Dust Concentration Research Articles

Wall-attached structure characteristics of flow and dust concentration fields in high-Reynolds-number particle-laden flows

The wall-attached structure characteristics of flow and dust concentration fields are investigated in this study based on high-Reynolds-number ( $Re_{\tau } \sim O(10^{6})$ ) synchronous multiphase observations from the Qingtu Lake observation array site (recorded by Liu et al., J. Fluid Mech., vol. 957, 2023, A14). The results show that not only the particle-free flow field but also the particle-laden flow and dust concentration field contain wall-attached structures. The linear coherence spectrum, as a data-driven filter, is adopted to separate the wall-attached portions from the premultiplied spectra. The decomposed spectra for wall-attached structures in streamwise velocity fluctuations under particle-free and particle-laden conditions show obvious outer-scaling and wall-scaling at large-scale and medium-scale ranges, respectively, but the spectra of dust concentration exhibit only wall-scaling rather than outer-scaling. The streamwise length of the most significant wall-attached dust clustering structures in the logarithmic region is approximately five times the boundary layer thickness, and does not change significantly with height. Furthermore, the streamwise turbulence intensity for wall-attached portions follows the universal Townsend–Perry constant, without particle mass loading effect. Correspondingly, the wall-attached portions of the dust concentration also exhibit universal logarithmic decay slope. The remaining non-attached portions for the turbulent velocity and dust concentration have significant dependence on the particle mass loading.

A Numerical Study on Dust Control: Evaluating the Impact of Spray Angle and Airflow Speed in the Coalescence of Droplets and Dust

Spray dust reduction is one of the most economical and effective technologies for controlling coal dust in coal mining faces. We aimed to reproduce a spray dust reduction process in a simulation and investigate the mechanism by which the spray angle and airflow speed influence the dust reduction effect. Based on the DPM (discrete phase model) and the mixture model, we constructed a spray dust reduction evaluation model by considering two-way momentum coupling between the discrete phase and the continuous phase. The results showed that installing nozzles near the dust source (coal mining drum) significantly reduced the dust concentration at the coal mining face from 0.0005 kg/m3 to 0.0001 kg/m3. The increase in airflow speed and spray angle enhanced the horizontal transportation of droplets and dust, providing opportunities for the droplets to condense the dust; however, if the droplets have too large an angle, this will result in an insufficient concentration of droplets in the vicinity of the dust source. When the spray angle is 45°, increasing the airflow speed provides a better dust reduction effect. The nozzle position should also be set scientifically according to the airflow speed. Based on simulation results, a mathematical calculation model of spray dust reduction efficiency was constructed. These results can guide the key parameters of spray dust reduction systems, such as the installation position of the nozzle, the spray angle, and the airflow speed. This paper provides ideas for simulating spray dust reduction for other dust types.

SIMULATION OF FLAME PROPAGATION IN A COAL-METHANE-AIR MIXTURE IN A CYLINDRICAL CHANNEL TAKEN INTO ACCOUNT OF GAS VISCOSITY

The paper presents the results of a numerical study of the patterns of flame propagation of a coal-methane-air mixture in a narrow cylindrical channel in the presence of viscous friction forces. The formulation of the problem is based on the approaches of the mechanics of two-phase reacting media. The method for solving the problem is based on an arbitrary discontinuity decay algorithm. The numerical study carried out made it possible to determine the speed of flame propagation of a coal-methane-air mixture in an axisymmetric channel. It is shown that at the initial stage, when the combustion front reaches the side walls of the channel, the flame speed increases. This effect was obtained previously for an inviscid gas. It was found that the flame front of a gas suspension with a low content of coal dust, as it moves along an open channel, tends to be flat, independent of the coordinate along the radius of the channel.

