Sum Of NO Research Articles

Analysis of urinary nitric oxide metabolites in healthy subjects.

Nitric oxide (NO) has divergent actions under physiological and pathological conditions. NO is rapidly decomposed to nitrite (NO2-) and nitrate (NO3-). Since these metabolites are stable, they are good indices of NO production under various conditions. In the present study, we measured NO2- and NO3- concentrations in the urine collected from 62 hospital controls and 504 healthy subjects by means of a new HPLC system combined with Griess reaction. NOx was the sum of NO2- and NO3-. There was no considerable inter-day variation in urinary NO metabolite levels, and there was close correlation between NO2-, NO3- and NOx values in spot urine obtained in the early morning and those in 24-h stored urine in hospital controls. Urinary NO metabolite levels, which were corrected by creatinine (Cr) excretion and expressed on a logarithmic scale, showed normal distribution and were independent of sex and age in healthy subjects. The normal ranges of urinary NO2-, NO3- and NOx levels were estimated as 17-72 micromol/g Cr, 1,023-2,818 pmol/g Cr, and 1,071-2,951 micromol/g Cr, respectively. We also found that urinary NO metabolite levels were lower than normal range in patients with various diseases.

Measuring inorganic nitrate species with short time resolution from an aircraft platform by dual‐channel ozone chemiluminescence

A measurement technique for determining nitrate (the sum of nitric acid and particulate nitrate) with a few seconds time resolution in plumes is needed to resolve within‐plume features. A technique using dual ozone‐chemiluminescent NO detectors with a selective nitrate scrubber in one sampling train is promising if used with an appropriate sampling inlet, and if nitrate is the desired analyte. We report the design of, and preliminary results from a dual channel ozone‐chemiluminescent system, each channel containing a gold‐CO catalyzed converter which reduces all odd nitrogen species (NOy) quantitatively to NO; one channel also contains a nylon filter to remove nitrate from the air stream prior to the converter (this signal is termed NOy*). This system was deployed successfully in a Bell 205 helicopter during the 1995 Southern Oxidants Study Nashville Ozone Study. The converters were mounted forward near the air intake, and zero air and calibration gases admitted simultaneously to both channels during flight operations. The difference signal between the two channels (NOy‐NOy*) indicated apparent nitrate levels in the sampled air with a time resolution of <5 s and a limit of detection of about 1 ppbv. Nitrate levels observed with this system in plumes and background air during the Nashville Ozone Study were highly correlated with ozone and varied from below detection limits to ≈20 ppbv. Nitrate levels were also highly correlated with the calculated difference between NOy and the sum of NO and NO2 (NOz). Higher nitrate levels as a fraction of NOz were found in power plant plumes (≥60%) compared with urban plumes (≈50%) and background air, consistent with apparently lower ozone production efficiencies in power plant plumes vis‐à‐vis urban plumes.

Expression of Inducible Nitric Oxide Synthase and Inflammatory Cytokines in Alveolar Macrophages of ARDS Following Sepsis

The objective of this study was to evaluate the role of inducible nitric oxide synthase (iNOS) and proinflammatory cytokines in alveolar macrophages (AMs) in the pathogenesis of ARDS following sepsis. ICU in a university hospital. Prospective exploratory, open-labeled study was carried out. A total of 24 patients were investigated: 8 patients diagnosed as having ARDS following sepsis (ARDS group); 8 patients under general anesthesia in the operating room whose lung functions were normal (control group); and 8 patients who were intubated and artificially ventilated for 1 week in the ICU whose lung functions were not deteriorated without fulfilling the ARDS criteria and whose general state fulfilled the sepsis criteria (long-term ventilation group, or LTV group). The expression of iNOS, interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and interleukin-8 (IL-8) in AMs obtained from BAL fluid (BALF) was determined by the immunofluorescent technique. We observed the significant expression of iNOS, IL-6, and IL-8 only in the ARDS group. Meanwhile, NOx (the sum of NO2- + NO3-) was elevated in the BALF supernatant, and IL-6 and IL-8 levels in both the BALF supernatant and the serum were also elevated in the ARDS group. No significant expressions were detected in the control and the LTV group. The result that iNOS was detected only in ARDS patients following sepsis suggests that iNOS together with proinflammatory cytokines produced by AMs might play a pivotal role in the pathogenesis of acute lung injury and be useful for monitoring disorders in the lung in such conditions.

