Absence Of NO Research Articles

Disproportionation of hydroxylamine by water-soluble iron(III) porphyrinate compounds

The reactions of hydroxylamine (HA) with several water-soluble iron(III) porphyrinate compounds, namely iron(III) meso-tetrakis-(N-ethylpyridinium-2yl)-porphyrinate ([Fe(III)(TEPyP)](5+)), iron(III) meso-tetrakis-(4-sulphonatophenyl)-porphyrinate ([Fe(III)(TPPS)](3-)), and microperoxidase 11 ([Fe(III)(MP11)]) were studied for different [Fe(III)(Porph)]/[HA] ratios, under anaerobic conditions at neutral pH. Efficient catalytic processes leading to the disproportionation of HA by these iron(III) porphyrinates were evidenced for the first time. As a common feature, only N(2) and N(2)O were found as gaseous, nitrogen-containing oxidation products, while NH(3) was the unique reduced species detected. Different N(2)/N(2)O ratios obtained with these three porphyrinates strongly suggest distinctive mechanistic scenarios: while [Fe(III)(TEPyP)](5+) and [Fe(III)(MP11)] formed unknown steady-state porphyrinic intermediates in the presence of HA, [Fe(III)(TPPS)](3-) led to the well characterized soluble intermediate, [Fe(II)(TPPS)NO](4-). Free-radical formation was only evidenced for [Fe(III)(TEPyP)](5+), as a consequence of a metal centered reduction. We discuss the catalytic pathways of HA disproportionation on the basis of the distribution of gaseous products, free radicals formation, the nature of porphyrinic intermediates, the Fe(II)/Fe(III) redox potential, the coordinating capabilities of each complex, and the kinetic analysis. The absence of NO(2)(-) revealed either that no HAO-like activity was operative under our reaction conditions, or that NO(2)(-), if formed, was consumed in the reaction milieu.

Increasing interannual and altitudinal ozone mixing ratios in the Catalan Pyrenees

Interannual, seasonal, daily and altitudinal patterns of tropospheric ozone mixing ratios, as well as ozone phytotoxicity and the relationship with NO x precursors and meteorological variables were monitored in the Central Catalan Pyrenees (Meranges valley and Forest of Guils) over a period of 5 years (2004–2008). Biweekly measurements using Radiello passive samplers were taken along two altitudinal transects comprised of thirteen stations ranging from 1040 to 2300 m a.s.l. Visual symptoms of ozone damage in Bel-W3 tobacco cultivars were evaluated biweekly for the first three years (2004–2006). High ozone mixing ratios, always above forest and vegetation protection AOT40 thresholds, were monitored every year. In the last 14 years, the AOT40 (Apr–Sept.) has increased significantly by 1047 μg m −3 h per year. Annual means of ozone mixing ratios ranged between 38 and 67 ppb v (38 and 74 ppb v during the warm period) at the highest site (2300 m) and increased at a rate of 5.1 ppb v year −1. The ozone mixing ratios were also on average 35–38% greater during the warm period and had a characteristic daily pattern with minimum values in the early morning, a rise during the morning and a decline overnight, that was less marked the higher the altitude. Whereas ozone mixing ratios increased significantly with altitude from 35 ppb v at 1040 m–56 ppb v at 2300 m (on average for 2004–2007 period), NO 2 mixing ratios decreased with altitude from 5.5 ppb v at 1040 m–1 ppb v at 2300 m. The analysis of meteorological variables and NO x values suggests that the ozone mainly originated from urban areas and was transported to high-mountain sites, remaining aloft in absence of NO. Ozone damage rates increased with altitude in response to increasing O 3 mixing ratios and a possible increase in O 3 uptake due to more favorable microclimatic conditions found at higher altitude, which confirms Bel-W3 as a suitable biomonitor for ozone concentrations during summer time. Compared to the valley-bottom site the annual means of ozone mixing ratios are 37% larger in the higher sites. Thus the AOT40 for the forest and vegetation protection threshold is greatly exceeded at higher sites. This could have substantial effects on plant life at high altitudes in the Pyrenees.