Mixing is easy: New insights for cosmochemical evolution from pre-stellar core collapse

Signposts of early planet formation are ubiquitous in substructured young discs. Dense, hot, and high-pressure regions that formed during the gravitational collapse process, integral to star formation, facilitate dynamical mixing of dust within the protostellar disc. This provides an incentive to constrain the role of gas and dust interaction and resolve potential zones of dust concentration during star and disc formation stages. We explore whether the thermal and dynamical conditions that developed during protostellar disc formation can generate gas flows that efficiently mix and transport the well-coupled gas and dust components. We simulated the collapse of dusty molecular cloud cores with the hydrodynamics code PLUTO augmented with radiation transport and self-gravity. We used a two-dimensional axisymmetric geometry and followed the azimuthal component of the velocity. The dust was treated as Lagrangian particles that are subject to drag from the gas, whose motion is computed on a Eulerian grid. We considered 1, 10, and 100 micron-sized neutral, spherical dust grains. Importantly, the equation of state accurately includes molecular hydrogen dissociation. We focus on molecular cloud core masses of 1 and 3 $M_ odot $ and explore the effects of different initial rotation rates and cloud core sizes. Our study underlines mechanisms for the early transport of dust from the inner hot disc regions via the occurrence of two transient gas motions, namely meridional flow and outflow. The vortical flow fosters dynamical mixing and retention of dust, while the thermal pressure driven outflow replenishes dust in the outer disc. Notably, these phenomena occur regardless of the initial cloud core mass, size, and rotation rate. Young dynamical precursors to planet-forming discs exhibit regions with complex hydrodynamical gas features and high-temperature structures. These can play a crucial role in concentrating dust for subsequent growth into protoplanets. Dust transport, especially, from sub-au scales surrounding the protostar to the outer relatively cooler parts, offers an efficient pathway for thermal reprocessing during pre-stellar core collapse.

An experimental investigation on the foam proportion for coal dust suppression in underground coal mines

Coal dust presents a grave peril to the well-being of miners and mine safety. In the absence of preventive measures, the concentration of dust in the working area can exceed one thousand milligrams per cubic meter. Foam-based dust removal, owing to its noteworthy merits such as minimal water consumption and high efficiency in removing dust, has emerged as one of the prevailing technologies for dust elimination. To mitigate dust generation during excavation, extensive investigations have been undertaken to explore the impact of foam reagent solution ratios on the efficacy of foam dust removal. By meticulously selecting surfactants, the consequences of varying concentrations and combinations of foam reagents, wetting reagents and foam stabilizers on foaming performance are examined. Valuable insights into the functional relationship between initial foam volume, volume decay rate, and foam reagent concentration are obtained. Furthermore, an in-depth analysis is conducted to probe the influence of wetting reagent addition on coal dust wetting, foam formation, and stability, thereby elucidating the functional connection between wetting time and the concentration of the wetting reagent. Additionally, the ramifications of stabilizer addition on foam stability and other relevant foam properties undergo comprehensive exploration, ultimately leading to the discovery of the functional relationship between foam performance and stabilizer concentration. Notably, experimental findings demonstrate that the optimum ratio for the foam reagent solution is AOS: SDS: STPP: CDEA: water=5:1:4:1:9989. This specific composition exhibits superlative foam foaming performance, stability, and wetting characteristics. Following a meticulous evaluation of gas supply volume, the optimal foam proportion is determined to be a foam reagent solution of 8 m3/h accompanied by a gas supply rate of 100 m3/h. The dust suppression efficiency of the foam produced by the optimal foam proportion reaches an about 97%, substantiating its effectiveness in dust removal.

Data-driven approach for intelligent tunnel dust concentration prediction

The precise evaluation of tunnel dust concentration (TDC) stands as a primary concern within engineering practices. However, comprehensive and accurate prediction of TDC becomes increasingly challenging due to the expanding multi-source datasets and cumulative errors. This study employs innovative data-driven ensemble learning methodologies, specifically random forest (RF) and gradient boosting regression tree (GBRT), to delineate the intricate relationships between TDC values and various rock tunnel characteristics. Five diverse variables sourced from multiple origins are examined and employed as inputs within the database, while the TDC values derived from the dust concentration meter serve as the target outputs. Subsequently, a Bayesian optimization approach, the Tree-structured Parzen Estimator (TPE), is introduced to automatically ascertain the optimal hyper-parameters for the ensemble models. A comprehensive comparison is conducted between the two ensemble learning models and a singular machine learning algorithm, the classification and regression tree (CART), concerning predictive accuracy and resilience via 10-fold cross-validation (CV). The findings reveal the superior performance of the hybrid ensemble learning models over the individual ML models. Notably, the TPE-GBRT algorithm adeptly captures the measurement evolution, showcasing the lowest prediction errors and the highest correlation coefficient. These predicted outcomes significantly contribute to enhancing the engineering comprehension of the interrelation between rock tunnel parameters and TDC values.

