Elevated NOx Research Articles

Spatio-temporal variability and trends of air pollutants in the Metropolitan Area of Curitiba

Monitoring air pollutants over time is essential for identifying and addressing trends, which may help improve air quality management and safeguard public health. This study investigates the spatio-temporal variability of air quality in the Metropolitan Area of Curitiba (MAC), Brazil, focusing on six pollutants (SO2, NO2, NOx, O3, CO, and PM10) measured at eight monitoring stations from 2003 to 2017. We conducted statistical analyses, including diurnal cycles, seasonal variability, spatio-temporal correlations, conditional bivariate probability functions, Theil-Sen trend analysis, and comparison with national quality standards (NAQS) and World Health Organization (WHO) guidelines. The analyses revealed large variations in pollutant concentrations across the study area. For instance, stations strongly impacted by industrial emissions presented the highest mean annual SO2 (20–28 μg/m3) and PM10 (32–34 μg/m3) concentrations, while those mostly impacted by traffic showed elevated NO2 (31–39 μg/m3), NOx (63–86 μg/m3) and CO (0.6–0.8 mg/m3) concentrations. The two residential stations recorded the highest O3 concentrations (annual mean of 30–32 μg/m3). Seasonal and diurnal patterns varied by pollutant, with winter experiencing higher concentrations and O3 peaking in spring. SO2 concentrations presented no clear seasonal or diurnal cycle patterns, and showed the highest spatial variability. Significant decreasing annual trends were observed for SO2 (−5.9%), NO2 (−2.6%), NOx (−2.6%), CO (−5.4%), and PM10 (−3.7%), which suggests the success of emission reduction programs implemented in the road transportation and industrial sectors. However, O3 concentrations increased at most stations (+3.3%/yr), likely due to reduced NOx emissions, increased emissions of volatile organic compounds from on-road transport biofuels, and regional O3 transport. Although exceedances of NAQS decreased over time, concentrations of most pollutants remained above WHO guidelines, except for CO. These results highlight the importance of targeted emission control strategies for both industrial and vehicular sources to improve local air quality and inform future policy decisions.

Investigation into the impact of acetylene on performance and emission characteristics of a compression ignition engine using a blended biodiesel of ethanol and tamanu oil.

Due to the significant increase in transportation, traditional fossil fuels utilised in internal combustion engines will only be accessible for a limited duration. Additionally, the harmful pollutants produced by these fuels, including CO, NOx, unburned hydrocarbons, smoke, and a small amount of particulate matter, have a severe negative impact on the environment. Although biodiesel proves efficient without necessitating engine modifications, its performance is hindered by its higher viscosity. Consequently, this research aims to enhance performance by introducing acetylene alongside tamanu methyl ester (biodiesel); however, this approach results in elevated NOx levels. To mitigate NOx emissions, a combination of ethanol and biodiesel is employed. This study investigates the performance and emission attributes of Acetylene + TME90E10 as the fuel. The combustion pressure and heat release rate of TME90E10 with 6 lpm, improved by 5.41% and 9.1% than diesel. When compared to regular diesel fuel, the introduction of 6l per minute of acetylene with TME90E10 yields a substantial 24.4% decrease in hydrocarbon (HC) emissions. Furthermore, employing TME90E10 at the same acetylene flow rate demonstrates the lowest carbon monoxide (CO) emissions, registering at 0.07%, in contrast to the 0.13% emissions observed throughout the exhaust cycle when using pure diesel fuel.

Turbocharged DISI engine low-load performance improvement investigation through ozone seeding with residual gases and excess air charge dilution

