Nitrogen Oxides Research Articles

Effect of Biofuel Use on Ship Engine

This research examines the effect of biofuel use on ship engine performance, with a focus on performance, efficiency and environmental impact. Experimental studies were conducted using four-stroke marine diesel engines operated with various blends of biofuels and conventional fuels. The measured parameters include engine power, specific fuel consumption, thermal efficiency, and exhaust emissions. The results showed that the use of biofuels at certain concentrations can produce performance comparable to conventional fuels, with some significant differences. Engine power decreased slightly (2-5%) at high biofuel blends, but thermal efficiency increased up to 3% at optimal blends. Specific fuel consumption increased by about 5-8% compared to conventional fuel. Exhaust emissions analysis showed a significant reduction in carbon monoxide (CO) and particulate emissions, with up to 30% and 40% reductions respectively. However, there was a slight increase in oxides of nitrogen (NOx) emissions by 5-10%. The study also identified several technical challenges in the use of biofuels, including the potential degradation of certain engine components and the need for fuel system modifications.

Unraveling Urban NOx Emission Sources in Polluted Arctic Wintertime Using NO2 Nitrogen Isotopes

AbstractNitrogen (N) isotopic fractionation during nitrogen oxides (NOx) cycling and conversion into atmospheric nitrate alters the original N isotopic composition (δ15N) of NOx emissions. Limited quantification of these isotopic effects in urban settings hampers the δ15N‐based identification and apportionment of NOx sources. δ15N of nitrogen dioxide (NO2) measured during winter in downtown Fairbanks, Alaska, displayed a large temporal variability, from −10.2 to 24.1‰. δ15N(NO2) records are found to be driven by equilibrium isotopic fractionation, at a rate in very close agreement with theoretical predictions. This result confirms that N isotopic partitioning between NO and NO2 can be accurately predicted over a wide range of conditions. This represents an important step for inferring NOx emission sources from isotopic composition measurement of reactive nitrogen species. After correcting our δ15N(NO2) measurements for N fractionation effects, a δ15N‐based source apportionment analysis identifies vehicle and space heating oil emissions as the dominant sources of breathing‐level NOx at this urban site. Despite their large NOx emissions, coal‐fired power plants with elevated chimney stacks (>26 m) appear to make a small contribution to surface NOx levels in downtown Fairbanks (likely less than 18% on average). The combined uncertainties of the δ15N of NOx from heating oil combustion and of the influence of low temperatures on the δ15N of NOx emitted by vehicle exhaust prevent a more detailed partitioning of surface NOx sources in Fairbanks.

COMPREHENSIVE CHARACTERISATION OF TEMPORAL VARIATIONS IN CONCENTRATIONS OF GASEOUS AMMONIA AND NITROGEN OXIDES IN TYPICAL URBAN ATMOSPHERE

Atmospheric ammonia (NH3) is a well-known contributor to secondary particle formation and canlead to severe environmental degradation and human health outcomes. In the context of the verylimited knowledge about updated data on NH3 levels in urban areas, this paper presents the results ofa one-year (Apr 2023 – Mar 2024) measurement campaign of NH3 concentrations conducted at theurban background site in Zabrze, located in the central part of the Upper Silesian Industrial District(USID) (southern Poland), which could be considered one of the European hotspots. The research wasperformed using an automatic ammonia analyzer Model T201 by Teledyne API, which provides dataon the levels of NH3 and other gaseous nitrogen compounds (NO (nitrogen oxide), NO2 (nitrogendioxide), NOx (nitrogen oxides) at hourly time resolution. Consequently, this enabled an analysisof specific temporal variations of NH3 concentrations, and therefore allowed the identification ofits possible emission sources and insight into processes involving ammonia. The results obtained inthis study revealed that ammonia stood out from nitrogen oxides and other atmospheric pollutants– with high NH3 concentrations recorded during spring and summer, which is related to the highintensity of gaseous NH3 formation under warm meteorological conditions. A different situationwas observed in the hourly NH3 concentration distribution scheme, which was manifested by muchless visible diurnal variations of NH3 levels, with no characteristic morning maximum, as well asthe occurrence of a broad afternoon maximum in the summer. In summary, anthropogenic sourceshad a significant impact on NH3 concentrations in the area under consideration, with a greater roleof traffic in the case of NOx, and a biomass and fossil fuel combustion and/or industrial sources –for NH3. Local meteorological conditions also had a notable influence on NH3 levels, of which airtemperature (positive correlation) and wind speed (negative correlation) were found to be the mostimportant. The ongoing research is planned to be continued, as it can provide valuable scientific datafor the development of air quality protection strategies and programmes in urban areas, especially inthe field of reducing emissions of gaseous precursors of particulate matter.

