High Levels Of Nitrogen Oxides Research Articles

Identification and detection of high NO x emitting inland ships using multi-source shore-based monitoring data

In urban areas situated along busy waterways like the Yangtze River, the diesel engines of inland navigation ships emerge as significant contributors to air pollution. Among these vessels, certain high-emission ships exhibit considerably higher levels of nitrogen oxides (NOx) emissions compared to others. To effectively identify such ships, this study employed a cost-effective ship emission monitoring sensor platform, comprising high-precision gas sensors, automatic identification system receiver, and sensitive meteorological sensors, along the Yangtze River in Wuhan City. By combining multi-source shore-based monitoring data, we identified ship emission signals and proposed a high-emission ship detection method using inverse modeling. Using this method, we successfully detected inland high-emission ships based on two months of monitoring data. Furthermore, the relationship between different ship types, sizes, speeds, and ship NO x emission rates were investigated. The results of this study are beneficial for strengthening the regulation of high-emission vessels in inland waterways, thereby reducing the adverse impact of ship emissions on the environment and climate. It also encourages the inland shipping industry to adopt more environmentally friendly technologies and fuels, as advocated by the International Maritime Organization.

Air Concentrations of Nitrogen Oxide Related to Tobacco Smoke: A Systematic Review

Environmental tobacco smoke (ETS), similar to firsthand and secondhand smoke, is a complex mixture containing thousands of chemicals, many of which are known as carcinogens. The high combustion temperature of tobacco and the presence of nitrogen in the tobacco can lead to the release of nitrogen oxides (NOx ). From the NOx , NO2 irritates the respiratory system and damages cells and mucous membranes of the lungs. The selected databases for this systematic review were Science Direct, Springer, PubMed, and Google Scholar, and the keywords of the search plan included "nitrogen oxide", "NOX", "ETS", "Cigarette smoke", "Waterpipe smoke", and "Tobacco smoke". Finally, 797 articles were found, and after reviewing, 7 articles met our criteria. The results demonstrated that the mean air concentration of tobacco smoke related-NOX was 9.71±11.03 ppm, which was higher than the annual guideline level of free air quality (0.053 ppm). The mean concentration of NOX in cigarette smoke was 329.45±465.43 ppm, and for smoking places, it was higher than for nonsmoking places (17.80 vs. 12.47 ppm). Moreover, for the cigarette smoke, it was higher than for the waterpipe smoke (5.66 vs. 0.16 ppm). In this regard, the cigarette is more suspected to the emission of NOx compared to waterpipe, and tobacco smoking can expose people to high levels of NOx regarding the limited guideline levels. Finally, the concentration of NO in cigarette smoke and air was higher than NO2 .

Experimental investigation of the achieving methods and the working characteristics of a near-zero NOx emission turbocharged direct-injection hydrogen engine

Hydrogen, as clean and renewable energy, is regarded as a promising fuel applied to internal combustion engines. The relatively high level of Nitrogen oxides (NOx) emissions is an important limiting factor to realize the application of hydrogen engine. Previous researches on the NOx emissions reduction were based on the naturally-aspired or supercharger hydrogen engine with medium load and efficiency. In this study, a 2.0 L turbocharged direct-injection engine is used to find the methods of achieving near-zero NOx emission (without any posttreatment equipment) with large power and high thermal efficiency. The effects of the coefficient of excess air (λ), the timing of the start of injection (SOI), and injection pressure on NOx emissions are investigated detailly with the engine speed range of 1000 rpm to 4000 rpm. The target of the NOx emission is set below 20 ppm according to the emission standards. A leaner combustion (λ = 3.29@ 3000 rpm) compared to λ = 2.62@ 2000 rpm is required to achieve near-zero emission. The utilization of the turbocharger and improved injection pressure increase the power and efficiency simultaneously. The maximum brake mean effective pressure (BMEP) can reach 13.3 bar@3000 rpm, and the maximum brake thermal efficiency (BTE) reaches 40.4% @2000 rpm with near-zero NOx emission. Various techniques, such as turbocharging, exhaust gas recirculation, and increased compression ratios, are also compared to qualify the trade-off relationships among the power, efficiency, and emission of the direct-injection hydrogen engine. These conclusions can be used to broaden the working boundary and optimize the fuel economy of turbocharged direct-injection hydrogen engines with near-zero NOx emission.