Time Domain Reflectometry Measurements of Nitrate Transport in Manure‐Amended Soil

AbstractTo obtain more detailed information about N processes in agricultural soils, nondestructive measurement techniques with high spatial and temporal resolution are needed. The ability of time domain reflectometry (TDR) in combination with small polysulfone hollow fiber (PHF) solution samplers to follow NO−3 production and transport in soil fertilized with cattle slurry and exposed to different rainfall events was investigated. The experiments were conducted in minilysimeters using a coarse sandy soil and two different slurry application methods: (i) surface application followed by harrowing (homogenous incorporation) or (ii) direct injection (incorporation as a manure string). Comparison between soil‐water electrical conductivity (ECw) obtained with TDR and the sum of NO−3 and Cl− concentrations in the soil water measured with solution samplers showed a good agreement both with respect to concentration levels and temporal and spatial development. Except for an initial leaching of the natural ion content in the soil water when water application was started, NO−3 released from the manure was the dominating anion in the soil water and changes in NO−3 corresponded well to changes in ECw. Both slurry and water application strategy had a large effect on the temporal development in nitrification and NO−3 leaching. In the case of homogeneously incorporated slurry and constant water application for 3 wk, NO−3 formation and leaching started after 4 to 5 d, while it started after 9 to 10 d in the case of directly injected slurry. If water was applied only in the last (third) week to the directly injected slurry system, a large amount of the NH+4 in the slurry was oxidized to NO−3 before water application and subsequently leached. The TDR measurements of ECw with high spatial and temporal resolution combined with a few measurements of ion concentrations by PHF solution samplers is a new, valuable method for analyzing turnover and transport of nonconservative ions in soil.

Emission Measurements of the Concorde Supersonic Aircraft in the Lower Stratosphere

Emission indices of reactive gases and particles were determined from measurements in the exhaust plume of a Concorde aircraft cruising at supersonic speeds in the stratosphere. Values for NO x (sum of NO and NO 2 ) agree well with ground-based estimates. Measurements of NO x and HO x indicate a limited role for nitric acid in the plume. The large number of submicrometer particles measured implies efficient conversion of fuel sulfur to sulfuric acid in the engine or at emission. A new fleet of supersonic aircraft with similar particle emissions would significantly increase stratospheric aerosol surface areas and may increase ozone loss above that expected for NO x emissions alone.

Total column densities of tropospheric and stratospheric trace gases in the undisturbed Arctic summer atmosphere

Ground-based FTIR measurements have been performed in the Arctic summer in July 1993 and June 1994 at 79 degrees N to study the zenith column densities of several trace gases in the undisturbed Arctic summer atmosphere. Zenith column densities of H2O, N2O, HNO3, NO2, NO, ClONO2, ClO, HCl, HF, COF2, OCS, SF6, HCN, CH4, C2H6, C2H2, CO, O-3, CFC-12, CFC-22, and CO2 were retrieved by line-by-line calculations. The results are compared with winter and springtime observations measured at the same site, with column densities obtained in the Antarctic summer atmosphere, and with measurements at midlatitudes. For HCl the spectra give lower total zenith columns than expected, but the ratio HF/HCl agrees well with midlatitude literature data. Measurements of ClONO2 give low total columns in agreement with observations at midlatitudes. In the undisturbed atmosphere HCl was found to be in excess of ClONO2. The total columns of HNO3, N2O and the sum of NO and NO2 agree with summer observations in Antarctica. Results for the tropospheric trace gas C2H6 are higher by 250% when compared with Antarctic observations. Contrary to N2O and CH4 the seasonal cycle of C2H6 and C2H2 give much higher total columns in winter/spring compared to the summer observations. This is assigned to transport of polluted airmasses from mid-latitudes into the Arctic.

