Sum Of NO Research Articles

Experimental Evaluation of the Effect of Replacing Diesel Fuel by CNG on the Emission of Harmful Exhaust Gas Components and Emission Changes in a Dual-Fuel Engine

The constant development of civilization increases environmental pollution as a result of industrial activity and transport. Consequently, human activity in this area is restricted by regulations governing the permissible emission of harmful substance components into the environment. These include substances emitted by combustion engines, the use of which remains high in many industries. Consequently, research is being conducted to reduce the emissions of harmful exhaust components from existing and newly manufactured internal combustion engines. This research presents a used semi-truck engine, in which an innovative Compressed Natural Gas (CNG) supply system was applied. Using this fuel supply installation allows a mass exchange of the base diesel fuel to natural gas of up to 90%. The study evaluated the effect of the diesel/CNG exchange ratio for different engine operating conditions (engine load, speed) on the concentration of toxic components, such as CO, NO, NO2, NOX, as a sum of NO, NO2, CH4, C2H4, C2H6, C3H8, NH3, and CH2O. The use of a dual-fuel system had a positive effect on the emissions of some harmful exhaust components, even in an engine from a vehicle that had been running for many years on diesel and at high mileage, but, simultaneously, the emissions of some harmful exhaust gas components increased.

A comprehensive study on ozone pollution in a megacity in North China Plain during summertime: Observations, source attributions and ozone sensitivity

Tropospheric ozone (O3) pollution has been becoming prominent in North China Plain (NCP) in China since last decade. In order to clarify the source contribution and formation mechanism of O3, the critical precursors of volatile organic compounds (VOCs) were measured with both on-line and off-line methods in Luoyang City in summer of 2019. The concentrations of nitrogen oxides (NOx, sum of NO and NO2) and O3 were simultaneously monitored. Fifty-seven VOCs measured in U.S. Photochemical Assessment Monitoring Station (PAMS) showed daily concentrations in a range of 14.5 ± 5.33 to 29.2 ± 11.2 ppbv in Luoyang, which were comparable with those in other Chinese megacities. The mass compositions of VOCs were determined, with comparatively low proportions of alkanes (<50%) but high fractions of photoreactive alkenes and alkyne. Source apportionment of VOCs was conducted by Hybrid Environmental Receptor Model (HERM). The results indicated that industrial (38.5%) and traffic (32.0%) were the two dominated pollution sources of VOCs in the urban, while the biogenic and residential sources had contributions of 15.8% and 13.8%, respectively. To further measure the O3 formation sensitivity and its source attribution, the WRF-CHEM model was adopted in this study. The variation of O3 between the observation and the stimulation using the local emission inventory showed an index of agreement (IOA) of 0.85. The simulation conducted by WRF-CHEM indicated an average of 43.5% of the O3 was associated with the regional transportation, revealing the importance of inter-regional prevention and control policy. Traffic and biogenic emissions were the two major pollution sources to an O3 episode occurred from July 21 to July 27, 2019 (when O3 concentration over 150 μg m−3) in Luoyang, with average contributions of 22.9% and 18.3%, respectively. The O3 isopleths proved that its formation in the atmosphere of Luoyang was in transitional regime and collectively controlled by both VOCs and NOx. This was different from the observations in main cities of NCP before implantations of strict emission controls. The isopleths additionally designated that the O3 formation regime would move forward or shift to NOx regime after a reduction of over 45% during the episode. Similar patterns were also reported in other Chinese megacities such as Beijing and Shanghai, due to the tightening of the NOx control policies. Our results do support that the simultaneous controls of NOx and VOCs were effective in reductions of tropospheric O3 in Luoyang. Meanwhile, joint regional control policies on the emissions of NOx and VOCs can potentially overwhelm the current O3 pollutions in China.