Prolonged exposure to air pollution and risk of acute kidney injury and related mortality: a prospective cohort study based on hospitalized AKI cases and general population controls from the UK Biobank

BackgroundPrevious investigations identified a connection between air pollution and kidney diseases. Nevertheless, there is a lack of comprehensive evidence on the long-term risks posed by air pollution with respect to acute kidney injury (AKI) and AKI-related death.MethodsThis prospective cohort analysis included 414,885 UK Biobank (UKB) participants who did not exhibit AKI at the study’s outset. AKI was defined based on ICD-10 codes recorded for hospitalized patients. Cox proportional hazards models were used to assess the association between prolonged exposure to air pollutants (particulate matter with diameters of 2.5 micrometers or less (PM2.5), between 2.5 and 10 micrometers (PM2.5−10), and 10 micrometers or less (PM10), along with nitrogen dioxide (NO2) and nitrogen oxides (NOx)) and the risk of AKI and AKI-related death, adjusting for potential confounders including sex, age, ethnicity, education, income, lifestyle factors, and relevant clinical covariates. Restricted cubic splines were applied to evaluate non-linear dose-response relationships, and stratified analyses were performed to explore potential effect modification across subgroups.ResultsOver an average follow-up duration of 11.7 years, 14,983 cases of AKI and 326 cases of AKI-related death were diagnosed. Quartile analysis showed individuals exposed to higher levels of these air pollutants had a significantly higher risk of developing AKI and AKI-related death compared to those in the lowest quartile (all P < 0.05). The RCS curves depicting the relationship between PM2.5, PM2.5−10, PM10, NO2, NOx, and the risk of AKI showed a significant departure from linearity (P for non−linearity < 0.05), while the relationships between PM2.5, NO2, NOx, and the risk of AKI-related death did not exhibit a significant departure from linearity (P for non−linearity > 0.05). Sensitivity analyses confirmed the robustness of our findings.ConclusionOur study reveals a direct association between prolonged air pollution exposure and elevated risks of both AKI and AKI-related death. These findings offer scientific validation for the adoption of environmental and public health measures directed towards the reduction of air pollution. Such initiatives could potentially ease the impact associated with AKI and AKI-related death.

Enhancing biodiesel engine performance and emission reduction using Fe and Zn coated zeolite catalytic converters

ABSTRACT This study evaluates the performance and emission characteristics of diesel, fish biodiesel (comprising 20% fish oil and 80% diesel), and fish biodiesel using Fe and Zn-coated zeolite catalytic converters. The research aims to mitigate environmental challenges associated with diesel engines by exploring the efficacy of metal-doped zeolite catalysts in reducing harmful emissions. Fish biodiesel was derived from fish waste via transesterification and tested in a single-cylinder diesel engine. Key performance metrics, including Brake Specific Fuel Consumption, Brake Thermal Efficiency, Exhaust Gas Temperature, cylinder pressure, Heat Release Rate, and ignition delay, were measured. Emission characteristics such as carbon monoxide, hydrocarbon, nitrogen oxide, and smoke opacity were also analyzed. Results showed diesel had the lowest Specific fuel consumption, ranging from 730 g/kWh at 25% load to 320 g/kWh at full load. Fish biodiesel exhibited higher Specific fuel consumption, from 770 g/kWh to 350 g/kWh. Regarding emissions, the NOx of the biodiesel increased significantly compared to diesel; the use of a catalytic converter has reduced the NOx emission to a maximum extent of 37.5% at full load for a Fe-coated converter. The Zn-coated converter also improved emissions by up to 33% for NO but was slightly less effective than the Fe-coated converter. The study concludes that Fe-coated zeolite catalytic converters significantly enhance biodiesel-fueled diesel engines’ performance and emission characteristics. Both catalytic converters reduced the smoke emission significantly. These findings highlight the potential for developing more efficient and eco-friendly emission control technologies and promoting using renewable transportation fuels.

