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This study investigated the possibility of extending the soot morphology analyses to acoustically agglomerated soot deposited on the surface of smoke alarms and of applying the validity of soot analysis for unique chemical signatures in the field of fire investigations. Through collecting soot samples, including agglomerated soot acquired from smoke alarms, this research presents a pioneering stride in soot morphology data analyses conducted by leveraging advanced deep learning methodologies. Preliminary outcomes underline that the proposed convolutional neural network model has the potential to decode intricate soot characteristics and to distinguish soot particle images between diverse fuel types and burning conditions. In particular, for the acoustically agglomerated soot collected by smoke alarms, it was also found possible to decode their intricate morphology by applying the proposed data-driven approach. [ABSTRACT FROM AUTHOR]

This study investigates the thermal–hydraulic behavior and deposition characteristics of a shell and tube exhaust heat exchanger using a CFD-based predictive model of soot deposition. Firstly, considering the influences of thermophoretic, wall shear stress, and other deposition and removal mechanisms, a predictive model is developed for long-term performance of heat exchangers under soot deposition. Then, the variations in exhaust heat exchanger performance during a 4 h deposition period are simulated based on the model. Subsequently, the variation of deposition distribution and different deposition velocities are also evaluated. Finally, an analysis of the long-term performance of the exhaust heat exchanger under varying gas velocities and temperature gradients is conducted, revealing the performance variations under all engine-operating conditions. Results show that the deterioration in normalized relative j / f 1 / 2 varies from 5.26% to 24.91% under different work conditions, and the exhaust heat exchanger with high gas velocity and low temperature gradient exhibits optimal long-term performance. [ABSTRACT FROM AUTHOR]

Surface sampling and laboratory analysis for soot/combustion particulates was conducted following a fire at an education/research facility in the southwest United States. This provided a bank of data by which to probabilistically evaluate the behavior of soot loading (counts/mm2) and relative soot concentration (percent ratio; %R) as useful metrics for quantifying differences in soot impact across a building. Surface tape sampling and analysis via light microscopy were conducted via industry standard protocols, and resulting data from various building zones were selected to construct various comparisons. The performance of counts/mm2 and %R as metrics to identify differences in soot impact for each comparison was assessed by comparing inference generated by traditional Student's t test, Mann Whitney U rank comparison (MW), and the directly calculated axiomatic probability associated with difference in detection (pΔfd). The fourteen (14) comparisons in which a significant difference was inferred via pΔfd was similarly indicated via Student's t and/or MW in only four (4) instances. Further, approximately one half of the comparisons generated different inference via pΔfd for counts/mm2 and %R, with the former demonstrating better discriminatory ability. In broad view, the heuristic concept of comparing numerical "soot levels" (e.g., average) by either metric was not generally suitable for the distribution of the data. In contrast, pΔfd avoids the statistical bias imposed by traditional statistical inference, and ultimately the efficacy of post fire comparative surface sampling is as dependent upon the metric and inference model utilized as it is on the sampling and laboratory analytical protocols. [ABSTRACT FROM AUTHOR]

In this study, Raman spectroscopy has been used to evaluate the evolution of the structural modification of soot during oxidation processes at various preset temperatures up to 700 °C. Two types of well-characterized mini-CAST soot, representing black soot and brown soot, were examined. The major difference between the signals from the two types of soot was the higher photoluminescence (PL) signal for brown soot compared with black soot, in addition to some variations in the first-order Raman signatures such as oxygenated groups and their evolutions during thermal oxidation treatment. An interesting observation was the increase in the PL signal for brown soot at increasing temperatures up to 150 °C probably due to the formation of small oxidized polycyclic aromatic hydrocarbon and defects, followed by a decrease in the PL signal until the soot was fully oxidized. We also demonstrated that brown soot is prone to oxidation in ex situ measurements, a factor that should be considered in the Raman analysis of soot. [ABSTRACT FROM AUTHOR]

Measuring soot concentration in a burner flame is essential for an in-depth understanding of the formation mechanism and to abate its generation. This paper presents an improved emission spectroscopy (ES) method that uses an adaptive particle swarm optimization (APSO) algorithm for measuring the concentration of soot in methane burner flames. Experimental tests were conducted on a laboratory-scale facility under a methane flowrate ranging between 0.6 and 0.9 L/min. A comparison analysis of the soot concentration measured by the ES method, the improved emission spectroscopy (IES) method, and the thermocouple particle density (TPD) method (as a reference) was conducted. The ES method obtained a maximum absolute deviation of 0.84 ppm from the average soot concentration at the three measurement points compared to the TPD method, while that of the IES was only 0.09 ppm. The experimental results demonstrate that the proposed IES method can obtain a more accurate soot concentration of diffusion flames. [ABSTRACT FROM AUTHOR]

To accurately evaluate the size and distribution characteristics of the emission particles exhausted from in-use motor vehicle engines, we independently developed a condensation particle counter (CPC) known as BHCPC. It was calibrated by conducting the calibration procedures stated in the International Standard ISO 27981. After calibration, we conducted on-site measurements and offline sampling analysis of soot particles exhausted from different engines at a motor vehicle inspection center. The calibration results show that the detection efficiency is 90% when the particle diameter is 20.6 nm and the startup response time of the instrument is 3.53 s. The experiment results show that the self-developed BHCPC demonstrates good consistency in measuring particle-number concentration (PNC) in motor vehicle exhaust, with significant count fluctuations only occurring when PNC is higher than 25,000 P/cc. Under idle conditions, motor vehicles compliant with China VI emission regulations exhibit markedly lower exhaust emission PNC compared to those adhering to China IV emission regulations. Moreover, the results obtained from the offline electron microscope analysis show that fuel content in particle samples significantly decreases as engine speed increases, and a similar variation was also found in particle size. The micro-characteristics of the particle can give potential support to the combustion diagnostics. [ABSTRACT FROM AUTHOR]

Co-firing hydrogen (H 2) with hydrocarbon fuels is widely seen as an effective pathway to reduce soot emissions. Nevertheless, the soot-reducing potential of H 2 can be strongly dependent on the type of the co-fired hydrocarbon and the combustion conditions. In extreme cases H 2 enrichment could even promote soot production in hydrocarbon flames, thus highlighting the necessity of an in-depth understanding on the roles of H 2 addition. The present study aims to clarify the effects of H 2 addition on soot formation in non-premixed flames of propane. The effects of He and N 2 addition are included for a cross-comparison to identify the different effects of H 2 (i.e. , direct chemical roles, dilution or transport effects associated with fuel stream's physical properties). The technique of laser-induced incandescence (LII) was used for soot volume fraction measurement, and accompanying soot modeling analysis was performed for additional kinetic insights into the experimental results. The measurements and modeling results consistently show that H 2 is a more effective soot inhibitor than the chemical inert additive of He. Considering the comparative transport properties between H 2 and He, we concluded that H 2 has additional chemically-inhibiting effects on soot formation; kinetic analysis indicates that the chemical roles of H 2 mainly occur in the stages of soot precursor formation and soot nucleation process. Another interesting finding is that while both He and N 2 are chemically inert, He has notably stronger soot-reducing ability than N 2 , suggesting the favorable physical properties of He (i.e. , the high diffusivity) in reducing soot formation. The major contributions of this work include: 1) experimentally identify the different effects of H 2 (chemical, dilution and physical) on soot formation in counterflow flames of propane, 2) unravel the chemical roles of H 2 in the different sooting stages including soot precursors formation, soot inception and surface growth process, 3) provide new datasets for mechanism validation and refinement related to sooting characteristics of H 2 /hydrocarbon mixture fuels. • H 2 more effective in inhibiting soot than He and N 2 in propane flames. • The high diffusivity of H 2 /He contributes notably to soot inhibition. • The chemical roles of H 2 in different sooting stages discussed. • New soot data provided for mechanism validation in H 2 -enriched flame. [ABSTRACT FROM AUTHOR]

Soot generation is a major challenge in industries. The elimination of soot is particularly crucial to reduce pollutant emissions and boost carbon conversion. The mechanisms for soot oxidation are complex, with quantified models obtained under in situ conditions still missing. We prepare soot samples via noncatalytic partial oxidation of methane. Various oxidation models are established based on the results of in situ transmission electron microscopy experiments. A quantified maturity parameter is proposed and used to categorize the soot particles according to the nanostructure at various maturity levels, which in turn lead to different oxidation mechanisms. To tackle the challenges in the kinetic analysis of soot aggregates, a simplification model is proposed and soot oxidation rates are quantified. In addition, a special core-shell separation model is revealed through in situ analysis and kinetic studies. In this study, we obtain important quantified models for soot oxidation under in situ conditions. In this work, authors investigate mechanisms of noncatalytic soot oxidation and establish models applicable to different types of soot based on the particles oxidation behaviour using in-situ transmission electron microscopy. [ABSTRACT FROM AUTHOR]