The automotive industry has long prioritized the search for more efficient engines, driven by environmental concerns, fuel prices, and consumer demand for fuel-efficient vehicles. Various technologies and strategies are explored to enhance performance while reducing fuel consumption and emissions. Despite potential combustion stability issues, techniques like using lean mixtures or retaining exhaust gases are commonly employed. Ozone seeding has emerged as a combustion enhancer for internal combustion engines, particularly effective under lean mixtures or high residual gas levels, aiming to stabilize de-throttling conditions, minimize pumping losses, and enhance engine efficiency by enhancing the reactivity of the mixture through the release of radicals that facilitate fuel oxidation. This study investigates the impact of ozone addition on engine performance, emissions, and fuel consumption using a turbocharged SI vehicular engine on a dynamometer bench under different loads. Ozone was introduced to the engine intake using an ozone generator with compressed air, considering two mixture dilution strategies: fresh air and residual gases. Results show that ozone application, with Brazilian Gasoline Type C, induces autoignition of the end-gas under specific low-load, low-engine speed conditions. Up to 1000 ppm, ozone has no discernible impact on DISI engine operation under excess air dilution, maintaining performance equivalent to the baseline. For specific operating conditions with 3 and 4 bar BMEP, where ozone stabilizes combustion with higher residual gas fraction (RGF) percentages, there is a notable reduction in specific fuel consumption, suggesting a potential 1%–1.5% increase in brake efficiency. However, ozone seeding with high RGF percentages leads to a slight increase in CO emissions, elevated NOX emissions, and a tendency to reduce THC emissions up to a certain RGF limit.

Transient NOx emission modeling of a hydrogen-diesel engine using hybrid machine learning methods

One promising approach to reduce carbon foot print of internal combustion engines (ICEs) is using alternative fuels like hydrogen, particularly by converting medium and heavy-duty diesel engines to dual-fuel hydrogen-diesel engines. To minimize elevated NOx emissions from hydrogen-fueled engine, fast and accurate emission models are essential for engine model-based control and for engine calibration and optimization using hardware-in-the-loop (HIL) setups. In this study, a fast-response NOx emissions sensor is used to measure the transient NOx emissions from a dual-fuel hydrogen-diesel engine. Subsequently, steady-state models (SSMs), quasi steady-state models (QSSMs), and transient sequential models (TSMs) in the form of black-box (BB) and gray-box (GB) models are developed for transient NOx emissions prediction. GB models utilize both information from a one dimensional (1D) physical engine model and experimental data for training, while BB models only use experimental data. SSMs are optimized artificial neural networks (ANNs) trained using steady-state data, QSSMs are optimized ANNs trained using transient data, and TSMs are time-series networks trained using transient data. Long short-term memory (LSTM) and gated recurrent unit (GRU) networks are used as the time-series deep learning networks. The results showed that the 1D physical model has the poorest performance with successive model performance improvement from SSM to QSSM and from QSSM to TSM. The developed BB TSM model in this study can predict transient NOx emissions with an R2 value greater than 0.96 at 89,000 predictions per second which makes this model suitable for real-time engine model-based control where computational efficiency is crucial. The developed GB TSM model can predict transient NOx emissions with an R2 value greater than 0.97 but it is computationally more expensive. The extra accuracy of the GB TSM models makes them the best choice for HIL setups where more computational power is available, and accuracy is more crucial.

Experimental study on emissions and particulate characteristics of diesel engine fueled with plastic waste oil, acetone-butanol-ethanol and diesel blends

Plastic waste poses a significant environmental challenge due to its non-biodegradable nature and accumulation in landfills. Converting plastic waste into usable fuel could offer a promising solution for mitigating these issues while addressing the emission-related challenges of diesel engines. This study investigates the impact of plastic waste oil (WPO) obtained through pretreatment and catalytic pyrolysis, blended with acetone-butanol-ethanol (ABE) and diesel fuel, on diesel engine. The aim was to evaluate how these blends affect gaseous emissions, organic compounds, and particle-bound carbon, focusing on their potential to reduce harmful pollutants compared to pure diesel fuel. The results indicated that the ABE5W15D blend significantly reduced smoke and CO emissions by 35.7 % and 17.43 %, respectively, with a slight decrease in HC emissions. However, the ABE20W blend showed elevated NOx levels due to higher ignition delay and increased cylinder pressure. Compared to pure diesel (D100), ABE10W10D and ABE5W15D blends reduced total polycyclic aromatic hydrocarbons (PAHs) emissions by 26.8 % and 37.4 %, respectively. Naphthalene was the dominant PAH, remarkably increasing with W20D use, while longer-chain alkanes associated with lubricant oil had higher W20D emissions. The ABE5W15D blend notably reduced organic carbon (OC) emissions by approximately 38.26 % compared to D100. ABE20D exhibited lower elemental carbon (EC) emissions than D100, although it had higher EC than OC. The W20D blend resulted in larger particle diameters, whereas ABE10W10D showed lower particle counts in the 7–15 nm range. In conclusion, blending plastic waste oil with ABE and diesel fuel can effectively mitigate certain pollutants, depending on the blend composition.

