Biofuel Combustion Research Articles

Wintertime black carbon assessment in dhaka, Bangladesh: Integrated health risk analysis.

This study investigated the ramifications of black carbon (BC) emissions on human health during the winter season of December 2019 to February 2020 in Dhaka, Bangladesh. BC, arising from incomplete combustion of fossil and biofuels, underwent meticulous measurement of densities, concentrations, and emissions at two pivotal sites. Employing low-volume air samplers with Quartz filters and subsequent analysis with an Aethalometer (Soot scanner, OT21, USA), the study unveiled monthly average BC densities of 1.64μgcm-2, concentrations of 4.99μgm-3, and emissions of 0.038μgJ-1. Health risk assessments revealed higher cancer risks (CRs) at Site-1 (children: 2.82×10-4 and adult: 4.72×10-4) compared to Site-2 (children: 2.56×10-4 and adult: 4.30×10-4). Hazard quotients (HQs) averaged 0.29 for children and 0.19 for adults in Dhaka. BC exposure escalated relative risks (RR) for all-cause mortality (RR=1.136), cardiovascular mortality (RR=1.169), and respiratory mortality (RR=1.277). These findings underscore the substantial implications of BC's influence, particularly in a nation like Bangladesh, and furnish invaluable insights into aerosol characteristics and emission sources in South Asia, facilitating the formulation of emission inventories.

Biofuels spray and combustion characteristics in a new micro gas turbine combustion chamber design with internal exhaust recycling

Biofuels spray and combustion characteristics in a new micro gas turbine combustion chamber design with internal exhaust recycling

Advancing the C[formula omitted] low-temperature oxidation chemistry through species measurements in a rapid compression machine, Part A: 1-Butene

Alkene chemistry plays a crucial role in the autoignition and oxidation of larger hydrocarbons. Unlike its other isomers, 1-butene is characterized by a two-stage ignition process. Various previous studies of 1-butene oxidation have used experimental techniques, including the measurement of ignition delay times in rapid compression machines (RCM) and in shock tubes, the determination of flame velocities, and the measurement of species concentrations in flames and in jet-stirred reactors (JSR). JSR studies provide an important insight into intermediate species formation at low temperatures but are constrained to low pressures and/or highly diluted conditions. To bridge the gap between JSR and engine-relevant conditions, this study presents species concentration measurements during the oxidation of 1-butene at 733 K and 30 bar under stoichiometric ’air-like’ conditions in an RCM, complemented by IDT measurements in the temperature range of 680–910 K. We designed an innovative 2-valve sampling setup to reduce quantitative uncertainties and the time required for species measurements. Our results indicate that existing 1-butene models fail to accurately predict the IDTs and the formation of the key oxidation intermediates. In response, potential optimizations for an improved kinetic model based on NUIGMech1.3 are discussed. Rate parameters for predominantly fuel consumption pathways, along with other reactions and thermochemical properties in the Waddington mechanism, have been altered within expected uncertainty limits to reflect the experimentally observed IDTs and species concentrations of this study and other validation data from the literature. However, the refined model does not predict the formation of 2-ethenyloxirane and ethene, indicating a gap in our understanding of the chemistry of these components. Overall, this study demonstrates the importance of measuring intermediates under the same conditions as IDTs to accurately address deficiencies in current kinetic mechanisms, and represents the first phase of a comprehensive investigation advancing the understanding of C4 oxidation chemistry.Novelty and significance statementThe novelty of this research lies in the design of an innovative sampling system for RCM species measurements, lowering the time for experimental execution and the uncertainties of the measurements. This enabled first-time species measurements during the oxidation of butene isomers in an RCM at high pressure and low level of dilution, contributing to the refinement of the 1-butene sub-mechanism within the NUIGMech1.3 framework. This research contributes to the understanding of the oxidation of alkenes, an important class of intermediates in gasoline and biofuel combustion. It emphasizes the need to measure intermediate species at the same conditions as ignition delay times, which are essential for understanding oxidation pathways under engine-relevant conditions. This research is part of a broader investigation of C4 oxidation chemistry, along with our companion work on n-butane. The resulting kinetic model is capable of reproducing most of the available n-butane and 1-butene validation targets.

