Decomposition of toluene in a steady-state atmospheric-pressure glow discharge

Results are presented from experimental studies of decomposition of toluene (C₆H₅CH₃) in a polluted air flow by means of a steady-state atmospheric pressure glow discharge at different water vapor contents in the working gas. The experimental results on the degree of C₆H₅CH₃ removal are compared with the results of computer simulations conducted in the framework of the developed kinetic model of plasma chemical decomposition of toluene in the N₂: O₂: H₂O gas mixture. A substantial influence of the gas flow humidity on toluene decomposition in the atmospheric pressure glow discharge is demonstrated. The main mechanisms of the influence of humidity on C₆H₅CH₃ decomposition are determined. The existence of two stages in the process of toluene removal, which differ in their duration and the intensity of plasma chemical decomposition of C₆H₅CH₃ is established. Based on the results of computer simulations, the composition of the products of plasma chemical reactions at the output of the reactor is analyzed as a function of the specific energy deposition and gas flow humidity. The existence of a catalytic cycle in which hydroxyl radical OH acts a catalyst and which substantially accelerates the recombination of oxygen atoms and suppression of ozone generation when the plasma-forming gas contains water vapor is established.     

Effect of cadmium on the distribution of hydroxyl radical, superoxide and hydrogen peroxide in barley root tip

In the present study, we investigated the alteration of reactive oxygen species production along the longitudinal axis of barley root tips during Cd treatment. In unstressed barley root tips, H₂O₂ production decreased from the root apex towards the differentiation zone where again, a slight increase was observed towards the more mature region of root. An opposite pattern was observed for O ₂ ^?? and OH^? generation. The amount of both O ₂ ^?? and OH^? was highest in the elongation zone, decreased in the root apex and at the differentiation zone of root, then increased again towards the more mature region of root. An elevated Cd-induced O ₂ ^?? production started in the elongation zone and increased further along the differentiation zone of barley root tip. In contrast, Cd-induced H₂O₂ production was localised to the root elongation zone and to the beginning of the differentiation zone. In contrast to Cd-induced H₂O₂ and O ₂ ^?? production, Cd reduced OH^? production along the whole barley root tip. Our results suggest that not only an increase but also the spatial distribution of reactive oxygen species production is involved in the Cd-induced stress response of barley root tip.     

Discharge dynamics and the production of active particles in a cathode-directed streamer

The emission spectroscopy technique is used to analyze a cathode-directed streamer discharge in air at atmospheric pressure in point-plane geometry at interelectrode distances of up to 100 mm and a high-voltage pulse amplitude of 18 kV. The densities of molecules in the N₂(C ³Π_u, v=0), N ₂ ⁺ (B ²Σ _u ⁺ , v=0) and NO(A ²Σ⁺, v=0) states are determined, and the reduced electric field in the streamer head is estimated. It is shown that the increase in the average electric field in the discharge gap substantially intensifies the production of active particles in the discharge plasma and makes the plasma more homogeneous. This effect is only related to the increase in the fraction of regions with a high electric field in the discharge gap and, as a result, the reduction of the discharge energy losses via rapidly thermalized degrees of freedom. The active particles are only produced in the streamer head, including the case in which the interelectrode gap is bridged by the streamer channel.     

Ionic balance,proton efflux,nitrate reductase activity and growth ofHippophaë rhamnoides L. ssp.rhamnoides as influenced by combined-N nutrition or N2 fixation

