conducted with two contrasting cultivars of wheat, Condor (spring) and Cappelle Desprez (winter), to determine whether development is affected by a season-long exposure to 360 and 720 ppmv CO 2 . Plants were vernalized for 50 d (8/4 °C, 8 h photoperiod) before their exposure to the CO 2 treatments. There were significant differences between cultivars in the duration of different phenophases as well as in the final number of leaves. However, CO 2 concentration had no effect in either cultivar on the duration of the early developmental phase to terminal spikelet initiation, or on the final number of leaves, though CO 2 -doubling did slightly increase the later phase from terminal spikelet initiation to heading in Cappelle Desprez. Condor and Cappelle Desprez also differed markedly in the dynamics of leaf appearance. While the former had a constant rate of leaf appearance throughout development, the latter had a fast rate initially (between leaves 1 and 7), similar to that of Condor, which was followed by a slower rate after the appearance of leaf 7. Overall, CO 2 -doubling did not significantly affect the rates of leaf appearance nor the shape of the relationship. Phyllochron for the first seven leaves was the same for both CO 2 concentrations. However, the change in phyllochron associated with CO 2 -doubling for leaves 7–12 in Cappelle Desprez, although quite small (4%), accounts for part of the slightly increased duration of the phase from terminal spikelet initiation to heading under high CO 2 concentration in that cultivar. We conclude that CO 2 concentration does not influence development in wheat to a degree relevant to agronomy.

Simulation of the effect of doubled atmospheric CO2 on the climate of northern and central California

A Local Climate Model (LCM) is described that can provide a high-resolution (10 km) simulation of climate resulting from a doubling of atmospheric CO2 concentrations. A canonicalregression function is used to compute the monthly temperature (mean of daily-maximum-temperature) and precipitation for any point, given a set of predictor variables. Predictor variables represent the influence of terrain, sea-surface temperature (SST), windfields, CO2 concentration, and solar radiation on climate. The canonical-regression function is calibrated and validated using empirical windfield, SST, and climate data from stations in the western U.S. To illustrate an application of the LCM, the climate of northern and central California is simulated for a doubled CO2 (600 ppmv) and a control scenario (300 ppmv CO2). Windfields and SSTs used to compute predictor variables are taken from general circulation model simulations for these two scenarios. LCM solutions indicate that doubling CO2 will result in a 3 C° increase in January temperature, a 2 C° increase in July temperature, a 16 mm (37%) increase in January precipitation, and a 3 mm (46%) increase in July precipitation.

Interactive effects of mycorrhization and elevated carbon dioxide on growth of young pedunculate oak (Quercus robur L.) trees

Pedunculate oak (Quercus robur L.) was germinated and grown at ambient CO2 level and 650 ppmv CO2 in the presence and absence of the ectomycorrhizal fungus Laccaria laccata for a total of 6 month under nutrient non-limiting conditions. Mycorrhization and elevated atmospheric CO2 each supported the growth of the trees. Stem height, stem diameter, and dry matter accumulation of pedunculate oak were increased by mycorrhization. Elevated atmospheric CO2 enhanced stem height, stem diameter, fresh weight and dry weight, as well as lateral root formation of the trees. In combination, mycorrhization and elevated atmospheric CO2 had a more than additive, positive effect on tree height and biomass accumulation, and further improved lateral root formation of the trees. From these findings it is suggested that the efficiency of the roots in supporting the growth of the shoot is increased in mycorrhized oak trees at elevated atmospheric CO2.

Possible effects of CO2 increase on the high‐speed civil transport impact on ozone

