Nitrogen Oxides Research Articles

Aspects of combustion in diesel engine at hydrogen use-a theoretical approach

The use of alternative fuel may be a viable solution in order to ameliorate the engine performance especially in terms of pollutant emissions. Among the alternative fuels that can be use to fuel internal combustion engines hydrogen can be a viable alternative fuel especially due to the advantage of reducing the carbon emission at its use as alternative fuel even for partial substitution of classic fuel. Hydrogen has good combustion properties like higher Lower Heating Value, large inflammability limits, higher combustion speed, which may has a benefic influence on combustion process. The use of hydrogen to diesel engine bring few important issues that must be solved in order to assure the normal engine operation, starting with the fuelling system and engine with the control of the combustion process. The paper presents some results obtained during the theoretical modeling of the in-cylinder process at a diesel engine fuelled with classic fuel and hydrogen. The diesel fuel is energetically substituted by hydrogen in percent’s of 25% and 30%. The influences of hydrogen use on in-cylinder maximum pressure, maximum pressure rise rate, heat release rate, combustion temperature, indicated thermal efficiency and nitrogen oxides and smoke emission levels are shown and analyzed.

The Impact of Lightning NOx Production on Ground‐Level Ozone in Tehran

AbstractLightning‐generated nitrogen oxides (LNOx) have an impact on the concentration of ground‐level ozone which acts as a toxic air pollutant, thereby negatively influencing human health and the environment. To understand the impact of LNOx on ground‐level ozone, we simulated four thunderstorm events in Tehran using the WRF‐Chem model. As observations of LNOx are not available, we evaluated the temporal distribution of the simulated ground‐level ozone concentration against an air quality monitoring station. We also compared the simulation results against the spatial distribution of the total column ozone from the Ozone Monitoring Instrument. WRF‐Chem performs well in the simulation of ground‐level ozone concentration, with the best performance for an event with the highest lightning activity (correlation coefficient of 0.91). The analysis of the spatial distribution of the observed and simulated total column ozone also indicates the good performance of WRF‐Chem. Hourly variation in the simulated LNOx during lightning activity is compared against both hourly variation in the observed ground‐level ozone and the number of lightning for four thunderstorm events. There is an agreement between the simulated LNOx and the observed ground‐level ozone during lightning for two events, with correlation coefficients of 0.55 and 0.57. LNOx emissions enhance ozone production in the middle to upper troposphere, which can subsequently contribute to an increase in ground‐level ozone by transport, vertical mixing, and chemistry. In addition, the initiation of chemical processes in response to cloud‐to‐ground lightning strikes may contribute to an increase in both LNOx and the concentration of ground‐level ozone.

Air pollutant emissions and sources in Lao People’s Democratic Republic: a provincial scale analysis for years 2013-2019

Recent rapid economic development in Lao People’s Democratic Republic (PDR) has increased national fuel consumption, vehicle fleet, industrial output, waste generation, and agricultural production. This has contributed to national average ambient fine particulate matter (PM2.5) air pollutant levels that are four times higher than World Health Organisation guidelines. Emission inventories are a key tool in understanding the major sources to these air pollution levels, and provide a starting point to identify where mitigation action can be targeted. A national air pollutant emission inventory has not been developed in Lao PDR and, combined with a limited air quality monitoring network means there is limited capacity to develop and track the effectiveness of mitigation actions. This study describes the first air pollutant emission inventory at the national and provincial scale for Lao PDR, covering 2013–2019. Emissions of nine air pollutants, and two greenhouse gases, were quantified using national statistics and international default emission factors. In 2019, national total PM2.5, Nitrogen Oxides (NOx), Black Carbon (BC), Sulphur Dioxide (SO2), Non-Methane Volatile Organic Carbons (NMVOCs), and Ammonia (NH3) were 125, 83, 9.7, 26, 219, and 99 thousand tonnes respectively. Key source sectors include forest fires, residential cooking, agriculture, electricity generation, and transport. However, the contribution of different sources varies across provinces. Forest fires are the primary source determining the spatial trend of particulate air pollution while residential and agricultural emissions contribute more significantly to rural provinces such as Savannakhet. Key sectors in major urban provinces (Vientiane Capital and Xayaboury) are industry, transport and electricity generation. These sectors are also significant sources of greenhouse gases (CO2 and CH4), demonstrating the potential for identification, evaluation and prioritisation of actions that simultaneously improve air quality and achieve Lao PDR’s international climate change commitments.

