Increase In Mass Concentration Research Articles

Impact of the Criegee Intermediate on the Formation of Secondary Organic Aerosols during E-4-Hexen-1-ol Ozonolysis.

Criegee intermediates (CIs), which are active species in the troposphere, play an important role in the formation of secondary organic aerosols (SOA). In this study, matrix isolation technology combined with a vacuum Fourier transform infrared spectrometer (MIFT-IR) and smog chamber method were used to study the typical green leaf volatiles (E-4-hexen-1-ol, E4H1O) ozonolysis process. The infrared characteristic peak resulting from the O-O stretching vibration of CH3CHOO was identified at 882 cm-1. And the characteristic infrared peaks of CH2OHCH2CH2CHOO were not detected, possibly due to the presence of extremely rapid unimolecular reaction channels. To investigate the subsequent atmospheric reaction process of these two CIs, additional smog chamber experiments with the E4H1O-O3 system were conducted to investigate the impact on SOA formation mechanisms. The ordered oligomers derived from the continuous oligomerization of RO2 radicals with several CIs were identified as the primary components of SOA without the addition of sulfur dioxide (SO2). The addition of SO2 in the concentration range of 14-159 ppb, acting as a scavenger for CIs, led to the disappearance of the oligomers, while the yield of SOA continued to increase. The reasons for the increased mass concentration of SOA may be a change in the chemical composition. The escalating concentrations of SO2 underwent reactions with CIs (or OH radicals) to generate H2SO4, subsequently elevating the acidity of the particles. The acid particles resulted in the changes in SOA composition, leading to the production of organic sulfates (OSs), thereby contributing to the increase in SOA yield. A number of OSs were detected in the presence of SO2, which may result from the heterogeneous reaction of oxygen-containing species with sulfuric acid under acidic conditions. Additionally, non-sulfur-containing molecular structures of emerging CxHyOz products in the particle phase were also identified. Our findings provided detailed molecular insights into the mechanism of E4H1O ozonolysis and its impact on SOA formation from the perspective of Criegee chemistry.

Changes in dust concentration in a gas-dust cloud during blasting in an iron ore pit

In open-pit extraction of minerals emit large amounts of harmful dust fractions and gas into the atmosphere. This leads to atmospheric pollution in open pit and sanitary protection zones. The largest dust emissions are observed during blasting operations in open pits. This is especially the cases when unfavorable meteorological conditions occur, means of dust sup-pression are not sufficiently effective, blasting technology was violated. Dust particles are known to be able to propagate long distances from the source of the explosion. Dust fractions up to 10 µm diameter are the most dangerous, as they are the main risk factor for the devel-opment of chronic respiratory diseases. In particular, according to European standards, the average daily concentration of dust particles with a diameter between 2.5 and 10 µm should not exceed 0.05 mg/m3. The paper estimates mass concentrations of dust fractions in the gas-dust cloud at the dynamic stage of its formation after a mass explosion in an iron ore open pit. The following assumptions were made in the calculations: no influence of the temperature factor (ejected air flows); dust particles are spherical; flow of dust fractions by the gas flow follows the Stokes law. The ranges of variation of ascent height and mass concentrations of dust fractions at the dynamic stage of gas-dust cloud formation are established. In particular, the lift height of the dust fraction is directly proportional to the value of the dynamic impulse. The differ-ence in mass concentrations of dust fractions in the gas-dust cloud is due to the physical and mechanical properties of rocks destroyed by boreholes explosive substance charge. When de-termining the mass concentrations of dust fractions, the results of experimental studies were used, which were carried out in the open pit of Ingulec Mining and Processing Combine. The graphical dependence of average mass concentrations of dust fractions depending on the height of their ascent at the dynamic stage of gas-dust cloud formation is presented, the re-gression equation in the form of a degree function is obtained. The results of calculations have shown that the greatest intensity of mass concentration increase in the gas-dust cloud at the dynamic stage of its formation is characteristic of dust fractions with diameter up to 31 μm. The intensity of growth of mass concentrations of larger dust fractions decreases markedly.

