Nitrogen Oxides Research Articles

Accurate and efficient prediction of atmospheric PM1, PM2.5, PM10, and O3 concentrations using a customized software package based on a machine-learning algorithm.

Particulate matter (PM) and ozone (O3) pollution have been attracting increasing attention recently due to their severe harm to human health. PM and O3 are secondary pollutants, and there remain significant challenges in accurately and efficiently predicting their concentrations in the atmosphere. In this study, one-year monitoring data of PM1, PM2.5, PM10, and O3 concentrations as well as meteorological parameters and concentrations of various precursors (i.e., nitrogen oxides, SO2, CO, alkanes, aldehydes, and ketones) are obtained at a monitoring site in central China's Hunan province. The eXtreme Gradient Boosting model is trained and tested to achieve efficient and accurate predictions of the concentrations of the four pollutants. The effects of different datasets, input features, and model parameters on the prediction accuracy are investigated. Principal component analysis is employed to further reduce the dimensions of features, increasing the prediction efficiency. Finally, all model training and prediction processes are incorporated in an executable application using the PyQt5 framework to build a user interface. The customized software supports user-defined modeling. The software can simultaneously predict PM1, PM2.5, PM10, and O3 concentrations, making the prediction process convenient.

TiO2 Surface Hybridisation with Ag and CuO for Solar‐Assisted Environmental Remediation and Sustainable Energy Applications

AbstractIndustrialisation has led to unprecedented levels of outdoor air pollution, posing a significant health risk to human beings. Consequently, there is an urgent need to replace fossil fuels with sustainable energy sources, thereby mitigating these risks and providing a safer outdoor and indoor environment. Titanium dioxide is a versatile transition metal oxide with applications ranging from energy conversion to environmental remediation. However, it faces limitations, particularly in its absorption spectrum and charge separation efficiency, and enhancing these properties remains a significant challenge. In this research work, we have decorated the surface of TiO2 hybridising it with noble‐metal and/or noble‐metal oxides (Ag and/or CuO) to improve the photocatalytic performances (monitoring the removal of nitrogen oxides and benzene, and hydrogen generation from water splitting) under simulated solar‐light irradiation. Our results showed that titania modified with an Ag : Cu molar ratio equal to 1 : 1, not only exhibited the most promising performance in terms of nitrogen oxides and benzene removal, it was the optimum amount for the light‐induced generation of hydrogen from water splitting.

Achieving High Photocatalytic NOx Removal Activity Using a Bi/BiOBr/TiO2 Composite Photocatalyst.

Fossil fuel combustion generates nitrogen oxides (NO + NO2 = NOx), which pose threats to the environment and human health. Although commercial products containing titanium dioxide (TiO2) can remedy NOx pollution by photocatalysis, they only function in the ultraviolet (UV). On the other hand, bismuth oxybromide (BiOBr) is active in the visible. BiOBr is stable, affordable, and non-toxic, making it an appealing alternative. In addition, nanoparticulate Bi metal can further enhance visible light absorption through its surface plasmon properties and charge carrier lifetime by spatially separating charge. In this study, to enhance the visible-light activity of TiO2-based photocatalysts for NOx pollution, a composite of Bi-decorated BiOBr/TiO2 was synthesized using a solvothermal method across varying the Ti/Bi atomic ratio (0.2, 2.2, 4.4, and 6.6), and synthesis duration (6h, 12h, and 18h). The photocatalytic performance of the synthesised composites for NO gas removal was investigated using an adapted ISO method (22197-1:2016). Analysis showed that the preferential growth of the (010) crystal facet in BiOBr and the presence of Bi metal both play an important role in the superior photocatalytic activity seen in our Bi-decorated BiOBr/TiO2 composite. The composites were characterised using X-ray diffraction (XRD), attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR), high-resolution scanning electron microscopy (HRSEM), UV-Vis diffuse reflectance (DRS) spectroscopy, transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Brunauer-Emmett-Teller (BET) analysis, thermogravimetric analysis (TGA), and diffuse reflectance transient absorption spectroscopy (DR-TAS). Our research shows that the Bi/BiOBr-TiO2 composite synthesised through the 12-hour solvothermal method with a Ti/Bi atomic ratio of 4.4 exhibits the highest photocatalytic performance towards both NO and NO2 oxidation; with 32.8% and 54.9% NO removal and 15.1% and 29.5% NO2 under visible and UV lamps, respectively.