High-risk human papillomavirus infection and cervical cytopathology: relationship with cervical nitric oxide levels

BackgroundNitric oxide (NO) may contribute to the persistence of high-risk human papillomavirus (hrHPV) infection, which has been linked to the development of premalignant lesions and cervical cancer. Our study aimed to examine the relationship between cervical NO metabolite (NOx) levels, hrHPV infection, and cytopathological findings. Additionally, we assessed cervical NOx levels as a biomarker for predicting hrHPV infection and epithelial atypia.MethodsThe study involved 74 women who attended the Gynecology and Obstetrics outpatient clinics at Cairo University Hospitals between November 2021 and August 2022. Cervical samples were subjected to Pap testing, assessment of NOx levels by the Griess method, and detection of hrHPV DNA by real-time polymerase chain reaction.ResultsHigh-risk HPV was detected in 37.8% of women. EA was found in 17.1% of cases, with a higher percentage among hrHPV-positive than negative cases (35.7% vs. 4.3%, p = 0.001). The most prevalent hrHPV genotype was HPV 16 (89.3%). The cervical NOx level in hrHPV-positive cases was significantly higher (37.4 µmol/mL, IQR: 34.5–45.8) compared to negative cases (2.3 µmol/mL, IQR: 1.2–9.8) (p = < 0.001). Patients with high-grade atypia showed significantly higher NOx levels (38.0 µmol/mL, IQR: 24.6–94.7) in comparison to NILM and low-grade atypia cases (5.0 µmol/mL, IQR: 1.6–33.3 and 34.5 µmol/mL, IQR: 11.7–61.7, respectively) (p = 0.006). Although the NOx levels among hrHPV-positive cases with low-grade atypia (40.4 µmol/mL, IQR: 33.3‒61.8) were higher than those with NILM (36.2 µmol/mL, IQR: 35.7‒44.0) and high-grade atypia (38.0 µmol/mL, IQR: 24.6‒94.7), the difference was not significant (p = 0.771). ROC curve analysis indicated that the cervical NOx cut-off values of > 23.61 µmol/mL and > 11.35 µmol/mL exhibited good diagnostic accuracy for the prediction of hrHPV infection and EA, respectively.ConclusionsThe high prevalence of hrHPV infection, particularly HPV 16, in our hospital warrants targeted treatment and comprehensive screening. Elevated cervical NOx levels are associated with hrHPV infection and high-grade atypia, suggesting their potential use as biomarkers for predicting the presence of hrHPV and abnormal cytological changes.

Kinetical driving force analysis of unstable combustion behavior in ammonia/hydrogen blending system

Unstable combustion states are frequently observed in ammonia/hydrogen blended combustion systems. This study aims to explore the underlying thermokinetic feedback driving forces responsible for the occurrence of unstable combustion states based on the identified dominant reactions. To achieve this, the newly developed functional weight analysis method is employed and compared with the combination of heat-release/temperature sensitivity anaylsis. Analysis conducted within several popular mechanisms over a wide temperature and pressure range reveals that the important reactions identified in different mechanisms consistently exhibit loop-formed kinetics with similar mechanism functions.These loops include a hydrogen chain-branching loop, a NH2 dehydrogenation-oxidation loop, and a NOx-DeNOx loop. All of these loops encompass a combination of exothermic and endothermic reactions, and they mutually promote each other due to their loop-formed kinetic. Consequently, when the heat release/heat absorption ratios within the loop kinetics meet specific quantitative criteria, they establish effective thermokinetic feedback. This feedback mechanism initiates and sustains non-constant heat release, serving as a monopole sound source that produces acoustic waves. It is worth noting that the discovery of NOx-DeNOx loop provides a compelling explaination for the frequently observed association between oscillatory combustion states and elevated NOx emissions.