Emulsification Stability of An Amphiphilic Polymer for Chemical Flooding

Background: Emulsification plays a pivotal role in the process of enhanced oil recovery, especially in chemical flooding. Emulsification has emerged as one of the key mechanisms facilitating oil recovery in polymer flooding. Aim: This study aimed to solve the problem of emulsification and stability of amphiphilic polymers in the process of oil displacement. Materials and methods: The emulsion was prepared by stirring emulsification method in the lab, and the dynamic stability of the emulsion was determined by stabilizer, and the size and distribution of droplets were determined by laser particle sizing instrument. Results: The experimental results show that, with the increasing mass concentration of amphiphilic polymer, the apparent viscosity of the solution is significantly increased. The emulsification ability and the stability of the emulsion are also enhanced. In addition, the microstructure of the emulsion shows that the amphiphilic polymer with higher concentration helps to reduce the particle size of the emulsified oil droplets and impels the more uniform distribution. Furthermore, the amphiphilic polymer system was conductive to improving the oil-water emulsification ability and prolonging the stability of the emulsion, especially in high-salinity and high-temperature environments. Conclusion: The results of the study are of guiding significance for the emulsification of amphiphilic polymers for oil recovery.

Study on preparation and influencing factors of coal gangue fill slurry material

The large quantity of coal gangue will become an increasingly serious part of environmental pollution. However, it can be aggregated with water and fly ash to form a slurry with a stabile rheology that can be used to fill underground mining areas to reduce environmental pollution. In this study, an orthogonal test scheme was formulated, and the significance of the influence of test factors on the test index was judged using variance analysis and range analysis. By analyzing the effects of mass concentration, fly ash percentage, and aggregate grade on the rheology and stability of the slurry, a fill slurry that meets the requirements of reasonable indexes was developed. Finally, the diffusion effect of the prepared slurry was explored using a simulation. The results show that the mass concentration had the strongest effect on the plastic viscosity, yield stress, extensibility, water secretion rate, and segregation rate of the gangue slurry. The effect of aggregate gradation on the yield stress, water secretion rate, and segregation rate of slurry was stronger than that of the fly ash content, while the effect of the fly ash content on the plastic viscosity and extensibility of the slurry was stronger than that of the aggregate gradation. With the increase in mass concentration and the content of fine particles in the aggregate, the plastic viscosity of the slurry increased, the slump extension decreased, and the fluidity decreases while the yield stress increased, the water secretion rate and segregation rate decreased, and the stability increased. The optimal ratio of the slurry was determined to be 70 % mass concentration, 10 % fly ash, and an aggregate grading consisting of 80.34 % 0–1 mm particles, 12.95 % 1–3 mm particles, and 6.71 % 3–5 mm particles. The flow and diffusion effect of the optimized gangue slurry in the mining area was observed through an image and stress data acquisition system, and it was determined that the slurry could well be filled into the rock voids in the mining area. The results of the study can provide some theoretical basis for the preparation of slurry to fill hollow zones.

Influence of Carboxymethyl Chitosan and Sodium Humate Composite Corrosion Inhibitor on the Corrosion Resistance of EH40 Steel in Seawater.