Signaling events in apoptotic photokilling of 5-aminolevulinic acid-treated tumor cells: Inhibitory effects of nitric oxide

Antitumor photodynamic therapy (PDT) employs a photosensitizing agent, molecular oxygen, and visible light to produce reactive oxygen species that can destroy tumor and tumor vasculature cells. NO produced by these cells could be procarcinogenic by inhibiting apoptosis and promoting angiogenesis and tumor growth. We recently showed that NO from a chemical donor or activated macrophages makes COH-BR1 breast tumor cells more resistant to photokilling sensitized by 5-aminolevulinic acid (ALA)-generated protoporphyrin IX (PpIX). Signaling events associated with this hyperresistance have now been examined. ALA-treated COH-BR1 cells containing mitochondria-localized PpIX died mainly by apoptosis after being irradiated. Underlying redox signaling associated with MAP kinase (ERK1/2, p38, JUN) phosphorylation–activation, and heme oxygenase-1 (HO-1) upregulation was studied using immunoprecipitation and Western blot methodology. ALA/light treatment resulted in activation of proapoptotic JNK and p38α, and deactivation of prosurvival p38β and ERK1/2. Involvement of both JNK and p38 in apoptosis was established by using a specific inhibitor for each. Spermine NONOate-derived NO, introduced immediately before irradiation, provided substantial protection against apoptosis. This was accompanied by greater HO-1 induction and a strong inhibition of each MAP kinase effect seen in the absence of NO. Downstream of JNK and p38α activation, a marked upregulation/activation of proapoptotic Bax and Bid was observed along with down-regulation of antiapoptotic Bcl-xL, each response being reversed by NO. These findings provide new insights into signaling activity associated with the intrinsic apoptotic pathway in ALA-PDT and how this activity can be modulated by NO.

Atmospheric Chemistry ofn-Butanol: Kinetics, Mechanisms, and Products of Cl Atom and OH Radical Initiated Oxidation in the Presence and Absence of NOx.

Smog chamber/FTIR techniques were used to determine rate constants of k(Cl+n-butanol) = (2.21 +/- 0.38) x 10(-10) and k(OH+n-butanol) = (8.86 +/- 0.85) x 10(-12) cm(3) molecule(-1) s(-1) in 700 Torr of N(2)/O(2) diluent at 296 +/- 2K. The sole primary product identified from the Cl atom initiated oxidation of n-butanol in the absence of NO was butyraldehyde (38 +/- 2%, molar yield). The primary products of the Cl atom initiated oxidation of n-butanol in the presence of NO were (molar yield) butyraldehyde (38 +/- 2%), propionaldehyde (23 +/- 3%), acetaldehyde (12 +/- 4%), and formaldehyde (33 +/- 3%). The substantially lower yields of propionaldehyde, acetaldehyde, and formaldehyde as primary products in experiments conducted in the absence of NO suggests that chemical activation is important in the atmospheric chemistry of CH(3)CH(2)CH(O)CH(2)OH and CH(3)CH(O)CH(2)CH(2)OH alkoxy radicals. The primary products of the OH radical initiated oxidation of n-butanol in the presence of NO were (molar yields) butyraldehyde (44 +/- 4%), propionaldehyde (19 +/- 2%), and acetaldehyde (12 +/- 3%). In all cases, the product yields were independent of oxygen concentration over the partial pressure range of 10-600 Torr. The yields of propionaldehyde, acetaldehyde, and formaldehyde quoted above were not corrected for secondary formation via oxidation of higher aldehydes and should be treated as upper limits. The reactions of Cl atoms and OH radicals with n-butanol proceed 38 +/- 2 and 44 +/- 4%, respectively, via attack on the alpha-position to give an alpha-hydroxy alkyl radical which reacts with O(2) to give butyraldehyde. The results are discussed with respect to the atmospheric chemistry of n-butanol.