Sensitivity analysis of isoprene and aerosol emission in a suburban plantation using long short-term memory model

Plants emit volatile organic compounds (VOCs), which undergo photochemical reactions to generate secondary organic aerosols and cause ozone (O3) accumulation; thus, they are the focus of urban pollution control strategies. Although some studies on biogenic VOCs and aerosols have been conducted, their environmental effects at the community scale are uncertain, particularly in suburban areas where abundant vegetation and pollutants coexist. Simple data processing methods cannot well address complex environmental conditions, whereas the long short-term memory (LSTM) model can learn relationships between research objects autonomously, thus enabling the analysis of influencing factors. Therefore, we collected 11 indicators of isoprene and submicron aerosol (PM1) concentrations, as well as other pollutants and meteorological factors, for six consecutive months in a suburban plantation in Shanghai. On the basis of correlation and redundancy analyses, LSTM was used to determine the main environmental factors influencing isoprene and PM1 concentrations. The results showed that nitrogen oxides (NOX), O3, photosynthetically active radiation (PAR), and temperature had the highest influence. The reactions between NOX, O3, and isoprene, PM1 are complex, and high levels of both isoprene and NOX in suburban areas may favor O3 production. PAR and temperature control the emission and photooxidation of isoprene and influence their conversion from a gaseous state to a particulate state. Considering the complex atmospheric environment, this study analyzed the sensitivity of isoprene and PM1 to environmental factors by artificial intelligence method. It demonstrated the effectiveness of LSTM for analyzing complex time-series data with unknown mapping relationships, which provided solutions for large-scale studies. And the results provided a scientific basis to further explain the mechanism through which influencing factors affect suburban communities and to control suburban air pollution.

Experimental and low-dimensional numerical study on the application of conventional NOx reduction methods in pulse detonation combustion

Although research interest in pressure gain combustion (PGC) remains high, information on pollutant emissions from detonation-based devices such as pulse detonation engines is sparse, especially lacking extensive experimental parameter studies. Nevertheless, available results indicate potentially very high exhaust levels of nitrogen oxides (NOx) due to the significantly increased combustion temperatures and pressures induced by the detonation wave. To counter this issue, this study applies conventional NOx reducing measures in the form of fuel-lean mixtures and nitrogen dilution (emulating exhaust gas recirculation) to a pulse detonation combustor in multi-cycle operation. Their impact on the exhaust gas composition is measured and compared to numerical predictions by two available simplified models. To allow for a broader range of comparison and better assess the capabilities of these numerical models, emissions from fuel-rich and oxygen-enriched mixtures are measured as well. Experimental results confirm high levels of NOx up to several thousand ppm for near-stoichiometric, undiluted mixtures. When conventional NOx reduction measures are applied, significant NOx abatement can be achieved, with further reduction potential primarily limited by unsuccessful deflagration to detonation transition (DDT). Comparison with numerical results shows that simplified models allow for good qualitative agreement and can also deliver good quantitative predictions over a wide range of conditions if a suitable heat-loss model is chosen.

Modeling the emissions of rural vehicles based on real-world driving cycles

Characterized by a high frequency of use, harsh working environments, poor maintenance, and low levels of emission controls, rural vehicles (RVs) are becoming an important source of air pollution. Our study used a portable emission measurement system (PEMS) to test the real-world emissions of 35 RVs on provincial, rural, and farm roads. The results show that high emission rates of carbon monoxide (CO) and hydrocarbons (HC) mainly occurred when accelerating at low speeds. However, high levels of nitrogen oxides (NOx) were emitted during high-speed acceleration. The particulate number (PN) of emissions was higher when the RVs were accelerating. According to the overall test results, the vehicle specific power (VSP) on the provincial road mostly ranged within (0, 3], accounting for 68.80% of the total. The VSP on rural and farm roads was concentrated within (0, 2] kW·ton−1, accounting for 67.09% and 76.64% of the total, respectively. We defined 14 bins based on the distribution of the VSP values and calculated the average emission rate of each bin. By comparing the average emission rate among the bins, we found that within Bins 1–7 (VSP < 0 kW·ton−1), CO, HC, and NOx emissions slowly increased as the VSP increased. In Bins 8–13 (VSP ≥ 0 kW·ton−1), the average emission rates of four pollutants increased as the VSP increased. However, all pollutants decreased in Bin 14 (VSP ≥ 6 kW·ton−1). We built a microscopic emission model according to the VSP distribution characteristics of RVs on different road types. We compared the measured and simulated emission factors and found that our emission model can greatly simulate the HC, NOx and PN emission factors of RVs.