The role of heterogeneous chemistry on the potential impact on ozone of a commercial fleet of high speed civil transport aircraft (HSCT) has been recently studied with assessment models. Here an attempt is made to model the effects of the carbon dioxide increase which is predicted in the future atmosphere when HSCT should be operational. For this purpose we have first used a three‐dimensional model for the radiative and dynamical calculations and then a photochemical two‐dimensional model including an explicit gas‐particle interaction in the process of aerosol formation. The denoxification and denitrification associated with the formation of nitric acid trihydrate (NAT) aerosols is shown to significantly affect the partition of chemical families. The radiative perturbation introduced by the CO2 increase is shown to perturb the stratospheric dynamics in such a way that the lower stratospheric residual circulation is enhanced. This has the effect of reducing by about 15% the stratospheric residence time of odd nitrogen injected by the aircraft, so that the overall perturbation of stratospheric chemistry due to HSCT is mitigated with respect to the reference case in which CO2 is kept at the present level. Another effect is found to be produced by the stratospheric temperature cooling following the CO2 increase. Our model predicts a large enhancement of the surface area density of NAT aerosols in the arctic region, so that the additional denitrification produces a further decrease of the relative role of the NOx catalytic cycle for ozone destruction in the lower stratosphere. For this reason, the ClO and OH decreases associated with the HSCT‐induced NOx increase are found to be dominant in the ozone budget, thus producing a global ozone increase in the case of 500 ppmv CO2 (+0.27% for mach 2.4 and NOx emission index 15). The balance between the different tendencies of ClO, NOx, and OH cycles is found to be closer in the reference case of 335 ppmv CO2, where a small column ozone depletion by HSCT is predicted (−0.53% globally).

Productivity response of climax temperate forests to elevated temperature and carbon dioxide: a north american comparison between two global models

We assess the appropriateness of using regression- and process-based approaches for predicting biogeochemical responses of ecosystems to global change. We applied a regression-based model, the Osnabruck Model (OBM), and a process-based model, the Terrestrial Ecosystem Model (TEM), to the historical range of temperate forests in North America in a factorial experiment with three levels of temperature (+0 °C, +2 °C, and +5 °C) and two levels of CO2 (350 ppmv and 700 ppmv) at a spatial resolution of 0.5° latitude by 0.5° longitude. For contemporary climate (+0 °C, 350 ppmv), OBM and TEM estimate the total net primary productivity (NPP) for temperate forests in North America to be 2.250 and 2.602 × 1015 g C ⋅ yr−1, respectively. Although the continental predictions for contemporary climate are similar, the responses of NPP to altered climates qualitatively differ; at +0 °C and 700 ppmv CO2, OBM and TEM predict median increases in NPP of 12.5% and 2.5%, respectively. The response of NPP to elevated temperature agrees most between the models in northern areas of moist temperate forest, but disagrees in southern areas and in regions of dry temperate forest. In all regions, the response to CO2 is qualitatively different between the models. These differences occur, in part, because TEM includes known feedbacks between temperature and ecosystem processes that affect N availability, photosynthesis, respiration, and soil moisture. Also, it may not be appropriate to extrapolate regression-based models for climatic conditions that are not now experienced by ecosystems. The results of this study suggest that the process-based approach is able to progress beyond the limitations of the regression-based approach for predicting biogeochemical responses to global change.

The Effects of Elevated Atmospheric Carbon Dioxide and Water Stress on Ligth Interception, Dry Matter Production and Yield in Stands of Groundnut (Arachis hypogaeaL.

Stands of groundnut (Arachis hypogaea L.), a C3 legume, were grown in controlled-environment glasshouses at 28 °C (±5°C) under two levels of atmospheric CO2 (350 ppmv or 700 ppmv) and two levels of soil moisture (irrigated weekly or no water from 35 d after sowing). Elevated CO2 increased the maximum rate of net photosynthesis by up to 40%, with an increase in conversion coefficient for intercepted radiation of 30% (from 1–66 to 2–16 g MJ−1) in well-irrigated conditions, and 94% (from 0–64 to 1·24 g MJ−1) on a drying soil profile. In plants well supplied with water, elevated CO2 increased dry matter accumulation by 16% (from 13·79 to 16·03 t −1 ) and pod yield by 25% (from 2·7 to 3·4t ha−1). However, the harvest index (total poddry weight/above-ground dry weight) was unaffected by CO2 treatment. The beneficial effects of elevated CO2 were enhanced under severe water stress, dry matter production increased by 112% (from 4·13 to 8·87 t ha−1) and a pod yield of 1·34t ha−1 was obtained in elevated CO2, whereas comparable plotsat 350 ppmv CO2 only yielded 0·22 t ha-1. There was a corresponding decrease in harvest index from 0·15 to 0·05. Following the withholding of irrigation, plants growing on a stored soil water profile in elevated CO2 could maintain significantly less negative leaf water potentials (P<0·01) for the remainder of the season than comparable plants grown in ambient CO2, allowing prolonged plant activity during drought. In plants which were well supplied with water, allocation of dry matter between leaves, stems, roots, and pods was similar in both CO2 treatments. On a drying soil profile, allocation in plants grown in 350 ppmv CO2 changed in favour of root development far earlier in the season than plants grown at 700 ppmv CO2, indicating that severe waterstress was reached earlier at 350 ppmv CO2. The primary effects of elevated CO2 on growth and yield of groundnut stands weremediated by an increase in the conversion coefficient for intercepted radiation and the prolonged maintenance of higher leaf water potentials during increasing drought stress.