The improvements of a diesel engine fueled with renewable and sustainable diesel/n-butanol/polyoxymethylene dimethyl ethers blended fuels at high altitudes

Atmospheric conditions at high altitudes deteriorate combustion in the cylinder of compression ignition (CI) engines, severely degrading engine performance and increasing soot emissions. The use of oxygenated fuels as an alternative fuel to diesel is an effective solution to improve performance and reduce emissions of highland CI engines. Before optimizing a highland CI engine, it is necessary to determine the law of influence of oxygenated fuels on the performance and emission characteristics of the engines. This paper focuses on the effect of diesel/n-butanol/polyformaldehyde dimethyl ether blends on the combustion, performance, and emission characteristics of a CI engine at different simulated altitudes (0 m, 2000 m, 3000 m, and 4000 m). First, a three-dimensional computational fluid dynamics (3D-CFD) simulation model was developed and validated by experimental results. Second, the 3D-CFD model coupled with a chemical kinetic mechanism including 164 species and 643 reactions was used to simulate the combustion process in the cylinder under different operating conditions. The results showed that the high-altitude environment increased the cylinder temperature, peak heat release rate, ignition delay, soot emissions, HC emissions, and brake specific fuel consumption, and reduced BTE, and NOx emissions of the CI engine compared with the plains. At the same altitude, the use of n-butanol and PODE3 provided oxygen for in-cylinder combustion, which somewhat promoted more complete combustion in the cylinder, reduced HC and soot emissions and increased BTE. Although the use of oxygenated fuels in highland CI engines elevated NOx emissions, the problem could be solved by methods such as LTC and SCR. Overall, n-butanol and PODE3 are promising alternative fuels for highland CI engines, mitigating to some extent the problems of higher soot and HC emissions and lower BTE associated with high-altitude environments.

The effects of combustion phasing induced by water injection on deNOx performance of GDI engine at MBT ignition timing

The call for greenhouse gas emission reduction as the result of global warming has been the main cause of the more rigorous emission legislation in the road transportation sector. In response to such requirements, car makers opt for the ‘down-sizing’ trend for engine displacement with the aim to increase brake thermal efficiency by increasing engine load (mean effective pressure). However, this leads to higher potential of engine knocking and elevated NOx emissions. This study investigates the effects of combustion phasing induced by water injection via the intake manifold of a naturally aspirated GDI engine at MBT ignition timing fuelled with E20. Water up to 30% of fuel mass is port-injected during high engine load and maximum NOx reduction of up to 82% could be achieved as the result of lower RoHR caused by vaporisation of water. Water injection prolonged the ignition delay and combustion duration (CA1090) without deterioration of combustion stability (%COV of IMEP). The optimisation of ignition timing based on MBT can improve CO emission compared to EGR systems. The proposed study demonstrates the possibility to achieve low nitrogen emissions without the need of precious metal-based catalysts.

Residential gasification of solid biomass: Influence of raw material on emissions

With interest rising in biomass use, biomass gasification has the potential to become an imperative mechanism to deliver clean conversion of various types of solid biomass to gas. But as biomass gasification attracts growing interest, it is important to focus not only on the technological feasibility but also fully understand its environmental impact to eliminate avoidable air pollution.In this study, we investigated relationships between the composition of 14 types of solid biomass fuels and their gasification emissions in a small-scale residential outdoor setting. Our results show that the amount and type of produced emissions are strongly influenced by the gasified feed.Combining chemical and petrographic analysis proved to be a robust quality assessment method of solid biomass fuels, allowing for quick detection of their contaminants. These impurities can be directly correlated with elevated particulate matter emissions, CO, H2S, HCHO, NH3, SO2, NOx, and respiratory tract irritants. These observations show that quality testing of biomass fuels is critical not only for ensuring their high quality but also for predicting avoidable air pollution during their utilization.Although our data revealed relationships between the type of biomass fuel and gasification emissions, in general, our experiments show that small-scale gasification in a residential setting is a safe technology, and potential hazards can be eliminated by using certified fuels and ensuring appropriate distance from the source of emissions.