Modeling Civil Aviation Emissions with Actual Flight Trajectories and Enhanced Aircraft Performance Model

Aviation emissions are continuously increasing along with the rapid development of air transportation, and results in the deterioration in regional air quality and the global climate. Accurate emission estimation is of great importance for relevant policies promotion and the sustainable development of the environment. Previous studies focused on the total emissions of a flight and lacked high precision in both spatial and temporal resolutions, especially aviation activities near ground. In this research, we propose an open-sourced emission calculation framework based on actual flight trajectories (TrajEmission), which calculates both the ground and airborne emissions simultaneously according to the configuration parameters, trajectory characteristics, and ambient conditions. We compare the emission results with five emission inventory methods. The results indicate that pollutant (nitrogen oxides, carbon monoxide, and unburned hydrocarbons) emissions in the landing and takeoff (LTO) cycle might usually be underestimated due to a lack of trajectory-based methods. In addition, in the overall results, the method based on the great circle route leads to an overestimation of 56.8% of pollutant emissions compared to the method based on actual routes. We also investigate the extent to which other factors could influence the emission results. To summarize, the TrajEmission framework can build inventories for the whole process of flight movements with high spatial–temporal resolutions and provide solid data support for environmental science and other related fields.

Metabolic mechanisms of carbon and nitrogen interactions during anaerobic digestion of coal

There was limited research on the impact of nitrogen metabolism in the process of methane production with coal, even if carbon and nitrogen metabolism were closely interconnected. Lignite was the source of carbon and nitrogen in anaerobic digestion system. The relationship between carbon and nitrogen metabolism was systematically discussed during the anaerobic digestion process. The results showed that phenolic carbon or ether carbon (C-O), pyridine-type nitrogen (N-6) and nitrogen oxide compound (N-X) in coal were decomposed under the action of Macellibacteroides, Sphaerochaeta and Trichococcus in the hydrolysis stage, respectively. In the acidogenesis stage, the stress of volatile fatty acids and ammonia produced by dissolved organic matter under the action of Syner-01 and Sphaerochaeta on hydrogenotrophic and acetoclastic methanogens was alleviated during the nitrogen cycle. In the acetogenesis stage, acetic acid produced from the decomposition of organic acids and alcohols by Synergistaceae and Sedimentibacter was competed by denitrifying bacteria and acetogenic methanogens. In the methanogenesis stage, CO2 was reduced by Methanobacterium and Methanoculleus to produce CH4, while acetic acid was decomposed by Methanosaeta to produce CH4. And methyl substances were generated into CH4 by Methanosarcina and Methanofastidiosum. This understanding will provide a basis for strengthening the favorable factors in biomethane production.

Biofuel blends and nano-additives: a sustainable approach to diesel engine performance and emissions improvement

Abstract The utilization of compression ignition (CI) diesel engines has seen a substantial increase in recent years owing to their numerous advantages. However, the widespread adoption of these engines has also significantly contributed to environmental pollution issues, with diesel engines being recognized as major global contributors to exhaust emissions-related pollution. To address this issue, comprehensive research has been carried out on both emissions from diesel exhaust pollutants and advanced after-treatment technologies for emission control. This study aims to evaluate the efficiency and emissions of diesel fuel mixed with various ratios of biofuel derived from Karanja seeds (B10, B15, and B20). Among the different blends examined, B20 demonstrated superior performance in terms of brake thermal efficiency (BTE) and brake-specific fuel consumption (BSFC), along with lower levels of hydrocarbon (HC) and carbon dioxide (CO2) emissions compared to pure diesel. Further, the impact of nanoadditives, specifically titanium dioxide (TiO2), at different concentrations (80 ppm, 100 ppm, and 120 ppm), on B20 blends was evaluated. The findings indicated that B20 blended with 100 ppm of TiO2 exhibited superior performance in terms of BTE, BSFC, and lower emissions of HC, CO2, nitrogen oxides (NOx), and carbon monoxide (CO). From the results, the BTE increases from 1% to 33%, illustrating enhanced thermal efficiency under similar conditions. The average BSFC across all loads and speeds in the table is approximately 0.89 kg/kWh, while the average BTE stands at approximately 23.1%.