Impact of nano cerium oxide addition with pyrolysis waste plastic oil on combustion, performance and emission characteristics of CRDI diesel engine

Abstract This investigation examined the effect of incorporating cerium oxide (CeO2) nanoparticle into diesel and waste plastic oil (WPO) blends on the combustion, performance and emission characteristics of the diesel engine. The WPO was extracted from low density polyethylene using plastic pyrolysis. The blending of diesel and WPO with combination of D70:WPO30 and D50:WPO50 was prepared to evaluate the engine operation. Additionally, the spherical sized CeO2 with 50 mg/L and 100 mg/L was added with this blend. The various blends named as Diesel, D-WPO30, D-WPO30+Ce50, D-WPO30+Ce100, D-WPO50, D-WPO50+Ce50 and D-WPO50+Ce100 were used in this investigation to operate the engine under various load conditions. The experiment was performed using water cooled common rail direct injection (CRDI) diesel engine with prepared D-WPO blend. Different characteristics such as In-cylinder pressure (CP), heat release rate (HRR), ignition delay time (IDT), brake thermal efficiency (BTE), brake specific fuel consumption (BSFC) and exhaust gas temperature (EGT), carbon monoxide (CO), hydrocarbon (HC), nitrogen oxide (NOx) and smoke opacity emission are studied with respect to the effect of different blends and applied load used. It was observed that increasing of CeO2 nanoparticles in blend improved the overall performance and emission of the engine. Form the results, D-WPO30+Ce100 blend showed enhanced brake thermal efficiency (BTE), brake specific fuel consumption (BSFC) and exhaust has temperature (EGT) are 28.2%, 3% and 465oC respectively. Similarly, reduced emission of CO, NOx, HC and smoke opacity was observed in the CeO2 added blends particularly at 100 mg/L. It was concluded that among all blends prepared, the D70:WPO30 with 100 mg/L of CeO2 showed improved combustion, performance and emission characteristics in proposed diesel engine.

Geolocation of Fixed Emission Sources Produced by Artisan Brick Kilns in the Atmospheric Basin of the City of Juliaca, Peru

Objective: The study objective is to investigate the application of georeferencing systems to identify the geospatial location of fixed sources of atmospheric emissions produced by artisanal brickyards in the air basin of Juliaca city-Peru. Theoretical Framework: Previous studies have shown that artisanal brickyards are a significant source of air pollution in developing urban and on the outskirts. Emissions of fine particles, nitrogen oxides and other pollutants from the burning of traditional fuels, such as firewood and coal contribute to the degradation of air quality and can have adverse effects on human health and the environment. The georeferencing application and geospatial analysis techniques in the atmospheric pollution study have allowed a better understanding of the spatial distribution of emission sources and their impact on the environment. These tools are essential to identify and map the artisanal brickyard locations and to evaluate their contribution to air pollution in urban and on the outskirts. Method: The methodology adopted for this research includes data collection and compilation of existing information; georeferencing of brickyards through the use of geographic information systems (GIS); analysis of geospatial data for the identification of spatial patterns; preparation of thematic and spatial distribution maps; and the interpretation of results. Results and Discussion: The study results highlight the importance of locating the fixed sources of emissions produced by artisanal brick factories in the Juliaca air basin. This precise spatial identification provides a solid basis for the formulation of policies and mitigation strategies aimed at reducing air pollution in the region, in addition to representing fundamental data for the use and exploitation of GIS for environmental protection and modelling, among others. Research Implications: The results can be applied or influence practices in the environmental and forestry engineering field, the ICTs application, modelling and simulation, and territorial planning, among others. Originality/Value: This study contributes to the literature using georeferencing techniques for environmental modelling purposes. The relevance and value of this research are evident in obtaining georeferenced points for the estimation of emission factors for the predictive calculation of volumes, flows and dispersion of pollutants in an air basin.