Abstract 13625: Autophagy Plays a Key Role in the Loss of Nitric Oxide Signaling and Endothelial Dysfunction in Pulmonary Vascular Diseases

Introduction: Congenital heart defects (CHDs) are the most common type of birth defect. Children or infants with CHD often develop pulmonary vascular diseases (PVD) due to increased pulmonary blood flow and pressure. Unfortunately, there is no effective therapy to limit the shared pathophysiologic features of pulmonary endothelial dysfunction and vascular remodeling. Autophagy, a lysosome-dependent proteolytic pathway, enables cells to sequester portions of cytosolic proteins or damaged organelles into autophagosomes and degrade them in autolysosomes. Studies have found that autophagy participates in pulmonary hypertension, acute lung injury, lung cancer, and other pulmonary diseases. Hypothesis: Autophagy plays a key role in the development of pulmonary endothelial dysfunction in PVD associated with CHD. Methods and Results: We utilized lung endothelial cells isolated from an ovine CHD model, created by the fetal placement of an aortopulmonary graft (Shunt). First, we confirmed that autophagy was activated in Shunt pulmonary artery endothelial cells (PAEC), with increased LC3-II/LC3-I ratio (1.45 fold increase, n=3, p&lt;0.05) and reduced p62 levels (64% reduction, n=3, p&lt;0.05). Shunt PAECs were found hyperproliferative (BrdU Assay A 450 : control vs. Shunt: 2.36 ± 0.05 vs . 2.58 ± 0.05, n=9, p&lt;0.01), which can be attenuated by pharmacologic autophagy inhibitor bafilomycin A1 (2.30 ± 0.05, n=9, p&lt;0.01 compared with Shunt) or 3-MA (2.20 ± 0.03, n=9, p&lt;0.001 compared with Shunt). Shunt PAECs exhibited significant endothelial Nitic Oxide Synthase (eNOS) uncoupling by BH4 reduction (31% reduction, n=3, p&lt;0.01). Bafilomycin A1 reversed eNOS uncoupling in Shunt PAECs by BH4 restoration (2.1 fold increase, n=3, p&lt;0.01), resulting in elevated cellular NOx level (1.8 increase fold, n=3, p&lt;0.01). Mechanistically, this was dependent on increased levels of GTP cyclohydrolase I (GCH1) protein in Shunt PAEC. Conclusions: Enhanced autophagy plays a key role in the loss of NO signaling and endothelial dysfunction associated with CHD. We speculate that autophagy might be an effective therapeutic target for pulmonary vascular diseases.

Rapamycin Suppresses Penile NADPH Oxidase Activity to Preserve Erectile Function in Mice Fed a Western Style High‐Fat, High‐Sucrose Diet

IntroductionThe mechanistic target of rapamycin (mTOR) is a nutrient‐sensitive cellular signaling kinase that has been shown to be activated by high‐fat and/or high‐sugar feeding in highly metabolic tissues such as adipose tissue, liver, and skeletal muscle. mTOR activation has been implicated in the excess production of reactive oxygen species (ROS) resulting from overnutrition, which has been associated with activation of NADPH oxidase (Nox) as a source of excess ROS production. A Western style high‐fat, high‐sucrose diet has recently been used to induce erectile dysfunction (ED) in rodents, in which elevated Nox has been implicated in ED pathogenesis. The objective of this study was to determine if mTOR is an upstream mediator of Nox in the penis in response to the Western diet (WD) and to determine if this pathway is relevant in WD‐induced ED.MethodsYoung male C57Bl/6 mice (n = 90) were fed a control diet (CD) or WD ad libitum for 12 weeks. For the final four weeks of the dietary intervention, mice were intraperitoneally injected with either vehicle (Veh) or the mTOR inhibitor rapamycin (Rap; 2 mg/kg) three days/week. Following the intervention, erectile function was assessed by measuring intracavernosal pressure (ICP) and mean arterial pressure (MAP) during cavernous nerve stimulation. In separate mice following the same intervention, in vivo ROS production was measured in the penis utilizing a microdialysis approach. Microdialysis probes were inserted into the penis of anesthetized mice and perfused with saline containing 100 μM Amplex Ultrared, 1 U/ml horseradish peroxidase, and 10 U/ml superoxide dismutase, and fluorescence was measured from three dialysate replicates. 300 μM apocynin, a Nox inhibitor, was then added to the perfusate, and additional dialysate samples were analyzed. Nox‐mediated ROS were determined by calculation of the ROS that was inhibited by apocynin. Western blots were performed on corpus cavernosum (CC) tissue for Nox subunits, phosphorylation of the mTOR active site, and phosphorylation of p70S6K, a downstream mediator of mTOR Complex 1 (mTORC1) signaling. Significant differences between groups were determined by two‐way ANOVA with Tukey’s multiple comparisons post‐hoc analysis.ResultsErectile function was significantly impaired in mice fed the WD in the vehicle condition, while Rap restored erectile function in the WD condition. P‐mTOR/mTOR and P‐p70S6K/p70S6K were increased in CC from WD‐Veh relative to CD‐Veh mice, while both of these measures were markedly suppressed by Rap treatment regardless of diet. Penile production of the ROS hydrogen peroxide and superoxide were elevated in vehicle treated WD‐fed mice, which was normalized in WD‐fed mice with Rap treatment. Similarly, Nox‐mediated penile ROS was elevated in vehicle treated WD‐fed mice, which was normalized in WD‐fed mice with Rap treatment. The Nox subunits Nox2, p47, and p22 were significantly elevated in CC from WD‐Veh mice, while Rap significantly blunted these expressions. The p67 and Nox4 subunits were not different amongst any groups.ConclusionsThe mTORC1/p70S6K axis appears to be an upstream mediator of Nox2 in the corpus cavernosum in response to chronic consumption of a high‐fat, high‐sucrose, Western pattern diet, which has a deleterious effect on erectile function.