3DVar sectoral emission inversion based on source apportionment and machine learning

Air quality models are increasingly important in air pollution forecasting and control. Sectoral emissions significantly impact the accuracy of air quality models and source apportionment. This paper studied the 3DVar (three-dimensional variational) emission inversion method, which is based on machine learning, and then expanded it to sectoral emission inversion combined with source apportionment. Two machine learning conversion matrices were established to implement this method: a matrix that converts the total pollutant concentration to sectoral source apportionment results and a matrix that converts the sectoral source apportionment results to corresponding emissions. Combined with the O3 (ozone) concentration contributed by VOCs (volatile organic compounds) and NOx (nitrogen oxides) precursors in source apportionment, the inversion ability for O3–NOx–VOCs nonlinear processes was improved. Taking the BTH (Beijing‒Tianjin–Hebei) region from January 15 to 30, 2019, as an example, the results revealed that the regional errors of PM2.5 and O3 in the inversion experiment were reduced by 47% and 45%, respectively, and the temporal errors were reduced by 44% and 16%, respectively.

Constructing dual-channel carrier transport in AgBr/BiOBr/Ag3PO4 heterojunctions for enhanced photocatalytic NO removal

Efficient and stable photocatalysts are indispensable for effectively reducing nitrogen oxide (NOx) emissions. This study presents a facile method for synthesizing AgBr/BiOBr/Ag3PO4 composites and investigates their application in photocatalytic NO removal. The optimized composite exhibited notable performance, achieving 54.95 % removal of NO (approximately 568 ppb reduced to 256 ppb) under visible light irradiation, which is about 1.6 and 2.0 times higher than single Ag3PO4 (34.95 %) and BiOBr (28.01 %), respectively. Comprehensive physicochemical characterization highlighted enhancements in light absorption and the generation of reactive radicals within the AgBr/BiOBr/Ag3PO4 composite. The favorable electronic structure, characterized by well-aligned redox band positions, facilitated efficient dual carrier transport routes, thereby promoting the separation of photo-generated charge carriers. Additionally, in-situ DRIFTS analysis revealed that the composite facilitated the conversion of intermediates into nitrates during the NO purification process. This work contributes valuable insights into designing and preparing of ternary heterojunction photocatalysts with dual carrier transport channels, advancing strategies for achieving superior photocatalytic performance.

Strategies to improve ammonia combustion in a dual fuel marine engine by using CFD

Maritime transportation is currently responsible for delivering most of the world trade, and it still plays a major role in the global economy and pollutant emissions. Due to their heavy loads and long distances, full electrification is generally assumed as an unsuitable pathway, leaving combustion engines as the dominant technology in the marine sector. For a long time, these engines have benefited from the low costs of heavy oils produced from oil refining, but these fuels present a difficult combustion and are associated with significant pollutant emissions and greenhouse gases. Today, carbon-free fuels such as hydrogen and ammonia are gradually getting a foothold in the shipping market.In the present paper, an investigation on several strategies to improve the oxidation of ammonia is carried out for a dual fuel (DF) medium speed marine engine. A CFD analysis using ANSYS FORTE® code is performed on an improved and more realistic bowl geometry by varying the premixed fuel according to methods validated in previous studies and introducing adequate kinetic mechanisms from the literature. Results show that the sole use of ammonia to replace natural gas, as premixed fuel, leads to incomplete combustion; the increase of diesel fuel can only mitigate this condition, but it cannot be considered as viable solution. Therefore, several blends of ammonia/hydrogen are tested to examine combustion development and pollutant emissions. The addition of hydrogen above 10% to the premixed charge composition demonstrates to promote the oxidation of ammonia and to effectively reduce CO2 emissions of 84% without a dramatic increase in nitrogen oxides. On the contrary, hydrogen percentages lower than 10% feature a worsening of the combustion of the premixed charge. Finally, the use of a fuel containing nitrogen promote a slight formation of NOx emissions.

