Formation Of PM Research Articles

Effect of primary air and coal properties on the formation of fine mode particles during low NOx gasification-combustion of coal in a self-sustaining furnace

Gasification-combustion technology can reduce NOx while the formation characteristics of fine mode PM is unclear. This research studied the impact of the excess air coefficient (αg) of the gasifier and the properties of coal on the formation and evolution of fine mode PM. The experiment was conducted on a self-sustaining furnace consisting of a gasifier where pyrolysis/gasification occurs and a combustion chamber where burnout of gasification gas and char occurs. The results showed that fine mode PM and NOx can be synergistically reduced by optimizing αg during gasification-combustion. A low or high αg can lead to a high furnace temperature in the gasifier or combustion chamber, respectively. Elimination of high temperature is crucial to reduce element vaporization which promotes the formation of fine mode PM. Additionally, an optimized combination of furnace temperature and reducing atmosphere in the gasifier can decrease NOx. The optimal αg was 0.32 for bituminous coal (BC). Fine mode PM generated from gasification-combustion of BC, lean coal (LC), and semi-char (SC) mainly consists of Ca, Si, Fe, and S. The vaporization of element from LC and BC primarily occurs during char combustion in the combustion chamber, while the vaporization of element from SC occurs almost equally in the gasifier and combustion chamber.

A Simulation Study on a Premixed-charge Compression Ignition Mode-based Engine Using a Blend of Biodiesel/Diesel Fuel under a Split Injection Strategy

Environmental pollution from transportation means and natural resource degradation are the top concern globally. According to statistics, NOx and PM emissions from vehicles account for 70% of total emissions in urban areas. Therefore, finding solutions to reduce NOx and PM emissions is necessary. Changing the engine's internal combustion method is considered promising and influential among the known solutions. One of the research directions is a combustion engine using the Premixed Charge Compression Ignition (PCCI) method combined with biofuels to improve the mixture formation and combustion process, reducing NOx and PM emissions. Therefore, this study presents the mechanism of the formation of PM and NOx emissions in the traditional combustion and the low-temperature combustion process of internal combustion engines. Besides, the theoretical basis of flame spread during combustion is also introduced. The key feature of this research is that it has modeled the combustion process in diesel engines under the PCCI modes. This was accomplished using blends of waste cooking oil (WCO)-based biodiesel and diesel fuel, as well as the ANSYS Fluent software. The results showed that PCCI combustion using B20 fuel can significantly reduce NOx and PM emissions, although HC and CO emissions tend to increase, and thermal efficiency tends to decrease. In further studies, different modes of the PCCI combustion process should be thoroughly examined so that this process can be implemented in practice to reduce pollutant emissions.

Effects of preheating temperature, O2 distribution concentration and combustion temperature on the formation of PM during preheating-low NO combustion

Clarifying the mechanism of multi-mode PM formation during pulverized coal preheating-combustion is expected to facilitate the synergistic control of NO and PM, and a significant low carbon way to achieve clean combustion. In this study, combustion experiments under different preheating-combustion conditions were conducted in a preheating-combustion furnace. Based on this, a system coupling design was explored by combining preheating-combustion with air staging. The results demonstrated a significant simultaneous reduction in both PM and NO during preheating-combustion, achieving a synergistic control of PM and NO emissions. With an increase in preheating temperature(Tp), the NO formation decreased, while the PM10 formation increased. Increasing the excess air coefficient(αp) reduced the PM10 formation, while the NO exhibited a trend of initially decreasing and then increasing. The impact of the combustion temperature(Tc) on NO and PM was more pronounced, especially with a significant increase of 80.59% in the PM0.3 (from 1300 K to 1700 K). Furthermore, the effect of the interaction of the three factors on NO: αp and Tc > αp and Tp > Tp and Tc. After coupling preheating-combustion with air staging, the formation of NO and PM0.3 decreased by 33.27% and 17.43%, respectively, compared to the preheating-combustion baseline.