It is widely acknowledged that the soot particulate pollutants pose a serious threat to both the environment and human health. Reducing the emission of these soot particulate pollutants from engines is very urgent, to which a highly efficient and robust modeling tool for soot emission prediction could contribute significantly. In this work, a new and robust numerical approach to handle the detailed soot models in engine combustion simulations is presented. The new approach adopts an advanced bi-variate moment projection method to treat the complex soot particle dynamics. The bi-variate moment projection method is superior to other methods of moments in terms that it is able to solve the soot moment closure problem due to oxidation, which governs the evolution of soot particle populations inside the engine cylinder. The proposed approach has been validated by simulating the detailed evolution processes of the soot particle population inside a dual-fueled, four-cylinder compression ignition engine. It is shown to be highly efficient and robust. It is able to provide a comprehensive investigation into the soot particle dynamics inside the engine cylinder at low computational cost. The emissions of soot particles under different engine operating conditions could be predicted with high accuracy. These findings suggest that the new approach proposed in this work is a promising framework for prediction and analysis of the emission of soot particulate pollutants from internal combustion engines. It is a useful tool to explore clean combustion technology. [ABSTRACT FROM AUTHOR]

This work reports an experimental and numerical analysis on the sooting characteristics of butanol isomers. Light extinction and gas chromatography were used to measure soot and gas-phase species, respectively. Kinetic analysis of the tested flames was performed with detailed gas-phase mechanism and a sectional soot model. The present work aims to provide an understanding on the effects of butanol isomeric structures on sooting tendencies. For a comprehensive analysis, flames of both neat butanol fuels and butanol/hydrocarbon mixtures were studied. The results showed that the relative ranking of sooting tendencies among the butanol isomers were similar in neat butanol flames and in butanol-doped ethylene flames. In addition, we show that a small amount of butanol addition in ethylene flame enhanced soot formation. It was found that different isomeric structures mainly affected the formation of C3H3, which led to the different concentrations of important aromatic soot precursors. In the butanol-doped ethylene flames, the blending of the four butanol isomers increased the number of C3H3 formation pathways, which in turn significantly increased the production of benzene. Structural effects explaining for the differences in the sooting tendencies of the four butanol isomers in neat butanol flames and ethylene/butanol flames were found to be the same. [ABSTRACT FROM AUTHOR]

Charcoal and micro-layers of soot trapped in speleothems from the inner galleries of Nerja Cave were analysed through an interdisciplinary study. The absolute dating of the prehistoric subterranean activity of the cave and the identification of different phases of visits to the deep parts are presented and discussed. The charcoal analysis includes anthracological analysis and SEM–EDX. The soot analysis includes optical microscopy, Raman spectroscopy and TEM–EDX, and the microcounting of soot microlayers. The 14C dating of 53 charcoals identified 12 phases of prehistoric visits to the cave between 41,218 and 3299 cal. BP, putting back the origin of human occupation of this emblematic cave by 10,000 years. The interdisciplinary analysis of the soot microlayers allowed us to perform a high-precision zoom on the last three visitation phases identified by Bayesian analysis (8003–2998 cal. BP.), demonstrating that these phases contain at least 64 distinct incursions, with an average of one visit every 35 years for the Neolithic period. Spatial analysis showed that not all areas of the cave were used in the same periods, highlighting the repetition of visits to certain specific sectors of the Lower Galleries of the cave. Lastly, the anthracological data indicate a cross-cultural and unique use of Pinus tp. sylvestris-nigra wood for lighting activities over an extended period between the Gravettian and Upper Magdalenian. [ABSTRACT FROM AUTHOR]

Oxygen concentration is a significant factor affecting soot formation and oxidation. However, there are few studies that have focused on the morphology and nanostructure characteristics of soot in aviation kerosene, oxygen-depleted combustion flames. In the present paper, five coflow flames under initial oxygen volume concentrations of 18.5%, 19%, 20%, 21%, and 23.5% were studied. The pneumatic probe sampling method and high-resolution transmission electron microscopy (HRTEM) analysis were conducted to quantify the morphology and nanostructure parameters, and laser extinction (LE) was applied to determine the soot volume fraction. Among the cases of different oxidizer oxygen concentrations (23.5% to 18.5%), the change in soot volume fraction was quantified, and the degree of graphitization of soot particles, i.e., the maturity, were compared. The results show that the peak value of soot volume fraction of the flames increased by 0.73 ppm as the oxygen concentration increased from 21% to 23.5%, and decreased by 1.25 ppm as the oxygen concentration decreased from 21% to 18.5%. When the oxygen concentration decreased from 23.5% to 18.5%, the soot primary particle diameter at the same dimensionless height decreased and then increased, which was attributed to the competition between the changes in the residence time and the growth rate of the soot particles. The quantitative analysis results of the soot nanostructure suggested that reduced oxygen concentration inhibited the graphitization process of carbon lattices and decreased the maturity and oxidation resistance of soot. When the oxygen concentration decreased from 23.5% to 18.5% at the same dimensionless height, the mean fringe length decreased by an average of 0.18 nm, and the mean value of fringe tortuosity and spacing increased by an average of 0.053 and 0.035 nm. [ABSTRACT FROM AUTHOR]

Oil has an enormous influence on the condition of the engine. Determining its degradation allows companies to maximize the availability of a specific vehicle and fleet of vehicles in general. In the evolution of engine oil degradation, one of the variables considered to be the most important is soot content. This article examines the direction and severity of soot content and dispersion changes in engine oil occurring during actual engine operation during four complete change intervals. The oil under study was operated in a city bus. It belonged to the fleet of vehicles of a transport company from new to the mileage of about 200,000 km. Soot content was determined in accordance with ASTM E2412-10, while dispersion size was determined using the dried drop test in accordance with ASTM D7899. The results obtained provide the basis for the conclusion that the direction of change in soot content in each interval is characterized by a high degree of homogeneity. With respect to the degree of soot build-up, a high level of similarity was observed between the intervals studied. The study of change in the degree of oil dispersion using the "drop on blotter" method made it possible to confirm the trend of decreasing dispersion as the run increases. The obtained results led to the development of a statistical model describing these relationships. [ABSTRACT FROM AUTHOR]

The effects of carbon dioxide (CO 2) addition to ethylene (C 2 H 4)/air inverse diffusion flames (IDFs) to the air stream on soot formation characteristics are investigated with the addition ratio of 0–13.64 %. The planar laser-induced fluorescence (PLIF) and planar laser-induced incandescence (PLII) techniques, in conjunction with CoFlame and Chemkin code simulations were utilized to assess the distributions of Polycyclic Aromatic Hydrocarbons (PAHs) and Soot Volume Fraction (SVF). The findings indicate that increasing CO 2 addition results in a gradual decrease in the mole fraction of hydroxyl (OH) radicals and flame temperature, accompanied by a reduction of approximately 15 % in the reaction zone height in experimental observations and 19 % in simulations. The inhibition of soot formation is evident through a consistent decline in the normalized total SVF, a decrease in the peak volume fraction of radial soot distribution, and reduced total SVFs observed across different flame sections at varying heights. In the meanwhile, increasing the CO 2 doping ratio significantly reduces the peak signal intensity of PAHs, particularly affecting high molecular weight PAHs (A3-A4, A2-A3) with reductions of up to 75.5 %. Furthermore, reductions are noted in the rates of soot inception and subsequent surface growth, accompanied by an upward displacement of the initial inception and growth location. The condensation of PAHs controls the soot surface growth. The thermal and chemical effects of CO 2 were differentiated by employing the virtual substance FCO 2. The results suggest that the thermal effect of CO 2 lowers flame temperature, reduces combustion intensity, and consequently inhibits soot nucleation. The chemical effect of CO 2 competes for H radicals through the reverse reaction of CO + OH ≤> CO 2 +H. This process suppresses the formation and growth of PAHs, consequently leading to a reduction in soot production. • This study investigates the formation of products in an ethylene inverse diffusion flame with varying CO 2 content using PAHs-PLIF and LII techniques. • A model of the ethylene/air laminar inverse diffusion flame was established using the CoFlame code, enabling two-dimensional numerical calculations to analyze the impact of CO 2 on soot formation under different mixing ratios. • The Chemkin software was employed to create a one-dimensional model of the ethylene/air laminar counter-flow diffusion flame, allowing for chemical kinetic analysis of soot precursors at various CO 2 concentrations. • By employing the virtual substance FCO 2 , the thermal and chemical effects of CO 2 was decoupled. The findings indicate that CO 2 primarily affects soot formation by competing for H radicals, thereby inhibiting the growth of polycyclic aromatic hydrocarbons and ultimately reducing soot generation. [ABSTRACT FROM AUTHOR]

Wear volumes were correlated with the lubricant properties of 11 used, heavy duty engine oil samples. The most important oil property in predicting wear volume is Total Acid Number, TAN. Here, the TAN value may be indicating ZDDP in its oxidised form and unable to participate in corrosive-abrasive wear. Low wear also correlates with mean soot particle size/circularity, which further suggests the abrasive aspect of this mechanism. Finally, low wear correlates with high calcium concentration in the fresh oil. This suggests a new wear reduction mechanism in which calcium from the detergent replenishes the iron within the ZDDP antiwear film. • Statistical analysis to predict wear based on 55 real-world engine oil properties. • Most important property predicting wear is Total Acid Number (low TAN, high wear). • Soot particle size correlates with low wear, supporting abrasive wear mechanism. • Detergent concentration correlates with low wear. • New wear mechanism shown where detergent ions replenish iron in the antiwear film. [ABSTRACT FROM AUTHOR]