Impact of biochar application on nitrous oxide and methane emissions in rainfed cropping systems within a semiarid region

AbstractThis study investigated the impact of biochar on Zea mays L. yield and greenhouse gas (GHG) emissions in rainfed maize fields in Northwest China. Four treatments were compared: unmodified control (CK), conventional nitrogen (BC0), nitrogen + 20 t ha−1 biochar (BC20), and nitrogen + 50 t ha−1 biochar (BC50). Results showed significant increases in grain yields with BC20 (11.1%) and BC50 (8.6%) compared to BC0. Emissions of nitrous oxide (N2O) were reduced by 14.0%–19.5% in biochar treatments compared to CK. Methane (CH4) uptake by the fields, acting as CH4 sinks, was not significantly impacted by biochar treatments, clarifying that the biochar did not alter the farmland's inherent ability to uptake CH4. Over 2 years, the addition of nitrogen fertilizer and biochar did not markedly alter cumulative CH4 uptake. Both net greenhouse gas (NGHG) emissions and yield‐scaled GHG intensity (NGHGI) were lowered by 16.7%–23.5% and 24.2%–30.3%, respectively, with biochar application. The integration of biochar effectively mitigated the GHG emission enhancement due to nitrogen fertilizer, mainly by decreasing nitrogen oxide emissions and boosting maize yields. Thus, proper biochar application would be an economical and effective strategy for mitigating gas emissions from rainfed maize cropping system in semiarid regions.

Implementation of Regenerative Thermal Oxidation Device Based on High-Heating Device for Low-Emission Combustion

In this paper, a heating device is implemented by considering two large factors in a 100 cmm RTO design. First, when the combustion chamber is used for a long time with a high temperature of 750–1100 °C depending on the high concentration VOC gas capacity, there is a problem that the combustion chamber explodes or the function of the rotary is stopped due to the fatigue and load of the device. To prevent this, the 100 cmm RTO design with a changed rotary position is improved. Second, an RTO design with a high-heating element is implemented to combust VOC gas discharged from the duct at a stable temperature. Through this, low-emission combustion emissions and energy consumption are reduced. By implementing a high heat generation device, the heat storage combustion oxidation function is improved through the preservation of renewable heat. Over 177 h of demonstration time, we improved the function of 100 cm by discharging 99% of VOC’s removal efficiency, 95.78% of waste heat recovery rate, 21.95% of fuel consumption, and 3.9 ppm of nitrogen oxide concentration.

Influence of Oil and Gas End-Use on Summertime Particulate Matter and Ozone Pollution in the Eastern US.

The influence of oil and gas end-use activities on ambient air quality is complex and understudied, particularly in regions where intensive end-use activities and large biogenic emissions of isoprene coincide. In these regions, vehicular emissions of nitrogen oxides (NOx≡NO + NO2) modulate the oxidative fate of isoprene, a biogenic precursor of the harmful air pollutants ozone, formaldehyde, and particulate matter (PM2.5). Here, we investigate the direct and indirect influence of the end-use emissions on ambient air quality. To do so, we use the GEOS-Chem model with focus on the eastern United States (US) in summer. Regional mean end-use NOx of 1.4 ppb suppresses isoprene secondary organic aerosol (OA) formation by just 0.02 μg m-3 and enhances abundance of the carcinogen formaldehyde by 0.3 ppb. Formation of other reactive oxygenated volatile organic compounds is also enhanced, contributing to end-use maximum daily mean 8-h ozone (MDA8 O3) of 8 ppb. End-use PM2.5 is mostly (67%) anthropogenic OA, followed by 20% secondary inorganic sulfate, nitrate and ammonium and 11% black carbon. These adverse effects on eastern US summertime air quality suggest potential for severe air quality degradation in regions like the tropics with year-round biogenic emissions, growing oil and gas end-use and limited environmental regulation.

Investigating the Synergistic Effect of Decoration and Doping in Silver/Strontium Titanate for Air Remediation.

