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Environmental Research Jan 2024We used black carbon data from a mobile monitoring campaign in Oakland, USA measuring street segments up to 40 times and compared a data-only, LUR model and mixed-model...
We used black carbon data from a mobile monitoring campaign in Oakland, USA measuring street segments up to 40 times and compared a data-only, LUR model and mixed-model approach with a long-term average, represented by the average concentration based on 40 drive days on that street segment. The mixed model outperformed the data-only and LUR model estimates, with 80% explained variance after 5 drive days and 90% after 14 drive days. The data-only approach needed 8 and 15 to achieve an explained variance of 80% and 90%, respectively, The LUR model never achieved an explained variance higher than 70%. The mixed model is a scalable approach, as it can be used before all street segments in a domain are measured by developing a LUR model and adds information with increasing repeats per street segment.
Topics: Air Pollutants; Air Pollution; Environmental Monitoring; Soot; Particulate Matter
PubMed: 37865326
DOI: 10.1016/j.envres.2023.117457 -
Environment International Nov 2023Air pollution has been linked to mortality, but there are few studies examining the association with different exposure time windows spanning across several decades. The...
BACKGROUND
Air pollution has been linked to mortality, but there are few studies examining the association with different exposure time windows spanning across several decades. The evidence for the effects of green space and mortality is contradictory.
OBJECTIVE
We investigated all-cause mortality in relation to exposure to particulate matter (PM and PM), black carbon (BC), nitrogen dioxide (NO), ozone (O) and greenness (normalized difference vegetation index - NDVI) across different exposure time windows.
METHODS
The exposure assessment was based on a combination of the Danish Eulerian Hemispheric Model and the Urban Background Model for the years 1990, 2000 and 2010. The analysis included a complete case dataset with 9,135 participants from the third Respiratory Health in Northern Europe study (RHINE III), aged 40-65 years in 2010, with mortality follow-up to 2021. We performed Cox proportional hazard models, adjusting for potential confounders.
RESULTS
Altogether, 327 (3.6 %) persons died in the period 2010-2021. Increased exposures in 1990 of PM, PM, BC and NO were associated with increased all-cause mortality hazard ratios of 1.40 (95 % CI1.04-1.87 per 5 μg/m), 1.33 (95 % CI: 1.02-1.74 per 10 μg/m), 1.16 (95 % CI: 0.98-1.38 per 0.4 μg/m) and 1.17 (95 % CI: 0.92-1.50 per 10 μg/m), respectively. No statistically significant associations were observed between air pollution and mortality in other time windows. O showed an inverse association with mortality, while no association was observed between greenness and mortality. Adjusting for NDVI increased the hazard ratios for PM, PM, BC and NO exposures in 1990. We did not find significant interactions between greenness and air pollution metrics.
CONCLUSION
Long term exposure to even low levels of air pollution is associated with mortality. Opening up for a long latency period, our findings indicate that air pollution exposures over time may be even more harmful than anticipated.
Topics: Humans; Nitrogen Dioxide; Air Pollution; Ozone; Europe; Particulate Matter; Soot; Air Pollutants; Environmental Exposure
PubMed: 37857189
DOI: 10.1016/j.envint.2023.108257 -
ACS Nano Nov 2023Nanoparticles (NPs) released from engineered materials or combustion processes as well as persistent herpesvirus infection are omnipresent and are associated with...
Nanoparticles (NPs) released from engineered materials or combustion processes as well as persistent herpesvirus infection are omnipresent and are associated with chronic lung diseases. Previously, we showed that pulmonary exposure of a single dose of soot-like carbonaceous NPs (CNPs) or fiber-shaped double-walled carbon nanotubes (DWCNTs) induced an increase of lytic virus protein expression in mouse lungs latently infected with murine γ-herpesvirus 68 (MHV-68), with a similar pattern to acute infection suggesting virus reactivation. Here we investigate the effects of a more relevant repeated NP exposure on lung disease development as well as herpesvirus reactivation mechanistically and suggest an avenue for therapeutic prevention. In the MHV-68 mouse model, progressive lung inflammation and emphysema-like injury were detected 1 week after repetitive CNP and DWCNT exposure. NPs reactivated the latent herpesvirus mainly in CD11b+ macrophages in the lungs. , in persistently MHV-68 infected bone marrow-derived macrophages, ERK1/2, JNK, and p38 MAPK were rapidly activated after CNP and DWCNT exposure, followed by viral gene expression and increased viral titer but without generating a pro-inflammatory signature. Pharmacological inhibition of p38 activation abrogated CNP- but not DWCNT-triggered virus reactivation , and inhibitor pretreatment of latently infected mice attenuated CNP-exposure-induced pulmonary MHV-68 reactivation. Our findings suggest a crucial contribution of particle-exposure-triggered herpesvirus reactivation for nanomaterial exposure or air pollution related lung emphysema development, and pharmacological p38 inhibition might serve as a protective target to alleviate air pollution related chronic lung disease exacerbations. Because of the required precondition of latent infection described here, the use of single hit models might have severe limitations when assessing the respiratory toxicity of nanoparticle exposure.