In this study, corrosion weight loss experiments were conducted to explore the corrosion-inhibiting properties of a composite inhibitor consisting of carboxymethyl chitosan (CMCS) and sodium humate (SH) at varying concentrations on EH40 steel in seawater. An investigation was conducted into the electrochemical behavior of EH40 steel in seawater and the mechanism of composite inhibitor consisting of carboxymethyl chitosan (CMCS) and sodium humate (SH) at varying concentrations on EH40 steel in seawater through an electrochemical test. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy and energy-dispersion spectroscopy (SEM-EDS), Fourier transform infrared absorption spectroscopy (FTIR), and contact angle measurements were performed to confirm the mechanism of CMCS and SH as well as their composite corrosion inhibitors at the interface between seawater and EH40 steel. Furthermore, density functional theory (DFT) calculation supports the experimental findings. The results show that CMCS, SH, and their composite inhibitor are a mixed type of corrosion inhibitor that mainly inhibits cathodic reactions and corrosion through the active site blocking mechanisms. Their corrosion inhibition effect increases with the increase of mass concentration, and the composite inhibitor performs better in corrosion inhibition and scale inhibition than the individual inhibitor. When the CMCS mass concentration reaches 100 mg/L and the SH mass concentration reaches 50 mg/L, the corrosion inhibition rate is 74.65%, the corrosion potential shifts by about 47.39 mV, the Rp value increases from 358.6 to 1102.4 Ω·cm2, and the Ydl value decreases from 177.31 Sn Ω-1cm-2 × 10-6 to 92.672 Sn Ω-1cm-2 × 10-6. CMCS and SH are adsorbed onto the surface of EH40 steel, forming a protective film through the complexation of carboxyl, amino, and other functional groups to inhibit corrosion and prevent the further formation of scale. In addition, synergistic coadsorption occurs between CMCS and SH, and the composite corrosion inhibitor exerts a better effect than the individual corrosion inhibitor.

Hygroscopic growth and activation changed submicron aerosol composition and properties in the North China Plain

Abstract. Aerosol hygroscopic growth and activation under high-relative-humidity (RH) conditions significantly influence the physicochemical properties of submicron aerosols (PM1). However, this process remains poorly characterized due to limited measurements. To address this gap, we deployed an advanced aerosol–fog sampling system that automatically switched between PM1, PM2.5 and total suspended particulate (TSP) inlets at a rural site in the North China Plain in the cold season. The results revealed that aerosol swelling due to water vapor uptake influenced aerosol sampling under high-RH conditions by shifting the cut-off size of impactors. At subsaturated high RH (> 90 %), over 25 % of aerosol mass with dry diameters below 1 µm resided in supermicron ranges, while in supersaturated foggy conditions, more than 70 % of submicron aerosol migrated to supermicron ranges. Hygroscopic growth and activation particularly affected highly hydrophilic inorganic salts, shifting a significant number of submicron sulfate and nitrate particles to supermicron ranges, with 27 %–33 % at 95 % ≤ RH ≤ 99 % and more than 78 % under supersaturated foggy conditions. Moreover, more than 10 % of submicron biomass burning organic aerosols grew beyond 2.5 µm during fog events, while fossil-fuel-related organic aerosol (FFOA) remained dominantly in submicron ranges, suggesting inefficient aqueous conversion of FFOA. The two secondary organic aerosol (SOA) factors (OOA1 and OOA2) behaved differently under supersaturated conditions, with OOA2 exhibiting a higher activated fraction despite a lower oxygen / carbon ratio. A substantial increase in organic nitrate and organosulfur mass concentrations in activated droplets during fog events suggested aqueous conversions and formations of brown carbon with potential radiative impacts. Overall, our study highlights remarkably different cloud and fog processing behaviors between primary and secondary aerosols, which would benefit a better understanding of aerosol–cloud interactions under distinct atmospheric conditions.

Observed and CMIP6-model-simulated organic aerosol response to drought in the contiguous United States during summertime

