Total Amount Of CO2 Research Articles

Recycling of Remediated Soil for Effective Composting Of Diesel-Contaminated Soil

Soil contaminated with diesel oil was remediated by the addition of remediated soil. Several mix ratios of contaminated soil to remediated soil were tested. Judging from TPH degradation rate and biochemical parameters, the optimum mix ratio (wet weight basis) was 1:1. In this mix ratio, the first order degradation rate constant of diesel oil based on TPH was 0.099/day. Degradation rate of TPH and total amount of CO2 evolved in this condition were two times larger than those of contaminated soil without adding remediated soil. The addition of remediated soil was a very effective treatment option to facilitate the degradation rate of diesel oil in contaminated soil.

Effect of hydrogen addition on the performance of methane-fueled vehicles. Part II: driving cycle simulations

The overall effect of hydrogen addition to methane fuel on the performance of an SI engine is determined for highway and urban driving cycles. Various engine operating schemes are investigated including fixed equivalence ratio and hydrogen fraction with varying load or throttle position (scheme 1), varying equivalence ratio and fixed hydrogen fraction with varying load (scheme 2), and varying equivalence ratio and hydrogen fraction with varying load (scheme 3). Scheme 2 is determined to be the best method of operating the engine with optimum hydrogen volume fractions in the range of approx. 11–31 vol% for the highway cycle and 11–38 vol% for the urban cycle. The optimum values are based on maximizing the total distance covered for a full tank of fuel and minimizing the total amount of CO 2 produced. It is also shown that except for unburned hydrocarbons, emissions of the other pollutants, CO and NO are substantially reduced below values for the base case of pure methane operating at a fixed equivalence ratio of unity.

Hydrogasification of Loy Yang Brown Coal by Ion-Exchanged Nickel Species

The hydrogasification behavior of Loy Yang brown coal with ion-exchanged nickel species was studied. The C1 gas evolution profile was affected by nickel species loaded. The peak of CH4 evolution appeared at 860−1010 K, depending on the amount of exchanged nickel species, became larger with increasing nickel loading. The total amounts of CO evolved were not enhanced by the presence of nickel, however, the maximum temperature shifted to 640−700 K, depending on the amount of exchanged nickel species, comparable to a broader peak at 810 K for an acid washed coal. The CO2 evolution peak at 650 K became slightly greater with nickel loadings, but the peak top temperature did not change. The agglomeration temperatures of the 1.1 wt %-, 6.6 wt %-, and 12.7 wt %-nickel-loaded samples were 700, 620, and 600 K, respectively. Large nickel metal particles catalyzed the CH4 formation from the Loy Yang coal under hydrogen atmosphere.

Temperature-programmed desorption study of water-gas shift and methane steam-reforming reactions over Li/MgO catalyst

The water-gas shift (WGS) and methane steam-reforming (MSR) reactions over 1% Li/MgO catalyst were investigated using thermal-programmed desorption (TPD) technique with isotope labelled compounds (C 16O, H 2 18O, C 16O and CD 4). The experimental results show that WGS reaction over 1% Li/MgO catalyst takes place in the temperature range 400–800 K following a Langmuir–Hinshelwood mechanism. The highest reaction rate was observed at 617 K and the estimated activation energy, from the desorption peak of reaction product, is 158 kJ/mol. The experimental results suggest that the contribution of WGS side reaction to the total amount of CO 2 and H 2, formed in the oxidative coupling of methane (OCM), is important. The MSR reaction between CD 4 and water over Li/MgO catalyst could not be evidenced by TPD method due to the weak adsorption of CD 4. However, a room-temperature isotope exchange between CD 4 and the hydroxyl groups of 1% Li/MgO could be observed.