Atmospheric chemistry of CF 3CF 2H and CF 3CF 2CF 2CF 2H: Kinetics and products of gas-phase reactions with Cl atoms and OH radicals, infrared spectra, and formation of perfluorocarboxylic acids

Relative rate techniques were used to determine k(Cl + C 2F 5H) = (2.93 ± 0.23) × 10 −16, k(Cl + n-C 4F 9H) = (2.77 ± 0.20) × 10 −16, k(OH + C 2F 5H) = (1.96 ± 0.25) × 10 −15, and k(OH + n-C 4F 9H) = (1.85 ± 0.29) × 10 −15 cm 3 molecule −1 s −1 at 296 K. The reactivity of C 2F 5H and n-C 4F 9H was indistinguishable. Atmospheric lifetimes, radiative efficiencies, and global warming potentials (100 year horizon) of C 2F 5H and n-C 4F 9H were estimated as 31 years, 0.21 and 0.31 W m −2 ppb −1, and 3280 and 2660, respectively. In the absence of NO x the chlorine-initiated oxidation of C 2F 5H and n-C 4F 9H gives perfluorocarboxylic acids in small (<2%) but detectable yields.

Phenanthrene and nitrite effects on juvenile sea bass, Dicentrarchus labrax, using hepatic biotransformation enzymes, biliary fluorescence, and micronuclei as biomarkers

Aquatic organisms may absorb organic compounds mainly from water and by ingestion of contaminated food. The toxicity of such compounds may be intensified by the presence of certain inorganic compounds such as nitrite (NO2–). In order to evaluate the effect of phenanthrene (PHE), a polycyclic aromatic hydrocarbon, in the presence and absence of NO2–, juvenile sea bass, Dicentrarchus labrax L, were exposed to PHE i.p. and to NO2– in water, and several endpoints were measured at days 1, 3, and 6 of exposure. Sea bass exposed to PHE exhibited lower hepatic 7-ethoxyresorufin O-deethylase (EROD) activity as compared to the control group. The activity of the phase II enzyme, glutathione S-transferase (GST), was similar in all the groups of fish. The concentration of PHE metabolites, determined as fluorescent aromatic compounds, was nearly 14 times higher both in the presence and absence of NO2–, showing that even at low EROD activities this PAH is metabolized. The presence of micronuclei was observed to be significantly higher only in sea bass treated with PHE alone, suggesting that different PHE metabolites, without genotoxic properties, were formed in the presence of NO2–.

Effects of NO2− and NO3− on the Fe(III)EDTA reduction in a chemical absorption–biological reduction integrated NOx removal system

The biological reduction of Fe(III) ethylenediaminetetraacetic acid (EDTA) is a key step for NO removal in a chemical absorption-biological reduction integrated process. Since typical flue gas contain oxygen, NO(2)(-) and NO(3)(-) would be present in the absorption solution after NO absorption. In this paper, the interaction of NO(2)(-), NO(3)(-), and Fe(III)EDTA reduction was investigated. The experimental results indicate that the Fe(III)EDTA reduction rate decrease with the increase of NO(2)(-) or NO(3)(-) addition. In the presence of 10 mM NO(2)(-) or NO(3)(-), the average reduction rate of Fe(III)EDTA during the first 6-h reaction was 0.076 and 0.17 mM h(-1), respectively, compared with 1.07 mM h(-1) in the absence of NO(2)(-) and NO(3)(-). Fe(III)EDTA and either NO(2)(-) or NO(3)(-) reduction occurred simultaneously. Interestingly, the reduction rate of NO(2)(-) or NO(3)(-) was enhanced in presence of Fe(III)EDTA. The inhibition patterns observed during the effect of NO(2)(-) and NO(3)(-) on the Fe(III)EDTA reduction experiments suggest that Escherichia coli can utilize NO(2)(-), NO(3)(-), and Fe(III)EDTA as terminal electron acceptors.