Star Formation and Dust in the Cosmic Web

The large-scale environment of the cosmic web is believed to impact galaxy evolution, but there is still no consensus regarding the mechanisms. We use a semi-analytic model (SAM) galaxy catalog to study the star formation and dust content of local galaxies in different cosmic environments of the cosmic web—namely voids, filaments, walls, and nodes. We find a strong impact of the environment only for galaxies with M stars ≲ 1010.8 M ⊙: the less dense the environment, the larger the star formation rate and dust content at fixed stellar mass. This is attributed to the fact that galaxies in less dense environments typically feature younger stellar populations, a slower evolution of their stellar mass, and delayed star formation compared to galaxies in denser environments. As for galaxies with M stars ≳ 1010.8 M ⊙, the differences among environments are milder, due to the disk-instability-driven supermassive black hole (SMBH) growth implemented in the SAM, which makes SMBH growth, and thus galaxy quenching, environment-insensitive. We qualitatively test our predictions against observations by identifying environments in Sloan Digital Sky Survey Data Release 16 using dust masses derived from the GAMA survey. The agreement is encouraging, particularly at logMstars/M⊙≳10.5–11 , where the specific star formation rates and dust masses appear quite environment-insensitive. This result confirms the importance of in situ growth channels of SMBHs.

Geographical, Seasonal and Diurnal Variations of Acoustic Attenuation, and Sound Speed in the Near‐Surface Martian Atmosphere

AbstractThis work introduces a comprehensive model of sound attenuation and speed on Mars, in light of the recent operation of several microphones on the surface of Mars. The proposed acoustic model calculates the sound speed and attenuation throughout the near‐surface Martian atmosphere based on first‐principles. We evaluate the effects of the seasonal and diurnal cycle of air temperature, pressure and CO2, as well as the concentration of airborne dust on the sound attenuation. The attenuation and speed of sound are most sensitive to the air temperature and, therefore, they vary with the diurnal temperature cycle and to a lesser degree with the seasonal changes in temperature. The speed of sound also varies with the seasonal variations of the concentration of CO2. The main outcome of this work is an acoustic model capable of computing the sound speed and attenuation for any location at the Martian surface at any time of year and any time of day.

Treatment of chromium-containing sludge using sintering and ironmaking combined technology: A risk-reducing strategy for environmental impact

The efficient, safe and eco-friendly disposal of the chromium-containing sludge (CCS) has attracted an increasing concern. In this study, Co-processing of CCS was developed via employing sintering and ironmaking combined technology for its harmless disposal and resource utilization. Crystalline phase and valence state transformation of chromium (Cr), technical feasibility assessment, leaching risk, characteristics of sintered products, and pollutant release during CCS co-processing were investigated through a series of laboratory-scale sintering pot experiments and large scale industrial trials. The results showed that the content of Cr(VI) in sintered products first increased then decreased with increasing temperature ranges of 300 °C–800 °C, and reached a maximum of 2189.64 mg/kg at 500 °C. 99.99% of Cr(VI) can be reduced to Cr(III) at above 1000 °C, which was attributed to the transformation of the Cr(VI)-containing crystalline phases (such as, MgCrO4 and CaCrO4) to the (Mg, Fe2+)(Cr, Al, Fe3+)2O4. The industrial trial results showed that adding 0.5 wt‰ CCS to sintering feed did not have adverse effects on the properties of the sintered ore and the plant's operating stability. The tumbler index of sinter was above 78% and the leaching concentrations of TCr (0.069 mg/L) was significantly lower than the Chinese National Standard of 1.0 mg/L (GB5085.3–2007). The TCr contents of sintering dust and blast furnace gas (BFG) scrubbing water were less than 0.19 wt‰ and 0.11 mg/L, respectively, which was far below the regulatory limit (1.5 mg/L, GB13456-2012). The mass balance evaluation results indicated that at least 89.9% of the Cr in the CCS migrated into the molten iron in the blast furnace (BF), which became a useful supplement to the molten iron. This study provided a new perspective strategy for the safe disposal and resource utilization of CCS in iron and steel industry.