Abstract. Drought events have been linked with the enhancements of organic aerosols (OAs), but the mechanisms have not been comprehensively understood. This study investigates the relationships between the monthly standardized precipitation–evapotranspiration index (SPEI) and surface OA in the contiguous United States (CONUS) during the summertime from 1998 to 2018. OA under severe drought conditions shows a significant increase in mass concentrations across most of the CONUS relative to non-drought periods, with the Pacific Northwest (PNW) and Southeast United States (SEUS) experiencing the highest average enhancement of 1.79 µg m−3 (112 %) and 0.92 µg m−3 (33 %), respectively. In the SEUS, a linear regression approach between OA and sulfate was used to estimate the epoxydiol-derived secondary organic aerosol (IEPOX SOA), which is the primary driver of the OA enhancements under droughts due to the simultaneous increase in emissions of biogenic volatile organic compounds (VOCs; such as isoprene and monoterpene) and sulfate. The rise in sulfate is mainly caused by the reduced wet deposition because of the up to 62 % lower precipitation amount. In the PNW, OA enhancements are closely linked to intensified wildfire emissions, which raise OA mass concentrations to be 4–8 times higher relative to non-fire conditions. All 10 Earth system models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6) can capture the slopes between SPEI and OA in the PNW, with CESM2-WACCM and GFDL-ESM4 performing the best and worst in predicting the OA enhancement under severe droughts. However, all models significantly underestimate the OA increase in the SEUS, with Nor-ESM2-LM and MIRCO6 showing relatively better performance. This study reveals the key drivers of the elevated OA levels under droughts in the CONUS and underscores the deficiencies of current climate models in their predictive capacity for assessing the impact of future droughts on air quality.

Removal of Rare Earth Elements from complex mixtures by using manganese ferrite nanoparticles: Optimization through surface response methodology

The crucial role of Rare Earth Elements (REEs) in the development of hi-tech in addition to their limited availability have urged countries to develop sustainable alternatives to their conventional primary sources (ore mining). Sorption technologies using magnetic materials such as spinel ferrite nanoparticles provide efficient removal of REEs from contaminated solutions and ease of separation through application of an external magnetic field. However, there is still limited knowledge available regarding the optimal operational conditions in which to use these materials, especially in complex aqueous mixtures with different REEs. In this study, we have used Surface Response Methodology (SRM) applied to MnFe2O4 nanosorbents to identify their ideal sorption conditions of pH (4–8), REEs concentration (1–5 μM) and sorbent mass (20–180 mg L−1) in a mixture of nine REEs in water samples of distinct salinity (NaCl: 0–30 g L−1). Our results indicated that high pH favored REEs sorption because of the material's surface charge, which promoted interactions with REEs ions at pH 6–8. Yttrium was the least removed element, but total removal was achieved for lowest REEs concentration using 151 mg L−1 of sorbent. High removals were also obtained for the concentration of 5 μM (100 % removal, except for Y and La). Salinity did not impair sorption significantly (<10 %), which was owed to the high sorbent mass used in those assays. An increase in sorbent mass and initial REEs concentration also promoted faster kinetics. The spinel type MnFe2O4 nanoparticles showed great promise in a realistic application, which is the next proposed step in this line of research.

Study of dust events based on multi-source data in the North Slope of the Tianshan Mountains

To reveal the spatial-temporal characteristics of atmospheric pollution during dust events on the North Slope of the Tianshan Mountains (NSTM), this study conducted a joint detection experiment from April to June from 2019 to 2021 at Shihezi, using satellite remote sensing, a microwave radiometer, meteorological sensors, and environmental monitors. Using long-term detection data from the aforementioned equipment, this study analyzed the characteristics of meteorological elements, Aerosol Optical Depth (AOD), PM, and gaseous pollutants. The main findings are as follows: The dust particles from the two severe pollution dust events on April 9, 2020, and May 1, 2021, on the NSTM originated from the Gurbantünggüt Desert and were transported along the northwest direction, leading to a significant increase in AOD (averaging 1.36 g/m2) and dust column mass concentration (averaging 1.58 g/m2). During the two dust storms, the PM10 concentration peaks reached 2536.5 μg/m³ and 1804.5 μg/m³, respectively. The average relative humidity (RH) was less than 30%, the average wind speed was more than 6 m/s, and the average visibility (V) was less than 1000 m. Moreover, during the dust events from April to June, the temperature and relative humidity were higher in June, but the wind speed was lower. The vertical thermodynamic interactions of the dust storms were stronger than those of the blowing and floating dust storms. Finally, the relationship between PM10 and V was fitted using the following equation: V=11326.8166e−0.0015PM10.This study provides scientific support for the prediction of dust storms on the NSTM.