Recent Advances in NO Reduction with NH3 and CO Over Cu-Ce Bimetallic and Derived Catalysts

Sintering flue gas contains significant amounts of harmful gases, such as carbon monoxide and nitrogen oxides (NOx), which pose severe threats to the ecological environment and human health. Selective catalytic reduction (SCR) technology is widely employed for the removal of nitrogen oxides, with copper-cerium-based bimetallic catalysts and their derivatives demonstrating excellent catalytic efficiency in SCR reactions, primarily due to the significant synergistic effect between copper and cerium. This paper summarizes the main factors affecting the catalytic performance of Cu-Ce-based bimetallic catalysts and their derivatives in the selective catalytic reduction of ammonia and carbon monoxide. Key considerations include various preparation methods, doping of active components, and the effects of loading catalysts on different supports. This paper also analyzes the influence of surface oxygen vacancies, redox capacity, acidity, and specific surface area on catalytic performance. Additionally, the anti-poisoning performance and reaction mechanisms of the catalysts are discussed. Finally, the paper proposes strategies for designing high-activity and high-stability catalysts, considering the development prospects and challenges of Cu-Ce-based bimetallic catalysts and their derivatives, with the aim of providing theoretical guidance for optimizing Cu-Ce-based catalysts and promoting their industrial applications.

Air pollution and skin aging

Air pollution is a leading environmental health risk worldwide, with detrimental effects not only on human health but also on skin aging. This review explores the link between air pollution and skin aging, focusing on the harmful effects of particulate matter (PM) and other pollutants such as polycyclic aromatic hydrocarbons (PAHs), nitrogen oxides (NO2), and ozone (O3). These pollutants penetrate the skin, inducing oxidative stress and inflammation, which accelerates the degradation of collagen and elastin in the extracellular matrix. This contributes to premature aging, wrinkles, hyperpigmentation, and inflammatory skin conditions. The smallest fractions of PM, particularly PM2.5, are the most harmful, causing significant cellular damage. Long-term exposure to these pollutants also disrupts the skin's microbiome, leading to dysbiosis and further weakening the skin's protective barrier. Current therapeutic strategies focus on protecting the skin using antioxidants, such as Vitamin C and Vitamin E, as well as probiotics and moisturizers that support the skin's natural defenses. Sunscreens also play a vital role in protecting the skin from UV-induced oxidative stress, further mitigating pollution-related damage. This review highlights the importance of developing comprehensive skincare regimens that target both pollution-induced oxidative stress and the maintenance of a healthy skin barrier. It also emphasizes the need for further research into personalized approaches to counteract the aging effects of air pollution on the skin.

The uniqueness of pollutant emission and fuel consumption test results for road vehicles tested on a chassis dynamometer

The article considers the issues of non-repeatability of exhaust emission and fuel consumption test results for road vehicles tested on a chassis dynamometer. Empirical results of passenger car tests on a chassis dynamometer in the WLTC (Worldwide Harmonized Light Vehicles Test Cycle) test were used. Tests were conducted in four repeated sets to assess the repeatability of the test results. The road emission of hydrocarbons, non-methane hydrocarbons, carbon monoxide, nitrogen oxides, particulate matter and carbon dioxide, the road number of particulate matter and operational fuel consumption were determined. The coefficient of variation of the values measured in the four tests was determined, taken as a measure of the repeatability of the test results. The coefficient of variation of the road emission of carbon dioxide and operational fuel consumption is the lowest. No significant differences were found in the values of the measured exhaust emission.

Mechanically Induced Green Targeted Conversion of Ammonia Nitrogen to N2: Based on Cavitation Effects and ROS Oxidation.