Methyl acetate reaction with OH and Cl: Reaction rates and products for a biodiesel analogue

Relative rate experiments performed in a photochemical reactor at 293 ± 0.5 K and a total air pressure of 980 mbar were used to determine k(CH 3C(O)OCH 3 + Cl) = (1.93 ± 0.27) × 10 −12 cm 3 molecule −1 s −1 and k(CH 3C(O)OCH 3 + OH) = (3.18 ± 0.13) × 10 −13 cm 3 molecule −1 s −1. The product branching ratio for the Cl-initiated oxidation of CH 3C(O)OCH 3 was investigated at 293 ± 0.5 K and 980 mbar N 2, air, or O 2, in the presence and absence of NO. Products observed were CH 3C(O)OCHO, CH 3C(O)OH, HC(O)OH, CO, and CO 2. The product branching ratios were dependent on NO, but not on the oxygen partial pressure.

Expression of a putative nitrite reductase and the reversible inhibition of nitrite‐dependent respiration by nitric oxide in Nitrobacter winogradskyi Nb‐255

The nitrite oxidizing Alphaproteobacterium, Nitrobacter winogradskyi, primarily conserves energy from the oxidation of nitrite (NO(2)(-))to nitrate (NO(3)(-)) through aerobic respiration. Almost 20 years ago, NO-dependent NADH formation was reported to occur in both aerobic and anaerobic cell suspensions of N. winogradskyi strain 'agilis', suggesting that NO oxidation might contribute to energy conservation by Nitrobacter. Recently, the N. winogradskyi Nb-255 genome was found to contain a gene (Nwin_2648) that encodes a putative copper-containing nitrite reductase (NirK), which may reduce NO(2)(-) to NO. In this study, the putative nirK was found to be maximally transcribed under low O(2) (between zero and 4% O(2)) in the presence of NO(2)(-). Transcription of nirK was not detected under anaerobic conditions in the absence of NO(2)(-) or in the presence of NO(3)(-) and pyruvate. Although net production of NO could not be detected from either aerobically grown or anaerobically incubated cells, exogenous NO was consumed by viable cells and concomitantly inhibited NO(2)(-)-dependent O(2) uptake in a reversible, concentration dependent manner. Both NO(2(-)-dependent O(2) uptake and NO consumption were inhibited by 1 mM cyanide suggesting involvement of cytochrome oxidase with NO consumption. Abiotic consumption of NO was measured, yet, both the rates and kinetics of NO transformation in buffer alone, or by heat killed, or cyanide-treated cells differed from those of viable cells. In light of this new information, a modified model is proposed to explain how NirK and NO manage electron flux in Nitrobacter.

Atmospheric Chemistry of 3-Pentanol: Kinetics, Mechanisms, and Products of Cl Atom and OH Radical Initiated Oxidation in the Presence and Absence of NOX

Smog chamber/FTIR techniques were used to study the atmospheric chemistry of 3-pentanol and determine rate constants of k(Cl+3-pentanol) = (2.03 +/- 0.23) x 10 (-10) and k(OH+3-pentanol) = (1.32 +/- 0.15) x 10 (-11) cm (3) molecule (-1) s (-1) in 700 Torr of N 2/O 2 diluent at 296 +/- 2 K. The primary products of the Cl atom initiated oxidation of 3-pentanol in the absence of NO were (with molar yields) 3-pentanone (26 +/- 2%), propionaldehyde (12 +/- 2%), acetaldehyde (13 +/- 2%) and formaldehyde (2 +/- 1%). The primary products of the Cl atom initiated oxidation of 3-pentanol in the presence of NO were (with molar yields) 3-pentanone (51 +/- 4%), propionaldehyde (39 +/- 2%), acetaldehyde (44 +/- 4%) and formaldehyde (4 +/- 1%). The primary products of the OH radical initiated oxidation of 3-pentanol in the presence of NO were (with molar yields) 3-pentanone (58 +/- 3%), propionaldehyde (28 +/- 2%), and acetaldehyde (37 +/- 2%). In all cases the product yields were independent of oxygen concentration over the partial pressure range 10-700 Torr. The reactions of Cl atoms and OH radicals with 3-pentanol proceed 26 +/- 2 and 58 +/- 3%, respectively, via attack on the 3-position to give an alpha-hydroxyalkyl radical, which reacts with O 2 to give 3-pentanone. The results are discussed with respect to the literature data and atmospheric chemistry of 3-pentanol.

