NO Concentration Levels Research Articles

Artificial neural network application for forecasting the nitrogen oxides in the atmosphere at the microclimate conditions: example of Iğdır city in Turkey

The aim of this research is forecasting the NOx, NO2 and NO concentration levels with different artificial neural networks structures (ANNs) and determining the best ANNs structure for forecasting emissions. For this aim, it was used one learning function and, six different transfer function pairs with three different neuron numbers. The MATLAB software helped constructing ANNs models. In addition, the air pollutants and meteorological factors were used as input parameters simultaneously at the ANNs. The end of the research, NOx, NO and NO2's concentration levels were modelled with high accurate levels. The R2 values of the NOx, NO and NO2 were calculated as 0.998, 0.995 and 0.997, respectively. The best results were obtained from ANNs structures which used Logarithmic sigmoid - Symmetric sigmoid transfer functions with 20 and 30 neuron number for forecasting of the NOx and NO concentration levels, respectively. In addition, the forecasting of NO2 emission rate, the best results were determined from the ANNs structure used Logarithmic sigmoid - Linear transfer function with 30 neuron number. According to sensitivity analyses and correlation tests, it was concluded that O3, SO2, wind direction, wind speed, and relative humidity inputs were more effective on the NO2, NO and NOx concentrations than the other inputs. Finally, it can be said that with the use of both air pollutants and meteorological factors as input parameters simultaneously the artificial neural network models can be simulated the concentration level of NO, NOx and NO2 with high accuracy.

South Pole Antarctica observations and modeling results: New insights on HO x radical and sulfur chemistry

Measurements of OH, H 2SO 4, and MSA at South Pole (SP) Antarctica were recorded as a part of the 2003 Antarctic Chemistry Investigation (ANTCI 2003). The time period 22 November, 2003–2 January, 2004 provided a unique opportunity to observe atmospheric chemistry at SP under both natural conditions as well as those uniquely defined by a solar eclipse event. Results under natural solar conditions generally confirmed those reported previously in the year 2000. In both years the major chemical driver leading to large scale fluctuations in OH was shifts in the concentration levels of NO. Like in 2000, however, the 2003 observational data were systematically lower than model predictions. This can be interpreted as indicating that the model mechanism is still missing a significant HO x sink reaction(s); or, alternatively, that the OH calibration source may have problems. Still a final possibility could involve the integrity of the OH sampling scheme which involved a fixed building site. As expected, during the peak in the solar eclipse both NO and OH showed large decreases in their respective concentrations. Interestingly, the observational OH profile could only be approximated by the model mechanism upon adding an additional HO x radical source in the form of snow emissions of CH 2O and/or H 2O 2. This would lead one to think that either CH 2O and/or H 2O 2 snow emissions represent a significant HO x radical source under summertime conditions at SP. Observations of H 2SO 4 and MSA revealed both species to be present at very low concentrations (e.g., 5 × 10 5 and 1 × 10 5 molec cm −3, respectively), but similar to those reported in 2000. The first measurements of SO 2 at SP demonstrated a close coupling with the oxidation product H 2SO 4. The observed low concentrations of MSA appear to be counter to the most recent thinking by glacio-chemists who have suggested that the plateau's lower atmosphere should have elevated levels of MSA. We speculate here that the absence of MSA may reflect efficient atmospheric removal mechanisms for this species involving either dynamical and/or chemical processes.

Potential Contribution of Traffic to Air Pollution in the State of Kuwait

Problem statement: The reduction in ambient air pollution is a universal goal-particularly in urban areas, the lack of resources often necessitates identification and prioritization of sources of air pollutants. Efficient planning and effective management of environmental pollutants is thus important for optimum utilization of limited resources. Approach: This study examined seven years of data from three air pollution monitoring stations in the State of Kuwait. The stations-each located at a different district-were selected such that the influence of traffic source and oil refineries/power stations on ambient air pollution contaminants could be detected. A sampling plan was developed and CH4, CO, O3, SO2, NO, NOX and TS concentrations were measured both during peak-traffic hours as well as off-peak hours. Results: Analyses of the data showed that concentrations of the air pollutants had slightly increased over the seven-year study period and only those of the NOX and SO2, exceed the permitted standard levels. Traffic was the main source of air pollution in the district located adjacent to the city centre, while oil refineries contributed most to ambient air pollution in the rural district. Conclusion: The concentration levels of NO, NOX and Total Sulfate (TS) were significantly less at the district located away from urban traffic and oil refineries compared to those of with heavy daily traffic congestions and those of the district in proximity to oil refineries.

PRIMARY EMISSION RATIOS OBTAINED FROM THE MONITORING OF CRITERIA POLLUTANTS IN REBOUÇAS TUNNEL, RIO DE JANEIRO, BRAZIL.