A portable instrument for measurement of atmospheric Ox and NO2 based on cavity ring-down spectroscopy

Atmospheric Ox (nitrogen dioxide (NO2) + ozone (O3)) can better reflect the local and regional change characteristics of oxidants compared to O3 alone, so obtaining Ox accurately and rapidly is the basis for evaluating the O3 production rate. Furthermore, Ox has proved to be a more representative indicator and can serve as a reflection of pollution prevention efficacy. A portable instrument for measuring atmospheric Ox and NO2 based on cavity ring-down spectroscopy (Ox/NO2-CRDS) was developed in this work. The NO2 concentration is accurately measured according to its absorption characteristic at 407.86 nm. Ambient O3 is converted into NO2 by chemical titration of high concentrations of nitrogen oxide (NO), and the O3 conversion efficiencies obtained are nearly 99%. The detection limit of the Ox/NO2-CRDS system for Ox is 0.024 ppbv (0.1 s), and the overall uncertainty of the instrument is ± 6%. Moreover, the Kalman filtering technique was applied to improve the measurement accuracy of Ox/NO2-CRDS. The system was applied in a comprehensive field observation campaign at Hefei Science Island from 26 to 30 September 2022, and the time concentration series and change characteristics of Ox and NO2 were obtained for five days. The measured Ox concentrations were compared with those of two commercial instruments, and the consistency was good (R2 = 0.98), indicating that this system can be deployed to accurately and rapidly obtain the concentrations of atmospheric Ox and NO2. It will be a useful tool for assessing the atmospheric oxidation capacity and controlling O3 pollution.摘要大气Ox (二氧化氮(NO2)+臭氧(O3))相比于O3能够更好的反应区域氧化剂的变化特征, Ox也是反应大气污染防治效果的一个关键指标. 本研究基于腔衰荡光谱技术研发了一套大气Ox和NO2同步测量系统 (Ox/NO2-CRDS). NO2浓度是利用其在407.86 nm处的特征吸收获取, 环境大气的O3通过高浓度的NO被转化为NO2进行间接测量, O3转化效率高于99%, Ox/NO2-CRDS的系统探测限为0.024 ppbv (0.1 s), 系统总不确定度为± 6%. 该Ox/NO2-CRDS系统成功应用于2022年9月26日–30日的合肥市科学岛综合外场观测中, 获取了连续5天的NO2和Ox的时间浓度序列和变化特征, 并将Ox的测量结果与商业化的设备进行了对比验证, 二者具有较好的一致性 (R2 = 0.98), 表明Ox/NO2-CRDS能够被应用于大气Ox和NO2的高灵敏探测. 未来该系统也将会变成评估大气氧化性以及控制臭氧污染的重要工具.

Air Quality and Health Impacts of Onshore Oil and Gas Flaring and Venting Activities Estimated Using Refined Satellite-Based Emissions.

Emissions from flaring and venting (FV) in oil and gas (O&G) production are difficult to quantify due to their intermittent activities and lack of adequate monitoring and reporting. Given their potentially significant contribution to total emissions from the O&G sector in the United States, we estimate emissions from FV using Visible Infrared Imaging Radiometer Suite satellite observations and state/local reported data on flared gas volume. These refined estimates are higher than those reported in the National Emission Inventory: by up to 15 times for fine particulate matter (PM2.5), two times for sulfur dioxides, and 22% higher for nitrogen oxides (NOx). Annual average contributions of FV to ozone (O3), NO2, and PM2.5 in the conterminous U.S. (CONUS) are less than 0.15%, but significant contributions of up to 60% are found in O&G fields with FV. FV contributions are higher in winter than in summer months for O3 and PM2.5; an inverse behavior is found for NO2. Nitrate aerosol contributions to PM2.5 are highest in the Denver basin whereas in the Permian and Bakken basins, sulfate and elemental carbon aerosols are the major contributors. Over four simulated months in 2016 for the entire CONUS, FV contributes 210 additional instances of exceedances to the daily maximum 8-hr average O3 and has negligible contributions to exceedance of NO2 and PM2.5, given the current form of the national ambient air quality standards. FV emissions are found to cause over $7.4 billion in health damages, 710 premature deaths, and 73,000 asthma exacerbations among children annually.