Diagnosing the Process of Forming Biofuel Combustion Mixtures in Diesel Engines by a Program to Compute Spray Volume

A diesel engine's injection and combustion mixture formation process are essential; it determines the engine's economic, technical, and environmental criteria. When the engine uses biofuel, fuel parameters such as viscosity, density, and surface tension affect the above process. Each engine using a specific fuel type will have to adjust injection parameters such as injection pressure and timing to ensure the injection process and formation of a homogeneous air-fuel mixture. Therefore, through the spray structure, it is possible to diagnose the process of combustion mixture formation, thereby making adjustments to the fuel injection system that will improve engine performance and reduce emissions of toxic exhaust gases. In this study, the article presents the content of building a program to compute spray volume using Matlab software. Through the spray volume, quickly diagnose the process of forming the biofuel-air mixture in the diesel engine combustion chamber, thereby determining the appropriate fuel injection system adjustment. Results of simulation and experimental research on 4CHE Yanmar engines installed on fishing vessels with fuel types DO, B5, B10, and B15 show that the B15 fuel mixture when used for the engine needs to be increased injection pressure is about 10% higher than DO fuel injection pressure.

Determining the impact of different types of biofuels on the quality of iron ore pellets

The object of this study is the process of roasting iron ore pellets. The study solves the task of replacing fossil fuel with plant-based fuel in order to reduce environmental load and ensure the stable quality of pellets, which is necessary for use in blast furnaces. The influence of biofuel content at a given temperature and air speed on the strength of pellets after roasting was studied. As a result of the research, it was established that the fuel content has a decisive effect on the strength of pellets. Among all types of fuel that were investigated, pellets with the addition of sunflower husks and wood had the highest strength that meets the requirements for blast furnace melting of 200 kilograms. The use of wheat straw and charcoal does not make it possible to completely replace solid fuel in the layer of pellets. The results show that the use of up to 0.36 % of sunflower husk makes it possible to increase the strength of burned pellets compared to samples without biofuel content. Adding all other considered types of fuel reduced the strength of the pellets. These results are explained by the different content of lignin, cellulose, and hemicellulose, which determines the characteristics of the biomass. The high content of cellulose and hemicellulose allows for high hydrophilicity due to the high number of OH groups and positively affects the formation of raw pellets. Volatile substances released during the combustion of biofuel contribute to the formation of spherical pores, as well as their uniform distribution, which prevents the propagation of cracks under load. Research results make it possible to establish the optimal roasting mode, decrease harmful emissions, and bring down costs by reducing fossil fuel consumption

Torrefied and pyrolyzed pellets and their environmental impact in household heating

The transition from original feedstock to torrefied and pyrolyzed biofuels was investigated on a small-scale automatic pellet boiler. Thermal treatment significantly improves fuel quality; however, several technological difficulties were encountered. The entrainment of unburnt fuel particles led to severe CO, TOC and PM emissions as well as a drop in power output. All these issues were exacerbated when firing herbaceous biomass. It was found that most of the emitted particles are smaller than 1 μm in aerodynamic diameter, which necessitates additional flue gas filtering. Furthermore, 16 selected PAHs were individually monitored to evaluate the effect of thermal treatment on PAHs emissions and composition. On average, the most abundant PAH was naphthalene (4135 μg·kgfuel−1), followed by phenanthrene (246 μg·kgfuel−1), acenaphthylene (145 μg·kgfuel−1), fluoranthene (97 μg·kgfuel−1) and pyrene (95 μg·kgfuel−1). Benzo(a)pyrene contributed minimally to the total PAHs emissions (on average 16.6 μg·kgfuel−1). The 16 selected PAHs constitute only about 0.1–1.1 % of the total organic carbon emitted from solid biofuel combustion.