D-Lactate metabolism and the obligate requirement for CO2 during growth on nitrite by the facultative lithoautotroph Nitrobacter hamburgensis

Nitrobacter hamburgensis X14 is a facultative lithoautotroph that conserves energy from the oxidation of nitrite (NO(-)2) and fixes carbon dioxide (CO(2)) as its sole source of carbon. The availability of the N. hamburgensis X14 genome sequence initiated a re-examination of its mixotrophic and organotrophic potential, as genes encoding three flavin-dependent oxidases were identified that may function to oxidize lactate, providing energy and carbon for growth. The response of N. hamburgensis to D- and L-lactate in the presence (mixotrophy) and absence (organotrophy) of NO(-)2 was examined. L-lactate did not support organotrophic growth or stimulate mixotrophic growth. In contrast, D-lactate enhanced the growth rate and yield of N. hamburgensis in the presence of NO(-)2, and served as the sole carbon and energy source for growth in the absence of NO(-)2 with ammonium as the sole nitrogen source. Lithoautotrophically grown cells immediately consumed D-lactate, suggesting that a lactate metabolic pathway is constitutively expressed. Nevertheless, a physiological adaptation to lactate occurred, as D-lactate-grown cells consumed and assimilated lactate at a faster rate than NO(-)2-grown cells, and the D-lactate-dependent O(2) uptake rate was significantly greater in cells grown either organotrophically or mixotrophically compared with cells grown lithoautotrophically. Although D-lactate was assimilated and metabolized to CO(2) in the presence or absence of NO(-)2, exposure to atmospheric CO(2) or the addition of 0.75 mM sodium carbonate was required for mixotrophic growth and for optimum organotrophic growth on D-lactate.

BASF sets plant for biodiesel catalyst

Relative rate experiments performed in a photochemical reactor at 293 ± 0.5 K and a total air pressure of 980 mbar were used to determine k(CH3C(O)OCH3 + Cl) = (1.93 ± 0.27) × 10−12 cm3 molecule−1 s−1 and k(CH3C(O)OCH3 + OH) = (3.18 ± 0.13) × 10−13 cm3 molecule−1 s−1. The product branching ratio for the Cl-initiated oxidation of CH3C(O)OCH3 was investigated at 293 ± 0.5 K and 980 mbar N2, air, or O2, in the presence and absence of NO. Products observed were CH3C(O)OCHO, CH3C(O)OH, HC(O)OH, CO, and CO2. The product branching ratios were dependent on NO, but not on the oxygen partial pressure.

Simultaneous Removal of SO2, NOX, and Hg from Coal Flue Gas Using a NaClO2-Enhanced Wet Scrubber

A bench-scale study was conducted on the simultaneous removal of SO2, NOX, and mercury (both Hg0 and Hg2+) from a simulated coal flue gas using a wet calcium carbonate scrubber. The multipollutant capacity of the scrubber was enhanced with the addition of the oxidizing salt, sodium chlorite. The results showed a maximum scrubbing of 100% for SO2 and Hg species and near complete NO oxidation with about 60% scrubbing of the resulting NOX species. The chlorite additive was less effective as an oxidant in the absence of SO2 and NO in the flue gas. Oxidation of NO and mercury were only about 50% and 80%, respectively, in the case of no SO2 in the simulated flue gas. The mercury oxidation was similarly affected by the absence of NO in the flue gas.