Inverse modeling of the global CO cycle: 2. Inversion of 13C/12C and 18O/16O isotope ratios

Following a three‐dimensional inverse modeling study on atmospheric CO mixing ratios [Bergamaschi et al., this issue], we present the expansion of our model for the treatment of the stable isotope ratios 13C/12C and 18O/16O in carbon monoxide. The individual isotopomers were included in the model as independent tracers, and the inversion scheme was extended, allowing the simultaneous optimization (with respect to observational data) of modeled atmospheric mixing and isotope ratios. Observational data of 13C/12C and 18O/16O ratios were taken from a set of five globally distributed sites, all of which exhibit pronounced seasonal cycles and which as a whole clearly define large latitudinal gradients. Incorporation of 13C/12C ratios in the inversion resulted in a clear constraining of the total amount of CO arising from CH4 oxidation. The present study suggests an average CO yield of 86% (80–88%), provided that (1) the reaction of CH4+Cl has no significant impact on the δ 13C of the resulting CO and (2) CO from the ocean helps to balance the δ13C in the Southern Hemisphere. Otherwise, a further reduced CO yield would be necessary, as low as 71% in case of an average kinetic isotope effect of 1.013 [Lowe et al., 1999] or 69% in case of a δ13C value of −25.0‰ for the oceanic source. Despite a lack of experimental investigations on 18O/16O in CO arising from CH4 or nonmethanehydrocarbons (NMHC) oxidation, inclusion of 18O/16O into the inversion gives further significant constraints on the global CO cycle. It is shown that apart from the large technological CO source, additional sources with dominant emissions in the Northern Hemisphere are required, such as biogenic emissions (either direct or via oxidation of biogenic NMHCs) or anthropogenic NMHCs, in order to reproduce observed atmospheric 18O/16O ratios. The extended inversion scheme allows CO budgets to be derived, which reproduce, within two standard deviations of observational data, simultaneously CO mixing ratios (from the National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostics Laboratory network), 13C/12C, and 18O/16O ratios. Incorporation of stable isotopes renders inversion results much more robust compared to inversions of CO mixing ratios only.

Short-term influence of tillage on CO 2 fluxes from a semi-arid soil on the Canadian Prairies

The flux of CO 2 from soil determines the extent to which carbon (C) deposited as plant litter is retained in the soil. Retention of soil C is beneficial for soil physical, chemical and biological properties, and is essential if soils are to be used as a repository of C to mitigate atmospheric CO 2 increases. Although tillage is assumed to have a major influence on soil C retention, the extent to which tillage enhances the transfer of soil C to the atmosphere is uncertain. We assessed the short-term (50 h) influence of tillage on CO 2 fluxes from Chernozemic soils under a two-year wheat ( Triticum aestivum L.)-summerfallow rotation in a semi-arid region of the Canadian Prairie. The tillage effect and its persistence were assessed by using a portable CO 2 analyzer to record several temporal series of CO 2 fluxes, along undisturbed and tilled transects, at successive time intervals (from −0.5 to 50 h) after a single pass with a heavy-duty cultivator. Immediately after tillage, CO 2 fluxes along the tilled transects increased from 2 to 4-fold above pre-tillage fluxes, but the increases were short-lived and fluxes along undisturbed and tilled transects were again similar within 24 h of cultivation. Total amounts of CO 2 released by a tillage operation were quantified by: 1. linear interpolations among successive fluxes along tilled and undisturbed transects, and 2. by fitting a model to successive differences between fluxes along the transects. Both methods estimated the amounts of tillage-susceptible CO 2 to be in the range of 3.6–7.2 kg C ha −1. The tillage-induced flush of CO 2 was attributed mainly to enhanced transport of CO 2 already in the soil, but enhanced production of CO 2 by heterotrophic soil organisms also may have contributed to the flush. Regardless of the sources of CO 2 released by single tillage operations, amounts of tillage-susceptible soil C were minor; even 10 passes with a cultivator would account for less than 5% of annual soil CO 2 emissions or crop residue production in these cropping systems. Our study suggested that the short-term influence of tillage on the transfer of soil C to atmospheric CO 2 is small under semi-arid conditions like those in southern Alberta, Canada.