Metabolic dysfunction modifies the influence of traffic-related air pollution and noise exposure on late-life dementia and cognitive impairment: A cohort study of older Mexican-Americans.

For 1,612 elderly Mexican-American participants of the Sacramento Area Latino Study on Aging (SALSA) followed for up to 10 years, we estimated residential-based local traffic-related exposures relying on the California Line Source Dispersion Model version 4 (CALINE4) for nitrogen oxides (NOx) and the SoundPLAN software package (Version 8.0; NAVCON, Fullerton, CA) that implements the Federal Highway Administration Traffic Noise Model (TNM) for noise, respectively. We used Cox proportional hazard models to estimate the joint effects of NOx or noise exposures and obesity, hyperglycemia, or low high-density lipoprotein (HDL) cholesterol. The risk of developing dementia/CIND among participants with hyperglycemia who also were exposed to high levels of NOx (≥3.44 parts per billion [ppb] [75th percentile]) or noise (≥65 dB) was 2.4 (1.4, 4.0) and 2.2 (1.7, 3.9), respectively. For participants with low HDL-cholesterol, the estimated hazard ratios for dementia/CIND were 2.5 (1.4, 4.3) and 1.8 (1.0, 3.0) for those also exposed to high levels of NOx (≥3.44 ppb) or noise (≥65 dB), respectively, compared with those without metabolic dysfunction exposed to low traffic-related air pollution or noise levels. Exposure to traffic-related air pollution or noise most strongly increases the risk of dementia/CIND among older Mexican-Americans living in California who also exhibit hyperglycemia or low HDL-cholesterol.

Impact of long-range atmospheric transport on volatile organic compounds and ozone photochemistry at a regional background site in central China

Ozone (O3) photochemistry in remote areas can be altered by the injection of long-range transported air masses which contain volatile organic compounds (VOCs) and nitrogen oxides (NOx). In this study, VOCs and trace gases (i.e., SO2, NO, NO2, CO, and O3) were measured in summer (August) and autumn (October) in 2018 at Jinsha (JSH), a regional background station in central China. A unique pattern that most short-lived VOCs species presented higher mixing ratios in summer while long-lived VOCs showed higher mixing ratios in autumn was observed. Backward trajectory analysis revealed that higher mixing ratios of long-lived hydrocarbons were mostly associated with air masses originating from northern China, while lower concentrations related to air masses passed over southeastern China and the East China Sea. An observation-constrained photochemical box model coupled with Master Chemical Mechanism (PBM-MCM) was applied to simulate the net ozone production. It was found that the net ozone production rate in summer (average: 4.7 ± 0.8 ppbv/h) was higher than that in autumn (average: 2.5 ± 0.1 ppbv/h). O3 formation at JSH switched from transition regime in summer to VOC-constrained regime in autumn due to the high level of NOx in autumn. The relative incremental reactivity (RIR) analysis showed the isoprene was the most reactive VOC species to in-situ O3 production. These findings highlight the impact of long-range air pollution transport on background O3 photochemistry in central China.