Mist cannon trucks can exacerbate the formation of water-soluble organic aerosol and PM2.5 pollution in the road environment

Abstract. Mist cannon trucks have been widely applied in megacities in China to reduce the road dust, since they are considered to be more water saving and efficient than the traditional sprinkling trucks. However, their effect on the formation of water-soluble organic compounds and the pollution control of fine particles (PM2.5) remains unknown. We characterized the variations of chemical compositions in PM2.5 collected on the road sides during the simulated operations of mist cannon truck and traditional sprinkling truck via Fourier transform ion cyclotron resonance mass spectrometry and ion chromatography. The mass concentrations of water-soluble organic carbon in PM2.5 showed a significant increase (62 %–70 %) after air spraying. Furthermore, we found that water-soluble organic compounds, particularly organic nitrates, increased significantly via the interactions of reactive gas-phase organics, atmospheric oxidants and aerosol liquid water after air spraying, although the air spraying had a better effect on suppressing road dust than the ground aspersion. Moreover, the formation of PM2.5 on the road segment where the mist cannon truck passed by was promoted, with an increase of up to 13 % in mass concentration after 25–35 min, on average. Thus, the application of mist cannon trucks potentially worsens the road atmospheric environment through the increase in PM2.5 levels and the production of a large number of water-soluble organic compounds in PM2.5. The overall results provide not only valuable insights to the formation processes of water-soluble organic compounds associated with aerosol liquid water in the road environment but also management strategies to regulate the operation of mist cannon trucks in China.

Effect of External Mineral Addition on PM Generated from Zhundong Coal Combustion

The effect of intrinsic metal mineral elements in the combustion process of pulverized coal on the formation and transformation mechanism of PM was investigated in a drop-tube furnace in air atmospheres at 1200 °C, which laid a solid foundation for the control of particulate pollutants. The results show that reducing the evaporation of mineral elements or the generated PM1 aggregating to form PM1–10 or particles bigger than 10µm can reduce the emission of PM1 in the coal combustion process. The amount of PM0.2, PM0.2–1, PM1–2.5 and PM2.5 produced by the raw coal-carrying Mg are reduced by 36.7%, 17.4%, 24.6% and 21.6%, respectively. The amount of PM10 is almost unchanged. The addition of Mg increases the viscosity of submicron particles effectively, making it easier to aggregate and bond together to form ultra-micron particles. The amount of PM0.2, PM0.2–1, PM1–2.5, PM2.5 and PM10 produced by the raw coal-carrying Ca are reduced by 36.3%, 33.0%, 42.8%, 38% and 17.7%, respectively. The effect of adding Ca compounds on the particles is better than that of Mg. The amount of PM0.2, PM0.2–1, PM1–2.5, PM2.5 and PM10 produced by the raw coal-carrying Fe are reduced by 15.6%, 16.2%, 31.1%, 22.4% and 5%, respectively. While the production of PM2.5–10 increased from 0.17 mg/g to 0.34 mg/g, it is clear that a significant fraction of the submicron particles produced during the combustion of the raw coal-carrying Fe are transformed into ultra-micron particles. After comparing the particulate matter produced by raw coal-carrying Mg, Ca and Fe, it shows that the addition of these three elements can effectively reduce the ash melting point, so that during the process of coal combustion, part of the sub-micron are transformed into ultra-micron particles, which are easy to remove.

Reducing the central mode particulate matter in coal combustion by additives: Impacts of nano Al2O3 and TiO2 addition

Current additives generally have lower efficiency on reducing PM2.5 than the ultrafine PM as they could not effectively reduce the central PM. To find additives that could effectively reduce the formation of central PM, two kinds of nano particles (namely Al2O3 and TiO2) were screened out, and coal combustion with the nano additives were performed. The generated PM10 were sampled to characterize their particle size distribution, mass yield, size-resolved composition and micro morphology with element map. The results showed that adding a small dose (0.6%) of nano Al2O3 and TiO2 reduced the mass yields of PM0.1-2.5 (i.e., central PM) and PM2.5 by 24.38%-26.06% and 12.85%-19.59% respectively, indicating quite different PM reduction characteristics than the conventional clay-mineral-derived additives. The nano additives on the fuel surface promoted the melting and coalescence of small ash particles, promoting their migration into coarse PM. Moreover, the added nano additives covering the coal particle scavenged the mineral vapors releasing from the coal particle during its pyrolysis/combustion, and thereby reduced their migration into central PM via the following heterogenous condensation. Finally, the added nano additives mainly migrated into the large ash particles and enhanced heterogeneous condensation/reaction of the released mineral vapor via providing larger specific surface area.