Consecutive adsorption as studied by electrochemical mass spectrometry: Coadsorption, desorption and displacement reactions on platinum

The consecutive adsorption of formic acid, benzene or benzyl alcohol with CO on Pt in acid media was studied by electrochemical mass spectrometry (DEMS). In all experiments, CO 2 is the sole oxidation product detected from the chemisorbates. Using isotopic labelled H 13COOH the contribution of species from formic acid and CO during the electrooxidation of the coadsorbate can be distinguished: the oxidation of the chemisorbates from formic acid is followed by the mass signal m/ z=45 ( 13CO 2) whereas for CO the corresponding mass signal is m/ z=44 ( 12CO 2). It is observed that 35.5% of the residues formed from formic acid are replaced by CO at E ad=0.20 V. The total amount of CO 2 is increased in relation to the individual adsorbates, suggesting that the coadsorbed layer becomes more compact. On the other hand, the adsorption of intact benzene molecules occurs at E ad=0.20 and 0.50 V, and these molecules can be displaced by CO: at E ad=0.20 V benzene is almost completely desorbed whereas at E ad=0.50 V only a small part is displaced and a coadsorbate is formed. For benzyl alcohol, the interaction with CO produces the desorption of benzene and toluene molecules, the extent of this reaction depending on E ad.

Electrooxidation of H 2, CO and H 2/CO mixtures on a well-characterized Pt–Re bulk alloy electrode and comparison with other Pt binary alloys

We report new results for the electrooxidation of H 2, CO and H 2/CO mixtures on a Pt 75Re 25 bulk alloy using surface preparation in a UHV chamber and characterization by X-ray photoelectron spectroscopy (XPS). Sputter-cleaned but not-annealed surfaces having the bulk composition were used. This alloy surface has unique properties for CO electrooxidation: finite current densities below 0.2 V (rhe), a positive reaction order in CO partial pressure of +0.5, but an unusually high slope in the log i vs E curve, about 220 mV per decade. Anodic stripping of the irreversibly adsorbed CO on this surface also occurs at an unusually low potential, initiating at about 0.15 V, but only about 1/3 of the total amount of CO on the surface is oxidized at 0.15–0.4 V, the remainder being oxidized at 0.6–0.8 V. The polarization curves for the oxidation of H 2/CO mixtures containing 0.1–2% CO are, however, very Pt-like. It appears that the low-potential oxidation of both dissolved CO and adsorbed CO on this surface occurs exclusively at Re sites, so that with the H 2/CO mixture the Pt sites remain fully covered (and thus deactivated) by CO ads.

Structure, Composition, and Morphology of Electrodeposited Co0.9Fe0.1 ( Cu ) Alloys

The successful use of the electrochemical process to produce compositional heterogeneous alloys is shown. Structure, composition, and morphology of the heterogeneous alloyed films, produced by the potentiostatic method, has been investigated by means of different techniques. Energy dispersive spectroscopy analyses reveal that the total amount of Co and Fe in the electrodeposits is strongly dependent on the Cu concentration in the plating solution at the potentiodynamic range investigated. The Co:Fe ratio does not change drastically due to Cu incorporation in the electrodeposits. It was also observed that by increasing the Cu content in the electrodeposits a granular morphology is obtained. Transmission electron microscopy was used to characterize the micromorphology and the heterogeneous composition of the alloys. The polycrystalline character of electrodeposits with a predominant face‐centered cubic structure was characterized by using selected area electron diffraction and x‐ray diffraction measurements.

Depletion of carbon monoxide from the nocturnal boundary layer

Measurements of carbon monoxide concentration were made at Bush Estate, Midlothian, Scotland, in May–June 1994. A diurnal pattern in CO concentration was observed, with a decrease in concentration during the night, increase during the early morning, and little change in the late morning and afternoon. The decrease in CO concentration at night was thought to be caused by deposition to the ground, and oxidation of CO by soil microorganisms. This was followed by an increase in the morning caused by mixing air from the free troposphere with that in the nocturnal boundary layer as it broke up, and by the start of photochemically driven CO production. Boundary layer heights and deposition velocities were calculated. The mean deposition velocity was 1.1 × 10 −3 ms −1. This is in reasonable agreement with values obtained by other methods. Appreciable proportions of the total amount of CO in the marine boundary layer were removed when the air had passed over land for approximately 100 km.