In combustion research, optical diagnostics often necessitate Abel inversion to deconvolve the measurements of axisymmetric flames, especially to determine local soot temperature fields from integrated flame radiative emission measurements. However, traditional Abel inversion methods can considerably amplify experimental noise, especially towards the flame centerline. Although various strategies exist to mitigate this issue, they typically do not address the correction of signal trapping within the flame. The present paper introduces an adapted Abel inversion tool that combines resistance to experimental noise with a mechanism to correct signal trapping effects. The tool employs noise-free Abel inversion using piecewise spline functions. Its effectiveness is validated through numerical comparisons with conventional methods. The practical application is demonstrated in the measurement of soot temperature in a canonical laminar diffusion ethylene flame. This is achieved by using multi-wavelength line-of-sight attenuation (LOSA) and emission measurements. The tool corrects for the signal trapping effect in emission data by integrating extinction profiles, thus enabling a more precise soot temperature analysis. The current study also compares two techniques of temperature measurement based on thermal emission: traditional two-color pyrometry and a calibrated emission and absorption ratio method. The study further explores the effects of signal trapping, scattering contribution, and the absorption function ratio on soot temperature determination based on experimental profiles. The findings suggest that signal trapping and scattering contributions have a negligible impact on measurements at the wavelengths examined. However, the choice of absorption function ratio significantly influences the outcomes of two-color pyrometry, highlighting the advantage of the one color emission/absorption technique for the determination of sooting flames temperature measurements. • A new Abel transform based on cubic splines considering signal trapping is proposed. • This method, slightly slower, is more robust than classical Onion-Peeling. • The method is applied to determine soot temperature in a canonical ethylene flame. • One-color SAT method is compared to classical 2C pyrometry. • The one-color approach is advantageous because it is independent of optical index. [ABSTRACT FROM AUTHOR]

The present work aims to understand the temperature dependence of the fuel chemical mixing effects on soot and gas product formation in ethylene pyrolysis in a laminar flow reactor. The chemical and dilution effects of ethanol and dimethyl ether addition were studied experimentally by gas chromatography measurements and computationally using a detailed soot model coupled with PAHs chemistry. The chemical effects of ethanol and dimethyl ether mixing increased the production of CO, H 2 , and CH 4 , but the dilution effects decreased the production of H 2 , CH 4 , and C 2 H 2. The chemical mixing effects inhibited the formation of C 2 H 2 except for the case in which 50% ethanol was mixed with 50% ethylene at 1273 K. Ethanol and dimethyl ether mixing inhibited soot production, but the fuel mixing effects on soot reduction decreased with increasing temperature. The temperature dependence of the fuel mixing effects on soot production was dominated by the chemical effects rather than the dilution effects. Kinetic analysis of the soot formation process indicated that the methyl radical (CH 3) from ethanol and dimethyl ether decomposition combined with C2 species (C 2 H 2 , C 2 H 4) from ethylene pyrolysis to generate plenty of C3 species (C 3 H 4 –P, C 3 H 6 , C 3 H 5 -A, C 3 H 4 -A, C 3 H 3), which further converted into benzene (C 6 H 6) and polycyclic aromatic hydrocarbons (C 10 H 8 , C 14 H 10 , and C 16 H 10). The reaction rate of the above C1+C2→C3→C6→PAHs pathway increased noticeably with increasing pyrolysis temperature, which strengthened the chemical effects of ethanol and dimethyl ether mixing on soot surface growth rate contributed by PAHs and therefore soot yield under high-temperature conditions. • Ethanol and dimethyl ether mixing effects in ethylene pyrolysis was investigated. • Soot and gas products from fuel mixture pyrolysis were measured. • A soot model coupled with gas-phase chemistry was applied in the kinetic study. • Temperature dependence of chemical mixing effect on soot formation was captured. [ABSTRACT FROM AUTHOR]

In metallurgical processes, coke is used, among other materials, in order to implement the process of removing zinc from waste by reduction and evaporation. Due to the implemented de-carbonization policy, we are dealing with an increase in costs and decreasing availability of coke, which leads to an intensive search for other possibilities for conducting the process, which may generate a fire and explosion hazard in the technological process. This article analyzes the possibility of using soot in the process of reducing the zinc content in deposited metallurgical waste, taking into account the issue of fire and explosion safety. The results of the research proved the possibility of the safe use of the reductor, which is soot and anthracite, as a material replacing coke in pyrometallurgical processes. [ABSTRACT FROM AUTHOR]

Currently, the soot load from solid fuel combustion is not measured or counted, because it is included as part of particulate matter emitted from combustion sources. However, recent reports indicate that after carbon dioxide, soot is the most important contributor to current climate change. Therefore, an attempt was made to assess the soot load that is emitted during the winter season from individual heat sources where hard coal was burned or co-fired. Soot emission analysis and assessment were carried out in the selected settlement unit. Soot was collected monthly throughout the heating period at the chimney flue outlet, and analyzed for the PAH content. From these results and the information obtained from the users of individual heat sources, the soot load emitted from the installation in question during the entire heating period and the load of the sum of 16 PAHs and benzo(a)pyrene also during the entire heating period were calculated. It was found that the PAH content in soot largely depends on the type of boiler, the form of hard coal and wood addition burned, and the age of the boiler. The soot load, on the other hand, depends on the amount of hard coal burned, the type of boiler, how the combustion process is carried out, etc. [ABSTRACT FROM AUTHOR]

Background & Objective: The use of machine learning for air pollution modelling is rapidly increasing. We conducted a systematic review of studies comparing statistical and machine learning models predicting the spatiotemporal variation of ambient nitrogen dioxide (NO 2 ), ultrafine particles (UFPs) and black carbon (BC) to determine whether and in which scenarios machine learning generates more accurate predictions., Methods: Web of Science and Scopus were searched up to June 13, 2024. All records were screened by two independent reviewers. Differences in the coefficient of determination (R 2 ) and Root Mean Square Error (RMSE) between best statistical and machine learning methods were compared across categories of methodological elements., Results: A total of 38 studies with 46 model comparisons (30 for NO 2 , 8 for UFPs and 8 for BC) were included. Linear non-regularized methods and Random Forest were most frequently used. Machine learning outperformed statistical models in 34 comparisons. Mean differences (95% confidence intervals) in R 2 and RMSE between best machine learning and statistical models were 0.12 (0.08, 0.17) and 20% (11%, 29%) respectively. Tree-based methods performed best in 12 of 17 multi-model comparisons. Nonlinear or regularization regression methods were used in only 12 comparisons and provided similar performance to machine learning methods., Conclusion: This systematic review suggests that machine learning methods, especially tree-based methods, may be superior to linear non-regularized methods for predicting ambient concentrations of NO 2 , UFPs and BC. Additional comparison studies using nonlinear, regularized and a wider array of machine learning methods are needed to confirm their relative performance. Future air pollution studies would also benefit from more explicit and standardized reporting of methodologies and results., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Assessing the emissions of heavy-duty diesel trucks (HDDTs) is crucial for managing air quality in megacities, especially concerning nitrogen oxides (NO X ) and black carbon (BC). This study employed mobile plume chasing to monitor the real-world emissions of over 7778 HDDTs in Shenzhen. The findings indicate that the real-world NO X emission factors (EF) of China IV trucks did not differ significantly from those of China III, whereas China V and VI vehicles demonstrated fleet-averaged reductions of 27% and 85%, respectively. For China V, a significant decrease in the NO X EF for HDDTs registered after 2017 was attributed to the installation of advanced aftertreatment systems, including diesel oxidation catalysts (DOC) and Diesel Particle Filters (DPF), along with selective catalytic reduction (SCR). These technologies led to an average reduction of 42% in NO X and 61% in BC emissions. Seasonal variations were pronounced, with winter (∼20 °C) NO X EF 40% higher than summer (∼35 °C) levels. Conversely, BC EF decreased by 26% in winter, indicating significant impacts of ambient temperature on emissions. Spatial analysis revealed that the average NO X EF of HDDTs on east freeways was 1.4 times higher than that on urban expressways, influenced by variations in the proportion of vehicle types segmented by usage. These findings offer a comprehensive perspective on HDDTs emissions, highlighting the importance of large-scale emission monitoring through plume chasing for precise and effective control of real-world HDDTs emissions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The increase in the frequency and severity of global wildfires has been largely influenced by climate change and land use changes. From February 2 to 6, 2024, central Chile experienced its most devastating wildland-urban interface wildfire in history, severely impacting the Valparaíso region. This catastrophic event, which led to extensive forest destruction, the loss of thousands of homes, and over a hundred human fatalities, directly impacted the area surrounding the campus of Federico Santa María Technical University. In that period, an air quality monitoring campaign was set up on the campus to measure black carbon (BC) and particulate matter (PM) during the wildfire season. The monitoring station was located directly within the smoke plume, allowing for the collection of unprecedented air quality data. Extremely high concentrations of BC at 880 nm were reported during the wildfires, with a daily mean (±σ) of 14.83 ± 19.52 μg m -3 . Peak concentrations measured at 880 nm and 375 nm reached 812.89 μg m -3 and 1561.24 μg m -3 , respectively. The maximum daily mean BC concentrations at these wavelengths were 55 and 99 times higher, respectively, compared to the pre-event period. The mean Ångström absorbing coefficient during the event was 1.66, indicating biomass burning as the primary BC source, while the maximum BC/PM 2.5 ratio (at 375 nm) reached 57 %. From February 2 to 5, 2024, PM concentrations exceeded the Chilean air quality standard by 82 % and 198 % for coarse and fine particles, respectively. These levels are 4.7 and 6.0 times higher than the World Health Organization's recommendations. These elevated concentrations persisted for up to three days after the fire was extinguished. This study provides unique evidence of the rapid deterioration of regional air quality during a wildfire event using in situ measurements, serving as a stark reminder of the far-reaching consequences of a warming climate., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Black carbon (BC) is a pollutant produced by the combustion of fossil fuels and biomass fuels, which has a huge impact on regional climate, atmospheric environment, and human health. In this study, based on MERRA-2 reanalysis data and ground-based observation data, the Mann-Kendall (MK) test and random forest (RF) model were used to explore the spatiotemporal variation characteristics of atmospheric BC concentration in Xinjiang, China and its correlation with meteorological and environmental covariates in 2010-2022. The results showed that the use of MERRA-2 reanalysis data to explore the spatiotemporal variation characteristics of BC concentration in Xinjiang had high reliability (relative average deviation (RAD) = 0.65). From 2010 to 2022, the annual average concentration of atmospheric BC in Xinjiang was 195.40 ± 15.55 ng/m 3 , and the multi-year average change rate was -0.05%. The winter season had the highest atmospheric BC concentration (145.52 ± 39.31 ng/m 3 ), followed by autumn (124.95 ± 28.82 ng/m 3 ), spring (74.05 ± 9.96 ng/m 3 ), and summer (73.41 ± 5.69 ng/m 3 ). The atmospheric BC concentration had a significant spatial variation, showing two high-BC-concentration areas on the northern slope of the Tianshan Mountains (centered on Urumqi-Changji-Shihezi region) and the urban agglomeration around the Tarim Basin (centered on Kashgar). The RF model analysis showed that meteorological factors including snow depth, surface temperature, and humidity as well as environmental factors including NO 2 , PM 10 , and SO 2 were the main factors affecting the BC concentration. This work is of great significance for clarifying the accumulation and spatial distribution characteristics of atmospheric BC in northwest China and the factors influencing the atmospheric BC concentration, and helps to raise public attention to the increasingly serious climate change and public health problems caused by BC., Competing Interests: The authors declare there are no competing interests., (©2024 Xie et al.)