Effects of nighttime heterogeneous reactions on the formation of secondary aerosols and ozone in the Pearl River Delta

<p indent="0mm">Fine particulate matter (PM_2.5) and ozone (O₃) are currently the most concerning air pollutants. Long-term exposure to PM_2.5 and O₃ can induce cardiovascular diseases, presbyopia, and preterm birth. Acute exposure to PM_2.5 and O₃ can also result in hypertension and decreased heart rate variability. In recent years, PM_2.5 pollution abatement in China has achieved remarkable results, but O₃ pollution issues have emerged. In the troposphere, O₃ and PM_2.5 have a close association, i.e., O₃ can oxidize gaseous precursors to form sulfate, nitrate, ammonium and secondary organic aerosols in PM_2.5, and PM_2.5 affects the generation and removal of O₃ by providing surfaces for heterogeneous reactions. Recent studies show that PM_2.5 and O₃ have a significant positive correlation in the photochemically active season in the Pearl River Delta (PRD) region. However, it is still difficult to achieve cooperative control for PM_2.5 and O₃ due to our limited knowledge of their coupling relationship. To date, most studies have focused on the photochemical mechanism in the daytime, and our understanding of the chemical processes at night is insufficient. As an important reactive intermediate, N₂O₅ mainly accumulates through the nocturnal reaction of NO₂ and O₃ and is removed by heterogeneous reactions to produce HNO₃. These processes directly affect ozone production and particulate matter formation. In addition to losing NO_{<italic>x</italic>}, the heterogeneous reaction of N₂O₅ would lead to particulate nitrate formation and photolabile species (i.e., ClNO₂) release. ClNO₂ is a reservoir of NO₂ and chlorine, providing a connection between nitrogen oxide pollution and halogen activation. The formation of ClNO₂ represents an activation process of chlorine from the aerosol phase to the gas phase. ClNO₂ photolysis releases chlorine radicals and oxidizes VOCs, which could increase radical levels and promote ozone formation. Moreover, NO₂ released via ClNO₂ photolysis also promotes O₃ formation in the morning. In coastal areas, sufficient particle chlorine in aerosols might be driven by sea salt chloride interactions, which lead to the formation of ClNO₂. Therefore, with high concentrations of nitrogen oxides, nighttime heterogeneous N₂O₅ reactions would make a substantial contribution to PM_2.5 and O₃ in coastal regions. Although several studies have shown that heterogeneous N₂O₅ reactions play an important role in the formation of PM_2.5 and O₃, related observations in China are limited. In this study, N₂O₅ and ClNO₂ were measured in Shenzhen during the season with severe ozone pollution in October 2018. Iodine chemical ionization time-of-flight mass spectrometry (TOF-CIMS, Aerodyne Inc.) was used to measure N₂O₅ and ClNO₂. Based on collocated measurements of gas- and particle-phase pollutants, we quantitatively calculated the nighttime heterogeneous reactions and assessed their reactivities. The results show that the highest concentrations of N₂O₅ and ClNO₂ could be up to 1524 and 477 pptv <sc>(5 min</sc> average, 1 pptv = <sc>1 pptv=10^–3 mm³/m³)),</sc> respectively, and they were affected by precursors. The concentrations of N₂O₅ and ClNO₂ had pronounced peaks from sunset to sunrise. The nitrate formed via N₂O₅ reactions at night contributed 24%−60% of the total nighttime nitrate particles. In particular, the concentration of ClNO₂ had a noticeable peak in the morning, and the photolysis of ClNO₂ generated Cl radicals, which quickly removed alkanes, and the maximum removal efficiency was 2−3 times higher than that of OH radicals. In addition, the diurnal variation in VOCs with different reactivities also implies that chlorine radicals participate in the VOC oxidation cycle in the morning. This reflects that Cl radical-induced oxidation reactions could promote the generation of ozone and secondary organic aerosols through the HO_{<italic>x</italic>} radical cycle. Our study shows that active nighttime heterogeneous reactions can significantly promote the formation of PM_2.5 and O₃ in the coastal areas of the PRD region. Thus, it is urgent to call for more studies in the future to coordinate the control of PM_2.5 and O₃ in the PRD region.