Slash pine growth and nitrogen leaching potential following fertilization and pinestraw removal

AbstractCommercial pine plantations in the southern United States are commonly fertilized to enhance growth and to replenish nutrients following timber harvests or repetitive raking of pinestraw, an important secondary product. We examined the effects of pinestraw removal and fertilization on pine growth and N leaching potential in an 8‐yr‐old slash pine (Pinus elliottii Engelm.) plantation in North Florida. Raking treatments (raked or nonraked) were applied annually in February 2014–2017. Fertilization treatments (controlled‐release polymer‐coated urea at 0, 28, 56, 140, or urea at 56 kg N ha–1 yr–1) were applied annually in June 2014–2016. Pinestraw removal had no effect on stand growth. Fertilization did not enhance pine growth and increased mortality at the highest application rate. All fertilized treatments raised ammonium N (NH4–N) and nitrate–nitrite N (NOx–N) concentrations in soil solution at 30‐cm depth, indicating increased leaching potential. The period of elevated NH4–N concentrations occurred from 1 to 4 wk after fertilization, and the period of elevated NOx–N concentrations occurred from 1 to 13 or 26 wk following fertilization, with NOx–N concentration peaks (up to 98 mg L–1) at 4 or 8 wk. Soil solution NH4–N and NOx–N concentrations increased with increasing N application rate and with consecutive fertilizations. Polymer‐coated urea had no advantage over urea in terms of pine growth but resulted in slightly lower soil solution NOx–N concentrations in raked plots.

Uncovering associations between mental illness diagnosis, nitric oxide synthase gene variation, and peripheral nitric oxide concentration

Nitric oxide (NO) signalling has been implicated in the pathogenesis of several mental illnesses; however, its specific contribution remains unclear. We investigated whether peripheral NO concentration is associated with specific diagnoses, and whether there is a correlation with genetic variation in NO synthase (NOS) genes. We included 185 participants in the study; 52 healthy controls, 43 major depressive disorder (MDD) patients, 41 bipolar disorder (BPD) patients, and 49 schizophrenia (SCZ) patients. Clinical, genetic, and biochemical data were collected at admission to a psychiatric hospital and at discharge. Serum was used to quantify concentration of the stable NO metabolites nitrite and nitrate. Individuals were genotyped for the NOS1 exon 1f variable number of tandem repeats 1 (VNTR1) polymorphism, and single nucleotide polymorphisms (SNPs) in the NOS1, NOS1AP and NOS3 genes. At admission, SCZ patients were found to have significantly higher peripheral NO metabolite (NOx-) concentrations compared to healthy controls, MDD and BPD patients. NOS1 exon 1f VNTR1 short allele carriers were found to have significantly increased NOx- concentration. Moreover, this result was still significant in patients even at discharge. The data also revealed that patients who did not remit in their depressive symptoms had significantly increased NOx- concentration compared to remitters at discharge, supported by the finding of a significant positive correlation between depression symptom severity and NOx- concentration. Taken together, it is possible that elevated peripheral NOx- concentration is associated with increased severity of psychopathology, potentially due to NOS1 exon1f VNTR1 genotype. Our results further implicate NO signalling in mental illness pathogenesis, supporting its possible use as a peripheral biomarker, and imply that NOS genotype may play a significant role in regulating peripheral NOx- concentration.