Topics: Animals; Mice; Nanotubes, Carbon; Lung; Pneumonia; Nanoparticles; Emphysema
PubMed: 37856828
DOI: 10.1021/acsnano.3c04111 -
Communications Chemistry Oct 2023Polycyclic aromatic hydrocarbons are the main precursors to soot particles in combustion systems. A lack of direct experimental evidence has led to controversial...
Polycyclic aromatic hydrocarbons are the main precursors to soot particles in combustion systems. A lack of direct experimental evidence has led to controversial theoretical explanations for the transition from gas-phase species to organic soot clusters. This work focuses on sampling infant soot particles from well-defined flames followed by analysis using state-of-the-art mass spectrometry. We found that PAH molecules present in soot particles are all stabilomers. Kinetic Monte Carlo simulations and thermodynamic stability calculations further identify the detected PAHs as peri-condensed and without aliphatic chains. Van der Waals forces can easily link PAHs of such size and shape to form PAH dimers and larger clusters under the specified flame conditions. Our results provide direct experimental evidence that soot inception is initiated by a physical process under typical flame conditions. This work improves our understanding of aerosol particulates, which has implications for their environmental and climate change impacts.
PubMed: 37845500
DOI: 10.1038/s42004-023-01017-x -
RSC Advances Oct 2023As an emission control device for diesel engines, DPF plays an important role in reducing particulate matter emissions. The research work on soot thermal aging will help...
As an emission control device for diesel engines, DPF plays an important role in reducing particulate matter emissions. The research work on soot thermal aging will help optimize DPF regeneration strategies, improve regeneration efficiency, and promote the progress of engine emission control technology. In order to explore the influence of thermal aging under different atmospheres on particle physicochemical characteristics from diesel engines, the oxidation activity of soot particles after different thermal aging were evaluated by thermogravimetric analysis (TGA) and pyrolysis kinetics calculation, and the distribution of functional groups and elemental composition on the soot surface were investigated by FT-IR and XPS analysis. Additionally, the microstructure and graphitization degree of basic carbon with O/NO aging were analyzed by HRTEM technology. The results show that the ignition temperature and activation energy of soot significantly increase after thermal aging, and their lowest values are 569 °C and 165.29 kJ mol in O/NO/N atmosphere, respectively. The branching degree and content of hydrocarbon functional groups on the soot surface decrease after thermal aging, and the relative content of hydrocarbon functional groups with NO participating in thermal aging is the highest. The content of O element on the soot surface decreases after thermal aging, and the maximum O/C molar ratio of soot particles after thermal aging in O/NO/N atmosphere is 0.15. After thermal aging, the hybridization degree of carbon atoms and the content of -C-OH and -C[double bond, length as m-dash]O functional groups on the soot surface decrease. The content of -C-OH functional group decreases to 0.21% and 0.53% respectively after the addition of O and NO in the thermal aging atmosphere, while the content of -C[double bond, length as m-dash]O functional group increases to 4.98% and 5.98% respectively. In addition, the layer spacing and microcrystalline curvature of basic carbon particles decrease after thermal aging, however, the microcrystalline size and the graphitization degree increase.
PubMed: 37842675
DOI: 10.1039/d3ra05340g -
Molecules (Basel, Switzerland) Sep 2023Soot formation is an inevitable consequence of the combustion of carbonaceous fuels in environments rich in reducing agents. Efficient management of pollution in various... (Review)
Review
Soot formation is an inevitable consequence of the combustion of carbonaceous fuels in environments rich in reducing agents. Efficient management of pollution in various contexts, such as industrial fires, vehicle engines, and similar applications, relies heavily on the subsequent oxidation of soot particles. Among the oxidizing agents employed for this purpose, oxygen, carbon dioxide, water vapor, and nitrogen dioxide have all demonstrated effectiveness. The scientific framework of this research can be elucidated through the following key aspects: (i) This review situates itself within the broader context of pollution management, emphasizing the importance of effective soot oxidation in reducing emissions and mitigating environmental impacts. (ii) The central research question of this study pertains to the identification and evaluation of catalysts for soot oxidation, with a specific emphasis on ceria-based catalysts. The formulation of this research question arises from the need to enhance our understanding of catalytic mechanisms and their application in environmental remediation. This question serves as the guiding principle that directs the research methodology. (iii) This review seeks to investigate the catalytic mechanisms involved in soot oxidation. (iv) This review highlights the efficacy of ceria-based catalysts as well as other types of catalysts in soot oxidation and elucidate the underlying mechanistic strategies. The significance of these findings is discussed in the context of pollution management and environmental sustainability. This study contributes to the advancement of knowledge in the field of catalysis and provides valuable insights for the development of effective strategies to combat air pollution, ultimately promoting a cleaner and healthier environment.
PubMed: 37836727
DOI: 10.3390/molecules28196884 -
Nature Communications Oct 2023Emission factors and inventories of black carbon (BC) aerosols are crucial for estimating their adverse atmospheric effect. However, it is imperative to separate BC...