Strontium titanate (STO) and its variants have emerged as leading materials in photocatalysis, particularly for degrading nitrogen oxides (NOx), due to their non-toxic nature, structural adaptability, and exceptional thermal stability. Although the one-pot sol-gel method leads to high-quality photocatalysts, areas remain for improvement. This study examines the impact of ethanol as a cosolvent in STO synthesis, focusing on optimizing the water-to-ethanol volume ratio. The findings reveal that a 1:3 ratio significantly enhances macropore formation and photocatalytic efficiency, achieving 42% NOx degradation under LED within three hours. Furthermore, incorporating 8.0 wt.% Ag into STO substantially improves visible light absorption and enables complete NOx elimination, thanks to enhanced charge separation and localized surface plasmon resonance. Even at high temperatures (1100 °C), the Ag-STO photocatalyst maintains partial activity, despite exceeding silver's melting point. These results highlight the potential of STO-based materials for industrial applications, positioning them as a promising solution for effective NOx mitigation.

Association of Ambient Air Pollution Exposure With Incident Glaucoma: 12-Year Evidence From the UK Biobank Cohort.

Glaucoma is the leading cause of irreversible blindness worldwide. Despite growing concerns about air quality and its impact on ocular health, there remains a knowledge gap regarding the long-term association between air pollution and glaucoma risk. This study investigates the relationship between exposure to ambient air pollution and incidence of glaucoma. In this prospective study, we used land use regression models to estimate levels of various air pollutants, including fine particulate matter (PM2.5), PM2.5 absorbance, PM2.5-10, PM10, nitrogen dioxide (NO2), and nitrogen oxides (NOx). Incidents of glaucoma were ascertained through routinely collected hospital admission records. Multivariate Cox proportional hazards models were used to examine the associations between air pollution exposure and glaucoma incidence, adjusting for potential confounding sociodemographic, physical, and lifestyle factors. Data from 481,113 participants were included. Over a median follow-up of 12.8 years, 9224 incident cases of glaucoma were identified. In the maximally adjusted model, per interquartile range increase in PM2.5 was associated with a 3% greater risk of developing glaucoma (hazard ratio [HR] = 1.03, 95% confidence interval [CI] = 1.00 to 1.06, P = 0.048). Participants in the highest quartile had a 10% increased risk of developing glaucoma compared to those in the lowest quartile (HR = 1.10, 95% CI = 1.03 to 1.17, P = 0.005). Higher levels of exposure to ambient air pollutants, particularly PM2.5, are associated with an increased risk of developing glaucoma. These results highlight the potential public health impact of ambient air pollution on glaucoma risk and underscore the urgent need for further research into targeted environmental interventions in this domain.

The Research of Diesel Engine Assembly Consistency Influence NOx Emission Based on Uniform Design Method

ABSTRACT Diesel engines need to meet the higher emission requirement according to the Euro VI emission standards, and changes in the assembly tolerance of diesel engines will affect the consistency of nitrogen oxides(NOx) emissions. To study the influence of assembly tolerance on NOx emission, a heavy diesel engine was used as the research prototype. The combustion model of the diesel engine was simulated by the Converge software and calibrated with the bench test data. Because the combustion system parameters have a significant impact on emissions, a three-factor eleven-level uniform design is arranged with three parameters, including compression ratio, fuel injection nozzle extension height and injection advance angle. The regression analysis method is used to obtain the relationship between the parameters and NOx emissions. The R2 test value of the regression equation is 0.916 and the F test value is 43.5, which shows that the results of the analysis are very effective. Then the single factor test method is applied to analyze the varying laws of compression ratio, nozzle extension height and fuel injection advance angle on NOx emissions, and the results reveal the inherent law similar to the regression equation. According to the Euro VI emission standards and the law of diesel engine emission performance consistency, the tolerance variation range of the key dimensions of the assembly parameters is obtained.

Open windrow composting of lignocellulosic crop residues and neem litter: Accounting for reactive nitrogen and greenhouse gas emissions