Atmospheric Age Distribution of Primary and Secondary Inorganic Aerosols in a Polluted Atmosphere.

The community multiscale air quality (CMAQ) model was modified to track the evolution of the atmospheric age (τ) distribution of primary particulate matter (PPM) and secondary inorganic aerosol components (nitrate, sulfate, and ammonium ion, NSA). The modified CMAQ gas and aerosol mechanisms represent the same species emitted at different times as an age-resolved mixture, using multiple age-tagged variables and a dynamic age-bin advancing scheme. The model was applied to study the spatial and temporal evolution of τ for PPM and NSA in January 2013 to understand the formation and regional transport of PM and the precursor gases during severe winter pollution episodes in China. The results showed that increases in PPM and NSA concentrations during high pollution periods in polluted urban areas were typically associated with increases in the mean atmospheric age (τ̅) due to the accumulation of local emissions and regional transport of aged pollutants. Some of the rapid sulfate growth events at the beginning of multiday air pollution episodes were driven by regional transport of aged particles. In heavily polluted cities, while most of the monthly average PPM had τ less than 10 h, more than half of the sulfate had τ greater than 20-30 h. Regional distributions showed that very aged sulfate particles with τ > 96 h accounted for a significant portion of the total sulfate and had a very broad spatial distribution. However, aged ammonium ions had very low concentrations. Aged nitrate also had lower concentrations and more limited spatial distributions than sulfate due to differences in the atmospheric lifetime between SO2 and NOx. The estimated NOx lifetime of approximately ∼24 h in China agrees with a satellite-based estimation of 21 h. Potential applications of the age distribution analysis include evaluating the impacts of meteorology on air quality and developing short-term emission control strategies.

Decreasing Emissions of PM by Vehicles through Brake Energy Recovery

A significant contribution to the formation of PM 10 and PM 2.5 in the atmosphere of large cities is made by frequent braking by friction brake mechanisms. The author considers electrodynamic regenerative braking as one of the advantages of hybrid and electric vehicles, which can significantly reduce the formation of PM during braking. Using experimental studies, the author estimates the wear of the brake pads of the same vehicle during regenerative and mechanical braking. During the experiment, a series of acceleration and braking cycles was performed from a given speed to a complete stop, after which the friction brake pads were dismantled and their weight was measured. Then, during the calculation and comparison, the PM emission reduction is determined in a test with braking energy recovery.

Thermodynamics of the P-type Ferryl Form of Bovine Cytochrome c Oxidase.

Several ferryl states of the catalytic heme a3-CuB center of the respiratory cytochrome c oxidases (CcOs) are observed during the reduction of O2 to H2O. One of the P-type ferryl forms, PM, is produced by the reaction of the two-electron reduced CcO with O2. In this state, the heme a3 iron is in the ferryl state and a free radical should be also present at the catalytic center. However, the energetics of the PM formation has not been experimentally established yet. Here, the generation of PM by the reaction of oxidized bovine CcO (O) with one molecule of H2O2 was investigated by the isothermal titration calorimetry and UV-Vis absorption spectroscopy. Two kinetic phases, corresponding to the formation of PM and its endogenous conversion back to O, were resolved by both methods. The ΔH of the entire process (-66 kcal/mol H2O2) was larger than the heat (-50.8 kcal/mol O2) liberated during O2 reduction by ferrocytochrome c (pH 8, 25°C). Interestingly, ΔH of the first phase (-32 kcal/mol ferryl state) far exceeds the enthalpy of the PM production. The data indicate that during the first phase, the radical in PM is quenched and spectrally similar second P-type ferryl form (PR) is produced. Additionally, it was shown that the entropy contribution to the Gibbs energy change (ΔG = -46 kcal/mol O2) during the catalytic reduction of O2 by ferrocytochrome c is negligible (-0.7 cal·mol-1·K-1).