Confronting Uncertainties of Simulated Air Pollution Concentrations during Persistent Cold Air Pool Events in the Salt Lake Valley, Utah.

Air pollutant accumulations during wintertime persistent cold air pool (PCAP) events in mountain valleys are of great concern for public health worldwide. Uncertainties associated with the simulated meteorology under stable conditions over complex terrain hinder realistic simulations of air quality using chemical transport models. We use the Community Multiscale Air Quality (CMAQ) model to simulate the gaseous and particulate species for 1 month in January 2011 during the Persistent Cold Air Pool Study (PCAPS) in the Salt Lake Valley (SLV), Utah (USA). Results indicate that the temporal variability associated with the elevated NOx and PM2.5 concentrations during PCAP events was captured by the model (r = 0.20 for NOx and r = 0.49 for PM2.5). However, concentrations were not at the correct magnitude (NMB = -35/12% for PM2.5 during PCAPs/non-PCAPs), where PM2.5 was underestimated during PCAP events and overestimated during non-PCAP periods. The underestimated PCAP strength is represented by valley heat deficit, which contributed to the underestimated PM2.5 concentrations compared with observations due to the model simulating more vertical mixing and less stable stratification than what was observed. Based on the observations, the dominant PM2.5 species were ammonium and nitrate. We provide a discussion that aims to investigate the emissions and chemistry model uncertainties using the nitrogen ratio method and the thermodynamic ammonium nitrate regime method.

A quantitative understanding of total OH reactivity and ozone production in a coastal industrial area during the Yokohama air quality study (AQUAS) campaign of summer 2019

Field measurements performed in the Keihin coastal industrial area during summer 2019 were used to characterize the air quality and ozone production potential. The total hydroxyl radical (OH) reactivity was found to be moderate, peaking with a 2-h average of 29.0 s−1, corresponding to an OH lifetime of ∼34 ms. The average hourly total OH reactivity was 11.4 ± 5.2 s−1 (average ± standard deviation), and the measured OH sinks (from over 90 trace species) accounted for 92.3% of the total OH reactivity. Compared with a previous series of campaigns in urban/suburban Japan, this field work investigated an area often overlooked for atmospheric observations and found the smallest missing OH reactivity (on average, 0.88 s−1). The near-zero missing OH reactivity indicated that photochemical procedures were less important to the Yokohama air quality study (AQUAS–Yokohama) than the ubiquitous substantial secondary products in other areas. This study also demonstrated that oceanic air masses may quickly flush coastal industrial areas and that a limited activity of photochemistry due to elevated NOx effectively terminates OH radical recycling. A comparison with other campaigns in Japan exhibited a positive correlation with oxidants (ozone and formaldehyde), indicating secondary products have a critical role in explaining missing OH reactivity. The ozone production potential was corresponding to a volatile organic compound (VOC)-limited regime, while the missing OH reactivity led to an ∼8% increase in ozone formation. Finally, a positive correlation was found between the ozone production rate and the reactivity ratio between VOCs and NOx, in both the current study and various other field campaigns in urban areas.

Production, characterization and utilization of second generation biodiesel blend in diesel engine using water and nanoparticles as additives