The Role of Nitric Oxide in Resolution of Vasospasam Corresponding with Cerebral Vasospasms after Subarachnoid Haemorrhage: Animal Model

Intracranial aneurysmal rupture is the common cause of spontaneous subarachnoid haemorrhage (SAH). This haemorrhage is typically diffuse and located in extracerebral subarachnoid space in which main cerebral arterial branches are situated. The intimate and long-term contact of arterial wall and blood products in the closed space causes the cerebral vasospasm as a serious and frequent complication of SAH. It is connected with significant morbidity and mortality due to developing of focal cerebral ischaemia and subsequently cerebral infarction. The aim of our experimental research was to create the animal model of vasospasm using the femoral artery due to examination of reduced basic dilator activity cause in arterial wall after SAH. The important characteristic of major cerebral arteries is their localization in the closed subarachnoid space which enables their to have long-term contact with blood products after haemorrhage. Thirty six femoral arteries (FA) of eighteen female rats weighing about 300 g were used. In vivo, femoral arteries are microsurgically prepared in both inguinal regions in all rats. Eighteen arteries were encompassed by polytetrafluoroethylene (PTFE) material forming closed tube and autologous blood was injected in the tube around the arterial wall. Additional eighteen arteries, as a control group, were also put in PTFE tube but without exposing to the blood. All rats are left to live for eight days. Afterwards, rats were sacrificed and their arteries were in vitro examined including an isometric tension measurement and histological changes analysis. The tension was measured during application of vasoconstrictors and vasodilatators (nitric oxide, NO). FA exposed to periadventitial blood exhibit hyper reactivity to constrictors (KCl, phenylephrine, acetylcholine) compared to control group. It was also found that NO donor (sodium nitroprusside) diminished arterial spasm induced by blood and vasoconstrictors. In conclusion, FA can be used as a model for vasospasm correlating with cerebral vasospasm after SAH and therefore this model can be utilized in future experiments assessing cerebral vasospasm. The reduced basic dilator activity of spastic femoral artery is caused by an absence of gaseous messenger NO next to the arteries but not by diminished response vasculature to NO. Absence of NO after SAH probably causes the reduced basic dilator activity of cerebral arteries as well. The guanylate-cyclase level in the arterial wall is consequently reduced after SAH primary due to absence of NO but not due to direct reduction of enzyme activities caused by process of blood degradation inside of subarachnoid space.

Atmospheric nitrogen dioxide at ambient levels stimulates growth and development of horticultural plants

We recently discovered that atmospheric nitrogen dioxide (NO2) at ambient levels acts as a signal to Nicotiana plumbaginifolia Viviani, causing these plants to double both their biomass and all of the cell contents. Herein, we addressed whether this effect of NO2 is also observed in various horticultural plants. Lettuce ( Lactuca sativa L.), sunflower ( Helianthus annuus L.), cucumber ( Cucumis sativus L.), and pumpkin ( Cucurbita moschata Duch. ex Lam.) were grown with 50, 200, 100, and 200 µL·L–1, respectively, of air supplemented with stable isotope-labelled (15N) NO2, for 5−6 weeks. Control plants were grown without NO2 (&lt;5 µL·L–1). All plants were irrigated with nonlabelled nitrate. The presence of NO2 doubled both the aboveground and belowground biomass in sunflowers compared with their growth in the absence of NO2, whereas lettuce, cucumber, and pumpkin doubled in aboveground biomass only. Contents per shoot of carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) were almost doubled during the “NO2-enhanced” growth in lettuce, but not in other plants. Mass spectrometry analysis of 15N/14N indicated that only a minor proportion (0.2%–14%) of total plant N was derived from NO2, implying that exogenous NO2 acts as a signal rather than a significant nutrient source in horticultural plants.