The characteristics of carbonaceous particles down to the nanoparticle range in Rangsit city in the Bangkok Metropolitan Region, Thailand.

Atmospheric size-classified particles in sizes ranging from small to nanoparticles (PM0.1) are reported for Rangsit City in the Bangkok Metropolitan Region (BMR) of Thailand, for October 2019 (wet season) and January-February 2020 (dry season). The sampling involved the use of a PM0.1 cascade air sampler to determine the mass concentration. The PMs consisted of six stages including TSP-PM10, PM2.5-10, PM1.0-2.5, PM0.5-1.0, PM0.5-1.0 and PM0.1. Elemental carbon (EC) and organic carbon (OC) were evaluated by a carbon analyzer following the IMPROVE_TOR protocol. The average PM0.1 mass concentrations were found to be 13.47±0.79 (wet season) and 18.88±3.99 (dry season) μg/m3, respectively. The average OC/EC ratio for the rainy season was lower than that in the dry season. The char-EC/soot-EC ratios were consistently below 1 for the PM0.1 fraction in both seasons indicating that vehicular traffic appeared to be the main emission source. However, the influence of open biomass burning on fine and coarse PM particles on local air pollution was found to be an important issue during the wet season. In addition, long-range transport from other countries may also contribute to the carbon content in the Bangkok Metropolitan Region (BMR) atmosphere during the dry season. The higher secondary organic carbon to organic carbon (SOC/OC) ratio in the dry season is indicative of the contribution of secondary sources to the formation of PM, especially finer particles. A strong correlation between OC and EC in nanoparticles was found, indicating that they are derived from sources of constant emission, likely the diesel engines. Conversely, the OC and EC correlation for other size-specific PMs decreased during the dry season, indicating that these emission sources were more varied.

Assessment of the Near-Road (monitoring) Network including comparison with nearby monitors within U.S. cities

Emissions from on-road mobile sources have historically been an important anthropogenic contributor to ambient air pollution leading to high levels of air pollution near major roadways. The U.S. EPA recently implemented the Near-Road (monitoring) Network to measure NO2 concentrations by high-traffic roadways in urban centers throughout the U.S., as these locations were believed to characterize worst-case human exposures to traffic-related air pollutants. Many near-road sites also include PM2.5 and CO measurements, which along with the NO2 observations, were compared in a pairwise manner against non-near-road monitors located within the city-scale boundary. After controlling for primary emissions from the target highways, we found the PM2.5 concentration difference (i.e. near-road concentration minus non-near-road site concentration) between the near-road and non-near-road urban sites to be δ = 0.42 µg m−3( H0: µdiff = 0; Ha: µdiff > 0 (µnon-near-road > µnear-road); p = 0.051; α = 0.05, 95% CI: −0.08–0.90 µg m−3, n = 35 comparisons). NO2 and CO levels were on average higher at the near-road sites compared to the non-near-road urban sites by 5.0 (95% CI: 3.4–6.5) ppb (n = 44 comparisons) and 9.2 × 10−2( 95% CI: 0.04–0.14) ppm (n = 42 comparisons), respectively. The average PM2.5 difference found here is 5%, and at 14 of the 35 (∼40%) urban monitor comparisons and 28 of the 72 (∼39%) overall comparisons, PM2.5 is actually higher at the non-near-road site relative to its near-road pair. Cleaner vehicle fleets, formation of secondary PM from on-road emissions occurring downwind (i.e. away from the road), decreased secondary organic aerosol (SOA) formation rates in the near-road environment, the prevalence of other low-volume vehicular and local, non-vehicular sources of emissions at the non-near-road sites (e.g. railyards, truck yards, ports, biomass-fueled heating, backyard barbecuing, and commercial cooking, etc) and local meteorology (e.g. wind speed and wind direction) explain this finding. The wintertime PM2.5 concentration difference was higher than the other seasons, likely a result of higher primary PM2.5 tailpipe emissions and lower temperatures that both reduced near-road PM volatility and decreased photochemical activity resulting in lower SOA production at the urban scale. Further, all near-road NO2 and CO concentrations were below the annual and hourly NAAQS, while eight (most of which were in wildfire-prone locations) of the 94 PM2.5 sites used in this study were above the annual National Ambient Air Quality Standards. In addition, strong agreement with both annual average daily traffic and fleet-equivalent AADT were found for near-road NO2 and CO concentrations, while weaker, but still positive relationships were found for near-road PM2.5 levels. Lastly, same observational data was used to assess on-road mobile source emission estimates from the EPA National Emission Inventory, and analysis of the observations are in rough agreement with the current ratio of NOx to CO emissions from on-road mobile sources.