The rapid burning of fossil fuels and their noxious impact on the environment impelled researchers to explore the alternative fuels. In recent time, biodiesel gained much attention due to its potential ability to mitigate the harmful pollutants emitted from internal combustion (IC) engines. However, elevated NOx emission from biodiesel fueled engine remains a key challenge in the large scale adoption of biodiesel. To address these challenges, a study was aimed on the production of a second generation biodiesel, its characterization and application of biodiesel-diesel blend in diesel engine using water and CeO2 nanoparticles. A total of four test fuels viz. CeO2 nanoparticles doped water-B20 emulsion fuel (NWB20E), water-B20 emulsion fuel (WB20E), biodiesel-diesel blend (B20) and diesel were used in the present study. These test fuels were checked for physico-chemical properties as per ASTM Standards prior to engine application. Thereafter, these were used in a 10 kW diesel engine to assess its working characteristics under variable loading cycle. Adding CeO2 nanoparticles with WB20E improved in-cylinder peak pressure, while reduced peak pressure rise rate as compared to diesel. Water and surfactants used in WB20E caused faster fuel burning under premixed and controlled burning phases, which further improved with NWB20E, shortening the total fuel burning time as compared to diesel. The brake thermal efficiency of engine improved while brake specific energy consumption reduced for NWB20E over diesel. The fuel energy losses with exhaust gases and unaccounted energy were lesser for water emulsified fuels than diesel. The secondary atomization of water droplets and catalytic activity of nanoparticles in NWB20 caused 19.4–55.6%, 6.5–52.8% and 23.2–41.5% lesser HC, CO and NOx emissions, respectively, over diesel. In summary, biodiesel-diesel blend dispersed with water and CeO2 nanoparticles could be a promising alternative fuel for diesel engine with lower emissions.

Plasma electrolytic oxidation thermal barrier coating for reduced heat losses in IC engines

The work involved the development and on-engine testing of a new “thermo-swing” barrier coating for reduced wall heat transfer and increased thermal efficiency in future diesel engines utilizing aluminium alloy pistons. Such swing coatings, of low thermal conductivity and low specific heat capacity, have recently been proposed to produce a dynamic thermal barrier layer that rapidly changes the temperature of the upper surface of the piston crown in response to the adjacent in-cylinder gas temperature. The new coating tested in this work was formed directly from the piston substrate material using an optimised plasma electrolytic oxidation process, with a silica top coat subsequently applied to entrap air within coating pores. Benchtop laser flash measurements were undertaken to quantify coating thermal properties and provide the required empirical data for future thermal simulation. Coatings of varying features were tested in a bespoke thermodynamic single cylinder diesel engine instrumented for precision measurements of in-cylinder pressure, fuel consumption and legislated engine-out emissions. The optimum coating applied across the full piston crown and bowl enabled up to 3% improvement in indicated thermal efficiency under idealised part load operating conditions. The coating reduced heat transfer during combustion, leading to elevated engine-out NOx. By retarding combustion phasing slightly from the optimum, the NOx increase could be mitigated while still retaining most of the fuel consumption benefit, with the remaining benefit associated with reduced heat transfer during the remaining power stroke. The emissions of other key pollutants (CO, unburned hydrocarbons and soot) were less affected under the part load conditions tested.

Recent Isotopic Evidence for Elevated Vehicular NOx Emission to Atmospheric Nitrate Formation in Chinese Megacities

As the primary component of air pollution, nitrogen oxides (NOx = NO + NO2) are responsible for the formation of ozone and fine particle matter (PM2.5), which together pose a threat to the environm...

Downscaling system for modeling of atmospheric composition on regional, urban and street scales

Abstract. In this study, the downscaling modeling chain for prediction of weather and atmospheric composition is described and evaluated against observations. The chain consists of interfacing models for forecasting at different spatiotemporal scales that run in a semi-operational mode. The forecasts were performed for European (EU) regional and Danish (DK) subregional-urban scales by the offline coupled numerical weather prediction HIRLAM and atmospheric chemical transport CAMx models, and for Copenhagen city-street scale by the online coupled computational fluid dynamics M2UE model. The results showed elevated NOx and lowered O3 concentrations over major urban, industrial, and transport land and water routes in both the EU and DK domain forecasts. The O3 diurnal cycle predictions in both these domains were equally good, although O3 values were closer to observations for Denmark. At the same time, the DK forecast of NOx and NO2 levels was more biased (with a better prediction score of the diurnal cycle) than the EU forecast, indicating a necessity to adjust emission rates. Further downscaling to the street level (Copenhagen) indicated that the NOx pollution was 2-fold higher on weekends and more than 5 times higher during the working day with high pollution episodes. Despite high uncertainty in road traffic emissions, the street-scale model effectively captured the NOx and NO2 diurnal cycles and the onset of elevated pollution episodes. The demonstrated downscaling system could be used in future online integrated meteorology and air quality research and operational forecasting, as well as for impact assessments on environment, population, and decision making for emergency preparedness and safety measures planning.