Forty-nine metagenomic-assembled genomes from an aquatic virome expand Caudoviricetes by 45 potential new families and the newly uncovered Gossevirus of Bamfordvirae.

Twenty complete genomes (29-63 kb) and 29 genomes with an estimated completeness of over 90 % (30-90 kb) were identified for novel dsDNA viruses in the Yangshan Harbor metavirome. These newly discovered viruses contribute to the expansion of viral taxonomy by introducing 46 potential new families. Except for one virus, all others belong to the class Caudoviricetes. The exception is a novel member of the recently characterized viral group known as Gossevirus. Fifteen viruses were predicted to be temperate. The predicted hosts for the viruses appear to be involved in various aspects of the nitrogen cycle, including nitrogen fixation, oxidation and denitrification. Two viruses were identified to have a host of Flavobacterium and Tepidimonas fonticaldi, respectively, by matching CRISPR spacers with viral protospacers. Our findings provide an overview for characterizing and identifying specific viruses from Yangshan Harbor. The Gossevirus-like virus uncovered emphasizes the need for further comprehensive isolation and investigation of polinton-like viruses.

Studies on Biodiesel and Hydrogen Powered Dual Fuel Common Rail Direct Injection Engine

Objectives: To evaluate the effect of hydrogen and used temple oil biodiesel (BTO) combination on the performance of Common Rail Direct Injection (CRDi) engine. To report the maximum possible flow rate (HFR) for knock free operation of the engine at a speed of 1500 RPM. Methods: Transesterification process was used to get BTO. was inducted through intake manifold. BTO was injected into engine cylinder using electronically controlled technique. Findings: The study revealed that the peak HFR was for BTO and 0.24 for diesel at an Injection Pressure (IP) of 800 bar and Injection Timing (IT) of before top dead center (bTDC). The Dual Fuel (DF) CRDi engine with Toriodal Reentrant Combustion Chamber (TRCC) shape yielded 6% to lower Brake Thermal Efficiency (BTE) with reduced exhaust gas emissions except 19 to higher oxides of nitrogen (NOx) at and 100% loads. Both Peak Combustion Pressure (PP) and Heat Release Rate (HRR) were 5 to 9% higher than BTO run diesel engine operation. Combustion Duration (CD) and Ignition Delay (ID) were 6 to 15% lower in DF CRDi operation with . Novelty: Diesel engine comes with hemispherical combustion chamber (HCC). Toriodal Reentrant Shaped Combustion Chamber (TRCC) was adopted in place of HCC which results better mixing of air and fuel. and BTO combination was used to power CRDi engine. Electronically controlled fuel injection system developed and fitted to conventional diesel engine. Keywords: Used temple oil biodiesel (BTO); Common rail direct injection (CRDi) engine; Toriodal reentrant combustion chamber (TRCC); Hydrogen flow rate (HFR); Hydrogen-biodiesel energy ratio (H2BER)

Bambusa tulda: A potential feedstock for bioethanol and its blending effects on the performance of spark ignition engine