The City of Baltimore, MD has a history of problems with environmental justice (EJ), air pollution, and the urban heat island (UHI) effect. Current chemical transport models lack the resolution to simulate concentrations on the scale needed, about 100 m, to identify the neighborhoods with anomalously high air pollution levels. In this paper we introduce the capabilities of a mobile laboratory and an initial survey of several pollutants in Baltimore to identify which communities are exposed to disproportionate concentrations of air pollution and to which species. High concentrations of black carbon (BC) stood out at some locations - near major highways, downtown, and in the Curtis Bay neighborhood of Baltimore. Results from the mobile lab are confirmed with longer-term, low-cost monitoring. In Curtis Bay, higher concentrations of BC were measured along Pennington Ave. (mean [5 th to 95 th percentiles] =  2.08 [2.0-10.9] μg m -3 ) than along Curtis Ave. just ~ 150 m away ( 0.67 [0.1 - 1.8] μg m -3 ). Other species, including criteria pollutants ozone (O 3 ), carbon monoxide (CO), nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), and fine particulate matter (PM 2.5 ), showed little gradient. Observations with high spatial and temporal resolution help isolate the mechanisms leading to locally high pollutant concentrations. The difference in BC appears to result not from heavier truck traffic or slower dispersion but from the interruptions in traffic flow. Pennington Ave. has three stoplights while Curtis Ave. has none. As heavy-duty diesel-powered vehicles accelerate, they experience turbo-lag and the resulting rich air-fuel mixture exacerbates BC emissions. Immediate mediation might be achieved through smoother traffic flow, and the long-term solution through replacing heavy-duty trucks with electric vehicles. Implications : We present results documenting the locations within Baltimore of high concentrations of Black Carbon pollution and identify the likely source - diesel exhaust emissions exacerbated by stop-and-go traffic and associated turbo-lag. This suggests solutions (smoother traffic, retrofit particulate filters, replacement of diesel with electric vehicles) that would enhance Environmental Justice (EJ) and could be applied to other cities with EJ problems. Synopsis : This paper presents observations of atmospheric black carbon aerosol showing impacts on environmental justice, then identifies causes and suggests solutions.

Despite the global transition towards cleaner energy sources observed over the last decade, disparities in access persist worldwide. The dependence on biomass for household heating exacerbates fuel poverty, as economically vulnerable households face challenges in obtaining certified firewood and often resort to using contaminated biomass as a substitute, either partially or completely. We examined black carbon (BC) particle concentrations -a marker for combustion- during wood stove operation through a five-day case study in a typical Chilean household. BC increased rapidly following the ignition of the stove, with the combustion of dry Eucalyptus globulus logs yielding a substantially lower peak (5.29 μg/m 3 ) than when using unclean biomass: 35.75 μg/m 3 with demolition wood and painted furniture, and 87.11 μg/m 3 with the addition of a blend of particleboard with polystyrene foam. During the latter two events, BC particles remained indoors for about 20 h before the concentrations reverted to pre-spike levels. The slow decay in BC concentrations was further influenced by the infiltration of outdoor air. The mean indoor BC concentrations were comparable to or even exceeded those observed on busy roads in major cities worldwide. These results highlight the risks associated with limited access to clean fuels for indoor heating, alongside inadequate insulation. This study sheds light on the problem of fuel poverty and its adverse effects on health and well-being., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Black carbon (BC) formed after straw burning remains in farmland soil and coexists with plastic mulch film (PMF) debris. It is unclear how BC influences soil multifunctionality in the presence of PMF debris. In this study, we determined the joint effects of BC and PMF debris on soil biochemical properties and microbial communities. We conducted a soil microcosm experiment by adding BC formed by direct burning of wheat straw and PMF debris (polyethylene (PE) and biodegradable PMF (BP)) into soil at the dosages of 1 %, and soils were sampled on the 15th, 30th, and 100th day of soil incubation for high-throughput sequencing. The results showed that the degradation of PMF debris was accompanied by the release of microplastics (MPs). BC decreased NH 4 + -N (PE: 68.63 %; BP: 58.97 %) and NO 3 - -N (PE: 12.83 %; BP: 51.37 %) and increased available phosphorus (AP) (PE: 79.12 %; BP: 26.09 %) in soil containing PMF debris. There were significant differences in enzyme activity among all the treatments. High-throughput sequencing indicated that BC reduced bacterial and fungal richness and fungal diversity in PMF debris-exposed soil, whereas PMF debris and BC resulted in significant changes in the proportion of dominant phyla and genera of bacteria and fungi, which were affected by incubation time. Furthermore, BC affected microorganisms by influencing soil properties, and pH and N content were the main influencing factors. In addition, FAPRPTAX analysis indicated that BC and PMF debris affected soil C and N cycling. These findings provide new insights into the response of soil multifunctionality to BC and PMF debris., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Urban Black Carbon (BC) emissions from light-duty gasoline vehicles (LDGVs) are challenging to quantify in real-world settings. This study employed a Portable Emission Measurement System (PEMS) to assess BC emissions from five LDGVs on urban roads. We also developed five machine learning (ML) models based on On-Board Diagnostics (OBD) data to predict BC emissions. Among these, the Random Forest (RF) model consistently demonstrates the best ability to predict BC emissions across all tested LDGVs, with R 2 values exceeding 0.6. Integrating OBD-based ML models within vehicles could enable real-time BC monitoring and aid emission reduction strategies. We observed a strong correlation between BC emissions and engine parameters, such as engine speed and load (R 2 values between 0.5 and 0.9). Furthermore, China VI standard-compliant LDGVs showed minor differences in BC emissions across urban road types. Vehicles equipped with gasoline direct injection (GDI) engines registered BC emission factors (EFs) of 0.141 ± 0.038 mg/km, an increase of 23.7% compared to their port fuel injection (PFI) counterparts, which averaged 0.114 ± 0.049 mg/km., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Asphalt pavement has been widely applied in the road tunnel. In tunnel fire, the combustion of asphalt pavement produces large quantities of toxic, carcinogenic and harmful black smoke, which causes serious environmental pollution. To explore the inhibition of composite fire retardant (CFR) on combustion soot release of asphalt mixtures for reducing environmental pollution, this paper investigated the combustion soot produced by asphalt mixtures using cone calorimeter (CONE) test. Then the influence of CFR on the composition of combustion residues in asphalt mixture was investigated employing the solid-phase microextraction combined with gas chromatography-mass spectrometry (SPME-GC-MS) technique to reveal the smoke suppression mechanism of each constituent of CFR on the combustion of asphalt mixture. Through the detection and analysis of the combustion soot of asphalt mixture and CFR asphalt mixture, it is found that the main types of alkanes are reduced, and the unsaturated alkenes and alkynes disappear after the addition of CFR. Test results show that the composition of combustion residues of CFR asphalt mixture is significantly reduced compared with that of asphalt mixture. Compared with the combustion soot and residues of CFR asphalt mixture, it is found that the molecular weights of characteristic substances of combustion soot and residues after the burning of asphalt mixture are smaller. Therefore, it is of great significance in the fire safety field to study the influence of newly developed CFR on the combustion soot and combustion residues of asphalt mixture when exposed to fire. [Display omitted] • The smoke suppression mechanism of CFR on asphalt mixture are further explored. • The smoke identification of asphalt mixture and CFR asphalt mixture was discussed. • Effects of CFR on combustion residues of asphalt mixture are studied by SPME-GC-MS. • Main combustion residues of asphalt mixture and CFR asphalt mixture are identified. • Harmful and toxic combustion soot and combustion residues are classified in detail. [ABSTRACT FROM AUTHOR]