Salicylic Acid Priming Improves Cotton Seedling Heat Tolerance through Photosynthetic Pigment Preservation, Enhanced Antioxidant Activity, and Osmoprotectant Levels.

The escalating global temperatures associated with climate change are detrimental to plant growth and development, leading to significant reductions in crop yields worldwide. Our research demonstrates that salicylic acid (SA), a phytohormone known for its growth-promoting properties, is crucial in enhancing heat tolerance in cotton (Gossypium hirsutum). This enhancement is achieved through modifications in various biochemical, physiological, and growth parameters. Under heat stress, cotton plants typically show significant growth disturbances, including leaf wilting, stunted growth, and reduced biomass. However, priming cotton plants with 1 mM SA significantly mitigated these adverse effects, evidenced by increases in shoot dry mass, leaf-water content, and chlorophyll concentrations in the heat-stressed plants. Heat stress also prompted an increase in hydrogen peroxide levels-a key reactive oxygen species-resulting in heightened electrolyte leakage and elevated malondialdehyde concentrations, which indicate severe impacts on cellular membrane integrity and oxidative stress. Remarkably, SA treatment significantly reduced these oxidative stresses by enhancing the activities of critical antioxidant enzymes, such as catalase, glutathione S-transferase, and ascorbate peroxidase. Additionally, the elevated levels of total soluble sugars in SA-treated plants enhanced osmotic regulation under heat stress. Overall, our findings reveal that SA-triggered protective mechanisms not only preserve photosynthetic pigments but also ameliorate oxidative stress and boost plant resilience in the face of elevated temperatures. In conclusion, the application of 1 mM SA is highly effective in enhancing heat tolerance in cotton and is recommended for field trials before being commercially used to improve crop resilience under increasing global temperatures.

Influence of Silica Oxide Nanofluid for Different Concentrations on Photovoltaic Cell

Photovoltaic (PV) cells, a renewable fuel, are widely employed. A conventional PV cell also loses efficiency as the temperature rises. This research addresses this issue by cooling the PV cell with nanofluid, specifically SiO2 and distilled water. Applying SiO2 nanofluid experimentally using a real experimental setup is hoped to cool the PV cell’s surface as it becomes heated. This research aims to use distilled water and various concentrations of SiO2 nanofluid, such as 0.1 wt%, 0.2 wt%, and 0.3 wt% on Photovoltaic Cell and flow rate of 2 LPM and a radiation rate of 800 W/m2. ANSYS is used to confirm experimental results by using SiO2 as a nanofluid to lower the PV cell’s temperature and boost its thermal efficiency. The experiment’s findings demonstrated that utilizing nanofluid as a coolant boosted the PV cell’s thermal efficiency and decreased its temperature. Results showed that the thermal efficiency increased with the use of nanofluid as a coolant and with increasing mass concentration. Thermal efficiency values for distilled water, 0.1%, 0.2%, and 0.3% SiO2 were 35.56%, 79.91%, 91.04%, and 104.01%, respectively. This study also discovered that SiO2 works better in terms of cooling the PV cell than normal fluid because of its higher thermal conductivity. The experimental and numerical data show the same decline in PV cell surface temperature and thermal efficiency, unlike the computational results.