Local and regional enhancements of CH4, CO, and CO2 inferred from TCCON column measurements

Abstract. In this study, we demonstrate the utility of available correlative measurements of carbon species to identify regional and local air mass characteristics as well as their associated source types. In particular, we combine different regression techniques and enhancement ratio algorithms with carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4) total column abundance from 11 sites of the Total Carbon Column Observing Network (TCCON) to infer relative contributions of regional and local sources to each of these sites. The enhancement ratios provide a viable alternative to univariate measures of relationships between the trace gases that are insufficient in capturing source-type and transport signatures. Regional enhancements are estimated from the difference between bivariate regressions across a specific time window of observed total abundance of these species (BERr for bulk enhancement regression ratio) and inferred anomalies (AERr for anomaly enhancement regression ratio) associated with a site-specific background. Since BERr and AERr represent the bulk and local species enhancement ratio, respectively, its difference simply represents the site-specific regional component of these ratios. We can then compare these enhancements for CO2 and CH4 with CO to differentiate between combustion and non-combustion air masses. Our results show that while the regional and local influences in enhancements vary across sites, dominant characteristics are found to be consistent with previous studies over these sites and with bottom-up anthropogenic and fire emission inventories. The site in Pasadena shows a dominant local influence (> 60 %) across all species enhancement ratios, which appear to come from a mixture of biospheric and combustion activities. In contrast, Anmyeondo shows more regionally influenced (> 60 %) air masses associated with high-temperature and/or biofuel combustion activities. Ascension Island appears to only show a large regional influence (> 80 %) on CO / CO2 and CO / CH4, which is indicative of transported and combustion-related CO from the nearby African region, consistent with a sharp rise in column CO (3.51 ± 0.43 % ppb yr−1) at this site. These methods have important applications to source analysis using spaceborne column retrievals of these species.

Projecting Future Mercury Emissions From Global Biofuel Combustion Under the Carbon Neutrality Target

AbstractBiomass plays a crucial role in the low‐carbon energy transition, with a projected contribution of 18.7% to the global energy supply by 2050. However, biofuel combustion has been a notable source of toxic mercury emissions, yet the future trends and distribution of the emissions remain inadequately understood. Here, we projected biofuel combustion under various Shared Socioeconomic Pathways (SSPs) using the Global Change Assessment Model and assessed associated mercury emissions in cooking, heating, and power generation over 2020–2050, aligning with the carbon neutrality target. Our analysis reveals that global biofuel mercury emissions are projected to be 9.90–18.40 tons by 2050, compared to the annual emissions of 13.89 tons in 2020. Notably, a substantial increase in emissions from power generation is expected, escalating from 0.57 tons in 2020 to 4.69–8.27 tons by 2050, with China and Southeast Asia emerging as primary contributors. Conversely, mercury emissions from cooking and heating are expected to decrease from 13.32 tons in 2020 to 4.40–11.53 tons by 2050, except in Africa under SSP2, where the emissions may increase from 5.91 to 6.69 tons. Our findings provide a scientific basis for policies aimed at achieving carbon neutrality targets while adhering to the Minamata Convention on Mercury.

Statistical analysis of fuel combustion and emissions considering the adverse effects of investment economic environment: Exploring alternatives amid oil prices Swings, digital economy, and local market inflation

The depletion of natural gas reserves, combined with rising oil prices, local market inflation, and concerns about pollution, has accelerated the search for alternative energy sources. As a result, research on turbines and internal combustion engines for electricity generation is increasingly focusing on using vaporized ethanol as a fuel substitute. However, the high cost of analyzing the chemical composition of these fuels often leads to an oversight of their impact on combustion characteristics, such as flame behavior, emission profiles, and temperature distribution.This study employs a statistical approach to assess the combustion and emission characteristics of biofuels, aiming to find suitable alternatives to petroleum-based fuels. By integrating considerations of oil price fluctuations and the digital economy's impact, the research proposes a cost-effective method for evaluating the chemical makeup of vaporized fuels and their effects on post-combustion pollution.Experimental data reveal that alternative fuels can offer stable ignition performance and lower pollution levels, contingent on their specific properties. Fuels with high aromatic content and viscosity tend to produce significant CO emissions, while reducing these characteristics may increase CO2 production. The study also highlights the challenge of simultaneously reducing both CO and NOx emissions. Additionally, the findings show that petroleum gasoline, due to its lower volatility, has favorable fire safety properties and generates fewer pollutants.In the context of economic pressures from rising oil prices and inflation, this research underscores the importance of exploring biofuels as viable, sustainable alternatives for the future energy landscape.