The total reactive oxidized nitrogen levels and the partitioning between the individual species at six rural sites in eastern North America

During the late summer and early fall of 1988, measurements of many trace species of tropospheric photochemical interest, including NO, NO2, PAN, HNO3, NO3−; NOY, and ozone were made at seven surface stations in the eastern United States and Canada. The NOY (as well as ozone) levels and its partitioning were strongly influenced by the diurnal evolution of the boundary layer at the sites that are beneath the nocturnal inversion. At the higher elevation sites the median levels of all species were much more nearly constant. During the daytime the median NOY levels were 2 to 5 ppbv at all sites, which may be representative of rural areas in the populated regions of eastern North America. Each site showed variations in the NOY levels of an order of magnitude or more. Measurements from all of the sites are consistent with the major contributors to NOY being NOX (the sum of NO and NO2), PAN, and nitric acid with a minor contribution from aerosol nitrate. At the lower elevation sites the median [NOX] to [NOY] ratios were 70% or more during the night and declined to minima of 25 to 40% during the day. During the daytime the ranges of the median contributions of PAN and HNO3 to NOY were 12 to 25% and approximately 20 to 30%, respectively. The distributions of the contributions about these medians are discussed. Results from all of the sites are consistent with the individually measured species accounting for about 90% of the simultaneously measured NOY.

Depletion of lower tropospheric ozone during Arctic spring: The Polar Sunrise Experiment 1988

Results are presented from the 2‐month Polar Sunrise Experiment 1988, which was undertaken to further investigate the cause of ozone destruction during spring in the lower Arctic atmosphere. A strong anticorrelation between the decrease in ozone and concurrent increase in bromine compounds collected on filters observed during a 21‐day period in 1986 was confirmed. It is shown that the reason for this observation is a meteorological modulation which alternately brings to the sampling location lower boundary layer air, depleted in ozone and enriched in filterable bromine, and free tropospheric air with abundant ozone and few bromine compounds. Several other compounds that may have a bearing on the chemical reactions leading to ozone depletion were measured. Bromoform, a potential source for Br atoms, was found to be present at levels between 1 and 10 parts per trillion by volume (pptv); good evidence was obtained that, as with filterable bromine, it had increased in ozone depleted boundary layer air. The mean NO2 level was 85 pptv with an estimated uncertainty of a factor less than 2. However, this measurement of NO2 may have been the sum of NO2+N2O5. The possibility that Br atoms are formed from an N2O5+NaBr interaction is therefore not ruled out. There was a good indication that apparent NO2 was depleted during episodes of low ozone. An upper limit for the mixing ratio of formaldehyde was found to be 39 pptv, while acetaldehyde was observed at mixing ratios of ca. 65 pptv. Ethylene and acetylene were also found to be depleted concurrently with O3. These compounds do react with Br radicals in air (as do the aldehydes) and it is speculated that they may create a link with HOx. chemistry. Data on several other chemical compounds are also presented. Their participation in the O3 depletion chemistry is less clear. The implications of the measurements with respect to the hypothesis that the ozone depletion are due to a BrOx‐O3 destruction cycle are explored.

A regional scale model for the calculation of episodic concentrations and depositions of acidifying components

An eulerian long-range transport model for the calculation of concentrations of SO2, SO4, NOx, and NO3 and wet and dry depositions of SOx (sum of SO2 and SO4) and NOy (sum of NO, NO2 and NO3) over Europe is presented. The model is developed in such a way that only routinely available, analyzed or prognostic meteorological fields are required as input data. In this way it is possible to obtain a forecast of the air quality during smog episodes. For evaluation of smog episodes the model provides a way to estimate the contributions of different sources and the effect of emission scenarios. The model has been evaluated for four winter and three summer episodes. The modeled concentrations of SO2 and SO, are in agreement with the available measurements. A less good agreement is found for NO2 and NOx (sum of NO and NO2) concentrations. For these components the model tends to underpredict the measured values.

Phytoplankton growth and new production in the Weddell Sea marginal ice zone in the austral spring and autumn