Efficient nonthermal plasma degradation of toluene over NiO catalyst with limited NOx generation

A problem encountered during nonthermal plasma destruction of pollutants in gas streams containing air is that high levels of nitrogen oxides may also be formed as a consequence of the complex processing conditions. In the work presented herein, a post nonthermal plasma catalytic system was evaluated for removal of toluene gas. NiO/γ-Al2O3 catalysts with different NiO loadings were prepared via the traditional impregnation method and their activity determined under certain conditions. The effects of the specific input energy (SIE), catalyst calcination temperature, and NiO loading on the toluene degradation were investigated. The catalyst prepared by calcination at 450 °C showed the highest activity. The catalytic activity of the catalysts first increased then decreased with increasing NiO loading, with the maximum toluene conversion of 93 % being achieved by 1.25 wt% NiO/γ-Al2O3 at 200 ppm. Meanwhile, the amount of NOx produced during the reaction was investigated. In the reaction process, a very small amount of NOx was produced, indicating that the catalyst is green and efficient.

Effects of Air Pollution and Land Use Characteristics on Development and Respiratory Health among Children in the Greater Taipei Area

Indoor and outdoor air pollution poses an important health threat to children. Exposure to air pollution may cause various acute and chronic respiratory diseases, and affect neurodevelopment and cognitive functions in children. To evaluate the impact of air pollution on children's health, we conduct a study to examine the effect of prenatal and early childhood exposure to air pollution on development and respiratory health in the first 3 years of life among a birth cohort in the Greater Taipei area. We will recruit 500 cohort children, and evaluate their development and respiratory diseases using standardized questionnaires and Bayley Scales of Infant and Toddler Development. One hundred children will be selected to conduct indoor and outdoor environmental samplings of their residences. Four hundred and fifty-six cohort children have been recruited so far, and environmental measurements have been implemented in 40 homes. According to our analyses, most ambient pollutant concentrations near participants' homes were lower than Taiwan National Ambient Air Quality Standard, expect PM2.5, which exceeded the annual average level (15µg/m3). A few households had elevated indoor pollution levels due to a low ventilation rate or recent remodeling. Several children's bed dust samples contained dust mite allergen levels &amp;gt; 2 µg/g, which may increase the risk of child sensitization to dust mites. According to multiple regression analyses, a high level of nitrogen oxides during first trimester near residence as well as living near gas stations, social welfare facilities, or high ways had adverse effects on children's health; living near green parks was beneficial to children's neurodevelopment. Overall, residential environments, such as air quality and land use type nearby, may significantly influence children's health and neurodevelopment.

Which processes drive observed variations of HCHO columns over India?

Abstract. We interpret HCHO column variations observed by the Ozone Monitoring Instrument (OMI), aboard the NASA Aura satellite, over India during 2014 using the GEOS-Chem atmospheric chemistry and transport model. We use a nested version of the model with a horizontal resolution of approximately 25 km. HCHO columns are related to local emissions of volatile organic compounds (VOCs) with a spatial smearing that increases with the VOC lifetime. Over India, HCHO has biogenic, pyrogenic, and anthropogenic VOC sources. Using a 0-D photochemistry model, we find that isoprene has the largest molar yield of HCHO which is typically realized within a few hours. We also find that forested regions that neighbour major urban conurbations are exposed to high levels of nitrogen oxides. This results in depleted hydroxyl radical concentrations and a delay in the production of HCHO from isoprene oxidation. We find that propene is the only anthropogenic VOC emitted in major Indian cities that produces HCHO at a comparable (but slower) rate to isoprene. The GEOS-Chem model reproduces the broad-scale annual mean HCHO column distribution observed by OMI (r = 0.6), which is dominated by a distinctive meridional gradient in the northern half of the country, and by localized regions of high columns that coincide with forests. Major discrepancies are noted over the Indo-Gangetic Plain (IGP) and Delhi. We find that the model has more skill at reproducing observations during winter (JF) and pre-monsoon (MAM) months with Pearson correlations r &gt; 0.5 but with a positive model bias of ≃ 1×1015 molec cm−2. During the monsoon season (JJAS) we reproduce only a diffuse version of the observed meridional gradient (r = 0.4). We find that on a continental scale most of the HCHO column seasonal cycle is explained by monthly variations in surface temperature (r = 0.9), suggesting a role for biogenic VOCs, in agreement with the 0-D and GEOS-Chem model calculations. We also find that the seasonal cycle during 2014 is not significantly different from the 2008 to 2015 mean seasonal variation. There are two main loci for biomass burning (the states of Punjab and Haryana, and northeastern India), which we find makes a significant contribution (up to 1×1015 molec cm−2) to observed HCHO columns only during March and April over northeastern India. The slow production of HCHO from propene oxidation results in a smeared hotspot over Delhi that we resolve only on an annual mean timescale by using a temporal oversampling method. Using a linear regression model to relate GEOS-Chem isoprene emissions to HCHO columns we infer seasonal isoprene emissions over two key forest regions from the OMI HCHO column data. We find that the a posteriori emissions are typically lower than the a priori emissions, with a much stronger reduction of emissions during the monsoon season. We find that this reduction in emissions during monsoon months coincides with a large drop in satellite observations of leaf phenology that recovers in post monsoon months. This may signal a forest-scale response to monsoon conditions.