Recent Patents on Device or System Innovation in Pneumatic Conveying

Abstract: Coal is mostly stored in coal bunkers. As the amount of coal in the bunker increases, the concentration of coal dust inside the bunker also increases, making it susceptible to accidents such as fires and explosions. Additionally, the leakage of coal dust particles can cause significant environmental pollution in the surrounding area, leading to resource wastage. To improve energy efficiency, reduce material transport dust concentration, and protect the surrounding environment, the efficient, energy-saving, and environmentally friendly characteristics of pneumatic conveying systems are utilized. This is achieved through the use of anti-dust telescopic pipeline equipment (DTPE), which effectively prevents external dust particles from entering the telescopic pipeline, thus reducing mechanical wear. In environments with high coal dust concentration, a coal particle pneumatic conveying storage system based on DTPE is used to extend the service life of pneumatic conveying pipelines and effectively reduce the coal dust concentration within the storage bin. This study reviews the patents and research achievements of scholars in the field of pneumatic conveying and focuses on the anti-dust telescopic pipeline equipment (DTPE) and the coal particle pneumatic conveying storage system based on DTPE. Experiments using pneumatic conveying, screw conveyors, and belt conveyors are conducted to compare conveying time and efficiency. Dust reduction experiments are carried out in the coal bunker to verify the dust reduction effect of the coal particle pneumatic conveying storage system based on DTPE. The anti-dust telescopic pipeline equipment (DTPE) features a telescopic shell to protect the telescopic pipeline, effectively reducing mechanical wear caused by coal particles entering the gaps in the pipeline during pneumatic conveying. The coal particle pneumatic conveying storage system based on DTPE includes a cyclone dust removal system and a dynamic monitoring system, which monitors the temperature inside the bin and reduces the coal dust concentration, thereby minimizing the occurrence of safety accidents. Through experimental verification, the coal particle pneumatic conveying storage system based on DTPE is found to be suitable for environments with high coal dust concentrations. The anti-dust telescopic pipeline equipment (DTPE) and the coal particle pneumatic conveying storage system based on DTPE achieve the automated feeding, dust removal, return, and discharge of coal particles. They offer advantages such as high system automation, minimal environmental pollution, and high coal transport rates, providing design references for the pneumatic conveying of coal and other ore particle materials.

Forming localized dust concentrations in a dust ring: DM Tau case study

Context. Previous high-angular-resolution 225 GHz (~1.3 mm) continuum observations of the transitional disk DM Tau have resolved an outer ring at 20–120 au radii that is weakly azimuthally asymmetric. Aims. We aim to examine dust growth and filtration in the outer ring of DM Tau. Methods. We performed ~0″.06 (~8.7 au) resolution Karl G. Jansky Very Large Array (JVLA) 40–48 GHz (~7 mm; Q band) continuum observations, along with complementary observations at lower frequencies. In addition, we analyzed the archival JVLA observations undertaken since 2010. Results. Intriguingly, the Q band image resolved the azimuthally highly asymmetric, knotty dust emission sources close to the inner edge of the outer ring. Fitting the 8–700 GHz spectral energy distribution (SED) with two dust components indicates that the maximum grain size (amax) in these knotty dust emission sources is likely ≳300 µm, whereas it is ≳50 µm in the rest of the ring. These results may be explained by a trapping of inwardly migrating “grown” dust close to the ring inner edge. The exact mechanism for developing the azimuthal asymmetry has not yet been identified, which may be due to planet-disk interaction that might also be responsible for the creation of the dust cavity and pressure bump. Otherwise, it may be due to the fluid instabilities and vortex formation as a result of shear motions. Finally, we remark that the asymmetries in DM Tau are difficult to diagnose from the ≳225 GHz observations, owing to a high optical depth at the ring. In other words, the apparent symmetric or asymmetric morphology of the transitional disks may be related to the optical depths of those disks at the observing frequency.

Universal, Low-cost Temperature, Humidity, and Dust Concentration Environmental Measurement and Visualization

Humans spend most of their lives indoors. A comfortable environment contributes to human health, but an indoor environment can change due to various factors. Monitoring indoor temperature, humidity, and dust concentration can help people improve the environment through various measures based on the current values. The author designed a circuit using Arduino and sensors to detect and visualize the values. In this study, two sensors, SHTC3 and GP2Y1014AU0F, were used for the measurements. And LEDs and speakers were used as indicators. The author used the brightness of the LEDs to show the values of temperature and humidity. The author used a speaker to play a melody to remind people to open the windows or turn on the purifier when the particle dust exceeds the normal range in the room. This detection device can help people to detect the environment and alert them simultaneously in order to continuously maintain a good and healthy indoor environment.