Addressing the mounting challenge of ammonia nitrogen pollution in aquatic ecosystems necessitates the selective oxidation of ammonia nitrogen to nitrogen gas, a pivotal aspect of eco-friendly nitrogen removal processes. Ultrasound cavitation, renowned for its capacity to generate reactive oxygen species (ROS), has garnered considerable attention in environmental remediation. This study reveals a highly synergistic mechanism in ultrasound coupled stirring (US-ST), establishing optimal coupling conditions through sound field monitoring and quantification of ROS. In comparison to ultrasound treatment alone (US), the sound pressure amplitude significantly increased from ±18 to ±30 kPa in US-ST, markedly reducing the cavitation nucleation threshold and augmenting the steady-state concentration of hydroxyl radicals (HO•) by 13-fold. Further, with appropriate charge transfer conditions enabled by the acoustoelectric characteristics of the passive film on stirring paddles, the concentrations of superoxide (•O2-) and singlet oxygen (1O2) elevated to 9.54 × 10-10 M and 8.43 × 10-13 M, respectively. Under the regulation of 500 rpm stirring vortex, a maximum sonochemical efficiency of 6.5 × 105 mg J-1 was achieved. In the context of domestic wastewater, ammonia nitrogen degradation was achieved through the oxidation and thermal dissociation effects of US-ST. The concentration decreased from 27.5 to 3.4 mg/L after 2 h, with an impressive N2 selectivity of 96.8%. This study elucidates the targeted conversion mechanism of ammonia nitrogen in US-ST, introducing an emerging water treatment technology propelled by mechanical energy.

Linking Electricity and Air Quality Models by Downscaling: Weather-Informed Hourly Dispatch of Generation Accounting for Renewable and Load Temporal Variability Scenarios.

National models of the electric sector typically consider a handful of generator operating periods per year, while pollutant fate and transport models have an hourly resolution. We bridge that scale gap by introducing a novel fundamental-based temporal downscaling method (TDM) for translating national or regional energy scenarios to hourly emissions. Optimization-based generator dispatch is used to account for variations in emissions stemming from weather-sensitive power demands and wind and solar generation. The TDM is demonstrated by downscaling emissions from the electricity market module in the National Energy Model System. As a case study, we implement the TDM in the Virginia-Carolinas region and compare its results with traditional statistical downscaling used in the Sparse Matrix Operator Kernel Emissions (SMOKE) processing model. We find that the TDM emission profiles respond to weather and that nitrogen oxide emissions are positively correlated with conditions conducive to ozone formation. In contrast, SMOKE emission time series, which are rooted in historical operating patterns, exhibit insensitivity to weather conditions and potential biases, particularly with high renewable penetration and climate change. Relying on SMOKE profiles can also obscure variations in emission patterns across different policy scenarios, potentially downplaying their impacts on power system operations and emissions.

Seasonal persistence of the nitrogen oxides production in Mexico City

AbstractThis study investigates the seasonal influence on the nitrogen oxide NOx pollution records at four monitoring sites in Mexico City from 2010 to 2018. The analysis employs the second-order structure function to examine the trends in NOx concentration fluctuations. The findings reveal that the fluctuations follow a power law pattern characterized by Hurst exponents, predominantly in the statistical persistence regime, with a scaling range spanning three orders of magnitude. Specifically, the autumn period exhibits fluctuations with an exponent of $$\overline{H}=0.72$$ H ¯ = 0.72 , indicating relatively smaller fluctuations compared to other seasons, but with the potential for NOx concentrations to surpass those in other periods. In contrast, for spring, summer, and winter, the fluctuations are characterized by exponents of$$\overline{H}=0.59$$ H ¯ = 0.59 ,$$\overline{H}=0.61$$ H ¯ = 0.61 , and$$\overline{H}=0.62$$ H ¯ = 0.62 , respectively, demonstrating greater fluctuations with lower NOx concentrations compared to autumn. These results are consistent with various studies conducted worldwide. Additionally, a negative correlation between NOx and ozone (O3) has been established during the winter season, as NOx and O3 fluctuations display persistent and anti-persistent behavior, respectively.