The detonation front's unstable structure leads to an unsteady and three-dimensional (3D) phenomenon that renders the study of the cell cycle challenging. Traditionally, fundamental studies are carried out in narrow channels where the detonation behavior is very peculiar (quasi two-dimensional with velocity deficit). In this study, we propose a fully experimental approach to study the cell cycle in the case of multicellular detonations. The cell cycle is characterized through three techniques: systematic and statistical analysis of soot foil, planar laser-induced fluorescence on nitric oxide, and Rayleigh scattering. These techniques provide measurements for cell size, local induction length, and local shock speed, respectively. The work is carried out in the 2 H 2 -O 2 -3.76Ar and the 2 H 2 -O 2 -3.76N 2 mixtures at 293 K, and 20 kPa and 25 kPa, respectively. These conditions ensure that the cell pattern is considered being between regular and weakly irregular, thus, a shot-to-shot reconstruction of the cell cycle is possible. The cell widths follow a normal distribution, from which a quantitative parameter (2 σ / λ) is proposed to assess the cell regularity, experimentally. The evolution of the speed and the local induction length are reconstructed along the cell cycle. The results agree with the available data for narrow channels and constitute the first of their kind for 3D detonation (i.e., multicellular in the transverse dimension). Two methods are proposed to analyze the local induction length δ i and compare it to the available literature (experimental and numerical studies). The technique can be applied to mixtures where the mean cell width is a meaningful parameter from highly regular to irregular mixtures. Novelty and Significance statement For the first time, combined soot-foils, NO-PLIF, and Rayleigh scattering measurements were used to reconstruct and characterize the cellular cycle of multicellular detonations using a 2 H 2 -O 2 -3.76Ar and 2 H 2 -O 2 -3.76N 2 mixtures at 293 K, and 20 kPa and 25 kPa, respectively. This constitutes the first combined measurements of local induction length and local front speed in a multicellular configuration, where the number of cells in the section is large, i.e., the cell width (λ) is small compared to all dimensions of the rig. This study provides two methodologies to extract an experimental Δ i , which is a quantity that can be compared with the ZND theory. Such measurements were not achievable in multicellular conditions until now. The measurement of the Δ i demonstrates that a fully experimental correlation between this experimental Δ i and λ can be obtained for the first time. These new results are important for the quantitative validation of chemical kinetic schemes for predictive simulations of detonations. [ABSTRACT FROM AUTHOR]

This study aims to investigate the interactions between marine oil snow (MOS) formation and soot particles derived from two distinct oils: condensate and heavy oil. Experimental findings demonstrate that the properties of oil droplets and soot particles play a key role in MOS formation. Peak MOS formation is observed within the initial days for condensate, while for heavy oil, peak formation occurs at a later stage. Furthermore, the addition of oils and soot particles influences the final concentrations of polycyclic aromatic hydrocarbons (PAHs) in MOS. Remarkably, the ranking order of PAHs with different rings in various MOS samples remains consistent: 4- > 3- > 5- > 2- > 6-ring. Specific diagnostic ratios such as Phe/Ant, Ant/(Ant + Phe), BaA/(Chr + BaA), and LMW/HMW effectively differentiate petrogenic and pyrogenic sources of PAHs in MOS. And stable ratios like Flu/(Pyr + Flu), InP/(InP + BghiP), and BaF/BkF are identified for source analysis of soot MOS. [Display omitted] • The properties of oil droplets and soot particles influence the MOS formation. • Peak MOS formation by light oil and soot occurs earlier than that of heavy oil. • The order of PAHs with different rings in MOS samples remains consistent. • PAH ratios are explored to demonstrated the source characteristics of soot MOS. [ABSTRACT FROM AUTHOR]

The uncertainty in soot kinetics parameters will lead to uncertainty in the prediction of soot characteristics, including particle size distribution (PSD) and soot volume fraction (SVF). Uncertainty quantification is an important way to evaluate the model performance not only in terms of nominal accuracy but also in terms of confidence intervals. In this work, an uncertainty analysis approach combined with sensitivity analysis and the active subspace method is proposed. This approach is demonstrated with a sectional soot kinetics scheme for two laminar benchmark flames: the burner stabilized stagnation (BSS) flame with ethylene as the fuel, and the laminar diffusion flame on the Yale burner with methane as the fuel. The uncertainties of PSDs are obtained from an ensemble of kinetics samples and compared with the local sensitivities, while the uncertainties of SVFs are quantitatively evaluated via the active subspace and the response surface techniques. With an assumed soot kinetics uncertainty factor of U F = 3 , the uncertainties of soot volume fractions in the BSS flame at different heights are around S V F m a x / S V F m i n ≈ 3. The peak soot volume fraction (PSVF) and peak soot volume fraction on the centerline (PSVF-c) in the Yale flame lie in the respective ranges of [0.91, 1.41] ppm and [0.84, 1.08] ppm for the 95% confidence intervals. Furthermore, the sensitivity of each reaction at different soot formation stages is quantitatively analyzed as a function of a newly defined soot progress variable. As expected, at the early stage of soot formation, SVFs are controlled by the nucleation reactions, especially reaction Rx3 (see Table1), and surface reactions gradually gain importance during the later stages of soot evolution. Ultimately, as indicated by the results of the Yale flame, the sensitivity of the surface growth reactions weakens, and oxidation and fragmentation reactions instead take control of the evolution of soot particles. These quantitative uncertainty results are performed for the first time and help reveal the control mechanism of soot formation in the studied flames. [ABSTRACT FROM AUTHOR]

In this work, a multi-wavelength pyrometry method is proposed in order to evaluate soot temperature for laminar axisymmetric non-premixed flames. A single radiative model that combines three detection wavelengths is developed to increase the spectral information used in the soot temperature determination. A simple set-up is used in order to capture the soot emission at two or three wavelengths. The robustness of the methodology is assessed by a radiative model, which includes a sensitivity and relative error analysis for the soot temperature, and accounts for self-absorption effects. The model and procedure are verified by employing numerical temperature and soot volume fraction fields to recreate the convoluted soot emissions. Soot emission measurements involve different combinations of wavelengths that are employed to evaluate soot temperature without requiring additional measurements of the soot absorption coefficient when soot self-absorption is neglected. The error on the determined soot temperature was estimated to be lower than 60 K under this assumption for soot volume fractions under 10 ppm. In addition, an analysis of the signal noise effect on the temperature shows that the modulated absorption/emission (MAE) technique is more sensitive than the emission (EMI) technique. A sensitivity analysis showed that the presented three-wavelength EMI model is less sensitive to small deviations on the measured soot emission ratio than the classical two-wavelength approach. This feature makes the model suitable to improve the accuracy on the determination of soot temperature when the noise level of the signal is significant. [ABSTRACT FROM AUTHOR]

A combined numerical and experimental investigation of the different chemical effects of H 2 (CE-H 2) on soot formation was conducted by applying the reactive molecular dynamics simulation (ReaxFF MD) and the pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) diagnostic technique. In addition, the detailed chemical reaction pathway for the different CE-H 2 was explored in the combustion of methane (CH 4) and ethylene (C 2 H 4) fuels. It was found that both the experimental and numerical results reflected the evolution of polycyclic aromatic hydrocarbons (PAHs) and initial soot particles and the different CE-H 2 on PAHs/soot formation. The primary reason for the different CE-H 2 was that the hydrogen addition led to the production of a large number of hydrogen atoms, which promoted acetylene (C 2 H 2) formation during the methane combustion through the chemical reactions C 2 H 5 + H ↔ C 2 H 4 + H 2 and C 2 H 4 + H ↔ C 2 H 3 + H 2 , but inhibited acetylene formation during the ethylene combustion through the chemical reaction C 2 H 3 ↔ C 2 H 2 + H. The hydrogen addition only increased the number of 6-membered rings in the largest PAH/soot particle of methane combustion but decreased the numbers of all ringed compounds in the largest PAH/soot particle of ethylene combustion. Moreover, the CE-H 2 promoted methane pyrolysis but inhibited ethylene pyrolysis. • Analyze Py-GC/MS results for methane and ethylene diffusion flame with H 2 addition. • Explore the chemical reaction mechanism for different chemical effects of H 2. • Analyze the ReaxFF MD results of hydrogen-doped methane and ethylene. [ABSTRACT FROM AUTHOR]