Study on the influencing factors of removal of NOX from cement kiln flue gas by sewage sludge as a denitration agent

Experimental study on the influencing factors of using sewage sludge as a denitration agent for cement industry was carried out on a self-made laboratory-scale fluid-bed reactor. Results indicate that sludge combustion at 900°C shows an ideal NOX (the sum of NO and NO2) removal activity under simulated working conditions of cement precalciner. The optimal removal efficiency of NOX can reach 70.36 ± 3.59% in the presence of cement raw meal (CRM) at a sludge particle size range of 0.18-0.25mm and the sludge dosage of 0.75g/min. Besides, the NOX removal efficiency increases to 76.94 ± 5.02% in the absence of CRM, indicating that cement raw meal inhibits the NOX removal. This phenomenon may be attributed to the fact that CRM has promotion effect on NH3 produced and obvious inhibitory effect on CO produced; while NH3 and CO play a leading role in NOX reduction, the combined effect leads to the decrease of NOX removal. Moreover, the relationship between the composition of CRM on the inhibition of NOX removal is MgO < CaCO3 < CRM < Al2O3 <Fe2O3. Meanwhile, the effect of additive variety on the sludge denitration activity indicates that urea significantly promotes the NOX removal, which is attributed to the decomposition of urea to form NH3. The stability experiment shows that sludge denitration efficiency remains stable above 70% in the presence of CRM and can reach over 80% when adding appropriate urea. This method can realize the removal of NOX in the cement kiln flue gas and the resource utilization of sludge. It is a promising method for sludge disposal.

Variations in the atmospheric pollutant immission (2009\u20132015) field near a large lignite-fired power plant (in Europe/Poland)

Emissions from the energy sector are one of the causes of poor air quality. The status of air pollution caused by the operation of large-size lignite-fired power plants was analyzed (in the years 2009–2015). Emission and immission data from a monitoring station located near a power plant were analyzed (in Europe/Poland in eastern Wielkopolska). The monitoring station conducts continuous measurements of immission concentrations of the following pollutants: PM10, sulfur dioxide (SO2), carbon monoxide (CO), nitrogen oxides NOx (separately and as the sum of NO and NO2), and ozone (O3) recording at the same time with meteorological parameters such as air temperature, relative air humidity, wind speed, and direction. The dependence of concentrations of selected pollutants on temperature at monitoring point was analyzed. The recorded concentrations were compared with values calculated as a result of modeling of pollutants dispersion in the atmosphere.

Prediction of voltage required for nonthermal plasma based diesel exhaust treatment for removal of nitrogen oxides.

A prior prediction of voltage required for the nonthermal plasma (NTP)-based diesel exhaust treatment toward removal of nitrogen oxides, i.e., NOX (sum of NO and NO2) would help the researchers to plan for the resources required for the treatment. In this present study, experimental data set of 4032 number of input-output pairs have been collected by taking flow rate (Fr), temperature (T), discharge gap (Dg), initial NOX concentration (NOXi), and NOX removal efficiency (ηr) as the 5 inputs and the voltage required for the treatment (Vrt) as the output. Then, an attempt has been made to predict Vrt for achieving particular ηr, while other input parameters have fixed values, using multivariable linear and quadratic polynomial regression techniques. The performances of these two predictive models have been assessed during training and testing. The root mean square error (RMSE) between experimental and predicted values of Vrt with both the models has been compared, where quadratic polynomial regression-based model has been found to be performing well with an RMSE of 0.85kV for a test data of 1210 sets. This study shows that the voltage required for the treatment, to achieve a particular amount of NOX removal from the exhaust, can be predicted with very good accuracy so that the necessary arrangements for the treatment can be made by the researchers.

Regression-based models for prediction of oxides of nitrogen in diesel exhaust with electric discharge-based treatment

A prior prediction of oxides of nitrogen, i.e., NOX (sum of NO and NO2), in diesel exhaust while treating with electric discharge-based nonthermal plasma (NTP) technique, would assist the researchers in planning the resources required for the treatment. In this present study, the performance of different regression-based models, i.e., linear, support vector regression and Gaussian process regression (GPR), has been analyzed for predicting the NOX concentrations based on the values of five dominating parameters of the NTP treatment. Experiments have been conducted and collected a dataset of 4032 number of input–output pairs to be used for training and testing of the regression models. The performances of these models have been assessed while testing them for the unseen set of data. A comparison of root-mean-square error (RMSE) has been made, where Matern 3/2 type of GPR model has been found to be the best among all the considered models with an RMSE of 1.86 ppm for a test data of 1210 sets. The model is shown to perform consistently well even when the test data are increased to 50% of total data. Regression analysis shows that the NOX can be predicted with very good accuracy using the Matern 3/2 type of GPR model.