Day–night variation and size distribution of water-soluble inorganic ions in particulate matter in Ulsan, South Korea

In the present study, 11 size classes of particulate matter were collected from a semi-rural site in the industrial city of Ulsan, South Korea in 2019 to investigate the size distribution and day–night variation of water-soluble inorganic ions (WSIIs). Approximately 70% of the detected WSIIs were found in fine particles, with Na+, Ca2+, Cl−, and NO3− dominant (~70%) in coarse particles and SO42−, NO3−, and NH4+ (SNA) dominant (~70%) in fine particles. Monthly variation in total WSIIs was observed, with the highest average concentration found in April for both coarse (2.71 μg/m3) and fine particles (5.75 μg/m3). Given that this month is characterized by prevailing southeasterly winds, these high levels may represent the adverse effects of industrial activity. Coefficients of divergence for individual WSIIs exhibited large variability, which is indicative of significant day–night differences in meteorology, chemistry, and source contributions. The size distributions of Na+, K+, F−, Cl−, NO3−, and SO42− were bimodal, while Mg2+, Ca2+, and NH4+ were unimodal. Peaks were generally found at 1.8–5.6 μm and 0.18–0.56 μm for coarse and fine particles, respectively. By plotting the linear relationship between the mole charge ratios of SNA, we found that coarse NO3− particles were mainly the result of heterogeneous reactions between HNO3 and sea salts or crustal species, while the homogeneous reaction of HNO3 and NH3 played a crucial role in the formation of fine NO3− particles. In conclusion, though day–night variation in WSIIs was apparent, especially in SNA, the formation pathways for both coarse and fine particles were similar for day and night. Based on the verification of the formation mechanisms for WSIIs at this semi-rural site, the influence of industrial activity on the secondary formation of PM in urban and industrial areas can be investigated further.

A novel CO2-water leaching method for AAEM removal from coal: Suppression of PM formation and release during Zhundong coal combustion

Zhundong coalfield is one of the core coalfields in Xinjiang, China. Due to its high alkali and alkaline earth metal (AAEM) contents, large amounts of PM were released during Zhundong coal combustion, causing serious environmental pollution. In this paper, a novel CO2-water leaching method was proposed to suppress the PM formation and release during Zhundong coal combustion. The results showed the CO2-water leaching effectively removed water insoluble minerals from coal, such as Na, Ca, Mg, Cl and S, and significantly reduced the PM formation and release during the Zhundong coal combustion, especially for submicron particle formation and release. The releases of PM1, PM2.5, PM10 were reduced by 29.09%, 22.68% and 18.48%, respectively. The detailed characterizations showed that the significant removal of the easily vaporized elements in the coal by CO2-water leaching, such as Na, Ca, Mg, S and Cl, was an main factor for the suppression of PM formation and release. Besides, after CO2-water leaching, the combustion characteristics of Zhundong coal were promoted. Thus, the CO2-water leaching was a feasible method to inhibit the formation and release of PM during Zhundong coal combustion. Furthermore, since the flue gas from coal-fired power plant can be used as a source of CO2, the CO2-water leaching method provided a new way for the efficient utilization of the coal-fired flue gas.