Determination of Poisson’s ratio of coal gangue-based shotcrete materials using a non-contact test method

ABSTRACT Preparing shotcrete materials using coal gangue is an effective method of disposal and use of gangue solid waste, while testing the Poisson’s ratio of coal gangue-based shotcrete materials (CGSM) is an important step in evaluating the mechanical properties of such materials. Therefore, to study the evolution of the Poisson’s ratio of CGSM under different influencing factors, detailed test schemes and procedures were designed based on the non-contact test method of Poisson’s ratio. The accuracy of the non-contact test method is verified. In addition, changes in the Poisson’s ratio of CGSM under different factors were studied. Results show that the Poisson’s ratio of CGSM tends to reduce with prolonged curing. When the particle sizes of coal gangue are 0 ~ 2.5 and 2.5 ~ 5 mm, fine particles can fill interstitial voids in shotcrete materials. As the mass concentration and cement content increase, the Poisson’s ratio of CGSM gradually decreases; as the sand content rises, the Poisson’s ratio gradually increases.

Severe microplastic pollution risks in urban freshwater system post-landfill fire: A case study from Brahmapuram, India

To investigate the escalating issue of microplastic (MP), pollution in urban water bodies, this study focuses on the aftermath of the Brahmapuram landfill fire in Kochi, India, analyzing its impact on MP concentrations in nearby freshwater system. The study conducted sampling sessions at the landfill site immediately before and after the fire. Post-fire, findings demonstrated a substantial increase in MP concentrations in surface waters, with levels rising from an average 25793.33 to 44863.33 particles/m³, featuring a notable presence of larger, predominantly black MPs. Sediment samples showed no significant change in MP count, but there was a significant increase in mass concentration. SEM/EDS analysis revealed changes in surface morphology and elemental composition, suggesting thermal degradation. Risk assessment using the Microplastic Pollution Index (MPI) and Risk Quotient (RQ) methods indicated heightened MP pollution risk in surface water post-fire. Hierarchical cluster analysis revealed the landfill's proximity as a significant factor influencing MP characteristics in the aquatic system. The study highlights the escalated challenge of MP pollution in urban water bodies following environmental disasters like landfill fires, underscoring the urgent need for policy and environmental management strategies.

Study on Explosion Characteristics and Mechanism of Electrostatic Spray Powder.

In order to fully understand the explosion risk of electrostatic spraying powder, corresponding preventive measures are put forward. The explosion characteristics, ignition sensitivity, and flame propagation of three typical electrostatic spraying powders were tested using a 20 L spherical explosion test device, a G-G furnace test device, and a Hartmann tube test device, and the explosion process and mechanism of electrostatic spraying powders were discussed. The results show that the maximum explosion pressure and the maximum explosion pressure rise rate increase first and then decrease with the increase in mass concentration. The maximum explosion pressure and the maximum explosion pressure rise rate of acrylic powder coating are the largest, which are 0.75 and 85.4 MPa/s, respectively. The shortest burning time is 97.5 ms, and the highest explosion danger level is 23.46 MPa·m/s. The flame propagation of electrostatic spraying powder develops slowly; the flame front spreads linearly and the average flame velocity increases first and then decreases. The explosive development process of powder coating particles is concentrated in the three-phase system of solid particles, molten particles, and pyrolytic gasification combustible gas, which goes through the kinetic process of particle heating melting, cross-linking curing, pyrolytic gasification, combustion, and extinction.

Hemolytic Properties of Fine Particulate Matter (PM2.5) in In Vitro Systems.

Epidemiological studies have suggested that inhalation exposure to particulate matter (PM) air pollution, especially fine particles (i.e., PM2.5 (PM with an aerodynamic diameter of 2.5 microns or less)), is causally associated with cardiovascular health risks. To explore the toxicological mechanisms behind the observed adverse health effects, the hemolytic activity of PM2.5 samples collected during different pollution levels in Beijing was evaluated. The results demonstrated that the hemolysis of PM2.5 ranged from 1.98% to 7.75% and demonstrated a clear dose-response relationship. The exposure toxicity index (TI) is proposed to represent the toxicity potential of PM2.5, which is calculated by the hemolysis percentage of erythrocytes (red blood cells, RBC) multiplied by the mass concentration of PM2.5. In a pollution episode, as the mass concentration increases, TI first increases and then decreases, that is, TI (low pollution levels) < TI (heavy pollution levels) < TI (medium pollution levels). In order to verify the feasibility of the hemolysis method for PM toxicity detection, the hemolytic properties of PM2.5 were compared with the plasmid scission assay (PSA). The hemolysis results had a significant positive correlation with the DNA damage percentages, indicating that the hemolysis assay is feasible for the detection of PM2.5 toxicity, thus providing more corroborating information regarding the risk to human cardiovascular health.