Numerical Modelling of Phase Transformations of Water Droplets for Efficient Heat Recovery from Biofuel Flue Gas

The phase transformations of water droplets in the humid air flow for water injection into the flue gas in biofuel combustion technology under typical boundary conditions have been simulated. The numerical study was performed in two stages. The first one defines the influence of radiation on the thermal state of the water droplets and on the cycle of phase transformation modes. It is shown that the influence of radiation in a flue gas flow of 150℃→200℃ temperature on the thermal state of quantitatively injected water droplets is not significant, but it induces qualitative changes in the temperature field and influences phase transformations cycle of the droplets. In the second step, the cycling of the droplet phase transformation modes for water injection into the exhaust flue gas prior to a condensing economiser under typical boundary conditions was numerically investigated. It was justified that for efficient cooling and humidification of the flue gas before the condensing economiser it is necessary to inject water heated above the dew-point temperature by dispersing it into fine droplets.

Unveiling the electron-induced ionization cross sections and fragmentation mechanisms of 3,4-dihydro-2H-pyran.

The interactions of electrons with molecular systems under various conditions are essential to interdisciplinary research fields extending over the fundamental and applied sciences. In particular, investigating electron-induced ionization and dissociation of molecules may shed light on the radiation damage to living cells, the physicochemical processes in interstellar environments, and reaction mechanisms occurring in combustion or plasma. We have, therefore, studied electron-induced ionization and dissociation of the gas phase 3,4-dihydro-2H-pyran (DHP), a cyclic ether appearing to be a viable moiety for developing efficient clinical pharmacokinetics and revealing the mechanisms of biofuel combustion. The mass spectra in the m/z = 10-90 mass range were measured at several different energies of the ionizing electron beam using mass spectrometry. The mass spectra of DHP at the same energies were simulated using on-the-fly semi-classical molecular dynamics (MD) within the framework of the QCxMS formalism. The MD settings were suitably adjusted until a good agreement with the experimental mass spectra intensities was achieved, thus enabling a reliable assignment of cations and unraveling the plausible fragmentation channels. Based on the measurement of the absolute total ionization cross section of DHP (18.1 ± 0.9) × 10-16cm2 at 100eV energy, the absolute total and partial ionization cross sections of DHP were determined in the 5-140eV electron energy. Moreover, a machine learning algorithm that was trained with measured cross sections from 25 different molecules was used to predict the total ionization cross section for DHP. Comparison of the machine learning simulation with the measured data showed acceptable agreement, similar to that achieved in past predictions of the algorithm.

Green fuel mediated Europium doped Lanthanum ferrites Synthesis, characterisation of and their application as photocatalyst and antibacterial agents

The focus of multiapplication of the nanomaterial is the recent research. Based on that the current work describes synthesis of nano Lanthanum ferrites doped with Europium (1 mol, 3 mol, 5 mol and 7 mol%) by cost effective biofuel combustion method, using Ocimum tenuiflorum extract as fuel. The doping possibly changed the size and morphology of the host as evident from results of XRD, SEM and TEM analysis. As there is increase in band gap from 2.2 to 2.5 eV for undoped to 5 mol% doped Europium which strongly supports the photocatalytic degradation of Congo Red dye in the UV and visible light. The 5 mol% doped Eu shows 65 % and 81 % in UV-light and Visible light respectively. The electrochemical studies indicates the accepted capacitance and semiconductor nature of synthesised nano ferrites. The antibacterial activity was tested against Escherichia coli and Staphylococcus aureus showed 5 mol% Eu doped LFO was more effective than other synthesized LFO.