Growth of 2-month-old nonnodulatedHippophaë rhamnoides seedlings supplied with combined N was compared with that of nodulated seedlings grown on zero N. Plant growth was significantly better with combined N than with N₂ fixation and, although not statistically significant for individual harvests, tended to be highest in the presence of NH ₄ ⁺ , a mixture of NH ₄ ⁺ and NO ₃ ^? producing the highest yields. Growth was severely reduced when solely dependent on N₂ fixation and, unlike the combined-N plants, shoot to root ratios had only slightly increased after an initial decrease. An apparently insufficient nodule mass (nodule weight ratio <5 per cent) during the greater part of the experimental period is suggested as the main cause of the growth reduction in N₂-fixing plants. Thein vivo nitrate reductase activity (NRA) of NO ₃ ^? dependent plants was almost entirely located in the roots. However, when grown with a combination of NO ₃ ^? and NH ₄ ⁺ , root NRA was decreased by approximately 85 per cent.H. rhamnoides demonstrated in the mixed supply a strong preference for uptake of N as NH ₄ ⁺ , NO ₃ ^? contributing only for approximately 20 per cent to the total N assimilation. Specific rates of N acquisition and ion uptake were generally highest in NO ₃ ^? +NH ₄ ⁺ plants. The generation of organic anions per unit total plant dry weight was approximately 40 per cent less in the NH ₄ ⁺ plants than in the NO ₃ ^? plants. Measured extrusions of H⁺ or OH^? (HCO ₃ ^? ) were generally in good agreement with calculated values on the basis of plant composition, and the acidity generated with N₂ fixation amounted to 0.45–0.55 meq H⁺. (mmol N_org)^?1. Without acidity control and in the presence of NH ₄ ⁺ , specific rates of ion uptake and carboxylate generation were strongly depressed and growth was reduced by 30–35 per cent. Growth of nonnodulatedH. rhamnoides plants ceased at the lower pH limit of 3.1–3.2 and deterioration set in; in the case of N₂-fixing plants the nutrient solution pH stabilized at a value of 3.8–3.9 without any apparent adverse effects upon plant performance. The chemical composition of experimental and field-growing plants is being compared and some comments are made on the nitrogen supply characteristics of their natural sites.     

Effects of nitrate concentration on the denitrification potential of a calcic cambisol and its fractions of N2, N2O and NO

Background and aims

The direct measurement of denitrification dynamics and its product fractions is important for parameterizing process-oriented model(s) for nitrogen cycling in various soils. The aims of this study are to a) directly measure the denitrification potential and the fractions of nitrogenous gases as products of the process in laboratory, b) investigate the effects of the nitrate (NO ₃ ^? ) concentration on emissions of denitrification gases, and c) test the hypothesis that denitrification can be a major pathway of nitrous oxide (N₂O) and nitric oxide (NO) production in calcic cambisols under conditions of simultaneously sufficient supplies of carbon and nitrogen substrates and anaerobiosis as to be found to occur commonly in agricultural lands.

Methods

Using the helium atmosphere (with or without oxygen) gas-flow-soil-core technique in laboratory, we directly measured the denitrification potential of a silt clay calcic cambisol and the production of nitrogen gas (N₂), N₂O and NO during denitrification under the conditions of seven levels of NO ₃ ^? concentrations (ranging from 10 to 250 mg N kg^?1 dry soil) and an almost constant initial dissolved organic carbon concentration (300 mg C kg^?1 dry soil).

Results

Almost all the soil NO ₃ ^? was consumed during anaerobic incubation, with 80–88 % of the consumed NO ₃ ^? recovered by measuring nitrogenous gases. The results showed that the increases in initial NO ₃ ^? concentrations significantly enhanced the denitrification potential and the emissions of N₂ and N₂O as products of this process. Despite the wide range of initial NO ₃ ^? concentrations, the ratios of N₂, N₂O and NO products to denitrification potential showed much narrower ranges of 51–78 % for N₂, 14–36 % for N₂O and 5–22 % for NO.

Conclusions

These results well support the above hypothesis and provide some parameters for simulating effects of variable soil NO ₃ ^? concentrations on denitrification process as needed for biogeochemical models.     