Meassurements of pollutants concentrations in tunnels can reflect the actual characteristics of mobile sources in order to provide a control strategy to reduce emissions and secondary pollutants formation. Concentration levels of CO, NOx, SO2 and PM10 (particulate matter less than 10 m in diameter) were recorded inside Rebouças Tunnel, in a continuous monitoring station installed at about 1,500 m from the entrance. The reported data are the hourly average values through the year of 2002, bracketed only for the weekdays, weekends excluded. In terms of typical day cycles, the highest concentration levels occur close to traffic peaks and the criteria pollutants show good overall correlation levels with CO, as expected, given their common combustion-bound origin. CO hourly averages ranged from 10 to 50 ppm and the average CO/NO ratio (on a ppm basis) was 0.011, in good agreement with preliminary data for other locations in Brazil. NO concentration levels ranged from less than 1 ppm to about 4 ppm and this form is by far the dominant for nitrogen oxides (NOx) found in the tunnel, accounting for more than 90% of the sum of NO plus NO2. Sulfur oxides (measured as SO2 ) and inhalable particles concentrations ranged from 55 to 140 ppb and about 60 to 250 µg m-3 , respectively, for the composite annual profiles.

Long-term study of NO x behavior at urban roadside and background locations in Seoul, Korea

In this study, the fundamental aspects governing the environmental behavior of nitrogen oxides were explored from two air quality-monitoring stations (AQM) in Seoul, Korea, over an 11-year period (1996–2006). The two stations were selected to represent an urban roadside (U-RS) and urban background station (U-BG). The mean concentration levels of NO x at the U-RS area exhibited a gradual decrease through years (from ∼290 ppb (1996) to 100 ppb (2003)), while those measured at the U-BG site maintained fairly stable values (∼70 ppb) throughout the years. The mean concentration levels of NO and NO 2 at the U-BG site were almost the same (∼35 ppb), while the U-RS site showed that the mean value of NO (∼127 ppb) is significantly higher than that of NO 2 (∼60 ppb). The observation of larger differences in NO level between the two sites reflects the direct impact of vehicular emissions at the U-RS site. Both correlation and factor analyses were conducted between the hourly data sets of NO x species ( N=∼90,000) and relevant environmental variables for both the sites. The results of both tests confirm the prominent role of vehicular activities in determining the level of nitrogen oxides at urban roadside environments, although such effects appear to be rather intricate at U-BG. Our comparative analysis of NO x data sets collected over varying temporal scales indicate that their distributions in the urban environment can be distinguished more clearly in spatial factors (i.e., between urban background and urban roadside) than other criteria.

A comparison of three street canyon models with measurements at an urban station in Antwerp, Belgium

We discuss the application of three street canyon models in order to evaluate the concentration levels of NO x , SO 2, PM 10 (1999/30/EC), CO and benzene (2000/69/EC) in one of the main passage roads in the city of Antwerp, the “Plantin en Moretuslei” in the city of Antwerp. The model results are based on identical urban transport emission input data for Antwerp and on the same meteorological input data derived from nearby meteorological towers. Background values are obtained from a regional air quality model, which is used as a reference model for environmental reporting in Flanders. For NO x , SO 2, PM 10 and benzene the results are compared with hourly observations from a monitoring station in the “Plantin en Moretuslei”. It was found that the annual averages are relatively well captured by the models. The higher percentiles (98th, 99th) are underestimated, due to the lack of hourly variation in the background concentration. A more sophisticated approach is needed to model these background concentrations more adequately.

Improved reversibility in aged porous silicon NO 2 sensors

Porous silicon (PS) conductometric gas sensors can exhibit large sensitivity to gases, due to the large surface versus volume ratio of porous silicon. A possible application is the detection of traces of nitrogen dioxide (NO 2), an air pollutant. Δ G/ G signals in excess of 10 in the presence of concentrations as low as 50 ppb in dry air can be demonstrated. Unfortunately, such high sensitivity to NO 2 is achieved, in fresh samples, with poor reversibility. Another problem is the interference of water vapor, which also affects the porous silicon conductivity. However, we show that reversibility is complete in aged samples, and sensitivity to water vapor is lowered. Although in aged samples large Δ G/ G signals are harder to achieve, we show that concentration levels of NO 2 at few tens of ppb are still detectable.

Integrated air quality modelling for the assessment of air quality in streets against the council directives

Abstract We discuss the application of the integrated air quality model AURORA to evaluate the concentration levels of NO 2 , SO 2 , PM 10 (1999/30/EC), CO and benzene (2000/69/EC) in 11 selected streets in the city of Antwerp. Together with the emission module, the analytical street box module of AURORA was used for the assessment of pollutant concentrations in street canyons. Comparisons with a measurement station located in one of the evaluated street canyons show agreements that are within the uncertainty range given by the guidelines in the EU directives, except for the NO 2 concentrations. An analysis of the measured and modelled concentrations and percentiles shows that concentrations of NO 2 , CO and benzene vary widely from street to street, whereas for SO 2 and PM 10 the model results show less variation between individual streets, indicating a more important contribution from the urban and regional background.