Dispersion and migration characteristics of multisource respirable dust in development panels during tunnelling processes

Underground miners in Australia are facing continued threats from dust-related diseases. To address these issues, improved knowledge of airflow migration patterns and respirable dust dispersion characteristics within a continuous-miner-driven heading under an exhausting ventilation system is required. Based on site-specific conditions of a development heading in New South Wales, a three-dimensional computational fluid dynamics (CFD) model was constructed and validated with onsite dust monitoring data, where a good agreement was achieved. Three scenarios of coal cutting at the middle, floor and roof positions were considered and simulated, with dust generated at four different sources. The simulation results indicated that the operators on the left-hand-side (LHS) with the extraction duct should be equipped with fit-for-purpose personal protective equipment and stay behind the ventilation duct inlet during coal cutting process, while miners standing at the right-hand-side (RHS) of the continuous miner for roof and rib bolting and machine operating should stay immediately behind the roof and rib bolting rig where dust concentration is relatively low. In addition, an increase in airflow rate through the exhausting ventilation duct or a reduction in the distance from the duct inlet to the heading face assisted in reducing dust levels within the heading, particularly at the LHS of the continuous miners. Finally, compared to the scenario of the current ventilation scheme, an on-board exhausting ventilation system could improve dust removal performance, with dust concentration at the breathing level reducing by approximately 43.6%. This modelling study can advance the understanding of multi-source dust diffusion characteristics in the heading face and provide guidance on dust mitigation, thus improving the health and safety of miners and creating a cleaner underground working environment.

Nontarget Identification of Novel Organophosphorus Flame Retardants and Plasticizers in Indoor Air and Dust from Multiple Microenvironments in China.

The indoor environment is a typical source for organophosphorus flame retardants and plasticizers (OPFRs), yet the source characteristics of OPFRs in different microenvironments remain less clear. This study collected 109 indoor air samples and 34 paired indoor dust samples from 4 typical microenvironments within a university in Tianjin, China, including the dormitory, office, library, and information center. 29 target OPFRs were analyzed, and novel organophosphorus compounds (NOPs) were identified by fragment-based nontarget analysis. Target OPFRs exhibited the highest air and dust concentrations of 46.2-234 ng/m3 and 20.4-76.0 μg/g, respectively, in the information center, where chlorinated OPFRs were dominant. Triphenyl phosphate (TPHP) was the primary OPFR in office air, while tris(2-chloroethyl) phosphate dominated in the dust. TPHP was predominant in the library. Triethyl phosphate (TEP) was ubiquitous in the dormitory, and tris(2-butoxyethyl) phosphate was particularly high in the dust. 9 of 25 NOPs were identified for the first time, mainly from the information center and office, such as bis(chloropropyl) 2,3-dichloropropyl phosphate. Diphenyl phosphinic acid, two hydroxylated and methylated metabolites of tris(2,4-ditert-butylphenyl) phosphite (AO168), and a dimer phosphate were newly reported in the indoor environment. NOPs were widely associated with target OPFRs, and their human exposure risk and environmental behaviors warrant further study.

Improvement and optimization of coal dust concentration detection technology: Based on the 3σ criterion and the kalman filtering composite algorithm

Due to the inherent time delay in dust concentration data transmission, dust reduction equipment is unable to respond according to the current moment's dust concentration. Hence, the focus of mine dust concentration detection technology extends beyond the current dust concentration to accurately predicting the next moment's dust concentration, allowing a response window for dust reduction equipment, leading to more optimal dust reduction effects. This necessitates the introduction of the Kalman filtering algorithm. Despite the traditional single Kalman filtering algorithm's ability to make certain dust concentration predictions, it is constrained by high-temperature, high-humidity underground environments and electromagnetic pulse signal interference from fan and coal mining machine operations, with an error rate reaching up to 40 %, seriously disrupting underground dust reduction equipment. However, the composite Kalman filtering algorithm incorporating the 3σ rule effectively eliminates bad values and removes instability from the underground environment and noise, rendering it applicable to most complex environments, providing accurate predicted concentrations for dust reduction equipment, and boosting overall universality. This study designed a fusion algorithm based on the Pauta criterion and Kalman filter to further optimize the dust concentration detection technology based on electrostatic induction. The sensor's model and measuring principle were first analyzed, and the initial calibration and precision testing of the sensor using the experimental system were completed. The dust concentration fluctuation characteristics were then modeled with Matlab, and the noise variance was estimated to process and filter the dust concentration data with the Pauta criterion, Kalman filter, and fusion algorithm respectively. The accuracy of the dust concentration sensor was tested again after applying the fusion algorithm, which proved to significantly enhance the stability and accuracy of the electrostatic induction-based dust concentration sensor. This study has critical implications for coal mine dust concentration monitoring and coal miner occupational health protection.