Production of H 3 + ions in low-energy collisions between hydrogen molecular ions

The effective cross section for the H ₂ ⁺ + H ₂ ⁺ → H ₃ ⁺ + p reaction in the energy range 5.7–11.5 eV is measured by the split beam method. The cross-section maximum at an energy of ～8 eV is related to the production of the H ₄ ⁺⁺ compound system. The reaction threshold W _thr ≈5 eV provides evidence in favor of the classical model with the H ₂ ⁺ ion charge fixed on one of the two nuclei during the entire collision event.     

Nitrous oxide emissions and nitrate leaching from a rain-fed wheat-maize rotation in the Sichuan Basin, China

Aims

A 3-year field experiment (October 2004–October 2007) was conducted to quantify N₂O fluxes and determine the regulating factors from rain-fed, N fertilized wheat-maize rotation in the Sichuan Basin, China.

Methods

Static chamber-GC techniques were used to measure soil N₂O fluxes in three treatments (three replicates per treatment): CK (no fertilizer); N150 (300 kg N fertilizer ha^?1 yr^?1 or 150 kg N?ha^?1 per crop); N250 (500 kg N fertilizer ha^?1 yr^?1 kg or 250 kg N?ha^?1 per crop). Nitrate (NO ₃ ^? ) leaching losses were measured at nearby sites using free-drained lysimeters.

Results

The annual N₂O fluxes from the N fertilized treatments were in the range of 1.9 to 6.7 kg N?ha^?1 yr^?1 corresponding to an N₂O emission factor ranging from 0.12 % to 1.06 % (mean value: 0.61 %). The relationship between monthly soil N₂O fluxes and NO ₃ ^- leaching losses can be described by a significant exponential decaying function.

Conclusions

The N₂O emission factor obtained in our study was somewhat lower than the current IPCC default emission factor (1 %). Nitrate leaching, through removal of topsoil NO ₃ ^? , is an underrated regulating factor of soil N₂O fluxes from cropland, especially in the regions where high NO ₃ ^- leaching losses occur.     

Biofortification of rice grain with zinc through zinc fertilization in different countries

Aims and background

The ability to suppress soil nitrification through the release of nitrification inhibitors from plant roots is termed ‘biological nitrification inhibition’ (BNI). Earlier, we reported that sorghum roots release higher BNI-activity when grown with NH ₄ ⁺ , but not with NO ₃ ^- as N source. Also for BNI release, rhizosphere pH of <5.0 is needed; beyond this, a negative effect on BNI release was observed with nearly 80% loss of BNI activity at pH >7.0. This study is aimed at understanding the inter-functional relationships associated with NH ₄ ⁺ uptake, rhizosphere-pH and plasma membrane H⁺-ATPase (PM H⁺-ATPase) activity in regulating the release of BNIs (biological nitrification inhibitors) from sorghum roots.

Methods

Sorghum was grown hydroponically and root exudates were collected from intact plants using a pH-stat system to separate the secondary acidification effects by NH ₄ ⁺ uptake on BNIs release. A recombinant luminescent Nitrosomonas europaea bioassay was used to determine BNI-activity. Root plasma membrane was isolated using a two-phase partitioning system. Hydrolytic H⁺-ATPase activity was determined. Split-root system setup was deployed to understand the localized responses to NH ₄ ⁺ , H⁺-ATPase-stimulator (fusicoccin) or H⁺-ATPase-inhibitor (vanadates) on BNI release by sorghum.

Results

Presence of NH ₄ ⁺ in the rhizosphere stimulated the expression of H⁺-ATPase activity and enhanced the release of BNIs from sorghum roots. Fusicoccin, which stimulates H⁺-ATPase activity, also stimulated BNIs release in the absence of NH ₄ ⁺ ; vanadate, which suppresses H⁺-ATPase activity, also suppressed the release of BNIs. NH ₄ ⁺ levels (in rhizosphere) positively influenced BNIs release and root H⁺-ATPase activity in the concentration range of 0-1.0 mM, indicating a close relationship between BNI release and root H⁺-ATPase activity with a possible involvement of carrier-mediated transport for the release of BNIs in sorghum.