Experimental investigation on pressure and heat release HCCI engine operated with chicken fat oil/diesel-gasoline blends

Low-temperature combustion is the individuality of Homogenous charge compression ignition (HCCI) engines where the combustion is achieved at the temperature lower than the temperature at which NOx is formed. By achieving this type of combustion in the engine it is possible to reduce the formation of Thermal NOx and PM. But on the other hand, the performance. In this current study, the combustion parameters of the engine are studied by varying the input parameters of the engine that has been modified to run in HCCI mode. The engine is fuelled with the blends of chicken fat oil biodiesel (CFOB) and gasoline. In the present work, the engine is tested for combustion properties such as in-cylinder pressure, heat release rate and the rate of pressure rise for different blend ratios. The ignition delay has persistently elevated for an increase in the gasoline concentration in blends. Also, the knock is consistently seen at higher engine loads with the blends of gasoline and diesel as well as gasoline with biodiesel. Diesel fuel exhibited lower peak pressure whereas, pure biodiesel exhibits higher peak pressure and the peak cylinder pressure within the engine at higher load varies from 40 to 75 bar. On comparing the heat release rate, the diesel fuel exhibit lower heat release as compared to fuel blended with chicken fat oil. Due to the delay in the start of low-temperature reactions the peaks on the rate of heat release is reduced. During higher engine load conditions, the engine seizes to operate in HCCI mode instead it operates in a conventional pattern which is clearly proved by the heat release curves obtained for the indicated pressure and crank angle data of the particular operating mode of the engine.

Monitoring of ultra-trace uranium and thorium in six-grade particles

The natural radioactive elements uranium(U) and thorium(Th) in atmospheric environment should be given attention, and their particle size distribution and concentration are important for estimating their hazardous effects to the human body. The concentrations of U and Th in 360 aerosol samples collected using six-stage aerosol collector from June - December, 2016 in Beijing were determinated using ICP-MS after acid digestion. The mass concentration ranges of U in PM0.39-0.69, PM0.69-1.3, PM1.3-2.1, PM2.1-4.2, PM4.2-10.2, and PM10.2- reached 0.0030-0.079, 0.0020-0.069, 0.0015-0.095, 0.0053-0.054, 0.0039-0.098, and 0.0083-0.10 ng/m3, respectively. The mass concentration range of Th in PM0.39-0.69, PM0.69-1.3, PM1.3-2.1, PM2.1-4.2, PM4.2-10.2, and PM10.2- amounted to 0.011-0.11, 0.0065-0.11, 0.0026-0.18, 0.0078-0.14, 0.015-0.30, and 0.0021-0.19 ng/m3, respectively. The contents of U and Th in all PM increased from June to December, and the contents in PM2.1 increased more sharply compared with those in other PM. A positive correlation was observed between the concentrations of U and Th and air quality index and relative humidity, whereas a negative correlation was identified between temperature and PM2.1, PM10.2, and total suspended particulates (TSP) after the Spearman-rank correlation test. The formation of PM was affected by meteorological conditions, which concurrently influenced the contents of U and Th in PM. The atmospheric contents of U and Th at night were higher than those in daytime. Compared with Th, the dose contribution of U to the public can be negligible. The median effective dose in public owing to inhalation of natural radioactive U and Th in the atmosphere measures 1.206 μSv/a.

Influences of In-Furnace Kaolin Addition on the Formation and Emission Characteristics of PM2.5 in a 1000 MW Coal-Fired Power Station.

The impacts of in-furnace kaolin addition on the formation and emission characteristics of PM2.5 from a 1000 MW coal-fired utility boiler equipped with electrostatic precipitators (ESPs) are investigated for the first time ever in this contribution. Detailed characterization of the chemical composition, micromorphology, melting characteristics of the fine PM, total fly ash, and/or bottom ash samples were carried out using the X-ray fluorescence probe, the field emission scanning electron microscope coupled with an energy dispersive X-ray detector, the ash fusion analyzer, and the dust specific resistivity analyzer. The results showed that the formation of fine PM was reduced when kaolin was added, and the mass concentrations of the particulate matter with the aerodynamic diameters of ≤0.3 and 2.5 μm (PM0.3 and PM2.5) were reduced by 55.97% and 5.48%, respectively. As expected, kaolin reacted with the volatile mineral vapors (e.g., Ca, Na) and inhibited their partitioning into ultrafine PM. It was interesting to find that the added kaolin modified the ash melting behavior, and promoted the capture of the ultrafine PM onto the coarse particles. What is more, the added kaolin reduced the specific resistivity of the fly ash and improved their capture efficiency in the ESPs. Finally, the above combined effects brought about the emission reductions of 41.27% and 36.72% for PM0.3 and PM2.5 after the ESPs. These results provided a direct confirmation on the feasibility of in-furnace kaolin addition on the PM reduction in the realistic combustion conditions.