Experimental investigation on the performance and emissions characteristics of ethanol/diesel dual-fuel combustion

The diesel compression ignition (CI) engine has higher durability and thermal efficiency than the gasoline spark ignition (SI) engine. However, the high levels of nitrogen oxides (NOx) and particulate matter (PM) emissions are major problems of diesel engines due to the auto-ignition of heterogeneous mixtures. The dual-fuel combustion concept could be solution to environmental concerns. Dual-fuel combustion can be implemented by substituting some of the diesel fuel with high-volatility fuels, such as gasoline and natural gas. The premixed mixture condition can be improved to diminish localized rich and stoichiometric regions. Notably, ethanol has greater potential to reduce PM emissions because it is highly volatile and readily oxidized.For these reasons, in this research, the effects of varying the ethanol substitution ratio on engine performance and emissions under the dual-fuel combustion condition were experimentally investigated under various load conditions. The test engine was a heavy-duty single-cylinder diesel engine with two direct injectors. Engine speed was fixed at 1000 rpm and the load condition was varied for an indicated mean effective pressure (IMEP) ranging from 0.2 to 0.8 MPa. The ratio of ethanol to the total input energy was controlled from zero to nearly 50% of the input energy. The NOx and PM emissions decreased with increasing ethanol substitution and the mean size of the PM emissions decreased. For the mid-load condition (IMEP 0.6 MPa), the substitution was increased to 63%, but for low and high loads, higher ethanol fractions could not be used because of insufficient ignition energy at low loads and sharp increment of the in-cylinder pressure under high loads.

Numerical model to analyze Nox reduction by ammonia injection in diesel-hydrogen engines

Nowadays, the even increasing stringent environmental legislations have promoted interest in alternative fuels for internal combustion engines. Particularly, hydrogen is becoming a promising fuel due to its high specific energy and low emissions production. Environmentally, the main disadvantage of hydrogen is the high level of nitrogen oxides (NOx) which produces. In this regard, this work proposes a NOx reduction method which consists on direct injection of ammonia (NH3) into the combustion chamber. A numerical model validated with experimental measurements was carried out to analyze emissions and brake specific consumption in a commercial engine operating with diesel-hydrogen blends. Comparing to diesel operation, a 10% hydrogen content increases a 5.3% the peak pressure and 5.7% the maximum temperature. The CO2, CO and HC emissions are reduced but NOx emissions increase up to 18.3%. Several injection instants and ammonia flow rates were analyzed, obtaining more than 70% NOx reductions with a negligible effect on other emissions and brake specific consumption. It was found that the start of ammonia injection is too critical since the maximum NOx reduction takes place when the temperature is around 1200 K. The NOx reduction increases with the ammonia flow rate but an excessive quantity of ammonia can lead to un-reacted ammonia slip to the exhaust.

The exposure of pedestrians, drivers and road transport passengers to nitrogen dioxide

People travelling by road transport are exposed to high levels of nitrogen oxides (NOx), that are considered to be one of the primary pollutants from motor vehicles. This study examines the exposure of drivers, passengers and pedestrians to NO2 during different trip scenarios: travelling by private or public means of transport, along the major commuter routes in one of the biggest Polish agglomerations - Silesia Agglomeration, and other important communication routes in Poland, as well as during walks in both city centers and residential areas. The NO2 samples were collected in cars, trucks and buses interiors, as well as in the ambient air by passive samplers and next NO2 concentrations were analyzed by means of the spectrophotometric technique. The obtained results indicate that travelling by cars through city centers is associated with the exposure to NO2 concentrations of about 15% higher than in the case of travelling suburban routes; 33% greater than travelling by bus in urban traffic; more than app. 60% higher than in the case of travelling by bus in suburban traffic or by foot in city centers and up to 80% higher than moving on foot near little-used roads. The exposure profile of six groups of road users exposed to NO2 was therefore determined in this study. The obtained results could be used by policy makers to minimize the exposure to transportation-related pollutants concentrations and for planning far-reaching changes in the field of urban road transport.