Rates of primary production, N03- uptake, and NH,l uptake by phytoplankton were measured in the marginal ice zone of the Weddell Sea in austral spring 1983 and autumn 1986. In spring Chl concentrations averaged 3 pg liter-‘, primary productivity 490 mg C m-2 d-l, and surface phytoplankton growth rates 0.30 doublings d-l. In autumn these rates were all much lower, averaging 0.14 pg liter- l, 126 mg C m-2 d-l, and 0.14 doublings d-l. During both seasons NH,+ was consistently the preferred source of N, but because of the much greater availability of N03- in the euphotic zone (21-28 PM NO,- vs. -0.4 yM NH,+ during both seasons), N03- uptake rates generally equaled or exceeded those of NH, +. Vertically integrated&ratios (the ratio of NO3- uptake to the sum of NO,- plus NH,+ uptake) averaged 0.52 (range from 0.35 to 0.70) in spring and 0.72 (range from 0.60 to 0.84) in autumn. In 1983 we observed sharply elevated relative preference indices for NH,+ whenever the ambient NH,+ concentration was ~0.3 PM, which we interpret as evidence that Antarctic phytoplankton growing at NH.,+ concentrations CO.3 PM have the ability to increase their rate of NH,+ uptake rapidly in response to increased availability. We estimate the new production of the marginal ice zone to be at least 49 g C m-2 yr-1 for the NovemberMarch period. This value supports previous findings that the ice edge is the main site of production in the Southern Ocean and that it is likely to dominate the annual cycle of organic matter flux from the euphotic zone.

Modeling study of SO x and NO x transport during the January 1985 SMOG episode

For the January 1985 smog episode concentrations of SO2, sulphate (SO4), NO x (sum of NO and NO2) and nitrate (NO3) have been calculated for north-western Europe by means of an atmospheric transport model. The unfavorable dispersion conditions (moderate to low wind speeds, a low mixing height and a strong inversion) and a reduced dry deposition over the snow-covered or frozen soil, in combination with increased space heating emissions due to the exceptionally cold weather, gave rise to high ground level concentrations. In order to study the effectiveness of control measures during this type of episodes, calculations were made for various emission scenarios. The results were evaluated for four receptor areas, two areas relatively close to the major sources (The Netherlands and the Black Forest) and two more remote areas (Scotland and the SW coast of Sweden, near Gothenburg).

Systematic variations in the concentration of NOx (NO Plus NO2) at Niwot Ridge, Colorado

Measurements of the concentrations of NO and NO2 were made in the rural troposphere during a year's period in 1980–1981, during the summers of 1983, 1984, and 1987, and during the fall of 1984. The field site was located near Niwot Ridge, Colorado, at an elevation of 3 km. NO was measured with a chemiluminescence instrument, and NO2 was photolyzed to NO and measured by the same instrument. The performance of this instrument is discussed in detail. Aspects of the NOx (sum of NO and NO2) concentrations discussed include the overall distribution, the seasonal and diurnal cycles, the interannual variations, and the correlation with meteorological parameters. The meteorological dependence of [NOx] elucidates the mechanisms that transport NOx to the site. Even though the Denver urban area lies downwind from the site with respect to the prevailing winds, it is NOx from that area that predominates and is responsible for the enhanced acidic deposition and elevated ozone levels at the site. The valley‐mountain flow that is primarily responsible for this transport also may be an important mechanism for transporting anthropogenic pollution from the planetary boundary layer to the free troposphere. The major photochemical loss processes of NOx are reaction of NO2 with hydroxyl radicals to form HNO3 and the formation of PAN (peroxyacetyl nitrate) and perhaps other organic nitrates in the summer and reaction of NO2 with O3 to form NO3, N2O5, and further oxidized species in the winter.

Calculation of long term averaged ground level ozone concentrations

Seasonal averaged ground level concentrations for O 3 have been calculated for The Netherlands by means of a two-layer Lagrangian long-range transport (LRT) model. The model includes emissions, nonlinear atmospheric chemistry, dry deposition, exchange between boundary layer (BL) and free troposphere (FT) and fumigation between a mixed layer and an aged smog layer. Concentrations of primary and secondary pollutants in the FT are obtained from a two-dimensional global model developed by Isaksen. In the reference calculation the modelled concentrations of Ox (sum of O 3 and NO 2) and O 3 are in fair agreement with measurements. The NO x (sum of NO and NO 2) and NO 2 concentrations are under-estimated by the model but there is a good temporal correlation between calculated and measured concentrations. Validation of other components involved in the chemical scheme is hardly possible due to the paucity of measured data. It can only be stated that the results presented in this paper are not in disagreement with measured or modelled data presented in the literature. In a number of sensitivity runs the influence of European anthropogenic emissions of NO x and volatile organic compounds (VOC) has been investigated. The calculations indicate that the influence of European emissions on the growing season, daytime averaged (May–September, 10–17 h) O 3 concentrations in The Netherlands is small. For European reductions in the order of tens of per cents a VOC emission reduction is more effective than a NO x emission reduction in lowering the O 3 concentrations. For strong reductions (about 70%) VOC and NO x are equally effective. The effects of the modelled underprediction of NO x concentrations on the production of O 3 on a European scale are probably small. On a local scale the effects are more pronounced due to the NO/O 3 titration (photostationary equilibrium). Therefore, an empirical correction is applied on the modelled O 3 concentrations. After this correction, it is shown that daytime O 3 levels during the growing season increase when European NO x emissions are reduced (2.0–7.7.% increase at 50% NO x emission reduction). A reduction in VOC emission leads to decreasing O 3 levels (9% reduction for 40% VOC emission reduction, 16% reduction for 70% VOC emission reduction). For a combined reduction of both VOC and NO x slightly decreasing ground level O 3 concentrations are expected.