Identification of Saharan-Dust Intrusions over Sofia, Bulgaria, Using Near-Ground PM10 and PM2.5 Mass Concentration Measurements

Intrusions of Saharan dust (SD) in the atmosphere over Sofia City, Bulgaria, are not a rare phenomenon. Since it can significantly affect the Earth’s radiative balance, various atmospheric processes, the climate and the living conditions on the land and in the ocean, as well as the air quality, it has been the subject of large-scale studies of considerable societal and scientific interest. In the present work, results were analyzed of: concurrent measurements of near-ground aerosol PM10 and PM2.5 mass concentrations and the aerosol’s optical and microphysical characteristics as obtained by an AERONET Cimel CE318–TS9 sun/sky/lunar photometer, the MONARCH Saharan-dust forecasting model and the HYSPLIT air-mass back-trajectory-recovering model. Data on the weather conditions in Sofia Valley and the fires in Bulgaria and neighboring countries were also considered. It was shown that the strong increases in the daily-mean PM10 mass concentration (> 50 µg m–3 or > 70 µg m–3) measured by a mountain ecological station are most frequently (74% and 86% of the cases, respectively) indications of relatively intense SD passages over the station. It was shown as well that during very intense Saharan dust intrusions over the region of Sofia (with dust load > 0.15–0.20 g m–2), the urban PM10 and PM2.5 mass concentrations noticeably increased, while the PM2.5/PM10 mass concentration ratio dropped down as a rule to values around 0.2 and below. The peculiarities found in the behavior of the particulate PM10 and PM2.5 mass concentrations contact-measured near the ground would allow one to recognize or confirm intense SD transport over Sofia and Sofia Valley.

Characteristic Behavior of Methane/Hydrogen Premixed Flame in Ultrafine Water Mist with Potassium Additives

ABSTRACT In order to improve the suppression effect of methane/hydrogen deflagration, it is essential to understand the effects of the addition of ultrafine water mist on their explosion characteristics. An experimental study on the flame propagation behavior of methane/hydrogen premix flames influenced by ultrafine water mist with K2C2O4·H2O additives was carried out in a 10 mm × 10 mm × 100 mm tube. The results confirmed that potassium additives can improve the inhibition effect of ultrafine water mist, but the inhibition effect shows an inverted “V” shape with the increase of mass concentration. Inhibitory effects from high to low are: 15% K2C2O4·H2O >3% K2C2O4·H2O >0% K2C2O4·H2O >9% K2C2O4·H2O The addition of ultrafine water mist has both an inhibiting and an enhancing effect on flame propagation. Physical inhibition includes energy absorption by droplet fragmentation, heat absorption by evaporation and dilution of combustible gas components with CO2 to reduce the rate of combustion. Chemical inhibition occurs when small molecule alkali metals reduce the concentration of free radicals such as •O, •H and •OH. In addition, the unevaporated droplets and CO from pyrolysis have an enhanced effect on deflagration.

Numerical Simulation on Erosion and Stress on a Small-Diameter Hydrajet Fracturing Tool.