Comparative properties and utilization of un-preheated degummed/esterified mixed crude palm oil-diesel blends in an agricultural engine

The production, property, and utilization of un-preheated degummed/esterified mixed crude palm oil (DgMCPO/EMCPO)-diesel blends in an agricultural engine were studied. The results reveal that DgMCPO and EMCPO can be produced easily with costs comparable to diesel. They had a poor liquid phase and high viscosity. Through blending with diesel at maximum portions of 20 vol% (DgMCPO20) and 30 vol% (EMCPO30), clear liquid blends were produced. Almost important fuel properties of these blends met Thailand agricultural engine diesel standard with slightly higher densities and viscosities than diesel, significantly higher oxygen content than diesel, good cetane numbers, and slightly lower heating values than diesel. At 2200 rpm under loads in the range of 1.28–5.6 kW, un-preheated blends were able to well operate the engine as same as diesel. Comparing this with diesel; the blends resulted in slightly higher brake specific fuel consumptions (+4.5% and +5.0%), slightly lower brake thermal efficiencies (−0.9% and −1.2%), significantly lower levels of carbon monoxide (−33.7% and −33.2%), slightly lower exhaust gas temperatures (−5.1% and −5.5%), and significantly higher levels of nitrogen oxides (+8.9% and +15.9%); (all paired values, DgMCPO20 and EMCPO30 respectively). In conclusion, these blends are recommended as effective diesel substitutes for use in agricultural engines.

The acclimation of Chlorella to high-level nitrite for potential application in biological NOx removal from industrial flue gases

Nitrogen oxides (NOx) are the components of fossil flue gas that give rise to the greatest environmental concerns. This study evaluated the ability of the green algae Chlorella to acclimate to high level of NOx and the potential utilization of Chlorella strains in biological NOx removal (DeNOx) from industrial flue gases. Fifteen Chlorella strains were subject to high-level of nitrite (HN, 176.5 mmolL−1 nitrite) to simulate exposure to high NOx. These strains were subsequently divided into four groups with respect to their ability to tolerate nitrite (excellent, good, fair, and poor). One strain from each group was selected to evaluate their photosynthetic response to HN condition, and the nitrite adaptability of the four Chlorella strains were further identified by using chlorophyll fluorescence. The outcome of our experiments shows that, although high concentrations of nitrite overall negatively affect growth and photosynthesis of Chlorella strains, the degree of nitrite tolerance is a strain-specific feature. Some Chlorella strains have an appreciably higher ability to acclimate to high-level of nitrite. Acclimation is achieved through a three-step process of restrict, acclimate, and thriving. Notably, Chlorella sp. C2 was found to have a high tolerance and to rapidly acclimate to high concentrations of nitrite; it is therefore a promising candidate for microalgae-based biological NOx removal.

Mathematical modeling of autotrophic denitrification (AD) process with sulphide as electron donor

Autotrophic denitrification (AD) plays a critical role in nitrate removal from organic carbon-deficient wastewaters with a high level of nitrogen oxides. However, the AD process is not included in the current denitrification models, which limits the application of AD technology for wastewater treatment. In this work, a kinetic model for AD process involved 4 processes and 5 components with 9 parameters is established to describe the sulphide biooxidation and nitrite removal process. In this model, 4 oxidation–reduction reactions using sulphide as electronic donor in the AD process are taken into account. The model parameters are optimized by fitting data from the experiments with different combinations of sulphide, sulphur, sulphate, nitrate and nitrite at various concentrations. Model calibration and validation results demonstrate that the developed model is able to reasonably describe the removal rates of nitrate, nitrite, sulphide and sulphur in the AD process. The model simulation results also show that the sulphur term (η(S)) in the kinetic equations of nitrate, nitrite, sulphur and sulphate remains constant, rather than being controlled by its own concentration. Furthermore, with this model the products of sulphide biooxidation in the AD process, sulphur and sulphate, and their concentrations can be accurately predicted. Therefore, this model provides a strategy to control the sulphate concentration below the discharge limits or recover sulphur as the main end product from sulphide biooxidation.