Feasibility of Artificial Neural Networks and Fuzzy Logic Models for Prediction of NO$_{X}$ Concentrations in Nonthermal Plasma-Treated Diesel Exhaust

High-voltage discharge-based nonthermal plasma (NTP) treatment for diesel exhaust is a laboratorial proven efficient technique. A prophecy of the treatment results based on the knowledge of its parameters would be a step forward toward bringing it into real-time applications of pollution control. In this paper, artificial neural networks (ANNs) and fuzzy logic model (FLM) have been used to model the NO $_{ X }$ (sum of NO and NO2) concentrations as a function of parameters of the NTP process. A data set of 4032 input–output pairs has been collected by conducting experiments, in which 70% of the data are used for the training of the models derived. The performances of all the considered models have been evaluated by testing them for the remaining 30% of the data, which is novel for the models. Furthermore, a comparison of the models has been made based on the root-mean-square error (RMSE) and mean relative error (MRE), where the FLM has been found to be the better compared to the ANN-based models, i.e., ANN, multilayer perceptrons (MLP), and functional link ANN (FLANN). The RMSE of FLM is 2.53 ppm for a test data of 1210 sets. It can be said from these results that the NO $_{ X }$ concentrations can be predicted using FLM with a good accuracy.

A proxy for atmospheric daytime gaseous sulfuric acid concentration in urban Beijing

Abstract. Gaseous sulfuric acid (H2SO4) is known as one of the key precursors for atmospheric new particle formation (NPF) processes, but its measurement remains challenging. Therefore, a proxy method that is able to derive gaseous sulfuric acid concentrations from parameters that can be measured relatively easily and accurately is highly desirable for the atmospheric chemistry community. Although such methods are available for clean atmospheric environments, a proxy that works well in a polluted atmosphere, such as that found in Chinese megacities, is yet to be developed. In this study, the gaseous sulfuric acid concentration was measured in February–March 2018, in urban Beijing using a nitrate based – long time-of-flight chemical ionization mass spectrometer (LToF-CIMS). A number of atmospheric parameters were recorded concurrently including the ultraviolet radiation B (UVB) intensity, the concentrations of O3, NOx (sum of NO and NO2), SO2, and HONO, and aerosol particle number size distributions. A proxy for atmospheric daytime gaseous sulfuric acid concentration was derived via a statistical analysis method using the UVB intensity, [SO2], the condensation sink (CS), [O3], and [HONO] (or [NOx]) as the predictor variables, where square brackets denote the concentrations of the corresponding species. In this proxy method, we considered the formation of gaseous sulfuric acid from reactions of SO2 and OH radicals during the daytime, and the loss of gaseous sulfuric acid due to its condensation onto the preexisting particles. In addition, we explored the formation of OH radicals from the conventional gas-phase photochemistry using O3 as a proxy and from the photolysis of HONO using HONO (and subsequently NOx) as a proxy. Our results showed that the UVB intensity and [SO2] are dominant factors in the production of gaseous sulfuric acid, and that the simplest proxy could be constructed with the UVB intensity and [SO2] alone. When the OH radical production from both homogenously and heterogeneously formed precursors were considered, the relative errors were reduced by up to 20 %.

Prediction of NO and NO2 Concentrations in NTP Treated Diesel Exhaust Using Multilayer Perceptrons

Non-thermal plasma technique (NTP) for mitigation of NOX from diesel engine exhaust is a laboratory proven technique with a good number of experimental studies. However, there are constraints which are preventing this technique to appear in practical applications. Prior prediction of exhaust characteristics with the NTP treatment according to the variations in its operating parameters can be a step ahead to make this technique applicable in real time. In this present study, experiments are conducted by varying parameters voltage, flow rate, temperature, discharge gap and initial sum of NO and NO2 concentrations. Six hundred number of datasets are collected to train and test the predictive models which are made using multilayer perceptrons (MLP). The objective of these models is to predict the sum of NO and NO2 concentrations at the downstream of the reactor during NTP based diesel exhaust treatment. As a part of the study, optimum number of neurons in the hidden layers is also found out. The root mean square error (RMSE) of an MLP with two hidden layers, each of 20 neurons, is found to be 3.29 ppm. Results assure that the prediction of sum of NO and NO2 concentrations can be achieved with a good accuracy using MLP.