Conventional hydrajet fracturing techniques are often frustrated when they are applied to some specific well types, such as casing-damaged and small-diameter wells. It is of great significance to investigate the erosion and stress on a small-diameter hydrajet fracturing tool during its service and clarify the relevant influencing factors. Based on the solid-liquid two-phase flow theory and erosion model, a numerical simulation was conducted on the erosion and stress on a small-diameter hydrajet fracturing tool by using the computational fluid dynamics approach in order to understand how the inlet flow rate, particle size, and particle mass concentration affect the erosion and stress on the tool. The results show that the erosion on the small-diameter hydrajet fracturing tool is generally a cutting erosion of proppant particles on the tool body. Such erosion occurs on the lower wall of the nozzle, and the erosion at the upper-0° nozzle is higher in rate and smaller in area than that at the lower-180° nozzle. The maximum stress of the small-diameter hydrajet fracturing tool is concentrated on the upper and lower walls of the upper and lower nozzles, especially the lower part inside the upper nozzle. The maximum erosion rate, average erosion rate, and maximum stress on the wall near the nozzle during fracturing increase as the inlet flow rate and particle mass concentration increase and decrease as the proppant particle size increases.

Temporal evolution and source apportionment of BC aerosols during autumn in the grassland of Ordos, China

AbstractMeteorological conditions and source emissions in grassland areas are quite different from those in urban areas, which significantly impacts the spatiotemporal characteristics of black carbon (BC). To obtain the characteristics of BC in the typical grassland environment in China, continuous observations of BC were carried out in Etuoke Banner, a typical grassland environment in Ordos, from September 8 to December 1, 2022. BC in Etuoke Banner in autumn is 22.4–4667.5 ng m−3, and the average concentration is 456.6 ng m−3, accounting for 2.20% of the mass fraction of PM2.5. BCliquid (BC generated from the combustion of liquid fuels) is the main component of BC (accounting for 79.2%); the average concentration is 361.7 ng m−3. The diurnal variations of BC, BCliquid, and BCsolid (BC generated from the combustion of solid fuels) are bimodal, with peaks at 08:00 and 18:00. The first peak is mainly related to traffic sources, cooking sources, and incomplete combustion of carbon‐containing substances; the second peak may be caused by emissions from residential cooking sources under the influence of meteorological conditions unfavorable to diffusion. The diurnal variation of absorption Ångström exponent (AAE) is unimodal, with the peak at 14:00. With the increase in BC mass concentration, AAE and visibility gradually decreased, wind speed first decreased and then increased, P and RH gradually increased, and the contribution of biomass combustion sources to BC decreased. In contrast, the contribution of traffic sources to BC increased. The evolution characteristics of atmospheric pollutants differed with the increase in BC concentration. The potential sources and affecting areas of BC and PM2.5 are mainly concentrated around Etuoke Banner and can affect the North China Plain after 48 h of transmission.

Rheological and mechanical performance analysis and proportion optimization of cemented gangue backfill materials based on response surface methodology.

Cemented backfill mining is a green mining method that enhances the coal mining rate and the safety of mined-out regions. To transport the cemented gangue backfill material (CGBM) into the mined-out regions, it is essential to ensure high flowability and adequate compressive strength after hardening. Based on the response surface methodology (RSM), 29 experiments were conducted in this paper to test the yield stress and plastic viscosity of CGBM slurry. Cubic specimens with dimensions of 100mm were prepared and underwent uniaxial compression tests to obtain the compressive strength at a curing age of 28days. Quadratic polynomial regression models were established for yield stress, plastic viscosity, and compressive strength to explore the effects of fly ash content, water-cement ratio, mass concentration, and superplasticizer dosage on the properties of CGBM. Multi-objective optimization was conducted to determine the optimal material proportion of CGBM. The research results indicate that (1) the mass concentration most profoundly affected the yield stress and plastic viscosity of CGBM, and it increased with an increase in mass concentration. Fly ash content had an inverse relationship with compressive strength. Superplasticizer was found to improve the flowability and strength of CGBM. (2) The established response surface model could reflect the relationship between CGBM's material proportion and rheological and mechanical properties, and predict relevant parameters. (3) Multi-objective optimization determined the optimal proportion of CGBM to be 80% fly ash content, 54% water-cement ratio, 79% mass concentration, and 3% superplasticizer dosage. The research findings offer valuable guidance to mining backfill engineering.