Conclusion

Our results suggest that NH ₄ ⁺ uptake, PM H⁺-ATPase activity, and rhizosphere acidification are functionally inter-connected with BNI release in sorghum. Such knowledge is critical to gain insights into why BNI function is more effective in light-textured, mildly acidic soils compared to other soil types.     

Relation between electron exchange and nuclear vibrations in the H 2 + +H 2 + → H 3 + +p exothermic ion-molecular reaction

The effective cross section for the H ₂ ⁺ +H ₂ ⁺ → H ₃ ⁺ +p reaction in the energy range 5.7–11.5 eV is measured by the split beam method. The maximum of the cross section at an energy of ～8 eV is related to the production of the H ₄ ⁺⁺ compound system. The reaction threshold W _thr≈5 eV provides evidence in favor of the classical model of the H ₂ ⁺ ion with the charge fixed on one of the nuclei throughout the collision event.     

Current dynamics and mechanisms for the instability of a non-self-sustained glow discharge in nitrogen

The current dynamics in a non-self-sustained glow discharge in atmospheric-pressure nitrogen (with a small admixture of oxygen) at cryogenic and room temperatures is studied experimentally and theoretically. For the first time, the theoretical model incorporates the processes of the decomposition of O ₂ ⁺ ·N₂ and NO⁺·N₂ complex ions in collisions with vibrationally excited nitrogen molecules and the associative ionization reactions with the participation of excited nitrogen and oxygen atoms. The computation results agree quite satisfactorily with the experimental data on the current dynamics and the duration of the stable phase of a non-self-sustained discharge for various applied voltages. Even a small (0.01%) oxygen admixture is found to greatly affect the dynamics of the ion composition and the characteristic duration of the stable phase of a non-self-sustained discharge in atmospheric-pressure nitrogen.     

Ion-molecule condensation reactions: A mechanism for organic synthesis in ionized reducing atmospheres

The CH₃ ⁺ ion, formed in ionized methane, undergoes consecutive eliminative condensation reactions with methane to form the carbonium ions C₂H₅ ⁺, i-C₃H₇ ⁺ and t-C₄H₉ ⁺. AtT<500°K, \(N_{CH_4 } \) ?10¹⁶ cm^?3 these ions react with NH₃ in competitive condensation-H⁺ transfer reactions, e.g. $$\begin{gathered} C_2 H_5 ^ + + NH_3 \xrightarrow{M} C_2 H_5 NH_3 ^ + \hfill \\ - - - \to NH_4 ^ + + C_2 H_4 \hfill \\ \end{gathered} $$ At particle densities of \(N_{CH_4 } \) <10¹⁶ cm^?3 proton transfer is the only significant reaction channel. At \(N_{CH_4 } \) >10¹⁷ cm^?3 condensation constitutes 5–20% of the overall reactions. The product of the condensation reaction further associates with CO₂ to form C₂H₅NH₃ ⁺·CO₂; the atomic composition of this cluster ion is identical with the protonated amino acid alanine. The carbonium ions i-C₃H₇ ⁺ and t-C₄H₉ ⁺ condense also with HCN to yield protonated isocyanides. HCNH⁺ also appears to condense with HCN atT>570°K, and form cluster ions with HCN at lower temperatures. The rate constants of the condensation reactions vary with temperature and pressure in a complex manner. Under conditions similar to those on Titan at an altitude of 100 km (T=100–150°K, \(N_{CH_4 } \) ≈10¹⁸ cm^?3), with a methane atmosphere containing 1% H₂ and traces of NH₃ and H₂O, ion-molecule condensation reactions followed by H⁺ transfer are expected to lead to the atmospheric synthesis of C₂H₆, C₃H₈, CH₃OH, C₂H₅OH and the terminal ions NH₄ ⁺, CH₃NH₃ ⁺ and C₂H₅NH₃ ⁺. At higher temperatures (250°K<T<400°K), the synthesis of i-C₄H₁₀, i-C₃H₇OH and t-C₄H₉OH and of the ions i-C₃H₇NH₃ ⁺ and t-C₄H₉NH₃ ⁺ is also expected. Electron recombination of the terminal ions may yield amines, imines and nitriles. Cycles of protonation and dissociative recombination of the alkanes and alcohols produced in condensation reactions will also produce unsaturated hydrocarbons, ketones and aldehydes in the ionized atmosphere.     