Benzene pyrolysis and PM formation study using a flow reactor

The main component of PM formed in the combustion field is soot, and its formation mechanism is hydrocarbon fuel partial oxidation. Then as the first step of this PM formation research work, benzene pyrolysis and formation of PM in a diluted benzene-oxygen mixture were studied using a flow reactor. Experimental studies were conducted under zero O2 condition and O2 exist condition, respectively, and the influence on benzene pyrolysis and formation of PM due to exist or absence of oxygen was discussed. The effects of temperature and oxygen on PM formation were also discussed by independent control of temperature and oxygen concentration. PM sampled from the flow reactor was dried up to separate volatile compositions from soot. PM composition change by oxygen concentration and temperature were analyzed in detail. As the result, it was found that PM formation behavior at low temperature condition was different from that of high temperature condition. The valley temperature between them was around 1273 K. It decreased with the addition of oxygen. Under low temperature condition, small amount of PM was formed from benzene-N2 mixture without oxygen. It increased with the addition of oxygen. Main composition of this PM was low boiling point SOF. Under high temperature condition, large amount of PM was formed from benzene-N2 mixture without oxygen. It decreased with the addition of oxygen.

Multi-Method Observation and Numerical Simulation of a PM2.5 Pollution Episode in Beijing in October, 2014

Multi-method observation and numerical simulation were applied to analyze a PM_(2.5) pollution episode in Beijing in October, 2014. The results of vertical observation showed that surface-level backscatter signal and extinction coefficient increased during the episode, suggesting that air pollutants accumulated near the ground. The main meteorological factors during this episode could be described as calm wind, high relative humidity and low surface pressure. The evolution of PM_(2.5) concentrations in this episode was divided into four stages, including two-steps type concentration climbing stages (P1 and P2), high concentration maintenance stage (P3) and rapid cleanup stage (P4). Analysis on ground-based observation, satellite remote sensing and atmospheric general circulation showed that regional transport, including crop residue burning, was the main incentive of this pollution episode. Subsequently, local pollutants emission and regional transport maintained and aggravated the episode under unfavorable meteorological conditions. Temporal variation of OX was in close agreement with that of PM_(2.5) and the concentration peaks of OX occurred few hours before those of PM_(2.5), which indicated that strong atmospheric oxidation could promote the formation of secondary PM_(2.5). The results of numerical simulation showed that during 8-10 October, the average contribution of regional transport to PM_(2.5) in the five sites exceeded 50%.

Prevalence of Freshly Generated Particles during Pollution Episodes in Santiago de Chile

A winter campaign was carried out in Santiago de Chile the year 2012 in two urban sites that can be considered representative for most of the city in order to characterize formation of primary and secondary PM_(1.0) during episodes. One site is located in the campus of the University of Santiago and measurements were carried out with an Aerosol Chemical Speciation Monitor and a black carbon monitor. Another site is located in a large park, about 2 km south-east of the first site, measurements of CO, NO_x, SO_2, O_3 were done in this site. A noticeable increase in most of the primary components of PM_(1.0) (black carbon and organics) and primary gases (CO and NO) was observed during days in which the average PM_(1.0) concentration was higher than 50 μg m^(-3) (episode). A small increase or no change was observed in the secondary pollutants (NH_4, NO_3, SO_4 and NO_2) at night during these episodes. Positive Matrix Factorization was used to extract four components from the ACSM data: hydrocarbon-like organic aerosol (HOA), biomass burning OA (BBOA), low volatility oxygenated OA (LV-OOA) and semi-volatile oxygenated OA (SV-OOA). The freshly generated components (HOA and BBOA) showed a clear increase at night during episodes, while the aged fraction of organic aerosol (LV-OOA and SVOOA) showed a smaller increase or a decrease at night during episodes. Correlation of HOA and BBOA components with primary pollutants was also high, indicating that freshly created aerosols (HOA, BBOA and BC) are in large part responsible for the increase in pollution at night during episodes in Santiago de Chile.