TEMPERATURE EFFECTS ON THE DECOMPOSITION OF PAPER MILL SLUDGES IN SOIL

Paper mills produce large amounts of sludge from the treatment of process water during the paper making process. These wastes comprise organic materials that differ significantly from municipal and other industrial wastewater sludges. Land-spreading paper mill wastes may be an acceptable alternative to other methods of disposal. More information is needed about these unique sludges in order to develop appropriate management practices for land-spreading programs. Rates of mineralization are key to understanding the dynamics of these soil-applied materials. A laboratory incubation was carried out to determine C and N mineralization of two contrasting paper mill sludges amended to an agricultural soil. The incubation lasted approximately 33 weeks at 12°C and 25°C, and at relatively constant soil moisture content. The combined sludge (a combination of primary and activated paper mill sludges; 0.8% N) was applied at rates up to 160 g kg -1 soil. The total amount of CO 2 produced was similar at 12°C and 25°C, but the 25°C incubation temperature elicited higher rates early in the incubation. The second treatment (activated sludge; 3.3% N) consisted of application rates up to 90 g kg -1 . C mineralization from this treatment was lower at 12°C than at 25°C, but the general shape of the curves was similar. N mineralization from the combined sludge at 12°C was proportional to rate of sludge application and was approximately linear. However, soil amended with combined sludge incubated at 25°C displayed a pronounced immobilization period during the first 80 days of incubation, followed by a high rate of N remineralization. N mineralization from the secondary sludge treatment revealed generally linear rates at 12°C, accumulating mineral N in approximate proportion to the amount of sludge added. The highest rate of addition resulted in approximately 165 mgN kg -1 released. At 25°C, N mineralized at higher rates than at 12°C and resulted in a higher total N accumulation; the highest sludge treatment contained greater than 220 mg mineral N kg -1 at the end of the incubation period. Differences in decomposition characteristics were attributed partly to substrate quality effects and partly to the influence of N availability on C mineralization in these sludges.

Gasless laparoscopic cholecystectomy

Induction and maintenance of CO2 pneumoperitoneum for laparoscopic cholecystectomy (LC) can have serious effects. Post-operative sequelae are not infrequently seen. [1] To avoid use of CO2 and high intra-abdominal pressure (IAP) we created the surgical view with a mechanical retractor. Twenty-six ASA I–II patients with Ethics Committee approval and informed consent were randomly allocated to one of two groups. Thirteen patients underwent LC with conventional pressure pneumoperitoneum (CPP) (IAP 11–12 mmHg). In 13 patients a retractor was used to elevate the abdominnal wall by 10–15 cm (retractor group). Anaesthesia (propofol, atracurium, alfentanil, desflurane in oxygen in air) and intravascular volume loading were standardized. Endtidal CO2 was kept below 5%. Haemodynamic, respiratory and recovery parameters were assessed and urine output registered. Mean arterial pressure increased in CPP group (P<0.01) during the first 15 min of the insufflation and remained at a higher level throughout the operation (P<0.05) (Fig. 13). In CPP group central venous pressure increased by 146% and remained elevated until 1 h post-operatively (P<0.05). No changes in minute volume of ventilation were required in retractor group. Pulmonary compliance decreased in CPP group (P<0.01) but remained at normal level in retractor group (P<0.001 between the groups). Core temperature decreased by 0.5° in CPP group. Diuresis during the first 30 min of operation was more generous in retractor group than CPP group (1.2 (1.0 SD) mL kg−1 vs. 0.4 (0.7) mL kg−1, P<0.05). In 7 patients in CPP group and in one in retractor group urine output discontinued totally during operation (P<0.05).Fig. 13. (abstract 52).Extubation could be performed earlier in retractor group than in CPP group (P<0.01). End tidal CO2 concentrations were higher after CPP for 30 min post-operatively (P<0.01). In CPP group, the deviation in Maddoxwing recordings from preoperative values was higher for 3 post-operative h (P<0.01) (Fig. 14). There was a positive correlation between the total amount of CO2 used (55 (34) 1), the duration of drowsiness (r=0.61, P<0.01) and the Maddox wing deviation (r=0.62, P<0.001). Post-operative nausea, vomiting (PONV) and right shoulder pain were seen less frequently after the gasless method (P<0.05). Late recovery criteria (ability to drink, void and walk) after the gasless method were fulfilled 7 h earlier than after CPP (P<0.01).Fig. 14. (abstract 52).Gasless LC provides stable peroperative haemodynamic conditions and ventilatory profile with adequate urinary output. Postoperative recovery is also faster with less PONV and right shoulder pain than with conventional CO2 pneumoperitoneum.