Alternatives to conventional fuel sources must be investigated due to strict regulatory requirements and the depletion of fossil fuel supplies. As a result, of better transportation and population growth, the requirement for energy is increasing daily. Bioethanol may be used successfully to replace both gasoline and spark ignition engine diesel. Most nations blend 10% bioethanol with gasoline in automobiles. Several nations, notably India, have announced that they will soon begin blending 20% bioethanol with gasoline. Bambusa Tulda is used as a raw material for the extraction of bioethanol, which is a type of Indian bamboo. This study covers both the ethanol extraction from bamboo and the effects of various mixtures on spark-ignited engine performance. Four separate blends were developed on a volumetric basis at varying engine speeds, and the wide-open throttle was utilized to evaluate the performance and emissions of each mix with a constant compression ratio of 10:1. When bioethanol was enhanced, combustion efficiency, indicated power, engine power, mechanical efficiency, and volumetric efficiency all increased. Hydrocarbon, carbon monoxide, and carbon dioxide emissions decreased, while nitrogen oxide emissions increased. The engine performance of BE 15 was found to be the greatest among all the gasoline blends tested. According to this study, when nitrogen oxide emission control methods are applied, bamboo may be used as a feedstock for the manufacture of second-generation bioethanol. This invention offers a bioethanol production process that is good for environmental sustainability.

Descriptor‐Based Volcano Relations Predict Single Atoms for Hydroxylamine Electrosynthesis

AbstractHydroxylamine (NH2OH) is an important feedstock in fuels, pharmaceuticals, and agrochemicals. Nanostructured electrocatalysts drive green electrosynthesis of hydroxylamine from nitrogen oxide species in water. However, current electrocatalysts still suffer from low selectivity and manpower‐consuming trial‐and‐error modes, leaving unclear selectivity/activity origins and a lack of catalyst design principles. Herein, we theoretically analyze key determinants of selectivity/activity and propose the adsorption energy of NHO (Gad(*NHO)) as a performance descriptor. A weak *NH2OH binding affinity and a favorable reaction pathway (*NHO pathway) jointly enable single‐atom catalysts (SACs) with superior NH2OH selectivity. Then, an activity volcano plot of Gad(*NHO) is established to predict a series of SACs and discover Mn SACs as optimal electrocatalysts that exhibit pH‐dependent activity. These theoretical prediction results are also confirmed by experimental results, rationalizing our Gad(*NHO) descriptor. Furthermore, Mn−Co geminal‐atom catalysts (GACs) are predicted to optimize Gad(*NHO) and are experimentally proved to enhance NH2OH formation.

Descriptor-Based Volcano Relations Predict Single Atoms for Hydroxylamine Electrosynthesis.

Hydroxylamine (NH2OH) is an important feedstock in fuels, pharmaceuticals, and agrochemicals. Nanostructured electrocatalysts drive green electrosynthesis of hydroxylamine from nitrogen oxide species in water. However, current electrocatalysts still suffer from low selectivity and manpower-consuming trial-and-error modes, leaving unclear selectivity/activity origins and a lack of catalyst design principles. Herein, we theoretically analyze key determinants of selectivity/activity and propose the adsorption energy of NHO (Gad(*NHO)) as a performance descriptor. A weak *NH2OH binding affinity and a favorable reaction pathway (*NHO pathway) jointly enable single-atom catalysts (SACs) with superior NH2OH selectivity. Then, an activity volcano plot of Gad(*NHO) is established to predict a series of SACs and discover Mn SACs as optimal electrocatalysts that exhibit pH-dependent activity. These theoretical prediction results are also confirmed by experimental results, rationalizing our Gad(*NHO) descriptor. Furthermore, Mn-Co geminal-atom catalysts (GACs) are predicted to optimize Gad(*NHO) and are experimentally proved to enhance NH2OH formation.

Low blank sampling method for measurement of the nitrogen isotopic composition of atmospheric NOx.

The nitrogen isotopic composition of nitrogen oxide (NOx) is useful for estimating its sources and sinks. Several methods have been developed to convert atmospheric nitric oxide (NO) and/or nitrogen dioxide (NO2) to nitrites and/or nitrates for collection. However, the collection efficiency and blanks are poorly evaluated for many collection methods. Here, we present a method for collecting ambient NOx (NO and NO2 simultaneously) with over 90% efficiency collection of NOx and low blank (approximately 0.5 μM) using a 3 wt% hydrogen peroxide (H2O2) and 0.5 M sodium hydride (NaOH) solution. The 1σ uncertainty of the nitrogen isotopic composition was ± 1.2 ‰. The advantages of this method include its portability, simplicity, and the ability to collect the required amount of sample to analyze the nitrogen isotopic composition of ambient NOx in a short period of time. Using this method, we observed the nitrogen isotopic compositions of NOx at the Tsukuba and Yoyogi sites in Japan. The averaged δ15N(NOx) value and standard deviation (1σ) in the Yoyogi site was (-2.7 ± 1.8) ‰ and in the Tsukuba site was (-1.7 ± 0.9) ‰ during the sampling period. The main NOx source appears to be the vehicle exhaust in the two sites.