Analyzing the influence of feedstock selection in pyrolysis on aviation gas turbine engines: A study on performance, combustion efficiency, and emission profiles

Commercial aviation is primarily reliant on fossil fuels, yet the depletion of these sources and the consequences of climate change necessitates the exploration of sustainable alternatives. The pyrolysis process offers a viable method for producing biofuels from various feedstocks. This research examines the combustion, emission, and performance characteristics of biofuels derived from agricultural residues, waste tyres, and plastics using pyrolysis. Pyrolysis oils derived from forestry or agricultural products exhibit high viscosity and moisture content, which impairs combustion efficiency and increases carbon monoxide (CO) from 70 % to 187 % and unburned hydrocarbon (UHC) emissions. Conversely, pyrolysis oils from plastics and waste tyres provide stable combustion with carbon monoxide and total hydrocarbon emissions (THC) comparable to those of commercial jet fuel. However, nitrogen oxide (NOX) emissions are significantly elevated from 57 % to 157 %. Engine performance tests demonstrated that forestry pyrolysis oils result in thrust loss due to their high viscosity value (14.3–113 mm2/s) and low calorific value (17.3–31.7 MJ/kg). In contrast, plastic and tyre pyrolysis oil perform similarly to commercial jet fuels but may potentially cause performance loss due to their high aromatic content (>47.67 %). Overall, upgrading the viscosity, moisture, and aromatic content of pyrolysis oils can enhance their suitability as alternative aviation fuels. These improvements could assist the aviation sector in achieving its carbon-neutral goals by making pyrolysis oils competitive with conventional jet fuels.

Методологічні основи визначення і контролю витрат біопалив у процесі руху автомобіля

The paper proposes a methodological approach to determine and control fuel consumption (biofuels) of a car that has known design parameters and moves in known conditions at known modes. It is noted that at this stage it is more attractive to use mixed fuels based on gasoline or diesel fuel with the addition of various impurities of biological origin. For gasoline-based fuels, impurities can be methyl or ethyl alcohol, for diesel fuel – vegetable oils, as well as their methyl and ethyl esters of these oils. A structural and logical scheme has been developed, which explains the main provisions of the proposed determining method and controlling the biofuels consumption. In the structural and logical scheme, the following groups of parameters that take place during the car movement are highlighted: parameters of the conditions, the driving mode design. The mutual influence of parameters among themselves and between groups, the influence of the biological component concentration on its consumption, which must be taken into account to determine and control the consumption of biofuels during the movement of the car, was analyzed. It is shown that when switching to the use of biofuel, there is a change in the indicator coefficient of the internal combustion engine, which also affects the change in consumption.It has been proven that in the process of using biofuel, important factors affecting its consumption are density, lower heat of combustion, and the theoretically required amount of air for kg of biofuel combustion, which depends on the volumetric a specific biological component concentration in it. It has been proven that in the biofuel use process, important factors affecting its consumption are density, lower heat of combustion and the theoretically necessary amount of air for combustion in 1 kg of biofuel, which depends on the volumetric a specific biological component concentration. Taking into account the relative indicators of the «main» fuel (lower combustion heat, density and theoretically necessary air amount for the combustion of 1 kg impurities), it was established that the smallest increase in fuel consumption by the car engine during operation occurs when rapeseed oil is added to diesel fuel.

Real biofuel and fossil-fuel soot combustion activities in active and passive regeneration of diesel/gasoline particulate filters under different O2/NOx concentrations.

In this work, we aim to investigate and compare the combustion reactivities of real biofuel soot and fossil-fuel soot in the active and passive regeneration conditions of DPF and GPF through temperature-programmed oxidation (TPO). Higher reactivity of biofuel soot is achieved even under GPF conditions with extremely low oxygen concentration (~ 1%), which provides a great potential for low-temperature regeneration of GPF. Such a result is mainly attributed to the low graphitization and less surface C = C groups of biofuel soot. Unfortunately, the presence of high-content ashes (~ 47%) and P impurity in real biofuel soot hinder its combustion reactivity. TPO evidences that the O2/NOX-lacking conditions in GPF are key factors to impact the combustion of soot, especially fossil-fuel soot. This work provides some useful information for understanding real biofuel and fossil-fuel soot combustion in GPF and DPF regeneration and further improvement in filter regeneration process.