Relative Chlorinating, Nitrating, and Oxidizing Capabilities of Neutrophils Determined with Phagocytosable Probes

The capabilities of stimulated neutrophils to initiate intraphagosomal and extracellular chlorination, nitration, and other oxidative reactions has been evaluated using a fluorescent particle and soluble phenolic compounds as target molecules. Neutrophils activated by the soluble stimulus, phorbol myristate acetate, both chlorinated fluorescein that was covalently attached to polyacrylamide microspheres and initiated tyrosine dimerization. When nitrite ion was present at millimolar concentration levels in the medium, nitration of the phenolic rings also occurred; the relative extent of nitration increased as the nitrite concentration was increased. Myeloperoxidase (MPO) also catalyzed nitration and chlorination of fluorescein and the fluorescein-conjugated particles in cell-free solutions; the relative nitration yields increased with increasing [NO2-]/[Cl-] ratios. Nitration did not involve intermediary formation of nitrating agents derived from reaction between MPO-generated HOCl and NO2- because this reaction also occurred in chloride-free media and direct addition of HOCl to solutions containing NO2- and fluorescein gave only chlorinated products. In marked contrast to these extracellular reactions, intraphagosomal nitration of the fluorescein-conjugated particles could not be detected (even at [NO2-] as high as 0.1 M), whereas chlorination of the probe was extensive. These data indicate that intraphagosomal aromatic nitration in neutrophils is negligible, although extracellular nitration of phenolic compounds by secreted MPO could occur at physiological concentration levels of NO2-.

Ambient atmospheric trace gas concentrations and meteorological parameters during the first BEMA measuring campaign on May 1994 at Castelporziano, Italy

During the first measuring campaign of the BEMA project, carried out in May 1994 at Castelporziano, near Rome, Italy, one of the tasks was to measure continuously meteorological parameters and tropospheric trace gas concentrations. The atmospheric species measured were ozone, NO x , anthropogenic and biogenic hydrocarbons, carbonyl compounds, hydrogen peroxide, organic peroxides and PAN. Another goal was the characterization of the atmospheric circulation patterns. The results showed that anthropogenic pollution is present at the Castelporziano site originating mainly from the Rome metropolitan area but also from other directions. The average concentration levels of NO x were about 9 ppb, the average total measured anthropogenic hydrocarbon concentration was 67 ppbC and the average ozone mixing ratio was 36 ppb. The possible role of naturally emitted VOCs in tropospheric ozone formation is discussed.

Simultaneous no and temperature imaging measurements in turbulent nonpremixed flames

A quantitative laser-induced fluorescence imaging technique was developed with sufficient sensitivity to detect low NO concentration levels present in turbulent flames. For this linear fluorescence technique, quenching and population corrections are necessary for quantitative NO imaging. A correction procedure was developed that utilizes temperature measurements and flamelet or distributed reaction model results. The model results showed that the quenching correction can be related to temperature. Simultaneously with NO imaging, Rayleigh scattering imaging was used to determine the temperature. The measured temperature was combined with model results to estimate the quenching and population corrections for the NO signal. Analysis showed that this data reduction methodology has less than 10% error and the total error is within 25%. The imaging setup uses a multipass cell, to create a thin sheet of laser light, and a 0.8/f collection optics for the NO signal. The in-flame detectability of the imaging system is 1 ppm. To validate the technique, NO was measured and compared at two different rotational levels. Imaging results were also compared with NO{sub x} probe and thermocouple temperature measurements. The results of different measurement methods compared well, thus confirming the validity of the technique. The technique was applied to the flame initiationmore » zone of lifted turbulent non-premixed-methane flames. NO was found to correspond closely to the temperature field. As the turbulence altered the structure of the temperature field, NO was similarly altered. Distributed reaction model results were favorably compared to the imaging data. This further supports the validity of both experimental and model results.« less

The role of mixing in burner-generated carbon monoxide and nitric oxide

Nonuniformities and rates of mixing are found to play an important role in determining emissions of carbon monoxide and nitric oxide from a kerosene-fueled atmospheric-pressure burner. Nonuniformaties are allowed for by assuming that burnt gas eddies have a normal distribution of equivalence ratios about the mean value. Mixedness is characterized by the ratio of the standard deviation of this distribution to the mean value and is related to combustor operating variables. A simple one-dimensional flow model is coupled with the mixing model to predict the variation of CO and NO concentrations with atomizing pressure and distance along the burner. The data obtained agree with the predictions and show clear mixing effects on both CO and NO concentration levels.