An Experimental Investigation on Enhancing Nitrogen Oxides Reduction of Non-Thermal Plasma (NTP) Aftertreatment System with Silver-Base Catalyst with NTP Downstream SCR Catalyst Configuration

An Experimental Investigation on Enhancing Nitrogen Oxides Reduction of Non-Thermal Plasma (NTP) Aftertreatment System with Silver-Base Catalyst with NTP Downstream SCR Catalyst Configuration

Pollutant emission during pyrolysis of waste wind turbine blades: Nitrogen-containing components and polycyclic aromatic hydrocarbons

Serious attention was lacked for various pollutants formed in both gas and tar phase during pyrolysis recycling of waste wind turbine blades (WWTB), especially for components of carcinogenic bisphenol A (BPA) and potentially toxic polycyclic aromatic hydrocarbons (PAHs) in tar. Pyrolysis temperature within 400–600 °C would significantly impact pollutant formations. Additionally, CO2 had a potential to mitigate pollutants emission as an economic alternative for N2. This article investigated the influence of these factors on nitrogenous and PAHs components during WWTB pyrolysis through fixed bed and thermogravimetric experiments. The results showed that NO2 was dominated in nitrogen containing pollutants and was related to the evolution of pyrrole nitrogen oxides. It was found 550 °C as a turning temperature, at which the polycondensation reaction appeared significantly. This resulted in a markedly increase for toxic N-PAHs in tar. At this temperature, CO2 could be used to mitigate nitrogen pollutants. 25% CO2 reduced NOX emission about 26% and selectively promoted NH3 releasing to over 4.3 times and depressed HCN generating to 0.6 times. Moreover, the primary depolymerization product of organic pact in WWTB was BPA. Increasing residence time, temperature and CO2 concentration were beneficial for converting hazardous BPA to high valued P-Isopropenylphenol (IPP). The value of IPP:BPA could increase to over 2 in this experiment. It was aimed to provide not only an evaluation for the yield and migration of pollutants, but also an cleaner recycling solution through graded pyrolysis WWTB to mitigate pollution and maximize the value of by-products.

Multi‐aspect assessment and multi‐objective optimization of preheated tallow biodiesel‐diesel blend as alternate fuel in CI engine

AbstractThis study meticulously examined the impact of preheated tallow biodiesel on the performance and emission characteristics of a diesel engine. Employing a single‐cylinder, water‐cooled diesel engine configured with exhaust gas recirculation in this investigation, exhaust gas temperature (EGT) could be used to preheat the biodiesel, reducing its viscosity and density. This improvement in viscosity and density could enhance the injection process, which is often hindered by the higher density and viscosity of biodiesel compared with diesel fuel. The investigation achieved a peak preheat temperature of 70°C for the biodiesel, leading to notable improvements in brake thermal efficiency and brake power, particularly under high‐load conditions. A significant reduction in emissions was observed, with hydrocarbon and carbon monoxide levels decreasing by 46.87% and 50%, respectively, when using preheated biodiesel. To refine the engine's performance further, this study utilized response surface methodology (RSM) for the optimization of operational parameters, including injection timing, engine load, and biodiesel preheat temperatures. Optimal conditions were identified at an injection timing of 21° before top dead centre, a preheat temperature of 64°C, and an engine load of 45.45% for which output response was 18.68% brake thermal efficiency, 307°C EGT, 0.0247% vol. CO, 15.32 ppm hydrocarbons, and 131.37 ppm nitrogen oxides (NOx). The successful implementation of preheated tallow biodiesel signifies a crucial step forward in the pursuit of a more sustainable and efficient transportation industry. This advancement holds the promise of reducing reliance on traditional fossil fuels, thereby contributing to the global efforts towards achieving a more environmentally friendly energy landscape.