Pyrolysis-derived waste polypropylene oils in gas turbine engines: a comprehensive performance and emission study

Addressing the burgeoning issue of polymer waste management and disposal, chemical recycling, specifically the production of highquality oil, presents an enticing solution. This research paper delves into the process of plastic waste pyrolysis, focusing on polypropylene, and thoroughly examines the physico-chemical properties of the resulting pyrolytic oil. The oils, obtained from waste plastic pyrolysis (referred to as WPPO), are then blended with kerosene and utilized as fuel for a gas turbine engine. The primary objective of this investigation is to ascertain how the blend composition influences the performance and emission parameters of the micro gas turbine. In our findings, it was observed that all tested waste plastic pyrolysis blends displayed a trend towards escalating regulated emissions such as nitrogen oxides (NOx) with an average increase of 26% for polypropylene pyrolysis oil (PPO). The emission index (EI) for carbon monoxide (CO) was found to be relatively consistent across all fuel blends tested in this study. Interestingly, when considering the thrust specific fuel consumption (TSFC) within the EI calculation, blends of aviation kerosene and plastic oil showed lower values in comparison to the pure Jet A-1 fuel. Furthermore, an augmentation in the proportion of WPPO in the blends consequently led to an elevation in the exhaust gas temperature (an average increase of 8.7% for PPO). Interestingly, the fuel efficiency of the Jet engine, expressed as TSFC, demonstrated a decrease, with an average reduction of 13.8% observed for PPO.

Experimental Study of a Homogeneous Charge Compression Ignition Engine Using Hydrogen at High-Altitude Conditions

One of the key factors of the current energy transition is the use of hydrogen (H2) as fuel in energy transformation technologies. This fuel has the advantage of being produced from the most primary forms of energy and has the potential to reduce carbon dioxide (CO2) emissions. In recent years, hydrogen or hydrogen-rich mixtures in internal combustion engines (ICEs) have gained popularity, with numerous reports documenting their use in spark ignition (SI) and compression ignition (CI) engines. Homogeneous charge compression ignition (HCCI) engines have the potential for substantial reductions in nitrogen oxides (NOx) and particulate matter (PM) emissions, and the use of hydrogen along with this kind of combustion could substantially reduce CO2 emissions. However, there have been few reports using hydrogen in HCCI engines, with most studies limited to evaluating technical feasibility, combustion characteristics, engine performance, and emissions in laboratory settings at sea level. This paper presents a study of HCCI combustion using hydrogen in a stationary air-cooled Lombardini 25 LD 425-2 modified diesel engine located at 1495 m above sea level. An experimental phase was conducted to determine the intake temperature requirements and equivalence ratios for stable HCCI combustion. These results were compared with previous research carried out at sea level. To the best knowledge of the authors, this is the first report on the combustion and operational limits for an HCCI engine fueled with hydrogen under the mentioned specific conditions. Equivalence ratios between 0.21 and 0.28 and intake temperatures between 188 °C and 235 °C effectively achieved the HCCI combustion. These temperature values were, on average, 100 °C higher than those reported in previous studies. The maximum value for the indicated mean effective pressure (IMEPn) was 1.75 bar, and the maximum thermal efficiency (ITEn) was 34.5%. The achieved results are important for the design and implementation of HCCI engines running solely on hydrogen in developing countries located at high altitudes above sea level.