Prediction of NO and NO2 Concentrations in Ozone Injected Diesel Exhaust after NTP Treatment Using Dimensional Analysis

NTP based Ozone injection cascaded with catalysts/adsorbents for diesel exhaust treatment has been demonstrated by various researchers as a competent method for mitigation of nitrogen oxides. In this present study, one more NTP reactor is cascaded instead of catalysts/adsorbents to treat the ozone mixed diesel exhaust. While most of the laboratory studies were carried out using expensive dry air cylinders for ozone generation, in the present study, ozone has been generated from atmospheric air only. The nitrogen oxides removal/conversion efficiency of this process depends on various electrical and physical parameters. A dimensionless relation has been obtained between the ratio of summation of NO and NO2 concentrations after treatment to that before treatment and other parameters affecting nitrogen oxides removal using dimensional analysis. Prediction of sum of NO and NO2 concentrations with the variation in six dominant parameters have been done using nonlinear regression technique. Six parameters, i.e. ozone concentration, voltage, frequency, flow rate, temperature and discharge gap have been varied to collect the experimental data required to train and test this model. The predicted sum of NO and NO2 concentrations are found to be well matching with the experimental results. The RMS error is found to be 3.7 % and 5.9 % respectively for training and test data.

Response surface methodology-based model for prediction of NO and NO2 concentrations in nonthermal plasma-treated diesel exhaust

Nonthermal plasma (NTP) technique for diesel exhaust emission control has been in the interest of the researchers from the last two decades, and it almost became a laboratory-proven technique for its efficiency over conventional techniques. A prior prediction of effectiveness of the process may lead to overcome the constraints in bringing this technique to real-time applications of diesel exhaust pollution control. In this present study, an attempt is made to find out the most dominating parameters and to predict the sum of NO and NO2 concentrations in NTP-treated diesel exhaust with respect to variations in operating parameter values using response surface methodology (RSM). Experiments have been conducted following 3N full factorial design and collected the data by varying voltage, flow rate, temperature, discharge gap and initial (NO + NO2) concentrations. The regression coefficients of the RSM-based mathematical model have been obtained by training it using these experimental data. The root-mean-square error (RMSE) is 4.7 ppm during the training. When this model is tested for a data other than that given during training (test data), the RMSE is 5.6 ppm. Further, the results are also compared with the model derived using the only available method in the literature, i.e., dimensional analysis, and found to be performing better.

Mercury emissions of a coal-fired power plant in Germany

Abstract. Hg ∕ SO2, Hg ∕ CO, NOx ∕ SO2 (NOx being the sum of NO and NO2) emission ratios (ERs) in the plume of the coal-fired power plant (CFPP), Lippendorf, near Leipzig, Germany, were determined within the European Tropospheric Mercury Experiment (ETMEP) aircraft campaign in August 2013. The gaseous oxidized mercury (GOM) fraction of mercury emissions was also assessed. Measured Hg ∕ SO2 and Hg ∕ CO ERs were within the measurement uncertainties consistent with the ratios calculated from annual emissions in 2013 reported by the CFPP operator, while the NOx ∕ SO2 ER was somewhat lower. The GOM fraction of total mercury emissions, estimated using three independent methods, was below ∼ 25 %. This result is consistent with other findings and suggests that GOM fractions of ∼ 40 % of CFPP mercury emissions in current emission inventories are overestimated.

Temporal persistence of intra-urban spatial contrasts in ambient NO2, O3 and Ox in Edinburgh, UK

Ambient NO2, O3 and Ox (the sum of NO2 and O3) are associated with adverse health outcomes. Quantitative assessment of the health burden from these pollutants requires knowledge of small-scale variations in their concentrations in urban environments. In particular, we were interested in the temporal stability of intra-urban spatial contrasts in these pollutants. This was investigated by concurrent measurements of NO2 and O3 by passive samplers at 30 sites in Edinburgh, UK, repeated 12 × 1-weekly for NO2 and 6 × 2-weekly for O3 in summer and winter. Temporally persistent and large spatial variations in both NO2 and O3 concentrations were observed. Concentrations of NO2 across the sites ranged on average by a factor of 14 between suburban parks and heavily-trafficked roadsides, corresponding to a difference in NO2 on average of ∼80 μg m−3. Intra-urban O3 concentrations also varied substantially, on average by a factor of 4 (average range 45 μg m−3) and with strong anticorrelation to NO2 concentrations across the 30 sites. Consequently intra-urban variability was considerably lower for Ox than for NO2 and O3. The temporal stability in relative NO2 and O3 concentrations indicate potential for deriving intra-urban spatial fields of NO2 and O3 at different times by scaling models of long-term spatial patterns of NO2 and O3 by the measurements at a single site. If Ox is a key determinant of adverse health then the large intra-urban spatial contrasts in NO2 and O3 may be less relevant, with Ox concentrations across an urban area determined at a suitable background site.