Ozone Forming Potential at Rio de Janeiro Petrochemical Complex, Brazil

Air dispersion models have been widely used to investigate air dispersion patterns, to predict emissions behaviour, to estimate potential risks to human health, to develop environmental policies and to evaluate their impact on air quality. This paper considers gaseous pollutants emitted by a petrochemical complex and presents an air dispersion case study using the AERMOD model and the OZIPR trajectory model along with the SAPRC chemical mechanism to evaluate tropospheric ozone formation. The petrochemical complex considered is being installed in the Rio de Janeiro Metropolitan Area and is planned to start operations in 2016. The present work indicates that nitrogen oxides (NOx) concentrations will likely exceed the primary and secondary Brazilian national standards in some areas. As a result high levels of NOx in the presence of high VOC emissions would contribute to high levels of ozone. DOI: 10.5935/1984-6835.20160071

Ozone formation in relation with combustion processes in highly populated urban areas

The complex chain of photochemical reactions is one of the most important tasks in the air quality evaluation, expecially in urban areas. In fact, in this case there are high emission levels of NOx and no-methane hydrocarbons by combustion processes such as autovehicular traffic, domestic heating and industrial plants. Ozone is not emitted directly into the atmosphere but it is formed from a complex series of reactions between emitted nitrogen oxides (NOx) and reactive organic compounds (ROC). The high ozone concentrations, which occur during photochemical episodes, are usually accompanied by elevated concentrations of other photochemical oxidants such as nitric acid (HNO3), peroxyacylnitrates (PANs), hydrogen peroxide (H2O2), etc. The complex series of these reactions constitutes the most important issue to the degradation of air quality. Further, the NMHCs play a key role in the formation of photochemical air pollution: they are considered as precursors for ozone production at the ground level when the sunlight and nitrogen oxides are present. From a practically point of view defining a quality standard or a limit is substantially correct but it is no sufficient to solve the problem. So it should become necessary to acquire knowledge on the different formation mechanisms of the photochemical pollution phenomena. In this paper there will be shown the results of a long-term study performed in Rome for evaluating the ozone formation in relationship with the autovehicular traffic density.

Post-discharge gas composition of a large-gap DBD in humid air by UV–Vis absorption spectroscopy

Large gap dielectric barrier discharges (DBD) provide non-thermal, non-equilibrium plasmas that can generate specific gas chemistry with enhanced bactericidal effects when working in humid air.The present study investigates the post-discharge gas composition of such plasmas operated in humid air using UV–Vis (200–800 nm) absorption spectroscopy. Absorbance spectra have been de-convoluted using direct deconvolution and iterative methods and results are correlated to the DBD electrical parameters.The high-voltage (56 and 70 kV rms) DBD plasma generated at 50 Hz frequency in a closed container over a 20 mm gap in air with relative humidity (RH) of 5–70% has been characterized by I–V and capacitive methods. The post-discharge gas composition at each RH is assessed by UV–Vis absorption spectroscopy for plasma exposure times of 15–120 s. The concentration of ozone and nitrogen oxides (O3, NO2, NO3, N2O4) increases with plasma exposure time but a strong decrease in [O3] levels is obtained with increase in RH. The decrease in [O3] and an abundance of nitrogen oxides is ascribed to high specific power densities in the closed container and to increasing RH levels. The absorbance residual following deconvolution shows a strong band at 230–270 nm consistent with the presence of pernitric acid (HNO4) and other HNOx (x = 1, 3) species. Humid air large gap DBD plasmas in closed containers generate along with O3, high levels of nitrogen oxides and HNOx (x = 1, 4) acids leading to increased bactericidal rates.