Low Temperature Combustion Modeling and Predictive Control of Marine Engines

The increase of popularity of reactivity-controlled compression ignition (RCCI) is attributed to its capability of achieving ultra-low nitrogen oxides (NOx) and soot emissions with high brake thermal efficiency (BTE). The complex and nonlinear nature of the RCCI combustion makes it challenging for model-based control design. In this work, a model-based control system is developed to control the combustion phasing and the indicated mean effective pressure (IMEP) of RCCI combustion through the adjustments of total fuel energy and blend ratio (BR) in fuel injection. A physics-based nonlinear control-oriented model (COM) is developed to predict the main combustion performance indicators of an RCCI marine engine. The model is validated against a detailed thermo-kinetic multizone model. A novel linear parameter-varying (LPV) model coupled with a model predictive controller (MPC) is utilized to control the aforementioned parameters of the developed COM. The developed system is able to control combustion phasing and IMEP with a tracking error that is within a 5% error margin for nominal and transient engine operating conditions. The developed control system promotes the adoption of RCCI combustion in commercial marine engines.

Numerical analysis of flow and combustion of Coal-Ammonia blend in coal-fired furnace

Co-firing ammonia (NH3) in coal-fired power plants presents an attractive method to expedite the global decarbonization process. Nevertheless, the challenge lies in reconciling the need for higher temperatures within the furnace with the imperative of maintaining low nitrogen oxides (NOx) emissions, which limits the widespread use of NH3 as a fuel. In this article, the flow and combustion of coal-NH3 blends in a 3 × 700 MW tangentially-fired utility coal boiler furnace are investigated using Computational Fluid Dynamics (CFD). The impact of NH3 blending ratios is examined through numerically simulated combustion involving five co-firing ratios (CRs) of NH3, including 0%, 10%, 20%, 30%, and 50%. Various combustion properties are assessed, including the furnace’s temperature profile, flow distribution, species emissions, pollutant formation, and heat generation. To validate the approach, single coal and coal blend simulations performed depicted reasonable agreement in predicting furnace flame temperatures. The predicted flue gas temperature exhibited a decrease with an increase in NH3 CR, leading to a reduction in the furnace’s heat generation. Regarding flow characteristics, there was a notable increase in velocity as the concentration of NH3 was raised. The elevated NH3 content correlated with an observed rise in oxygen (O2) residue in the rear pass, coupled with a decrease in both carbon dioxide (CO2) and carbon monoxide (CO) concentrations. Pollutant formation, assessed in terms of nitrogen oxide (NO) emissions, revealed an increase in concentration with the rise in NH3 CR. Indeed, these findings suggest a promising strategy for adopting NH3 as a viable alternative to coal, representing an effective carbon-neutral fuel for the future.

Early-Life Exposure to Air Pollution and Childhood Asthma Cumulative Incidence in the ECHO CREW Consortium

Exposure to outdoor air pollution contributes to childhood asthma development, but many studies lack the geographic, racial and ethnic, and socioeconomic diversity to evaluate susceptibility by individual-level and community-level contextual factors. To examine early life exposure to fine particulate matter (PM2.5) and nitrogen oxide (NO2) air pollution and asthma risk by early and middle childhood, and whether individual and community-level characteristics modify associations between air pollution exposure and asthma. This cohort study included children enrolled in cohorts participating in the Children's Respiratory and Environmental Workgroup consortium. The birth cohorts were located throughout the US, recruited between 1987 and 2007, and followed up through age 11 years. The survival analysis was adjusted for mother's education, parental asthma, smoking during pregnancy, child's race and ethnicity, sex, neighborhood characteristics, and cohort. Statistical analysis was performed from February 2022 to December 2023. Early-life exposures to PM2.5 and NO2 according to participants' birth address. Caregiver report of physician-diagnosed asthma through early (age 4 years) and middle (age 11 years) childhood. Among 5279 children included, 1659 (31.4%) were Black, 835 (15.8%) were Hispanic, 2555 (48.4%) where White, and 229 (4.3%) were other race or ethnicity; 2721 (51.5%) were male and 2596 (49.2%) were female; 1305 children (24.7%) had asthma by 11 years of age and 954 (18.1%) had asthma by 4 years of age. Mean values of pollutants over the first 3 years of life were associated with asthma incidence. A 1 IQR increase in NO2 (6.1 μg/m3) was associated with increased asthma incidence among children younger than 5 years (HR, 1.25 [95% CI, 1.03-1.52]) and children younger than 11 years (HR, 1.22 [95% CI, 1.04-1.44]). A 1 IQR increase in PM2.5 (3.4 μg/m3) was associated with increased asthma incidence among children younger than 5 years (HR, 1.31 [95% CI, 1.04-1.66]) and children younger than 11 years (OR, 1.23 [95% CI, 1.01-1.50]). Associations of PM2.5 or NO2 with asthma were increased when mothers had less than a high school diploma, among Black children, in communities with fewer child opportunities, and in census tracts with higher percentage Black population and population density; for example, there was a significantly higher association between PM2.5 and asthma incidence by younger than 5 years of age in Black children (HR, 1.60 [95% CI, 1.15-2.22]) compared with White children (HR, 1.17 [95% CI, 0.90-1.52]). In this cohort study, early life air pollution was associated with increased asthma incidence by early and middle childhood, with higher risk among minoritized families living in urban communities characterized by fewer opportunities and resources and multiple environmental coexposures. Reducing asthma risk in the US requires air pollution regulation and reduction combined with greater environmental, educational, and health equity at the community level.