The next challenge in emissions control for heavy-duty diesel vehicles: From NOx to N2O

Vehicle emissions are a major source of greenhouse gases globally. Dual selective catalytic reduction (SCR), an advanced version of single SCR, is crucial under stricter nitrogen oxide (NOx) emission standards for heavy-duty diesel vehicles (HDDVs). However, the emission characteristics of nitrous oxide (N2O), a byproduct of SCR and a potent greenhouse gas, remain unclear. This study investigates the N2O emissions from HDDVs equipped with single or dual SCR systems using heavy-duty chassis dynamometers under various ambient temperatures, altitudes, and loading masses. The results showed that the brake-specific emissions (EFb) of N2O from HDDVs with single and dual SCRs were 76.28–269.65 mg/kWh and 147.50–170.22 mg/kWh, respectively. Notably, the dual SCR-equipped HDDV emitted 6–22 times more N2O than NOx under all tested conditions. As ambient temperature increased from −10 °C to 25 °C and from 25 °C to 40 °C, the average distance-based emission factors (EFd) of N2O for the single SCR-equipped HDDV increased by 87.73% and 48.26%, respectively. However, the variation was not significant for the dual SCR-equipped HDDV. Under half- and full-load conditions, the average EFd of N2O for the single SCR-equipped HDDV increased by 47.57% and 110.92%, respectively, compared to those without loading. Similarly, N2O emissions for dual SCR-equipped HDDV increased by 41.40% and 65.37% under the same loading variations. As altitude increased from 0 m to 3000 m, the average EFd of N2O for the single SCR-equipped HDDV decreased by 64.31%. Additionally, N2O emissions were significantly affected by SCR temperature, engine power, and nitric oxide (NO)/nitrogen dioxide (NO2) ratio. These findings are crucial for setting future greenhouse gas limits of HDDVs and informing carbon reduction strategies.

Temporal characterization of NOx and its relationship with O3 at a riverine site of Foshan

Nitrogen dioxide (NO2) is a crucial precursor of tropospheric O3. This study undertakes continuous measurements of nitric oxide (NO), nitrogen dioxide (NO2) and ozone (O3) at Shishan Port (SSP), a riverine site in Foshan, China. Oxides of nitrogen (NOx = NO + NO2) exhibit a distinct seasonality, with high concentrations in winter and low concentrations in summer. The daily average concentration of NOx is 30.5 ppb, with high concentrations in the evening and morning and low concentrations in the afternoon. The variation of the total oxidant (Ox = O3 + NO2) with the levels of NOx was examined to infer the atmospheric sources of Ox as the sum of a local contribution dependent on NOx and a regional contribution independent of NOx. The local contribution predominates during low wind speed and calm weather in winter. The case analysis of a typical NO2 pollution episode affirms that the increase of NO2 at night in SSP is significantly influenced by the exhaust emissions of passing ships, atmospheric diffusion conditions and the O3 concentration generated during the day. Due to the chemical coupling of NOx and O3, along with regional transport, the levels of NOx and O3 are inextricably linked yet complicated.

Research Progress in the Composition and Performance of Mn-Based Low-Temperature Selective Catalytic Reduction Catalysts

NH3 selective catalytic reduction (NH3-SCR) is the most prevalent and effective method for removing nitrogen oxides. Over the past few decades, manganese (Mn)-based catalysts have demonstrated strong catalytic activity and have been extensively studied for low-temperature NH3-SCR reactions. This paper provides an in-depth introduction to four forms of Mn-based catalysts: single manganese oxide-based catalysts, binary Mn-based metal oxide catalysts, ternary and multivariate Mn-based metal oxide catalysts, and nano-Mn-based catalysts. Advances have been made in enhancing Mn-based catalysts’ redox performance and acidity, increasing the active component’s dispersion, lowering binding energy, enlarging specific surface area, raising the Mn4+/Mn3+ ratio, and enriching surface adsorbed oxygen by optimizing preparation methods, altering the oxidation state of active components, modifying crystal phases, and adjusting morphology and dispersion, along with various metal modifications. The mechanism of low-temperature NH3-SCR reactions has been elucidated using various characterization techniques. Finally, the research directions and future prospects of Mn-based catalysts for low-temperature NH3-SCR reactions are discussed, aiming to accelerate the commercial application of new Mn-based catalysts.