Nitration of respiratory epithelial cells by myeloperoxidase depends on extracellular nitrite

To investigate peroxidase induced 3′-nitrotyrosine (3NT) formation, neutrophil derived myeloperoxidase (MPO) (0.025 μM) was directly administered to A549 epithelial cells with or without H 2O 2 (150 μM). Little evidence of 3NT was found. In contrast, there was a dose dependent increase in intracellular NO ( p < 0.001, n = 8) following MPO (0.025 μM) treatment, which was further enhanced ( p < 0.0003, n = 8) by addition of H 2O 2. Extracellular NO also increased after MPO ( p < 0.002, n = 5) and with MPO and H 2O 2 ( p < 0.004, n = 5). Substantial 3NT formation was only detected following addition of nitrite (NO 2 −, ⩾100 μM), which induced a dose dependent increase in epithelial 3NT. In contrast, protein carbonyl formation and increased GSSG/GSH ratios were associated with MPO treatment even in the absence of NO 2 −. Co-culture of A549 epithelial cells with polymorphonuclear leukocytes (PMN) (10 6/ml) led to immunocytochemical detection of epithelial 3NT and induction of nitric oxide synthase (NOS2). However, in a Transwell system direct contact between PMN and A549 cells was necessary for immunodetection of 3NT but not of NOS2 consistent with a role for high local nitrite concentrations. These findings demonstrate dissociation between epithelial endogenous NO production and 3NT formation. Although MPO can influence cellular oxidative stress, particularly in the presence of H 2O 2, 3NT formation requires the presence of high concentrations of NO 2 − in the milieu.

Mechanisms of Enhanced Rice Growth and Nitrogen Uptake by Nitrate

Rice is being increasingly cultivated in intermittently irrigated regions and also in aerobic soil in which Nitrate (NO − 3) plays important role in nutrition of plant. However, there is no information regarding the influence of nitrate on the overall growth and uptake of nitrogen (N) in rice plant. Solution culture experiments were carried out to study the effects of NO − 3 on the plant growth, uptake of N, and uptake kinetics of NH + 4 in four typical rice ( Oryza sativa L.) cultivars (conventional indica, conventional japonica, hybrid indica, and hybrid japonica), and on plasma membrane potential in roots of two conventional rice cultivars ( indica and japonica) at the seedling stage. The results obtained indicated that a ratio of 50/50 NH + 4 -N/NO − 3-N increased the average biomass of rice shoots and roots by 20% when compared with that of 100/0 NH + 4 -N/NO − 3-N. In case of the 50/50 ratio, as compared with the 100/0 ratio, total N accumulated in shoots and roots of rice increased on an average by 42% and 57%, respectively. Conventional indica responds to NO − 3more than any other cultivars that were tested. The NO − 3supply increased the maximum uptake rate ( V max) of NH + 4 by rice but did not show any effect on the apparent Michaelis-Menten constant ( K m) value, with the average value of V max for NH + 4 among the four cultivars being increased by 31.5% in comparison with those in the absence of NO − 3. This suggested that NO − 3 significantly increased the numbers of the ammonium transporters. However, the lack of effect on the K m value also suggested that the presence of NO − 3had no effect on the affnity of the transporters for NH + 4. The plasma membrane potential in the roots of conventional indica and japonica were greatly increased by the addition of NO − 3, suggesting that NO − 3could improve the uptake of N by roots of the rice plant. In conclusion, the mechanisms by which NO − 3enhances the growth and N uptake of rice plant was found by the increased value of V max of NH + 4 and increased plasma membrane potential. Thus promotion of nitrification in paddy soil is of great significance for improving the production of rice.