The relationship between plasma and salivary NOx

Several studies have shown that fasting plasma nitrite (NO2−) is an indicator of endothelial nitric oxide synthase (NOS) activity while plasma nitrate (NO3−) or the sum of NO2− and NO3− (NOx) does not reflect NOS function. Plasma NO2− can also be elevated through dietary NO3− where the NO3− is partially reduced to NO2− by oral bacteria and enters the plasma through the digestive system. NO3− is taken up from plasma by salivary glands and the cycle repeats itself. Thus, one may propose that salivary NO2− is an indicator of plasma NO2− and consequently of NO production. Many brands of nitric oxide (NO) saliva test strips have been developed that suggest that their product is indicative of circulatory NO availability. However, data supporting a relationship between salivary and plasma NO2− or NO bioavailability are lacking. Here we have measured basal salivary and plasma NO2− and NO3− to determine if any correlation exists between these in 13 adult volunteers. We found no significant correlation between basal salivary and plasma NO2−. Also no correlation exists between salivary NO3− and plasma NO2−. However, we did see a correlation between salivary NO3− and plasma NO3−, and between salivary NO2− and plasma NO3−. In a separate study, we compared the efficiency of salivary NO3− reduction with the efficacy of increasing plasma NO3− and NO2− after drinking beet juice, a high NO3−-containing beverage, in 10 adult volunteers. No significant correlation was observed between the ex vivo salivary reduction of NO3− to NO2− and plasma increases in NO3− or NO2−. These results suggest that measures of salivary NO3−, NO2− or NOx are not good indicators of endothelial function. In addition, the efficiency of saliva to reduce NO3− to NO2− ex-vivo does not demonstrate one's ability to increase plasma NO2− following consumption of dietary NO3−.

Colorimetric NOx sensor based on a porous glass-based NO2 sensing chip and a permanganate oxidizer

A new type of chemical sensor for gaseous nitrogen oxides (NOx, the sum of NO and NO2) has been fabricated by combining a porous glass-based NO2 sensing chip with an oxidizing agent. In this device, NO is first oxidized to NO2 over the oxidizer on a porous glass sheet (8mm square, 1mm thick) prepared by soaking in a sulfuric acid/potassium permanganate solution, after which the NO2 is detected by a second chip, the same size as the oxidizing chip, impregnated with Saltzman's reagent. A sensor of this type placed in a miniature aluminum holder (3cm×5cm×1.5cm) was passively exposed to air containing ppm levels of NO or NO2. As a result, the chip changed from colorless to dark red and a plot of absorbance at 525nm against the total exposure (defined as the sum of the product of the instantaneous gas concentration by the exposure interval) was linear. Based on the slope of the plot obtained from the NO2 exposure trials, the detection limit of the sensor was approximately 0.2ppm NO2 assuming a 1h exposure. It was also found that these devices exhibited equivalent sensitivity to both NO and NO2, indicating that these sensors are capable of measuring the combined NO and NO2 concentration.

Spatial Distribution of Submarine Groundwater Discharge and Associated Nutrients within a Local Coastal Area

To understand the local-scale distribution of submarine groundwater discharge (SGD) and dissolved nutrients, a multiple-detector (222)Rn monitoring survey was undertaken along the Mt. Chokai volcanic coast in northern Japan. The surveys revealed that the highest SGD (calculated to be 6.2 × 10(4) m(3) d(-1), within an area of 2 × 10(4) m(2)) with the greatest nutrient fluxes (sum of NO(3)(-), NO(2)(-), and NH(4)(+) (DIN): 9.2 × 10(2) mol d(-1); PO(4)(3-) (DIP): 56 mol d(-1)) is present at the edge of the youngest volcanic lava flow in the area. Recharged groundwater transports nutrients through porous volcanic flows and discharges as SGD near shore. Our results demonstrate that the spatial distribution of SGD in the study area is closely regulated by the local geology and topography. Furthermore, we show that continuous (222)Rn monitoring with a multidetector system at boat speeds of 1-2 knots provides details at a scale one order of magnitude greater than has been reported previously. In addition, the results of our study suggest that SGD-borne DIP may play an important role in the important local oyster production.