Aircraft measurements of oxides of nitrogen along the eastern rim of the Asian continent: Winter observations

Aircraft observations of oxides of nitrogen (NO y ), measured with a ferrous sulfate converter, over the sea surrounding the Japanese islands (30–43° N, 131–141° E) were carried out in the winter of 1983 and 1984 at altitudes mostly between 3 and 8 km. NO y defined here is the sum of NO, NO2, and other unstable oxides of nitrogen that are converted to NO by ferrous sulfate. The main observations were:

Simultaneous in situ measurements of nitrogen dioxide, nitric oxide, and ozone between 20 and 31 km

Simultaneous in situ measurements of NO, NO2, O3, and temperature were made from approximately 20 to 31 km in the stratosphere during July, August, and November. Two of the balloon flights were made from Palestine, Texas (32°N), the third from Gimli, Manitoba (50°N). NO was detected using the chemiluminescence technique; NO2 was photolyzed to NO prior to detection. Both the NO and NO2 mixing ratios are in good agreement with most other measurements in this altitude region. To within the combined uncertainties the measured NO2 to NO ratios agree with those calculated assuming photochemical steady state. There is, however, a tendency for the observed ratio to be larger than the calculated ratio at low altitudes near 32°N, but not at 50°N. Refinements to the experiment will be required to elucidate unequivocal discrepancies. From the observation of a temporal increase in the sum of NO and NO2 while at constant altitude, it is possible to infer the abundance of N2O5 near noon. Further, a lower‐limit estimate of the total odd nitrogen mixing ratio of 16–19 parts per billion by volume near 30 km is made using the observations of NOx, the estimated N2O5 mixing ratio, and previous measurements of HNO3.

Wheat Fallow Tillage Systems' Effect on a Newly Cultivated Grassland Soils' Nitrogen Budget

The objective of this study was to examine soil nitrogen (N) losses from grassland soil as affected by time since the beginning of cultivation. A native grassland site was cultivated for winter wheat (Triticum aestivum L.) production in a crop-fallow rotation under three tillage systems; no-till, stubble mulch, and plow (bare fallow). The experiment was located in Western Nebraska on a Duroc loam (fine silty, mixed, mesic, Pachic Haplustolls). After 12 yr of cultivation, losses of soil N from the 0 to 30 cm depth were 3% for no-till, 8% for stubble mulch, and 19% for the plow tillages. Potential loss by erosion was small because of protection from wind by the surrounding grasslands. These results suggest decreased stirring of the soil resulted in major N savings beyond erosion losses. The sum of NO−3-N greater than that found below the sod control plus crop removal of N accounted for essentially all of the soil N lost from stubble mulch and plow tillages. In the no-till environment, crop removal of N and leached NO−3-N accounted for more N than had been lost from the soil since cultivation began. Plow tillage system resulted in leaching of 100 kg ha−1 more NO−3-N than occurred with no-till or stubble mulch. Soil N in the 0-to 30-cm soil depth was fractionated into exchangeable NH+4-N, nonexchangeable NH+4-N, and nonhydrolyzable N. The nonexchangeable and exchangeable NH+4-N fractions were not affected by cultivation. The nonhydrolyzable N fraction was reduced by all forms of tillage and accounted for a substantial part of the soil N losses.