Retrievable carbon dioxide in the state of Bahrain

The present study investigates which sources of CO 2 in the state of Bahrain could provide the CO 2 required for the enhanced oil-recovery program proposed by the Bahrain National Oil Company (BANOCO). It is found that the major sources of retrievable CO 2 are the oil refinery plant and the major industries that utilize natural gas for power generation. The average amount of natural gas consumed by those industries is 224 886 million scf/year. More than 85% of this was burnt. Since natural gas is the only energy source for the major industries in Bahrain, the amount of CO 2 produced was estimated from a material balance calculation, except that the amount of CO 2 produced by the refinery was measured experimentally. The total amount of CO 2 produced was about 11 million tonnes/year.

Neuroendocrine response to laparoscopic cholecystectomy with abdominal wall lift or conventional method

Increases in plasma renin activity (PRA) and noradrenaline (NA) concentrations in a response to CO2 insufflation during laparoscopic cholecystectomy (LC) have been measured [1]. We compare conventional CO2-pneumoperitoneum (CPP) to abdominal wall lift method (AWL) [2] for LC with special reference to release of PRA and NA. Twenty-four ASA I-II patients undergoing elective LC with standardized anaesthesia were randomly allocated to two groups. Patients in one group underwent LC with CO2 insufflation to achieve CPP. In the other group the AWL method was used by elevating the abdominal wall 10-15 cm upwards with a Hoffmans trocare necessitating minimal CO2 insufflation for the surgical view. Intra-abdominal pressure (IAP) was continuously measured. Blood samples for PRA and NA were collected from the subclavian vein before and during insufflation. Total amount of CO2 was 42 (±23 SD) L with CPP and 9 (7) L with AWL method (P<0.001). The figures for IAP at 15 min of insufflation were 11 (2) mmHg and 3 (9) mmHg, respectively (P<0.01). In the CPP group, PRA increased from 5.5 (2.1) ng mL−1 to 6.1 (2) ng mL−1 during the first 55 min of LC. In the AWL group, these figures were 5.3 (2.7) ng mL−1 and 3.8 (0.9) ng mL−1 (P<0.01), respectively (Fig. 1). Increase in NA was significant in both groups (P<0.001), but the increase in NA was slightly higher in the CPP group during the first 15 min of insufflation (Fig. 1b).Fig. 1: (abstract 1). Changes in plasma renin activity and noradrenaline concentrations with conventional CO2 pneumoperitoneum (CPP) and abdominal wall lift (AWL).Renal function deteriorates at high IAP [3]. Insufflation of cool CO2 into abdominal cavity may dose dependently cause renal vasoconstriction. Avoiding excessive CO2 insufflation and high IAP with AWL resulted in a smaller PRA response and reduced NA release.