Analyses of the Ozone Weekend Effect in Tokyo, Japan: Regime of Oxidant (O3 + NO2) Production

The ozone weekend effect (OWE) in Tokyo, the capital of Japan, was analyzed from April 2005 to March 2008 with respect to the photochemical ozone production, focusing on the ozone production regime. For most periods, the OWE was confirmed in the wintertime as well as in the summertime. The comparison of Ox ([Ox] = [O3] + [NO2] – 0.1[NOx]) concentrations between weekdays and weekends suggests that there are some periods when the photochemical ozone production on the weekends could be larger than on the weekdays (defined as the POP group). We compared NOx (the sum of NO and NO2) and Ox concentrations on the weekends with those on the weekdays for several distinct ranges of the non-methane hydrocarbons (NMHCs) concentrations, and NOx and Ox concentrations on the weekends are significantly lower and higher than those on the weekdays in the POP group. Therefore, the ozone production regime would be NMHC-limited in the POP group. The ozone production regime in the summertime in Tokyo could be in the boundary area between NMHC- and NOx-limited in terms of the NMHCs/NOx ratios. The NMHCs/NOx ratios in the NMHC-limited regime are smaller than those in the NOx-limited regime in general. However, the NMHCs/NOx ratios in the POP group were not smaller than those in the non-POP group.

Measurement of Atmospheric Ozone by Cavity Ring-down Spectroscopy

Ozone plays a key role in both the Earth's radiative budget and photochemistry. Accurate, robust analytical techniques for measuring its atmospheric abundance are of critical importance. Cavity ring-down spectroscopy has been successfully used for sensitive and accurate measurements of many atmospheric species. However, this technique has not been used for atmospheric measurements of ozone, because the strongest ozone absorption bands occur in the ultraviolet spectral region, where Rayleigh and Mie scattering cause significant cavity losses and dielectric mirror reflectivities are limited. Here, we describe a compact instrument that measures O3 by chemical conversion to NO2 in excess NO, with subsequent detection by cavity ring-down spectroscopy. This method provides a simple, accurate, and high-precision measurement of atmospheric ozone. The instrument consists of two channels. The sum of NO2 and converted O3 (defined as Ox) is measured in the first channel, while NO2 alone is measured in the second channel. NO2 is directly detected in each channel by cavity ring-down spectroscopy with a laser diode light source at 404 nm. The limit of detection for O3 is 26 pptv (2 sigma precision) at 1 s time resolution. The accuracy of the measurement is ±2.2%, with the largest uncertainty being the effective NO2 absorption cross-section. The linear dynamic range of the instrument has been verified from the detection limit to above 200 ppbv (r2>99.99%). The observed precision on signal (2 sigma) with 41 ppbv O3 is 130 pptv in 1 s. Comparison of this instrument to UV absorbance instruments for ambient O3 concentrations shows linear agreement (r2=99.1%) with slope of 1.012±0.002.

S082013 O_2/CO_2石炭燃焼における窒素化合物の生成メカニズムと極低NO_X化への応用([S08201]高効率火力発電およびCCS技術)

In this study, pulverized coal was combusted in air and O_2/CO_2 atmosphere, and characteristic of nitrogen compounds formation in fuel-rich condition was investigated. In O_2/CO_2 coal combustion, more NO was formed than in air combustion, contrastively less HCN was formed. Comparing the sum of NO and HCN, O_2/CO_2 coal combustion emitted less amount of nitrogen compounds in fuel-rich condition. HCN is expected to be oxidized in second stage of combustion and converted to NO. Finally, less amount of NO is expected to emit in O_2/CO_2 coal combustion because of less amount of nitrogen compounds.

Gas chemical studies using corona discharge reactors

Corona discharges with voltages up to 60 kV (DC) were studied with the aim to induce chemical reactions in flue gases at atmospheric pressure. Various plasma reactors with different geometries of multi-needle arrays were tested. The power input was optimised by studying the electrical parameters of the set-up systematically. Both, solid and liquid electrodes were used in combination with the needle arrays. A precise positioning of the corona needles allowed operation without a ballast resistor. Formation rates for CO and the sum of NO2 and O3 are reported and discussed. Three catalytic anode-coatings were tested for their potential to decompose carbon dioxide.