Response of commercial chemiluminescent nitric oxide-nitrogen dioxide analyzers to other nitrogen-containing compounds

Commercial chemiluminescent oxides of nitrogen analyzers employing carbon or molybdenum converters are nonspecific for determination of nitrogen dioxide (NO/sub 2/). The instruments not only measure NO/sub 2/, but also simultaneously respond nearly quantitatively to peroxyacetyl nitrate (PAN), and a variety of other organic nitrates and nitrites. Furthermore, they respond nonquantitatively to compounds such as nitroethane and nitric acid. The implications of these observations are not serious for most ambient air analyses where the concentrations of the interfering nitrogenous compounds are low relative to NO/sub 2/ levels. However, for highly quantitative ambient air or smog chamber measurements under circumstances where relatively low concentrations of NO/sub 2/ occur simultaneously with high concentrations of PAN and other nitrogen-containing compounds, corrections for interference by these compounds can be significant. In the absence of such corrections, the NO/sub x/ mode of commercial chemiluminescent analyzers must be viewed to the good approximation as measuring total gas phase ''oxides of nitrogen,'' not simply the sum of NO and NO/sub 2/.

Photochemistry of minor constituents in the troposphere

Altitude profiles for the number densities of NO, NO 2, NO 3, N 2O 5, HNO 2, CH 3O, CH 3O 2, H 2CO, OH, and HO 2 are calculated as a function of time of day with a steady-state photochemical model in which the altitude profiles for the number densities of H 2O, CH 4, H 2, CO, O 3, and the sum of NO and NO 2 are fixed at values appropriate to a summer latitude of 34°. Average daily profiles are calculated for the long-lived species, HNO 3, H 2O 2, and CH 3O 2H. The major nitrogen compound HNO 3 may have a number density approaching 5 × 10 11 molecules cm −3 at the surface, although an effective loss path due to collisions with particulates could greatly reduce this value. The number density of OH remains relatively unchanged in the first 6 km and reaches 1 × 10 7 molecules cm −3 at noon, while the number density of HO 2 decreases throughout the lower troposphere from its noontime value of 8 × 10 8 molecules cm −3 at the surface. H 2O 2 and H 2CO both have number densities in the ppb range in the lower troposphere. Owing to decreasing temperature and water concentration, the production of radicals and their steady-state number densities decrease with altitude, reaching a noontime minimum of 1 × 10 8 molecules cm −3 for OH and 3 × 10 7 molecules cm −3 for HO 2 at the tropopause. The related minor species show even sharper decreases with increasing altitude. The primary path for interconverting OH and HO 2 serves as the major sink for CO and leads to a tropospheric lifetime for CO of ~0.1 yr. Another reaction cycle, the oxidation of CH 4, is quite important in the lower troposphere and leads to the production of H 2CO along with the destruction of CH 4 for which a tropospheric lifetime of ~2 yr is estimated. The destruction of H 2CO that was produced in the CH 4 oxidation cycle provides the major source of CO and H 2 in the atmosphere.

INDUCTION OF PULMONARY TUMOURS IN MICE BY MITROSONORNICOTINE, A POSSIBLE CONSTITUENT OF TOBACCO SMOKE.

NITROSAMINES could be formed in cigarette smoke by reactions between secondary amines and oxides of nitrogen1,2. Several secondary amines, including anabasine, nornicotine, dimethylamine, diethylamine, pyrrolidine, piperidine and proline, have been detected in cigarette smoke, which also contains about 200 parts per million of oxides of nitrogen (as the sum of NO and NO2) (refs. 3 and 4). The nitrosamine derivatives of some of these amines have already been shown to be carcinogenic5,6. We have reported that nitrosoanabasine administered in the drinking water induced benign and malignant tumours of the œsophagus of rats1. In parallel with these biological investigations, attempts have been made to detect nitrosoanabasine and nitrosonornicotine in cigarette smoke. So far these attempts have not been successful, although methods capable of detecting small amounts (for example, 5 µg) of specific nitrosamines have been developed1. Lack of success may be due either to instability of nitrosamines under the conditions prevailing in cigarette smoke or to interference in their detection by other constituents of the smoke. Nitrosoanabasine could not be detected in cigarette smoke condensates to which it had been deliberately added nor in the smoke of cigarettes which had been impregnated with the substance before smoking. If these negative results are due to instability of the nitrosamines, the possibility of their biological importance is only ruled out if their half-lives are very short. Further investigations into these problems are in progress.