Diesel engine exhaust (DEE) is carcinogenic and potentially hazardous for those working in close proximity to diesel-powered machines. This study characterizes workplace exposure to DEE and its associated particulate matter (PM) during outdoor construction activities. We sampled at 4 construction sites in the Copenhagen metropolitan area. We used portable constant-flow pumps and quartz-fiber filters to quantify personal exposure to elemental carbon (EC), and used real-time instruments to collect activity-based information about particle number and size distribution, as well as black carbon (BC) concentration. Full-shift measurements of EC concentration ranged from < 0.3 to 6.4 µg/m3. Geometric mean (GM) EC exposure was highest for ground workers (3.4 µg/m3 EC; geometric standard deviation, GSD = 1.3), followed by drilling rig operators (2.6 µg/m3 EC; GSD = 1.4). Exposure for non-drilling-rig machine operators (1.2 µg/m3 EC; GSD = 2.9) did not differ significantly from background (0.9 µg/m3 EC; GSD = 1.7). The maximum 15-min moving average concentration of BC was 17 µg/m3, and the highest recorded peak concentration was 44 µg/m3. In numbers, the particle size distributions were dominated by ultrafine particles ascribed to DEE and occasional welding activities at the sites. The average total particle number concentrations (PNCs) measured in near-field and far-field positions across all worksites were 10,600 (GSD = 3.0) and 6,000 (GSD = 2.8)/cm3, respectively. Sites with active drilling rigs saw significantly higher average total PNCs at their near-field stations (13,600, 32,000, and 9,700/cm3; GSD = 2.4, 3.4, and 2.4) than sites without (4,700/cm3; GSD = 1.6). Overall, the DEE exposures at these outdoor construction sites were below current occupational exposure limits for EC (10 µg/m3 in Denmark; 50 µg/m3 in the European Union), but extended durations of exposure to the observed DEE levels may still be a health risk., (© The Author(s) 2024. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.)

The 31st FISU Summer World University Games (SWUG) was held in Chengdu, southwestern China, from July 22 to August 8, 2023. A series of control measures were carried out to ensure good air quality during the SWUG, providing an opportunity to investigate the atmospheric behaviors of light-absorbing aerosols under such a substantial disturbance caused by the control measures. To assess the impacts of emission controls on primary pollutants, a field campaign was conducted at a rural site in Chengdu to investigate the characterization of equivalent black carbon (eBC). The changes of eBC concentrations before, during, and after the SWUG were characterized. The sources of eBC were resolved, and the impacts of atmospheric processes on the absorption capacity were also investigated. During the SWUG, the eBC concentration decreased by 12.1 % and 25.3 % compared with those before and after the SWUG. A fossil fuel combustion (eBC ff ) and a biomass burning (eBC bb ) originated eBC were resolved using the aethalometer model. Both eBC ff and eBC bb decreased during the SWUG, indicating the effectiveness of control measures. After the SWUG, the influence of biomass burning emissions became more and more significant, and the contribution of brown carbon (BrC) to light absorption at 370-660 nm increased by 52, 19, 7, 6, and 17 % compared to those during the SWUG. As the biomass burning emitted aerosols aged, the absorption Ångström exponent and b abs (BrC 370nm ) decreased gradually, which was mainly due to the photobleaching of the chromophores during the daytime. eBC ff was mainly affected by strong wind, while high eBC bb concentration was mainly attributed to the gradual accumulation of biomass-burning emissions near the observation site. The results show the significant reduction of eBC with the implementation of the air pollution mitigation campaign, and provide insights on the impacts of atmospheric processes on BC optical properties during summertime., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Seasonal variations in black carbon (BC) pollution characteristics during haze episodes in Benxi city, Liaoning province, were analyzed using year-long measurements of BC, carbon monoxide (CO), and PM 2.5. Haze frequencies were recorded to be 0.07, 0.03 and 0.14 in spring, autumn, and winter respectively. Solid fuel contributions increased notably by 7%-8% during haze events compared to clean periods in all seasons. Transitioning from clean to haze periods led to ΔBC/ΔCO increases of 16% in spring and autumn, and 6.8% in winter, while BC/PM 2.5 ratios decreased by approximately 33%, 50%, and 24% for spring, autumn, and winter respectively, likely indicating enhanced residential and industrial contributions. These further led to an increase in BC absorption capacities by factors of around 2.2 in spring and autumn, and up to 2.6 in winter during haze periods. Despite liquid fuel sources dominating BC emissions, certain haze episodes (frequency <10%) showed solid fuel contributions of up to 65%, highlighting BC pollution complexity in the region during haze. Backward trajectories analysis revealed local air masses from Liaoning province arrived consistently with the most occurrence of haze events across all seasons, while long-range air masses from Mongolian regions, though with less frequent occurrence during haze periods, significantly elevated BC loadings from solid fuel sources, particularly in spring and autumn due to biomass burning. Despite higher BC wet scavenging rates (WSR) in long-range air masses (0.072 ng m -3  ppbv -1 mm -1 ) compared to local air masses (0.039 ng m -3  ppbv -1 mm -1 ), significant BC transport persisted due to limited precipitation along transport pathways, especially during haze periods. These findings provide crucial insights for policymakers, highlighting the need for targeted haze prevention and control strategies focusing on mitigating BC emissions in Northeast China., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: Since there are known adverse health impacts of traffic-related air pollution, while at the same time there are potential health benefits from greenness, it is important to examine more closely the impacts of these factors on indoor air quality in urban schools., Objective: This study investigates the association of road proximity and urban greenness to indoor traffic-related fine particulate matter (PM 2.5 ), nitrogen dioxide (NO 2 ), and black carbon (BC) in inner-city schools., Methods: PM 2.5 , NO 2 , and BC were measured indoors at 74 schools and outdoors at a central urban over a 10-year period. Seasonal urban greenness was estimated using the Normalized Difference Vegetation Index (NDVI) with 270 and 1230 m buffers. The associations between indoor traffic-related air pollution and road proximity and greenness were investigated with mixed-effects models., Results: The analysis showed linear decays of indoor traffic-related PM 2.5 , NO 2 , and BC by 60%, 35%, and 22%, respectively for schools located at a greater distance from major roads. The results further showed that surrounding school greenness at 270 m buffer was significantly associated (p < 0.05) with lower indoor traffic-related PM 2.5 : -0.068 (95% CI: -0.124, -0.013), NO 2 : -0.139 (95% CI: -0.185, -0.092), and BC: -0.060 (95% CI: -0.115, -0.005). These associations were stronger for surrounding greenness at a greater distance from the schools (buffer 1230 m) PM 2.5 : -0.101 (95% CI: -0.156, -0.046) NO 2 : -0.122 (95% CI: -0.169, -0.075) BC: -0.080 (95% CI: -0.136, -0.026). These inverse associations were stronger after fully adjusting for regional pollution and meteorological conditions., Impact Statement: More than 90% of children under the age of 15 worldwide are exposed to elevated air pollution levels exceeding the WHO's guidelines. The study investigates the impact that urban infrastructure and greenness, in particular green areas and road proximity, have on indoor exposures to traffic-related PM 2.5 , NO 2 , and BC in inner-city schools. By examining a 10-year period the study provides insights for air quality management, into how road proximity and greenness at different buffers from the school locations can affect indoor exposure., (© 2024. The Author(s).)

Glacial bodies in the Peruvian Andes Mountains store and supply freshwater to hundreds of thousands of people in central Peru. Atmospheric black carbon (BC) is known to accelerate melting of snow and ice, in addition to contributing to air pollution and the health of people. Currently there is limited understanding on the sources and temporal variability of BC in valley and mountain environments in Peru. To address this problem, this study combined surface observations of BC collected during 2022-2023 with WRF model simulations and HYSPLIT trajectories to analyze the dispersion and sources of BC in valley and high elevation environments and the associated local atmospheric circulations. Results show high BC concentrations are associated with the valley-mountain wind system that occurs on both sides of the Huaytapallana mountain range. A pronounced circulation occurs on the western slopes of Huaytapallana when concentrations of BC increase during daylight hours, which transports atmospheric pollutants from cities in the Mantaro River Valley to the Huaytapallana mountain range. Low concentrations of BC are associated with circulations from the east that are channeled by the pronounced ravines of the Andes-Amazon transition. On average, during the season of highest BC concentrations (July-November), the relative contributions of fossil fuels are dominant to biomass burning at the valley observatory and are slightly lower at the Huaytapallana observatory. These results demonstrate the need to promote mitigation actions to reduce emissions of BC and air pollution associated with forest fires and local anthropogenic activity., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Elver Villalobos Puma reports was provided by National Institute for Research on Glaciers and Mountain Ecosystems. Elver Villalobos-Puma reports a relationship with National Institute for Research on Glaciers and Mountain Ecosystems that includes: employment. Elver Villalobos-Puma has patent pending to Lincensee. co-author previously employed by INAIGEM Company-A.M If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Communities near transportation sources can be impacted by higher concentrations of particulate matter (PM) and other air pollutants. Few studies have reported on air quality in complex urban environments with multiple transportation sources. To better understand these environments, the Kansas City Transportation and Local-Scale Air Quality Study (KC-TRAQS) was conducted in three neighborhoods in Southeast Kansas City, Kansas. This area has several emissions sources including transportation (railyards, vehicles, diesel trucks), light industry, commercial facilities, and residential areas. Stationary samples were collected for 1-year (October 24, 2017, to October 31, 2018) at six sites using traditional sampling methods and lower-cost air sensor packages. This work examines PM less than 2.5 μm in diameter (PM 2.5 ), black carbon (BC), and trace metals data collected during KC-TRAQS. PM 2.5 filter samples showed the highest 24-h mean concentrations (9.34 μg/m 3 ) at the sites located within 20-50 m of the railyard. Mean 24-h PM 2.5 concentrations, ranging from 7.96 to 9.34 μg/m 3 , at all sites were lower than that of the nearby regulatory site (9.83 μg/m 3 ). Daily maximum PM 2.5 concentrations were higher at the KC-TRAQS sites (ranging from 25.31 to 43.76 μg/m 3 ) compared to the regulatory site (20.50 μg/m 3 ), suggesting short-duration impacts of localized emissions sources. Across the KC-TRAQS sites, 24-h averaged PM 2.5 concentrations from the sensor package (P-POD) ranged from 3.24 to 5.69 µg/m 3 showing that, out-of-the-box, the PM sensor underestimated the reference concentrations. KC-TRAQS was supplemented by elemental and organic carbon (EC/OC) and trace metal analysis of filter samples. The EC/OC data suggested the presence of secondary organic aerosol formation, with the highest mean concentrations observed at the site within 20 m of the railyard. Trace metals data showed daily, monthly, and seasonal variations for iron, copper, zinc, chromium, and nickel, with elevated concentrations occurring during the summer at most of the sites. Implications : This work reports on findings from a year-long air quality study in Southeast Kansas City, Kansas to understand micro-scale air quality in neighborhoods impacted by multiple emissions sources such as transportation sources (including a large railyard operation), light industry, commercial facilities, and residential areas. While dozens of studies have reported on air quality near roadways, this work will provide more information on PM 2.5 , black carbon, and trace metals concentrations near other transportation sources in particular railyards. This work can also inform additional field studies near railyards.