A comprehensive combustion, performance, and environmental analyses of algae biofuel, hydrogen gas, and nano-sized particles (liquid-gas-solid mix) in agricultural CRDI engines

The present research encompasses the utilization of TiO2 nano particles with enrichment of H2 (10 lpm) with Chlorella Emersonii Methyl Ester (CEME) on an agricultural-based CRDI engine. CEME20 (20% chlorella emersonii methyl ester blended with 80% mineral diesel) is employed for the tests. The nanoparticle concentration is limited to 50 ppm which has been considered according to O2 concentration in biodiesel. Experimentation revealed that, with hydrogen gas and TiO2 nanoparticles, the BTE and BSFC were improved significantly. At full load conditions, BTE is enlarged by 7.3%. In addition, there is a simultaneous decrease in HC and CO emissions (by about 36.3 and 40.9% respectively) for algal biofuel blends, while NOx emissions increased by 27.3% with respect to mineral diesel. 5.1% and 6.5% increase in combustion characteristics (79.8 bar combustion pressure and 89.2 J/°CA heat release rate)were observed for the CEME/H2/TiO2 blend which could be attributed to effective combustion of hydrogen and catalytic combustion activity provided by TiO2 nano additives. CEME/H2/TiO2blend recorded maximum Mass Fraction burnt (MFB) (74.7%) as well as lowered PSD (Particle size Diameter) profile (34.8 nm @ 0.29 E+08 dN/dlogDp (#/cm3)) at full engine load condition indicating the presence of H2 and nano additives which has influence over the combustion.

Influence of the type of fuel used on the content of gamma radionuclides in the soot from the smoke ducts of the home furnaces

Abstract This paper presents the results of the measurements of gamma radioactive isotopes in soot samples from 15 different chimneys of household furnaces fired with various types of solid fuel. Soot samples were collected by the chimney sweep during the mandatory periodic cleaning of the chimneys. The γ-spectrometry technique using the high-purity germanium (HPGe) detector was employed for radiometry of the above-mentioned soot. It was found that the determined activity of gamma isotopes in soot is at a level similar to that in fly ash from power plants around the world. Artificial 137Cs was detected only in the soot from the combustion of biofuel or mixed fuel. The results obtained were chemometrically analyzed to find the relationship between the fuel used and the gamma isotope content in the soot. The analysis of 137Cs, 40K, 228Th, and 226Ra is sufficient to differentiate between the soot obtained and tested, and it varied with the fuel type burned (fossil fuels/biofuels).

Direct radiative forcing of light-absorbing carbonaceous aerosols in China

China is an important emitter of light-absorbing carbonaceous aerosols (LACs), including black carbon (BC) and brown carbon (BrC). Currently, there are large uncertainties in model-estimated direct radiative forcing (DRF) of LACs, partially due to the poor understanding of the emissions and optical properties of LACs. In this study, we estimated the DRF of LACs over China during the implementation of the Air Pollution Prevention and Control Action Plan (APPCAP) using the global chemical transport model (GEOS-Chem) coupled with the Rapid Radiative Transfer Model of GCMs (RRTMG). We updated the refractive index of BC, includedbiomass burning (BB) sources, biofuel (BF) and coal combustion (CC) sources in the residential sector as BrC emission sources and the optical properties were updated, which were not fully considered in the previous model studies. Our results showed that model could reasonably capture the spatial and temporal variations of LACs in China with the correlation coefficients between model simulated and Aerosol Robotic Network (AERONET) observed daily absorption aerosol optical depth (AAOD) of LACs at 440 nm above 0.63 and the corresponding values of the normalized mean bias within ±30%. The simulated annual mean LACs AAOD at 440 nm in China was 0.016 (0.021) in 2017 (2014) and BrC contributed about 20% (21%). The estimated annual mean clear-sky LACs DRF at the top of the atmosphere in China was 1.02 W m−2 in 2017 and 1.38 W m−2 in 2014, and the contribution of BrC was about 10% and 11%, respectively, which was dominated by the BF sources (46% in 2017 and 44% in 2014) and the BB sources (38% in 2017 and 43% in 2014), with CC sources being low (16% in 2017 and 13% in 2014). The annual mean AAOD and DRF of LACs in China decreased by 0.005 and 0.36 W m−2 from 2014 to 2017, which were largely attributed to the reductions of anthropogenic emissions during the implementation of APPCAP. Our results would improve the understanding of the light absorption capacity and climate effects of LACs in China.