Crop residue management plays a key role in reducing the environmental impact of agriculture, particularly through composting. Compost application to soil replenishes organic matter. A study was conducted to quantify the greenhouse gas emissions (GHG) (carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O)) and reactive nitrogen (Nr) losses (ammonia (NH3) and oxides of nitrogen (NOx)) from the open windrow composting of crop residues from three cereal crops (rice, maize and pearl millet) and neem litter. The windrow moisture was maintained between 50 and 60% with mechanical turning every 25 days. Compost maturity was reached after 137 days, indicated by a germination index (GI) > 80% and the ratio of initial to final C/N ratio, which was <0.4. CO2 and N2O emissions increased after turning, while CH4 emissions declined. The global warming potentials of the composts were 169.71, 184.13, 200.15, and 217.3 g CO2 eq. kg⁻1 initial dry matter (DM) for rice straw, maize stover, pearl millet stover, and neem litter, respectively. NH3 emissions ranged from 1.13 to 2.13 mg kg⁻1 initial DM, with neem litter producing more NH3 and less N2O due to its lower C/N ratio and nitrification inhibitory properties. Rice straw emitted the highest NOx (75.48 mg kg⁻1 DM), while maize stover had the lowest (28.39 mg kg⁻1 DM). Nitrogen losses from compost ranged from 8.16% in paddy straw to 0.53% in neem compost, with carbon losses ranging from 82.35% to 85.57%. The study concluded that careful management of moisture and aeration is critical for minimizing gaseous emissions from open windrow composting.

Formic Acid-Intensified Photoreduction of NOx on Iron Minerals Triggers Daytime HONO Formation through Active Hydrogen.

Nitrous acid (HONO) is crucial in atmospheric chemistry as a precursor to morning peak hydroxyl radicals and significantly affects urban air quality by forming secondary pollutants, yet the mechanisms of its daytime formation is not fully understood. This study investigates the role of formic acid (HCOOH), a prevalent electron and proton donor, in the transformation of nitrogen oxides (NOx) and the formation of HONO on photoactive mineral dust. Exploiting hematite (Fe2O3) as an environmental indicator, we demonstrate that HCOOH significantly promotes the photoreduction of NO2 to HONO, while suppressing nitrate accumulation. This occurs through the formation of a surface ≡Fe-OOCH complex, where sunlight activates the C-H bond to generate and transfer active hydrogen, directly converting NO2 to HONO. Additionally, HCOOH can trigger the photolysis of nitrates as predeposited on Fe2O3, further increasing HONO production. These findings show that HCOOH-mediated photochemical reactions on iron minerals may contribute to elevated atmospheric HONO levels, highlighting a crucial pathway with broad effects on atmospheric chemistry and public health.

Fossil Diesel, Soybean Biodiesel and Hydrotreated Vegetable Oil: A Numerical Analysis of Emissions Using Detailed Chemical Kinetics at Diesel Engine Like Conditions

Nowadays, emissions from internal combustion engines are a relevant topic of investigation, taking into account the continuous reduction of emission limits imposed by environmental regulatory agencies around the world, obviously as the result of earnest studies that have pointed out the impact on the human health of high levels of contaminants released into the environment. Over recent years, the use of biofuels has contributed to attenuating this environmental issue; however, new problems have been raised, such as NOx emissions tend to increase as the biofuel percentage in the fuel used in engines increases. In this research, the emissions of a compression ignition internal combustion engine modeled as a variable volume reactor with homogeneous combustion were numerically investigated. To analyze the combustion process, a detailed kinetics model tailored specifically for this purpose was used. The kinetics model comprised 30,975 chemical reactions involving 691 chemical species. Mixtures of fuel surrogates were then created to represent the fuel used in the Brazilian fuel marketplace, involving (i) fossil diesel—“diesel A”, (ii) soybean diesel—“biodiesel”, and (iii) hydrotreated vegetable oil— “HVO”. Surrogate species were then selected for each of the aforementioned fuels, and blends of those surrogates were then proposed as mixture M1 (diesel A:biodiesel:HVO—90:10:0), mixture M2 (diesel A:biodiesel:HVO—85:15:0), and mixture M3 (diesel A:biodiesel:HVO—80:15:5). The species allowed in the kinetics model included all the fuel surrogates used in this research as well as the target emission species of this study: total hydrocarbons, non-methane hydrocarbons, carbon monoxide, methane, nitrogen oxides, carbon dioxide, soot, and soot precursors. When compared to experimental trends of emissions available in the literature, it was observed that, for all the proposed fuel surrogates blends, the numerical approach performed in this research was able to capture qualitative trends for engine power and the target emissions in the whole ranges of engine speeds and engine loads, despite the CO and NOx emissions at specific engine speeds and loads.