Simulation and synoptic investigation of a severe dust storm originated from the Urmia Lake in the Middle East

Dried lake beds are one of the largest sources of dust in the world, causing environmental problems in the surrounding areas. In this study, the desiccated Urmia Lake was the primary source of dust for all nearby synoptic stations during the April 24-25, 2017 dust episode. Synoptic analysis revealed that the heavy dust storm was triggered by a strong Black Sea cyclone and a low-pressure system over central Iraq in conjunction with a vast high-pressure system. HYSPLIT-based trajectory analysis showed that high PM10 recorded over the Urmia Lake region on April 23-26, 2017, influenced western Azerbaijan, the south of the Caspian Sea, southwestern Kazakhstan, northwestern Uzbekistan, and western Turkmenistan. The dustiest air masses (PM10 > 400 µg m–3) affected the south of the Caspian Sea and western Azerbaijan. Furthermore, the WRF-Chem model was run to evaluate the spatial distribution of dust particles in the study region. The vertical profile revealed that the simulated dust concentration ascended to 5 km from the lake. The WRF-Chem dust schemes accurately simulated dust propagation and the vertical dust profile over Urmia Lake; however, the AFWA and GOCART dust schemes showed that PM10 fluctuating changes were earlier than the measured surface PM10 at five stations around Urmia Lake on April 23-26, 2017. Furthermore, the maximum amount anticipated by the model simulation was 12 h earlier than the maximum surface mass concentration of measured PM10 at the stations throughout the period.

Modern environmental art design based on Artificial Intelligence technology and ecological civilization

This study delves into a novel approach for energy conservation and environmental pollution reduction through modern environmental art design, guided by the ecological civilization concept and powered by artificial intelligence (AI) technology. The environmental art framework, aligning with the ecological civilization paradigm, is intricately designed. The data acquisition layer employs diverse sensors to gather equipment status, environmental, and pollution data, transmitting it to the executive controller layer via internal WIFI connectivity. The collected data undergoes meticulous analysis and processing within the data layer before reaching the actuator control layer. Leveraging support vector machines in artificial intelligence, the executive controller layer amalgamates the analyzed equipment and environmental data to devise energy-saving equipment and environmental pollution control schemes. Real-time visualization of these outcomes is achieved through the display operation layer. Findings affirm the effectiveness of this method in acquiring pertinent data for modern environmental art design and managing equipment states. Implementation of this approach successfully diminishes power consumption, dust concentration, and formaldehyde levels in the modern environmental art design zone, showcasing its prowess in energy conservation and pollution control. The integration of AI within the ecological civilization framework highlights its potential in fostering sustainable and environmentally conscious practices in modern art creation.

Lagging pollution of polycyclic aromatic hydrocarbons in the rebuilt e-waste site: From the perspective of characteristics, sources, and risk assessment