Regulation of morphological and functional properties of astrocytes by hydrogen peroxide

Effects of hydrogen peroxide on morphological characteristics, proliferation index, and menadione-dependent lucigenin-enhanced chemiluminescence of C6 glioma cells were studied. It was established that H₂O₂ at 5 × 10^?7?1 × 10^?8 M concentrations acted as a regulator of morphological and functional properties of astrocytes, inducing their reactivation, which is manifested as cell body hypertrophy and an increase of proliferative activity and menadione-induced production of superoxide anion radicals (O ₂ ^?? ). Cytodestructive action of hydrogen peroxide at a concentration higher than 1 × 10^?6 M on C6 glioma cells shows itself as a decrease of their proliferation index and the ability to generate O ₂ ^?? under the effect of menadione. Use of lipopolysaccharide B as a functional stimulator has shown that H₂O₂ modifies signaling pathways leading to an increase of mitotic activity of C6 glioma cells and decreases the yield of lucigenin-dependent chemiluminescence of astrocytes under the action of menadione to the level of control values.     

Microbial N turnover processes in three forest soil layers following clear cutting of an N saturated mature spruce stand

Microbial N turnover processes were investigated in three different forest soil layers [organic (O) layer, 0–10 cm depth (M₁), 10–40 cm depth (M₂)] after the clear cutting of a nitrogen (N) saturated spruce stand at the Höglwald Forest (Bavaria, Germany). The aim of the study was to provide detailed insight into soil-layer specific microbial production and the consumption of inorganic N within the main rooting zone. Furthermore, we intended to clarify the relevance of each soil layer investigated in respect of the observed high spatial variation of seepage water nitrate (NO ₃ ^? ) concentration at a depth of 40 cm. The buried bag and the ¹⁵N pool dilution techniques were applied to determine the net and gross N turnover rates. In addition, soil pH, C:N ratio, pool sizes of soil ammonium (NH ₄ ⁺ ) and NO ₃ ^? , as well as quantities of microbial biomass carbon (C_mic) and nitrogen (N_mic) were determined. The 40 cm thick upper mineral soil was found to be the main place of NO ₃ ^? production with a NO ₃ ^? supply or net nitrification three times higher than in the considerably thinner O layer. Nevertheless, O layer nitrification processes determined via in situ field experiments showed significant correlation with seepage water NO ₃ ^? . An improved correlation noted several months after the cut may result from a transport-induced time shift of NO ₃ ^? with downstream hydrological pathways. In contrast, the soil laboratory incubation experiments found no indication that mineral soil is relevant for the spatial heterogeneity of seepage water NO ₃ ^? . The results from our study imply that in situ experiments may be better suited to studies investigating N turnover in relation to NO ₃ ^? loss via seepage water in similar ecosystems in order to gain representative data.     