Warm CO2 insufflation for laparoscopic surgery

Laparoscopic surgery has gained wide acceptance for abdominal hernioplasty. We have found problems in urinary output when room temperature CO2 is insufflated. We, therefore, evaluated the consequences of room temperature and warm CO2 insufflation for pneumoperitoneum. Twenty-eight patients undergoing laparoscopic surgery or transabdominal inguinal hernioplasty were randomly allocated to receive either cool (21°C) CO2 (CI group) or warm (37°C) CO2 (WI group) for insufflation (I). After standardized anaesthesia induction pulmonary and radial artery and urinary catheters were inserted. Intravascular volume loading was carried out with Ringer's acetated solution and hydroxyethylstarch. Haemodynamic measurements, pulmonary artery temperature and urine output were recorded perioperatively. If urine excretion did not achieve 1 mL kg−1 15% mannitol 100 mL was administered. The groups were comparable in age, weight, total amount of CO2, volume loading and duration of operation. Haemodynamic changes were similar in the two groups. Eleven patients in the CI group and three in the WI group required mannitol during surgery (P<0.01). At 60 min of insufflation the cumulative diuresis was smaller in the CI group than in the WI group (Table 6). Mean (SD).Table 6: (abstract 17). Effects of cool or warm carbon dioxide insufflation on core temperature, cumulative diuresis and shivering During the recovery room period five patients in the CI group suffered shivering (P<0.05). The central temperature of these patients was 0.6°C lower than that of other patients in the CI group. The difference in the central temperature between the groups was about 0.5°C at the end of insufflation. Although the central temperature did not decrease significantly during surgery the diuresis declined in the majority of the patients in the CI group. This may be due to renal vasoconstriction associated with cool intra-abdominal CO2. Vasopressin is activated during cool insufflation [1]. This may be deleterious for patients with compromised renal function.

Analysis of Kerr rotation from Cu/Co, Pd/Co, and Pt/Co superlattices

Numerical simulations of the Kerr signals from Cu/Co, Pd/Co, and Pt/Co superlattices show, in general, a scaling of the signal with the amount of Co in the superlattice. Experimentally, however, the signal from Pt/Co superlattices at ∼4 eV is larger than that from bulk Co, despite the lesser total amount of Co. This is due to the magnetization induced in the Pt by the Co. Comparison of the Pd/Co and Pt/Co results with experiment indicates that the magnetization induced in the Pt by the Co plays a more important role in the magneto-optic activity than does the induced magnetization of Pd.

Cost and performance of CO 2 storage in forestry projects

In order to include forestry projects in a possible CO 2 emission reduction regime, and to compare the costs of individual projects or national programs, it is necessary to determine the rate of equivalency between carbon in fossil fuel emissions and carbon stored in different types of forestry projects. This paper presents a comprehensive and consistent methodology to account for the costs and carbon flows of different categories of forestry projects and describes the application of the methodology to a set of projects in Central America. Several estimates have been made to date of the overall potential for carbon storage through global reforestation and the costs of such efforts, based on global macroeconomic estimates and extrapolations from current forest-sector experience. However, there has yet to be a consistent analysis of the magnitude and cost of carbon savings by a “bottom-up” approach to sustainable forestry development This methodology is applied to a set of projects proposed in Costa Rica and other Central American countries under the Tropical Forest Action Plan, to estimate a sample set of national CO 2 reduction cost curves. The costs of carbon savings in the forestry projects studied in Central America mostly fall between $5 and $13 ton-C 1, depending on the type of project, the climate, and the opportunity cost of land. These projects also promise socio-economic benefits at the local level, provided they are adequately endowed with funding, training and institutional support. The total amount of CO 2 storage potential is significant, about 100 million tons per country, but not enough to suggest that forestry can offset more than a few percent of global CO 2 emissions from fossil fuel use.