Unraveling the Ultrafast Photochemical Dynamics of Nitrobenzene in Aqueous Solution.

Nitroaromatic compounds are major constituents of the brown carbon aerosol particles in the troposphere that absorb near-ultraviolet (UV) and visible solar radiation and have a profound effect on the Earth's climate. The primary sources of brown carbon include biomass burning, forest fires, and residential burning of biofuels, and an important secondary source is photochemistry in aqueous cloud and fog droplets. Nitrobenzene is the smallest nitroaromatic molecule and a model for the photochemical behavior of larger nitroaromatic compounds. Despite the obvious importance of its droplet photochemistry to the atmospheric environment, there have not been any detailed studies of the ultrafast photochemical dynamics of nitrobenzene in aqueous solution. Here, we combine femtosecond transient absorption spectroscopy, time-resolved infrared spectroscopy, and quantum chemistry calculations to investigate the primary steps following the near-UV (λ ≥ 340 nm) photoexcitation of aqueous nitrobenzene. To understand the role of the surrounding water molecules in the photochemical dynamics of nitrobenzene, we compare the results of these investigations with analogous measurements in solutions of methanol, acetonitrile, and cyclohexane. We find that vibrational energy transfer to the aqueous environment quenches internal excitation, and therefore, unlike the gas phase, we do not observe any evidence for formation of photoproducts on timescales up to 500 ns. We also find that hydrogen bonding between nitrobenzene and surrounding water molecules slows the S1/S0 internal conversion process.

Impacts of emissions and meteorological conditions in three different phases of aerosol pollution during 2013–2022 in Anhui, China

The PM2.5 concentrations in Anhui, which links the Yangtze River Delta region, China's fastest growing economy area, with the Beijing-Tianjin-Hebei (BTH) region, China's most polluted region, are influenced not only by emissions, but also by variation of meteorological conditions. A comprehensive understanding of the relative impacts of meteorology and emissions on heavy pollution in Anhui at three phases (i.e., phase1: from 2013 to 2017; phase2: from 2018 to 2020; phase 3: from 2021 to 2022) from 2013 to 2022, which can provide suggestions for pollution prevention and control in the future. The decrease in pollutant concentrations from 2013 to 2022 is mainly attributed to the continued reduction in emissions, while the year-to-year fluctuations in pollutant concentrations are largely influenced by meteorological conditions. Although emissions are decreasing, the proportions of residential biofuel combustion and cement are increasing. In addition to the effects of prevailing northeasterly and northwesterly winds (i.e., Type1 and Type2), there is also concern about the influences of static weather and neighboring regional transport (i.e., Type5 and Type6), especially in 2016. The contribution of emissions is greater in phase 2 and phase 3, with a 17 % increase compared to phase 1. Overall, approximately 57 % of explosive growth in PM2.5 concentration during the cumulative stage (CS) can be regarded as the feedback effect of the deteriorating meteorological conditions. Therefore, statistical analyses show that limiting PM2.5 concentrations below about 73 μg m−3 would weaken the feedback effects, which in turn would avoid most of the explosive growth processes in the CS of the 60 heavy pollution processes, which can provide a reference for the government to set a target for sustained emission reduction.