In near-road neighborhoods, residents are more frequently exposed to traffic-related air pollution (TRAP), and they are increasingly aware of pollution levels. Given this consideration, this study adopted portable air pollutant sensors to conduct a mobile monitoring campaign in two near-road neighborhoods, one in an urban area and one in a suburban area of Shanghai, China. The campaign characterized spatiotemporal distributions of fine particulate matter (PM 2.5 ) and black carbon (BC) to help identify appropriate mitigation measures in these near-road micro-environments. The study identified higher mean TRAP concentrations (up to 4.7-fold and 1.7-fold higher for PM 2.5 and BC, respectively), lower spatial variability, and a stronger inter-pollutant correlation in winter compared to summer. The temporal variations of TRAP between peak hour and off-peak hour were also investigated. It was identified that district-level PM 2.5 increments occurred from off-peak to peak hours, with BC concentrations attributed more to traffic emissions. In addition, the spatiotemporal distribution of TRAP inside neighborhoods revealed that PM 2.5 concentrations presented great temporal variability but almost remained invariant in space, while the BC concentrations showed notable spatiotemporal variability. These findings provide valuable insights into the unique spatiotemporal distributions of TRAP in different near-road neighborhoods, highlighting the important role of hyperlocal monitoring in urban micro-environments to support tailored designing and implementing appropriate mitigation measures., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

There is a notable lack of continuous monitoring of air pollutants in the Global South, especially for measuring chemical composition, due to the high cost of regulatory monitors. Using our previously developed low-cost method to quantify black carbon (BC) in fine particulate matter (PM 2.5 ) by analyzing reflected red light from ambient particle deposits on glass fiber filters, we estimated hourly ambient BC concentrations with filter tapes from beta attenuation monitors (BAMs). BC measurements obtained through this method were validated against a reference aethalometer between August 2 and 23, 2023 in Addis Ababa, Ethiopia, demonstrating a very strong agreement ( R 2 = 0.95 and slope = 0.97). We present hourly BC for three cities in sub-Saharan Africa (SSA) and one in North America: Abidjan (Côte d'Ivoire), Accra (Ghana), Addis Ababa (Ethiopia), and Pittsburgh (USA). The average BC concentrations for the measurement period at the Abidjan, Accra, Addis Ababa Central summer, Addis Ababa Central winter, Addis Ababa Jacros winter, and Pittsburgh sites were 3.85 μg/m 3 , 5.33 μg/m 3 , 5.63 μg/m 3 , 3.89 μg/m 3 , 9.14 μg/m 3 , and 0.52 μg/m 3 , respectively. BC made up 14-20% of PM 2.5 mass in the SSA cities compared to only 5.6% in Pittsburgh. The hourly BC data at all sites (SSA and North America) show a pronounced diurnal pattern with prominent peaks during the morning and evening rush hours on workdays. A comparison between our measurements and the Goddard Earth Observing System Composition Forecast (GEOS-CF) estimates shows that the model performs well in predicting PM 2.5 for most sites but struggles to predict BC at an hourly resolution. Adding more ground measurements could help evaluate and improve the performance of chemical transport models. Our method can potentially use existing BAM networks, such as BAMs at U.S. Embassies around the globe, to measure hourly BC concentrations. The PM 2.5 composition data, thus acquired, can be crucial in identifying emission sources and help in effective policymaking in SSA.

Introduction: Numerous studies support an important relationship between long-term exposure to outdoor fine particulate air pollution (PM 2.5 ) and both nonaccidental and cause-specific mortality. Less is known about the long-term health consequences of other traffic pollutants, including ultrafine particles (UFPs, <0.1 μm) and black carbon (BC), which are often present at elevated concentrations in urban areas but are not currently regulated. Knowledge is lacking largely because these pollutants generally are not monitored by governments and vary greatly over small spatial scales, hindering the evaluation of long-term exposures in population-based studies., Methods: We aimed to estimate associations between long-term exposures to outdoor UFPs and BC and nonaccidental and cause-specific mortality in Canada's two largest cities, Montreal and Toronto. We considered several approaches to exposure assessment: (1) land use regression (LUR) models based on large-scale year-long mobile monitoring campaigns combined with detailed land use and traffic information; (2) machine learning (i.e., convolutional neural networks [CNN]) models trained by combining mobile monitoring data with aerial images; and (3) the combined use of these two approaches. We also examined exposure models with and without backcasting based on historical trends in vehicle emissions (to capture potential trends in pollutant concentrations over time) and with and without accounting for neighborhood-level mobility patterns (based on travel demand surveys). These exposure models were linked to members of the Canadian Census Health and Environment Cohorts (CanCHEC) residing in Montreal or Toronto (including census years 1991, 1996, 2001, and 2006) with mortality follow-up from 2001 (or cohort entry for the 2006 cohort) to 2016. Cox proportional hazard models were used to estimate associations between long-term exposures to outdoor UFPs and BC, adjusting for sociodemographic factors and co-pollutants identified as potential confounding factors. Concentration-response relationships for outdoor UFPs and BC were also examined for nonaccidental and cause-specific mortality using smoothing splines., Results: Our cohort study included approximately 1.5 million people with 174,200 nonaccidental deaths observed during the follow-up period. Combined LUR and machine learning model predictions performed slightly better than LUR models alone and were used as the main exposure models in all epidemiological analyses. Long-term exposures to outdoor UFP number concentrations were consistently positively associated with nonaccidental and cause-specific mortality. Importantly, hazard ratios (HRs) for outdoor UFP number concentrations were sensitive to adjustment for UFP size: UFP size was inversely related to number concentrations and independently associated with mortality, resulting in underestimation of mortality risk for outdoor UFP number concentrations when UFP size was excluded. HRs for outdoor UFP number concentrations were robust to backcasting and mobility weighting but varied slightly in analyses using LUR and machine learning models alone, with stronger associations typically observed for the machine learning models. Associations between outdoor BC concentrations and mortality were generally weak or null, but a positive association was observed for cardiovascular mortality., Conclusions: Outdoor UFP number concentrations were consistently associated with increased risks of nonaccidental and cause-specific mortality in Montreal and Toronto. Our results suggest that UFP size should be considered in epidemiological analyses of outdoor UFP number concentrations, as excluding size can lead to an underestimation of health risks. Our results suggest that outdoor UFP number concentrations are positively associated with mortality independent of other outdoor air pollutants, including PM 2.5 mass concentrations and oxidant gases (i.e., nitrogen dioxide [NO 2 ] and ozone [O 3 ]). As outdoor UFPs are currently unregulated, interventions targeting these pollutants could significantly affect population health., (© 2024 Health Effects Institute. All rights reserved.)