Photosynthetic metabolism of an antarctic diatom and its physiological responses to fluctuations in light

The short-term incorporation of NaH14CO3 (10 to 60 s) into photosynthetic products has been studied in the antarctic diatom Nitzschia turgiduloides. It appears that there are two pathways of inorganic carbon assimilation: the C3 pathway (Calvin cycle) principally, on which are superimposed β-carboxylation reactions. Photorespiration, which contributes to decrease the net photosynthesis rate, has also been reported. With regard to these results the antarctic diatom was not different from the temperate one. However, the antarctic diatom presents some distinctive features. β-carboxylation reactions which are probably favoured in Antarctic waters because of the high nitrate or ammonium concentrations, and also because they are more economical in terms of energy, are enhanced at the expense of the Calvin cycle reactions. On the other hand, the photorespiration rate is lower than that observed in temperate species, leading to an enhancement of net photosynthesis rate; this seems to occur principally by the more advantageous tartronic semialdehyde pathway. These two features are more pronounced for cells grown under light: dark cycles, particularly a 2:2 hour regime, as compared to continuous light. By contrast to the temperate species Skeletonema costatum, changes in the light regime modifies not only the relative amount of inorganic carbon assimilated by the C3 or the β-carboxylation pathways, but also the total amount of CO2 incorporated per μg Chl a. The productivity is highest in 2:2 regime, which simulates conditions of vertical mixing encountered in Antarctic Ocean more than does a 12:12 regime. This finding corroborates the view that the antarctic diatom is well adapted to its environment, although its production is not optimal compared to that of the temperate species grown under the same conditions of irradiance and temperature. Whether this is a genetic adaptation needs to be examined.

Soil respiration in conventional and no-tillage agroecosystems under different winter cover crop rotations

Carbon-dioxide efflux from conventional (CT) and no-tillage (NT) soils under winter ryegrain sorghum and crimson clover-grain sorghum rotations was measured for two consecutive cropping seasons using a static-absorption technique. Overall, CO 2 output was significantly higher from NT than from CT soils, and from soils cropped to clover than from those cropped to rye. During the cool season, soil respiration was similar in NT and CT soils, and in an adjacent forest and old field. Carbon dioxide production ranged from 5 to 50 g CO 2 m −2 day −1 over the 17 months of observation. Pulses of CO 2 production were observed, following mowing of the winter crops, in both CT and NT. Plowing did not stimulate CO 2 production in CT as was expected, but annual CO 2 production in these systems may have been underestimated. Tillage appeared to affect the timing rather than the total amount of CO 2 production. Linear regressions showed strong relationships between temperature and respiration in both CT ( r = 0.88) and NT ( r = 0.80) soils but not between soil moisture and respiration. However, soil moisture was significantly related to the contribution of surface residue to total respiration in NT ( r = 0.80), suggesting that wetting and drying cycles may be more important to the decomposition of residues in NT than in CT.

Radiotracer studies of chemisorption on copper-based catalysts. Part 2.—Adsorption of carbon monoxide, carbon dioxide and dihydrogen on partially and fully oxidised copper–zinc oxide–alumina catalysts

The adsorption of 14CO and 14CO2 at 293 K, on the surface of a copper–zinc oxide–alumina catalyst, which had been partially (30%) or completely oxidised by reaction with N2O at 353 K, is reported. The reactive adsorption technique for H2 at 293 K on a fully oxidised Cu–ZnO–Al2O3 catalyst and of CO2 at 503 K on a hydrogen-reduced Cu–ZnO–Al2O3 catalyst is also reported. Adsorption of hydrogen on a 100% oxidised surface occurs at 293 K to give a surface stoichiometry of 2 Cus : 1 Hads : 1 Hads : 1Oads, although no water is desorbed below 373 K. At low coverages of surface oxygen, the amount of CO2 adsorbed and retained as a strongly bound species on the copper component is increased compared with the corresponding values on a freshly reduced surface. Adsorption of CO2 at 293 K on oxidised surfaces in the presence of H2 results in a further enhancement in both the amounts adsorbed and retained on the copper component. Little adsorption of CO2 occurs on fully oxidised surfaces. Admission of CO to partially or fully oxidised surfaces, both in the presence and absence of hydrogen, results in the formation of CO2, which is subsequently adsorbed on the surface. Whilst the presence of H2 reduces the total amount of CO adsorbed, the amount of strongly adsorbed CO is significantly increased. The results are interpreted in terms of the formation of OHads by reaction of hydrogen with preadsorbed oxygen and formation of a surface formate species by interaction of either CO2 or CO with the OHads.