Nitrogen turnover in fresh Douglas fir litter directly after additions of moisture and inorganic nitrogen

The effects of wetting and drying and inorganic nitrogen (N) addition on carbon (C) and N turnover in fresh Douglas fir litter (Speuld forest, the Netherlands) were investigated. Litter was incubated for 9 days in the laboratory, receiving different moisture and N addition treatments. Following the additions, a series of reactions were observed of which most notable were a rapid retention of added ammonium and nitrate (NO ₃ ^- ) and a sudden increase in CO₂ respiration. For the rewetted-and-moist incubations, respiration levels remained elevated, N was net immobilized and nitrous oxide (N₂O) production increased throughout the experiment. About 80% of the NO ₃ ^- produced was lost again as N₂O. In the rewetted-and-dried incubations, respiration decreased during the drying phase; no clear patterns in N mineralization were detected; and N₂O production remained at constant levels, but still resulted in gaseous loss for half of the NO ₃ ^- net produced. The experiments thus revealed two important NO ₃ ^- sinks in LF1 litter, namely rapid retention of added NO ₃ ^- and gaseous loss as N₂O. The maximum NO ₃ ^- loss via these sinks was estimated at 2 kg-N ha^-1 yr^-1, which is small compared to annual NO ₃ ^- leaching at 90 cm soil depth (31 kg-N ha^-1 yr^-1).     

Denitrification in soil amended with thermophile-fermented compost suppresses nitrate accumulation in plants

NO ₃ ^? is a major nitrogen source for plant nutrition, and plant cells store NO ₃ ^? in their vacuoles. Here, we report that a unique compost made from marine animal resources by thermophiles represses NO ₃ ^? accumulation in plants. A decrease in the leaf NO ₃ ^? content occurred in parallel with a decrease in the soil NO ₃ ^? level, and the degree of the soil NO ₃ ^? decrease was proportional to the compost concentration in the soil. The compost-induced reduction of the soil NO ₃ ^? level was blocked by incubation with chloramphenicol, indicating that the soil NO ₃ ^? was reduced by chloramphenicol-sensitive microbes. The compost-induced denitrification activity was assessed by the acetylene block method. To eliminate denitrification by the soil bacterial habitants, soil was sterilized with γ irradiation and then compost was amended. After the 24-h incubation, the N₂O level in the compost soil with presence of acetylene was approximately fourfold higher than that in the compost soil with absence of acetylene. These results indicate that the low NO ₃ ^? levels that are often found in the leaves of organic vegetables can be explained by compost-mediated denitrification in the soil.     

The Ammonia Transport, Retention and Futile Cycling Problem in Cyanobacteria

Ammonia is the preferred nitrogen source for many algae including the cyanobacterium Synechococcus elongatis (Synechococcus R-2; PCC 7942). Modelling ammonia uptake by cells is not straightforward because it exists in solution as NH₃ and NH ₄ ⁺ . NH₃ is readily diffusible not only via the lipid bilayer but also through aquaporins and other more specific porins. On the other hand, NH ₄ ⁺ requires cationic transporters to cross a membrane. Significant intracellular ammonia pools (≈1–10 mol?m^?3) are essential for the synthesis of amino acids from ammonia. The most common model envisaged for how cells take up ammonia and use it as a nitrogen source is the “pump–leak model” where uptake occurs through a simple diffusion of NH₃ or through an energy-driven NH ₄ ⁺ pump balancing a leak of NH₃ out of the cell. The flaw in such models is that cells maintain intracellular pools of ammonia much higher than predicted by such models. With caution, [¹⁴C]-methylamine can be used as an analogue tracer for ammonia and has been used to test various models of ammonia transport and metabolism. In this study, simple “proton trapping” accumulation by the diffusion of uncharged CH₃NH₂ has been compared to systems where CH₃NH ₃ ⁺ is taken up through channels, driven by the membrane potential (ΔU _i,o) or the electrochemical potential for Na⁺ (ΔμNa _i,o ⁺ ). No model can be reconciled with experimental data unless the permeability of CH₃NH₂ across the cell membrane is asymmetric: permeability into the cell is very high through gated porins, whereas permeability out of the cell is very low (≈40 nm?s^?1) and independent of the extracellular pH. The best model is a Na _in ⁺ /CH₃NH ₃ ⁺ _in co-porter driven by ΔμNa _i,o ⁺ balancing synthesis of methylglutamine and a slow leak governed by Ficks law, and so there is significant futile cycling of methylamine across the cell membrane to maintain intracellular methylamine pools high enough for fixation by glutamine synthetase. The modified pump–leak model with asymmetric permeability of the uncharged form is a viable model for understanding ammonia uptake and retention in plants, free-living microbes and organisms in symbiotic relationships.     