Objective: To investigate the black carbon (BC) pollution in the indoor air of typical residential houses in urban areas of Beijing, and to explore the relationship between indoor and outdoor BC concentrations as well as the main influencing factors., Methods: The indoor and outdoor PM&#95;(2.5) samples were collected simultaneously from 33 apartments in the urban areas of Beijing during both the heating season (January to March) and the non-heating season (June to August) in 2016. Subsequently, optical method were employed to analyze BC concentrations in PM&#95;(2.5)samples. The Spearman correlation coefficient (r&#95;s) and the indoor/outdoor (I/O) ratio of BC concentrations were both calculated to characterize the relationship between indoor and outdoor BC concentrations. The factors may influence indoor BC pollution was collected through a questionnaire, including the basic characteristics of the residential buildings and households, smoking, cooking, window opening behavior, the use of air conditioner or air purifier and so on. Additionally, a linear mixed-effects model or multiple linear regression model was applied to identify the main factors influencing the I/O ratio., Results: The(M(P25, P75)) concentrations of indoor and outdoor BC for season-pooled analysis were2.84 (2.59, 3.26)μg/m~3 and 3.08 (2.90, 3.63)μg/m~3, respectively. There were significant seasonal differences in both indoor and outdoor concentrations (P&lt;0.05), with higher levels observed during the heating season compared to the non-heating season. There was a strong correlation between indoor and outdoor BC (r&#95;s=0.74). The correlation during the heating season (r&#95;s=0.78) was stronger than that during the non-heating season (r&#95;s=0.44). The ■ of I/O ratio was 0.90±0.11, with 93.5%(29/31)and 86.7%(26/30) of I/O ratios being less than 1 during the heating season and non-heating season, respectively. Statistical analysis also showed that outdoor BCconcentrations were significantly higher than indoors (P&lt;0.05). In season-pooled analysis, the result of the linear mixed-effects model showed that window opening duration was the most important factor affecting the I/O ratio, explaining 21.3%of the total variation. The I/O ratio increased with longer window opening duration. In season-specific analysis, the characteristics of residential buildings (including building age and floor level) and window opening duration were the main factors affecting the I/O ratio during the heating season and non-heating season, respectively in 2016., Conclusion: Residents in the urban areas of Beijing experienced relatively high indoor levels of BCpollution, but lower than the outdoor concentration during the same period in 2016. The window opening and the characteristics of residential buildings were the most important factors affecting the I/O ratio of BC.

Engineering systems continuously interact with nano-sized particles coming from natural or artificial sources. Considering nano-sized contaminants the detrimental effects are known as soiling and fouling phenomena. The objective of the present work is to gather morphological and three-dimensional quantitative information of discontinuities such as voids and pores within the nano-sized particle layer and in correspondence to the substrate/layer interface using microtomography. Deposits are obtained through impact tests using fine powder (soil and soot), and there are realized on a low-density material substrate characterized by different surface roughness values. The packing process and the discontinuities at the substrate-to-layer interfaces explain macroscopic effects as detachment and spallation but at the same time, give the possibility to understand more in detail the process related to the deposition mechanisms involved in this type of test defining general guidelines to predict the fouling phenomenon and to improve the capability of the removal process. [Display omitted] • Micro-sized soil and soot particles adhere to the substrate forming a compact layer. • X-ray analysis allows the detection of morphological and internal features. • The uniformity of soot particles shape contributes to their stickiness. • Soil deposits show greater volume void at the layer/substrate interface. [ABSTRACT FROM AUTHOR]

Atmospheric aerosol particles are known to have detrimental effects on human health and climate. Black carbon is an important constituent of atmospheric aerosol particulate matter (PM), emitted from incomplete combustion. Source apportionment of BC is very important, to evaluate the influence of different sources. The high-resolution soot particle aerosol mass spectrometer (HR-SP-AMS) instrument uses a laser vaporiser, which allows the real-time detection and characterisation of refractory black carbon (rBC) and its internally mixed particles such as metals, coating species, and rBC subcomponents in the form of HOA + fullerene. In this case study, the soot data were collected by using HR-SP-AMS during Guy Fawkes Night on 5 November 2014. Positive matrix factorisation was applied to positively discriminate between different wood-burning and bonfire sources for the first time, which no existing black carbon source apportionment technique is currently able to do. Along with this, the use of the fullerene signals in differentiating between soot sources and the use of metals as a tracer for fireworks has also been investigated, which did not significantly contribute to the rBC concentrations. The addition of fullerene signals and successful positive matrix factorisation (PMF) application to HR-SP-AMS data apportioned rBC into more than two sources. These bonfire sources are HOA + fullerene, biomass burning organic aerosol, more oxidised oxygenated organic aerosol (MO-OOA), and non-bonfire sources such as hydrocarbon-like OA and domestic burning. The result of correlation analysis between HR-SP-AMS data and previously published Aethalometer, MAAP, and CIMS data provides an effective way of gaining insights into the relationships between the variables and provide a quantitative estimate of the source contributions to the BC budget during this period. This research study is an important demonstration of using HR-SP-AMS for the purpose of BC source apportionment. [ABSTRACT FROM AUTHOR]

• Co, Cu, and Ag - doped Ce-Tb nanofibres were developed using electrospinning. • From FE-SEM analysis, the fibers were porous and had a 100 to 600 nm diameter. • XRD studies displayed a similar trend for cubic fluorite structure. • Raman spectra revealed the presence of a secondary phase in CeTbCo nanofibers. • CeTbCo nanofibers showed better T 50 (347 ℃) than the other nanofibers. Ceria-based materials have an excellent potential to be catalysts for catalytic three-way converters in the automobile industry. Developing Ceria-based nanofiber catalysts can be a significant approach for further exploring the application of these materials in automobile industries. In this study, Ag, Cu, or Co doped Ceria–Terbium nanofibers were synthesized using the electrospinning technique. The obtained nanofiber catalysts were characterized using FE-SEM, XRD, FT-Raman Spectroscopy, and BET-BJH analysis and tested for soot oxidation activity and its kinetics. FE-SEM examination reveals that the obtained nanofibers have a diameter ranging from around 100 to 600 nm. CeTbCo nanofibers exhibited a reduced particle size and enhanced pore formation. The XRD investigation revealed that all the nanofibers displayed a face-centered fluorite structure of CeO 2. In Raman spectroscopy analysis, CeTbCo nanofibes showed the emergence of a secondary Co 3 O 4 phase. The CeTbCo nanofiber catalyst showed better S BET (specific surface area) (66 m2/g) and average pore size (12.08 nm) and total pore volume (0.223 cc/g)), better soot oxidation activity (T 50 = 347 ℃) than other nanofiber catalysts. The CeTbCo nanofiber catalyst exhibited an activation energy of 132 kJ mol−1 and a pre-exponential factor (ln (A)) of 25.63 min−1. [Display omitted] [ABSTRACT FROM AUTHOR]

Counterflow diffusion flame is an attractive platform for fundamental research on kinetics of soot formation. Accurate determination of soot volume fraction in the flame is a prerequisite for in-depth analysis of the sooting characteristics and assessment of predictive soot models. Light extinction has been proven to be an efficient technique for measuring soot volume fraction thanks to its non-intrusiveness and its simple optical setup. Nevertheless, tomographic inversion needs to be performed if spatially resolved soot volume fraction is to be obtained from the measured light extinction data which is essentially a projection along the line-of-sight. In this regard, radial distribution of soot volume fraction would affect the accuracy of the measurement through its influences on the inversion processes. In this work, we show that the curtain flow, which is necessary to avoid the formation of the undesired secondary diffusion flame and to keep the core counterflow from ambient disturbances, has notable effects on spatially resolved soot volume fraction measurements with line-of-sight measurements. In particular, different flow rate settings of the curtain flow can result in different soot distributions at the edges of soot fields: upwards curved, outwards extended, and downwards curved, which may influence the measurement of centerline soot volume fraction distribution. The necessity of tomographic inversion, the minimal region of the projection image necessary for tomographic inversion (when necessary), the quasi-one-dimensional feature of soot distribution, and the sensitivity of measurement to slight flame asymmetry were investigated where possible to determine the most suitable curtain flow configuration for soot volume fraction measurements by light extinction. Recommendations on curtain flow setting are finally made. • Curtain flow notably affect light extinction soot measurement in counterflow flame. • Equal settings for upper/lower curtain flow pose challenges for LE measurement. • CDF with soot edge curving downwards is favorable for LE measurement. [ABSTRACT FROM AUTHOR]

One of the major concerns in high pressure combustion is its high soot yield. An exact and comprehensive mechanism behind this phenomenon, from a chemical kinetics perspective, is still elusive. In this study, a series of pressurized (1–16 atm) co-flow ethylene diffusion sooting flames are simulated with detailed finite-rate chemistry and molecular transport. The experimental maximum soot volume fraction and its scaling law with pressure are well reproduced by the simulations. To extract kinetic information from the complex sooting reacting system, a Soot-based Global Pathway Analysis (SGPA) method is developed to identify the dominant Global Pathways (GPs) from fuel to soot by considering carbon element flux from gaseous species to soot. Using SGPA, the dominance and sensitivity of soot chemical pathways at elevated pressures are revealed. It is found that increasing pressure shifts the first ring Polycyclic Aromatic Hydrocarbon (PAH) formation from C 3 H 3 recombination to reactions involving C 2 H 2. At 1 atm, the production of C 2 H 2 for surface growth is purely controlled by the H-abstraction of C 2 H 4 and C 2 H 3. In contrast, at elevated pressures, the production of C 2 H 2 for surface growth is also influenced by many other reactions including some third body reactions. The SGPA method reveals that the mismatch of predicted PAH with the experimental data at 12 atm is majorly caused by the rate coefficient uncertainty of the reaction C 2 H 2 + A1CH 2 = C 9 H 8 + H. Based on the analysis by SGPA, the mechanism reduction based on Directed Relation Graph with Error Propagation (DRGEP) with A2 and C 2 H 2 as the target species deleted significant species such as C 9 H 8 , C 9 H 7 , incurring inaccurate soot field prediction. It is also found that the combined dominance of GPs with heavier PAH species (A4-A7) is even greater than the most dominant GP at the flame wing regions, indicating that heavier PAH species play critical roles for soot nucleation and condensation, especially at the flame wing regions. [ABSTRACT FROM AUTHOR]