Emission factors and inventories of black carbon (BC) aerosols are crucial for estimating their adverse atmospheric effect. However, it is imperative to separate BC emissions into char and soot subgroups due to their significantly different physicochemical properties and potential effects. Here, we present a substantial dataset of char and soot emission factors derived from field and laboratory measurements. Based on the latest results of the char-to-soot ratio, we further reconstructed the emission inventories of char and soot for the years 1960-2017 in China. Our findings indicate that char dominates annual BC emissions and its huge historical reduction, which can be attributable to the rapid changes in energy structure, combustion technology and emission standards in recent decades. Our results suggest that further BC emission reductions in both China and the world should focus on char, which mainly derives from lower-temperature combustion and is easier to decrease compared to soot.
PubMed: 37833278
DOI: 10.1038/s41467-023-42192-8 -
ACS Omega Oct 2023By effective utilization of the dynamic mesh and coordinate transformation techniques, an ultrasonic horn is physically integrated in the chamber of an internal...
By effective utilization of the dynamic mesh and coordinate transformation techniques, an ultrasonic horn is physically integrated in the chamber of an internal combustion engine. The consequences of multiple ultrasonic-fed strategies on the flow field, combustion process, and emission formation under the same working conditions are studied by numerical simulation. Based precisely on the bench test data, GT-Power and CONVERGE set up the original engine one-dimension (1d) and three-dimension (3d) simulation models. The chamber pressure and heat release rate of the 1d and 3d models under a full load condition of 3000 r·min were validated, and the maximum relative error is less than 5%, proving the accuracy of the model. By reforming the 3d numerical model, ultrasonics is added to the gasoline engine's combustion chamber. Six different ultrasonic-fed schemes with 20 kHz amplitude of 30-300 μm are typically selected for in-depth research. The larger the amplitude, the stronger the turbulent kinetic energy (TKE), and the maximum TKE exceeds 46.6% at the ignition time. Stronger TKE can energetically encourage the generation of OH, O, and H radicals and improve the combustion reaction rate, and the peak pressure () is increased by 1.9 MPa compared with scheme No. However, NO and HC emissions gradually increase, reaching a maximum of 32.4 and 43.8%, respectively, while CO and soot emissions decrease, reaching a maximum of 11.4 and 11%, respectively. Four groups of ultrasonic-fed schemes with an amplitude of 100 μm and frequency of 20-50 kHz are scientifically studied. The findings indicated that the TKE level steadily increases as the frequency increases and the in-cylinder TKE increases by 16.4% at ignition time. The increase in ultrasonic frequency can promote the generation of active free radicals and meaningfully improve the combustion reaction rate to a certain extent. The can be increased up to 1 MPa compared with scheme No. At the same time, the NO, HC, and soot also increased considerably, reaching 31.8, 17.9, and 21.9%, respectively. The CO showed a downward trend but gradually slowed, with a maximum decline of 6.5% at 20 kHz. The above simulation analysis is based on the full load condition of 3000 r·min, sufficiently proving that ultrasonics has a regulation effect on emissions and can achieve specific emissions through later optimization.
PubMed: 37810679
DOI: 10.1021/acsomega.3c05415 -
Heliyon Sep 2023This work investigated and compared the impact on performance and emission characteristics of diesel engine fueled with five different proportions of biodiesel blends....
This work investigated and compared the impact on performance and emission characteristics of diesel engine fueled with five different proportions of biodiesel blends. Firstly, the three-dimensional simulation software CONVERGE was used to create a 3D simulation model of in-cylinder combustion for a diesel engine. Secondly, the experimental data of cylinder pressure and NO emissions at 50% and 100% loads were employed to verify the simulation model. Finally, the combustion processes of blends with proportions of 0%, 5%, 10%, 15%, and 20% biodiesel were simulated and compared by using the model. The study showed that the brake thermal efficiencies (BTEs) of biodiesel blends with 5%, 10%, 15%, and 20% of biodiesel were increased by 1.24%, 1.89%, 3.13%, and 3.82% at 50% load, respectively, compared with pure diesel. In addition, the soot emissions were decreased by 1.20%, 2.64%, 3.88%, and 4.65%, respectively. However, as the proportion of biodiesel in the biodiesel blends increased, the brake specific fuel consumption (BSFC) and NO emissions increased. At 50% load, the BSFCs of biodiesel blends with 5%, 10%, 15%, and 20% of biodiesel increased by 0.61%, 1.34%, 1.42%, and 2.17%, respectively, compared with pure diesel. Additionally, the brake powers (BPs) were decreased by 0.64%, 1.31%, 1.88%, and 2.62% at 100% load, respectively.
PubMed: 37809447
DOI: 10.1016/j.heliyon.2023.e19196 -
Nature Communications Oct 2023Soot generation is a major challenge in industries. The elimination of soot is particularly crucial to reduce pollutant emissions and boost carbon conversion. The...
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.
PubMed: 37802991
DOI: 10.1038/s41467-023-41726-4