Ammonium nutrition increases water absorption in rice seedlings (Oryza sativa L.) under water stress

Water stress is a primary limitation on plant growth. In previous studies, it has been found that ammonium enhances the tolerance of rice plants to water stress, but how water is related to nitrogen form and water stress remains unknown. To study the effects of nitrogen form (NH ₄ ⁺ , NO ₃ ^? , and a mixture of NH ₄ ⁺ and NO ₃ ^? ) on the growth and water absorption of rice (Oryza sativa L.) seedlings, a hydroponic experiment with water stress, simulated by the addition of polyethylene glycol (PEG, 10% w/v, MW 6000), was conducted in a greenhouse. The results showed that, compared with non-water stress, under water stress, the fresh weight of rice seedlings increased by 14% with NH ₄ ⁺ nutrition, whereas it had decreased by about 20% with either NO ₃ ^? or mixed nitrogen nutrition. No significant difference was found in the transpiration rate of excised shoots or in xylem exudation of excised roots in NH ₄ ⁺ supply between the two water situations, whereas xylem flow decreased by 57% and 24% under water stress in NO ₃ ^? and mixed nutrition, and root hydraulic conductivity decreased by 29% and 54% in plants in NH ₄ ⁺ and NO ₃ ^? nutrition conditions, respectively. Although water absorption ability decreased in both NH ₄ ⁺ and NO ₃ ^? nutrition, aquaporin activity was higher in NH ₄ ⁺ than in NO ₃ ^? nutrition, regardless of water stress. We conclude that NH ₄ ⁺ nutrition can improve water handling in rice seedlings and subsequently enhance their resistance to drought.     

Enhanced growth of the red algaPorphyra yezoensis Ueda in high CO2 concentrations

Leafy thalli of the red algaPorphyra yezoensis Ueda, initiated from conchospores released from free-living conchocelis, were cultured using aeration with high CO₂. It was found that the higher the CO₂ concentration, the faster the growth of the thalli. Aeration with elevated CO₂ lowered pH in dark, but raised pH remarkably in light with the thalli, because the photosynthetic conversion of HCO ₃ ^? to OH^? and CO₂ proceeded much faster than the dissociation of hydrated CO₂ releasing H⁺. Photosynthesis of the alga was found to be enhanced in the seawater of elevated dissolved inorganic carbon (DIC, CO₂ + HCO ₃ ^? + CO ₃ ^? ). It is concluded that the increased pH in the light resulted in the increase of DIC in the culture media, thus enhancing photosynthesis and growth. The relevance of the results to removal of atmospheric CO₂ by marine algae is discussed.     

Mechanism for electric breakdown in a chemically nonequilibrium system and the influence of the chain oxidation reaction in an H2-air mixture on the breakdown threshold

A mathematical model is developed and a numerical analysis is performed for an electric breakdown in a hydrogen-air mixture with a low concentration of H₂. It is shown that, at sufficiently low pressures p<10^?2 atm, a small molecular-hydrogen additive (η=5×10^?5–5×10^?3) decreases the reduced field of an electric breakdown in air by a factor of more than 2 because of the appearance of an additional detachment process associated with the chain hydrogen-oxidation reaction. Detailed calculations are performed for the mean number density of negative oxygen ions [O ₂ ^? ]=10³ cm^?3 and the hydrogen concentration in air [H₂]=0.5, 0.05, and 0.005%. It is found that, for [H₂]=0.005%, the breakdown can develop under the action of a geoelectric field of 1.3 V/cm at p?10^?4 atm.