Anterograde trans-neuronal labeling of striatal interneurons in relation to dopamine neurons in the substantia nigra pars compacta.

Recent advances in neural tracing have unveiled numerous neural circuits characterized by brain region and cell type specificity, illuminating the underpinnings of specific functions and behaviors. Dopaminergic (DA) neurons in the midbrain are highly heterogeneous in terms of gene and protein expression and axonal projections. Different cell types within the substantia nigra pars compacta (SNc) tend to project to the striatum in a cell-type-dependent manner characterized by specific topography. Given the wide and dense distribution of DA axons, coupled with a combination of synaptic and volume transmission, it remains unclear how DA release is spatially and temporally regulated, to appropriately achieve specific behaviors and functions. Our hypothesis posits that hidden rules governing synapse formation between pre-synaptic DA neuron types and striatal neuron types may modulate the effect of DA at a single-cell level. To address this conjecture, we employed adeno-associated virus serotype 1 (AAV1) to visualize the neural circuitry of DA neurons. AAV1 has emerged as a potent anatomical instrument capable of labeling and visualizing pre- and post-synaptic neurons simultaneously through anterograde trans-synaptic labeling. First, AAV1-Cre was injected into the SNc, resulting in Cre expression in both medium spiny neurons and interneurons in the striatum. Due to the potential occurrence of the retrograde transfer of AAV1, only striatal interneurons were considered for trans-synaptic or trans-neuronal labeling. Interneuron types expressing parvalbumin, choline acetyltransferase, somatostatin, or nitrogen oxide synthase exhibited Cre expression. Using a combination of AAV1-Cre and Cre-driven fluorophore expressing AAVs, striatal interneurons and the axons originating from the SNc were visualized in distinct colors. Using immunofluorescence against neurotransmitter transporters, almost all axons in the striatum visualized using this approach were confirmed to be dopaminergic. Moreover, individual DA axons established multiple appositions on the somata and proximal dendrites of interneurons. This finding suggests that irrespective of the extensive and widespread axonal arborization of DA neurons, a particular DA neuron may exert a significant influence on specific interneurons. Thus, AAV1-based labeling of the DA system can be a valuable tool to uncover the concealed rules governing these intricate relationships.

Explainable ensemble machine learning revealing the effect of meteorology and sources on ozone formation in megacity Hangzhou, China