Reduction of nitric oxide to elemental nitrogen byThiobacillus Denitrificans

A need exists for new technology for the disposal of concentrated NOx streams obtained from certain regenerable, dry scrubbing processes, such as the NOXSO process, and the removal and disposal of NOx from more dilute gas streams produced by nitric acid plants. It has been demonstrated that the facultative anaerobe and autotroph, Thiobacillus denitrificans, may be cultured anaerobically in batch reactors using NO (g) as a terminal electron acceptor. Thiosulfate served as an energy source, CO2 (g) as a carbon source, and ammonium ion as a source of reduced nitrogen. The growth of T.denitrificans was indicated by depletion of thiosulfate and ammonium ion and the accumulation of biomass. The feed gas consisted of 5000 ppmv NO, 5%, CO2, and balance nitrogen. The NO concentration in the outlet gas was typically 200 ppmv.

Optimizing energy transition paths in CO 2 emission reduction strategies

In the consideration of energy use scenarios designed to avoid excessive build-up of atmospheric carbon dioxide and the effects of the associated climatic changes it can be anticipated that difficulties will ensue if needed rates of increased deployment of non-fossil fuel burning energy plants become very large. This may result if allowable maximum CO 2 concentrations are set sufficiently low, or if acceleration of non-fossil fuel energy use is sufficiently delayed. In a broad ranging numerical investigation of this problem, Perry et al. 1 have suggested that difficulty will be experienced in the transition to a non-fossil based economy, not only if the rate of growth of non-fossil fuel energy use rate, E ̇ N is excessive, but also if the second derivative, E ̈ N , becomes too large. This observation has important ramifications, since E ̈ N may exceed tolerable limits, whilst E ̇ N still remain modest in size. In making the estimates an empirical method for joining early and asymptotic energy use rates was employed. In order to make sure that the conclusions reached were not sensitive to the ad hoc nature of this technique, we have introduced a more rigorous approach by using a variational interpolation approach that minimizes the peak value of E ̈ N (or a combination of E ̈ N and E ̈ N . E ̇ N We find that such an optimization procedure can reduce the maximum values of E ̈ N by as much as 50% from those calculated by Perry et al. This indicates that the energy transition process should be easier that concluded by them, at least as far as a criterion based upon E ̈ N variation is concerned, but can still create difficulties, especially if a 500 ppmv CO 2 ceiling is considered hazardous and if actions to reduce fossil fuel use are delayed too long.

Utilization of traces of carbon monoxide by aerobic oligotrophic microorganisms in ocean, lake and soil

Carbon monoxide at trace concentrations (≦1 nM) was utilized in ocean water, lake water and soil. By boiling or by poisoning the water with HgCl2, NaCN or NaN3 must read CO consumption was switched off; this demonstrated that CO utilization was due to metabolic processes. Since CO consumption activity was removed by filtration through 0.2 μm filters, but not by filtration through 3.0 μm filters, CO consumption was most probably due to single bacterial cells. CO consumption followed Michaelis-Menten kinetics withKm-values of 7–9 nM CO. Enrichment experiments were carried out by gassing lake water and soil suspensions with ambient pressurized air containing 0.5–1.0 ppmv CO. After a total supply of approximately 2 ml CO, utilization of CO became detectable. Then, the CO consumption rates of the suspensions increased steadily with incubation time indicating the growth of a specific CO-utilizing microbial population. No CO consumption activity was detectable in control suspensions, which were gassed with CO-free air. The high affinity of soil and water for CO as well as the increase of CO consumption activity upon incubation under ambient atmospheric CO is indicative for the oligotrophic nature of a specific CO-utilizing microflora.