Reforming Natural Gas for CO2 Pre-Combustion Capture in Trinary Cycle Power Plant

Today, most of the world’s electric energy is generated by burning hydrocarbon fuels, which causes significant emissions of harmful substances into the atmosphere by thermal power plants. In world practice, flue gas cleaning systems for removing nitrogen oxides, sulfur, and ash are successfully used at power facilities but reducing carbon dioxide emissions at thermal power plants is still difficult for technical and economic reasons. Thus, the introduction of carbon dioxide capture systems at modern power plants is accompanied by a decrease in net efficiency by 8–12%, which determines the high relevance of developing methods for increasing the energy efficiency of modern environmentally friendly power units. This paper presents the results of the development and study of the process flow charts of binary and trinary combined-cycle gas turbines with minimal emissions of harmful substances into the atmosphere. This research revealed that the net efficiency rate of a binary CCGT with integrated post-combustion technology capture is 39.10%; for a binary CCGT with integrated pre-combustion technology capture it is 40.26%; a trinary CCGT with integrated post-combustion technology capture is 40.35%; and for a trinary combined-cycle gas turbine with integrated pre-combustion technology capture it is 41.62%. The highest efficiency of a trinary CCGT with integrated pre-combustion technology capture is due to a reduction in the energy costs for carbon dioxide capture by 5.67 MW—compared to combined-cycle plants with integrated post-combustion technology capture—as well as an increase in the efficiency of the steam–water circuit of the combined-cycle plant by 3.09% relative to binary cycles.

Retrospective assessment of sulfur dioxide and nitrogen oxide emissions from stationary sources in Belarus

Retrospective assessment of sulfur dioxide and nitrogen oxide emissions from stationary sources in Belarus

Tropospheric ozone precursors: global and regional distributions, trends, and variability

Abstract. Tropospheric ozone results from in situ chemical formation and stratosphere–troposphere exchange (STE), with the latter being more important in the middle and upper troposphere than in the lower troposphere. Ozone photochemical formation is nonlinear and results from the oxidation of methane and non-methane hydrocarbons (NMHCs) in the presence of nitrogen oxide (NOx=NO+NO2). Previous studies showed that O3 short- and long-term trends are nonlinearly controlled by near-surface anthropogenic emissions of carbon monoxide (CO), volatile organic compounds (VOCs), and nitrogen oxides, which may also be impacted by the long-range transport (LRT) of O3 and its precursors. In addition, several studies have demonstrated the important role of STE in enhancing ozone levels, especially in the midlatitudes. In this article, we investigate tropospheric ozone spatial variability and trends from 2005 to 2019 and relate those to ozone precursors on global and regional scales. We also investigate the spatiotemporal characteristics of the ozone formation regime in relation to ozone chemical sources and sinks. Our analysis is based on remote sensing products of the tropospheric column of ozone (TrC-O3) and its precursors, nitrogen dioxide (TrC-NO2), formaldehyde (TrC-HCHO), and total column CO (TC-CO), as well as ozonesonde data and model simulations. Our results indicate a complex relationship between tropospheric ozone column levels, surface ozone levels, and ozone precursors. While the increasing trends of near-surface ozone concentrations can largely be explained by variations in VOC and NOx concentration under different regimes, TrC-O3 may also be affected by other variables such as tropopause height and STE as well as LRT. Decreasing or increasing trends in TrC-NO2 have varying effects on TrC-O3, which is related to the different local chemistry in each region. We also shed light on the contribution of NOx lightning and soil NO and nitrous acid (HONO) emissions to trends of tropospheric ozone on regional and global scales.