Megacity Hangzhou, located in eastern China, has experienced severe O3 pollution in recent years, thereby clarifying the key drivers of the formation is essential to suppress O3 deterioration. In this study, the ensemble machine learning model (EML) coupled with Shapley additive explanations (SHAP), and positive matrix factorization were used to explore the impact of various factors (including meteorology, chemical components, sources) on O3 formation during the whole period, pollution days, and typical persistent pollution events from April to October in 2021–2022. The EML model achieved better performance than the single model, with R2 values of 0.91. SHAP analysis revealed that meteorological conditions had the greatest effects on O3 variability with the contribution of 57 %–60 % for different pollution levels, and the main drivers were relative humidity and radiation. The effects of chemical factors on O3 formation presented a positive response to volatile organic compounds (VOCs) and fine particulate matter (PM2.5), and a negative response to nitrogen oxides (NOx). Oxygenated compounds (OVOCs), alkenes, and aromatic of VOCs subgroups had higher contribution; additionally, the effects of PM2.5 and NOx were also important and increased with the O3 deterioration. The impact of seven emission sources on O3 formation in Hangzhou indicated that vehicle exhaust (35 %), biomass combustion (16 %), and biogenic emissions (12 %) were the dominant drivers. However, for the O3 pollution days, the effects of biomass combustion and biogenic emissions increased. Especially in persistent pollution events with highest O3 concentrations, the magnitude of biogenic emission effect elevated significantly by 156 % compared to the whole situations. Our finding revealed that the combination of the EML model and SHAP analysis could provide a reliable method for rapid diagnosis of the cause of O3 pollution at different event scales, supporting the formulation of control measures.

Dispersion Model of NOx Emissions from a Liquefied Natural Gas Facility

Natural gas used widely in terms of energy production. Energy production is among the most prominent sectors of humankind. Combustion processes inevitably produces air pollutants. The major pollutant during a combustion process is nitrogen oxide emissions. The term of nitrogen oxides primarily include nitrogen monoxide and nitrogen dioxide. These pollutants are generated regardless of the fuel content since air composition itself is the major source for these pollutants. It is possible to calculate emissions through the activity data and emission factors. Calculation of emissions is not enough for an environmental assessment. The impact of pollutants on human health relies on their concentration in the atmosphere. In order to determine their concentrations several modelling practices are developed. In this study, AERMOD used for modelling purpose of NOx emissions from a liquefied natural gas facility. It was observed that the pollutants were dispersed mostly towards south-southwest of the facility, where Marmaraereğlisi district is located. Although the pollutants transported directly to the settlement, the concentrations remained limited. During operation conditions, the highest daily NOx concentration was 1.7 μg/m3 and the highest annual concentration was 0.1 μg/m3. At maximum operating conditions, the highest daily NOx concentration was 16.2 μg/m3 and the highest annual concentration was 2.5 μg/m3. At minimum operating conditions, the highest daily NOx concentration was 1.1 μg/m3 and the highest annual concentration was 0.2 μg/m3.

High-resolution dispersion modelling of PM2.5, PM10, NOx and NO2 exposure in metropolitan areas in Sweden 2000‒2018 – large health gains due to decreased population exposure

AbstractAmbient air pollution remains the major environmental cause of disease. Accurate assessment of population exposure and small-scale spatial exposure variations over long time periods is essential for epidemiological studies. We estimated annual exposure to fine and coarse particulate matter (PM2.5, PM10), and nitrogen oxides (NOx, NO2) with high spatial resolution to examine time trends 2000‒2018, compliance with the WHO Air Quality Guidelines, and assess the health impact. The modelling area covered six metropolitan areas in Sweden with a combined population of 5.5 million. Long-range transported air pollutants were modelled using a chemical transport model with bias correction, and locally emitted air pollutants using source-specific Gaussian-type dispersion models at resolutions up to 50 × 50 m. The modelled concentrations were validated using quality-controlled monitoring data. Lastly, we estimated the reduction in mortality associated with the decrease in population exposure. The validity of modelled air pollutant concentrations was good (R2 for PM2.5 0.84, PM10 0.61, and NOx 0.87). Air pollution exposure decreased substantially, from a population weighted mean exposure to PM2.5 of 12.2 µg m−3 in 2000 to 5.4 µg m−3 in 2018. We estimated that the decreased exposure was associated with a reduction of 2719 (95% CI 2046–3055) premature deaths annually. However, in 2018, 65%, 8%, and 42% of residents in the modelled areas were still exposed to PM2.5, PM10, or NO2 levels, respectively, that exceeded the current WHO Air Quality Guidelines for annual average exposure. This emphasises the potential public health benefits of reductions in air pollution emissions.