On the reactivity of NO/N 2 mixtures with aluminum surfaces: A combined PM-IRRAS and QCM investigation

The interaction of NO, and the further reactivity of oxygen, with water-passivated aluminum surfaces are investigated for the first time by in situ polarization modulation infrared reflexion absorption spectroscopy (PM-IRRAS) coupled with quartz crystal microbalance (QCM). Chemical and quantitative complementary information are thus obtained. Exposure of water-passivated plane aluminum samples to NO/N 2 mainly results in the formation of nitrites, as identified by PM-IRRAS. O 2 hardly reacts with adsorbed nitrites in the absence of NO in the gaseous atmosphere. In contrast, the introduction of O 2 to a NO/N 2 mixture leads to the rapid transformation of nitrites to nitrates, both water-solvated and oxide-coordinated species. The fact that the transformation of nitrites to nitrates occurs only in the presence of NO and O 2 may suggest that nitrites react with gas phase NO 2 to form nitrates and NO. The evolution of the PM-IRRAS spectra of the Al surface with the composition of the gaseous phase is fully correlated to the mass uptake changes measured by QCM. From the PM-IRRAS and QCM measurements obtained during the same experiments, the ratio of the IR response coefficient of nitrates to that of nitrites (3) is reported for the first time.

Atmospheric chemistry of alkanes: Review and recent developments

Alkanes comprise a significant fraction of gasolines and of the non-methane volatile organic compounds present in ambient air in urban areas. In this work, we have extended our previous studies to investigate the formation of 1,4-hydroxycarbonyls (and other products) from the reactions of OH radicals with C 5–C 8 n-alkanes in the absence of NO, and have investigated the rates of conversion of the commercially available 4,5-dihydro-2-methylfuran (DHMF) into 5-hydroxy-2-pentanone under various conditions in a ∼6900 l Teflon chamber in order to assess whether this conversion is a homogenous gas-phase or a heterogeneous wall process. We observe that the same 1,4-hydroxycarbonyls are formed in the absence of NO as in the presence of NO, but with formation yields approximately a factor of 10 lower as expected from the reaction mechanisms involved. The results of the experiments to investigate the conversion of 4,5-dihydro-2-methylfuran to 5-hydroxy-2-pentanone indicate that this conversion is not a homogeneous gas-phase process, but is a heterogeneous reaction at the chamber wall which is probably acid-catalyzed. The current understanding of the mechanisms and products of the atmospheric degradation reactions of alkanes is also presented.

Primary product distribution from the Cl-atom initiated atmospheric degradation of furan: Environmental implications

Furan is an aromatic hydrocarbon present in both urban and rural atmospheres, which is emitted mainly by biomass burning and the combustion of fossil fuel. Reaction of furan and Cl atoms may be important in areas where chlorine atom concentrations are potentially high such as marine and coastal regions or continental atmospheres where industrial activity emits molecular chlorine or photo-labile Cl-containing compounds. To assess the importance of this reaction and to investigate whether any unique chlorine-containing product is formed the products of the reaction of Cl atoms with furan have been determined under atmospheric conditions. For the study two different sampling/detection methods have been used: (1) Solid-Phase MicroExtraction, with subsequent analysis by thermal desorption, and gas chromatography with mass spectrometry or flame ionization detection (SPME/GC-MS/FID), and 2-“in situ” with long path fourier transform infrared spectroscopy (FTIR). The yields of primary reaction products in the absence of NO were: 5-chloro-2(5H)-furanone (64.5±10.7)%, E-butenedial (11±3)%, 5-hydroxy-2(5H)-furanone (⩽2.4%) and Z-butenedial (1.6±0.5)%. Other products generated by secondary reactions were 2(3H)-furanone (2.8±1.9)%, HCl (21.1±3%) and CO. Maleic anhydride was detected with a yield of about 2%, however, this yield may be a combination of both primary and secondary reactions. All errors are ±2 σ. The observed products confirm that addition of Cl atoms to the double bond of furan is the dominant reaction pathway.