Little information is known regarding how the lagged pollution of polycyclic aromatic hydrocarbon (PAH) influenced the environment and human health after an e-waste dismantling site was rebuilt. This study investigated the characteristics, sources, and risk assessment of PAHs in a rebuilt e-waste site and its surrounding farmland by analyzing the samples of soil, dust, water, and vegetable. Concentrations of PAHs in soil, vegetable and water in the rebuilt site were relatively higher than in its surrounding farmland. The concentrations in surface soils, soil columns, dust, vegetables, and water varied from 55.4 to 3990 ng g−1, 1.65 to 5060 ng g−1, 2190 to 2420 ng g−1, 2670 to 10,300 ng g−1, and 46.8 to 110 μg L−1 in the e-waste site, respectively. On the farmland, PAH concentrations in surface soils, vegetables, and water ranged from 41.5 to 2760 ng g−1, 506 to 7640 ng g−1, and 56.6 to 89.2 μg L−1, respectively. A higher proportion of high-molecular-weight PAHs (HMW-PAHs) appeared in all multimedia compared with low-molecular-weight PAHs (LMW-PAHs). Diagnostic ratio together with positive matrix factorization (PMF) revealed that vehicle emission was the primary source in this area, and the activity of e-waste disposal was another important source in the rebuilt e-waste site. Based on the deterministic health risks, people working in the reconstructed e-waste site were exposed to low risks, whereas the residents living near the surrounding farmland were exposed to low risk. Sensitivity analyses indicated that exposure frequency and PAH concentrations were the main factors that influenced exposure risk. This study provides valuable insight into the comprehension of the lagging pollution effects of PAH on the environment and human health after the e-waste site was rebuilt.

Gas-Solid Flow Characteristics of Airflow and Dust Particles in Blasting Excavation of Underground Metal Mine Tunnels.

Effective dust removal has long been a challenge in the blasting mining of underground metal mine tunnels, and uncontrolled dust diffusion seriously endangers workers' respiratory systems and the underground space safety environment. However, the vast majority of existing numerical studies on dust diffusion are focused on coal mine fully mechanized mining, which is different from metal mine blasting excavation in terms of stope structure and dust properties. Furthermore, the mechanism by which the forced and exhaust ventilation modes affect the diffusion characteristics of inhalable particles is unclear. In this work, gas-solid flow characteristics for dust diffusion in a typical metal mine blasting tunnel were numerically investigated based on the Euler-Lagrange method, where the blasting face instantly released 6.37 × 107 particles with 100 different sizes, ranging from 0.8 to 200 μm. The interphase forces between airflow and dust particles are comprehensively modeled, and the particle diffusion effect caused by fluid turbulence is described by a discrete random walk model. Detailed information for airflow turbulence and particle migration was revealed, and dust removal efficiencies for inhalable particulate matter (PM10) by forced, exhaust, and hybrid ventilation were analyzed. Numerical results predict a complex airflow pattern in the working roadway, including the jet-flow region, return airflow core region, airflow disorder region, and secondary flow region. Dust diffusion temporal characteristics can be divided into three stages, namely, the initial stage of dust generation, the efficient ventilation and dust removal stage, and the later stage of dust diffusion. Dust diffusion spatial characteristics indicate that under the Coanda wall attachment effect, the dust concentration exhibits nonuniform distribution in both vertical and horizontal directions of the return air roadway. The dust removal efficiency of hybrid ventilation on inhalable particles above respiratory height is better than that of forced ventilation, especially in the return air roadway. The additional exhaust air duct based on forced ventilation can discharge more inhalable particles from the tunnel.

Study on multiple influence mechanism of airflow-dust-gas coupling diffusion under large vortex flow technology

In response to the serious dust pollution and excessive gas concentration in fully mechanized excavation face, a multi-phase coupling diffusion model of airflow-dust-gas was established, and the influence of pressure pumping ratio and air volume on dust and gas diffusion was studied. The results showed that the dust of the traditional ventilation mode was diffused to the whole roadway, and the high-concentration gas accumulated obviously. However, after adopting the new ventilation mode of large vortex flow, a quantity of dust was controlled in the eddy field, and high-concentration gas was dissipated by strong airflow, so there was no gas accumulation. As the pressure pumping ratio decreases, the extraction effect increases, the eddy current intensity also increases, and the control effect on dust is enhanced. The pressure pumping ratio with the best dust control effect is 0.6, and there is no dust pollution and no gas accumulation in the driver's location. The fixed pressure pumping ratio is 0.6, and the diffusion of dust and gas is not significantly affected by an increase in air volume, but high-speed airflow can dilute and reduce the concentration of dust and gas. When Qb = 600.0 mg/m³, the high-speed airflow can dilute the dust concentration, accelerate the dispersion of high-concentration gas, keep the gas below the safe level, and have a good dust control effect. The increase of air volume will further reduce the dust and gas concentration. This study provides a theoretical basis for the promotion and utilization of new ventilation method on-site.