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In November 2015, the PM 2.5 and PM 10 particulate matter (PM) levels in platforms, station halls, and rail areas of the Shangcheng and Jiashan Road Station were monitored to investigate air pollution in the Shanghai subway system. The results revealed that in subway stations, PM 2.5 and PM 10 concentrations were significantly higher than those in outdoor environments. In addition, particle concentrations in the platforms exceeded maximum levels that domestic safety standards allowed. Particularly on clear days, PM 2.5 and PM 10 concentrations in platforms were significantly higher than maximum standards levels. Owing to the piston effect, consistent time-varying trends were exhibited by PM 2.5 concentrations in platforms, station halls, and rail areas. Platform particle concentrations were higher than the amount in station halls, and they were higher on clear days than on rainy days. The time-varying trends of PM 10 and PM 2.5 concentrations in platforms and station halls were similar to each other. Activities within the station led to most of the inhalable particles within the station area. The mass concentration ratios of PM 2.5 and PM 10 in platforms were within 0.65-0.93, and fine particles were the dominant components.

In this work, a new method of simulating fiber capturing particles was proposed, aiming to reveal the effects of fine particles turbulent aggregation on the capture performance of single fibers in the flow field. The process was numerically simulated based on a computational fluid dynamics–population balance method (CFD-PBM) and Eulerian wall film (EWF) model. The CFD-PBM method was used to calculate the turbulent aggregation of fine particles, and the EWF model was used to calculate the particle deposition of the fiber surface. The results showed that the numerical simulation results were consistent with the formulas. For the particle diameter range of 0.5–5.0 µm, the error of the numerical simulation results of capturing efficiency was reduced from 16.14% to 4.500% after considering the turbulent aggregation of fine particles. The deposition thickness of single fibers surface had a linear functional relationship with the residence time and the particle diameter. Moreover, when 0.5 µm ≤ dp ≤ 2.5 µm, the capture of single fibers had an inhibitory effect on the turbulent aggregation of particles. These studies provided a research clue for developing methods for scientific researchers to improve numerical simulation accuracy. [ABSTRACT FROM AUTHOR]

In this work, a new method using an external magnetic field enhanced the capture of Fe-based fine particles by magnetic fibers was proposed. The process of Fe-based fine particle capture by magnetic fibers in two structure arrangements (staggered/parallel) was numerically simulated based on a computational fluid dynamics-discrete phase model (CFD-DPM) method. Different magnetic fields could be formed by adding uniform magnetic fields along with the X-, Y-, and Z-axes were added to the domain where the magnetic fibers were located. The movement trajectories and filtration efficiencies in two structure arrangements under different magnetic fields were compared. The results showed that when v = 0.1 m/s, and 0.5 µm ≤ dp ≤ 2.5 µm, the results were relatively stable when the external magnetic field was along the X-, and Y-axes, and the filtration efficiency of the staggered structure was higher than that of the parallel structure. The results fluctuated greatly when the external magnetic field was along the Z-axis. Within the same fibrous structure arrangement, when the direction of the uniform magnetic field was the same as the direction of the face velocity ( H → // v → ⊥ l → fiber ), the performance of Fe-based fine particle capture by the magnetic fibers was the best. [ABSTRACT FROM AUTHOR]

In this work, an existing method of capturing Fe-based fine particles by magnetic fiber is improved, and a weaving method for the fiber filter material is further determined. Different combinations of magnetic fields could form around the magnetic fibers, which change the interaction between orthogonal magnetic fibers when a uniform magnetic field is applied along the X -, Y-, and Z -axes. Therefore, the process of particle capture by the orthogonal magnetic fibers under three configurations was compared using the computational fluid dynamics-discrete phase model (CFD-DPM) and a special user-defined function (UDF) of the magnetic force. The results show that the interaction between orthogonal magnetic fibers could either inhibit or promote the capture of Fe-based fine particles by adjacent magnetic fibers. In industrial production, the magnetic filter material is suitable for the weaving method for the alternate use of magnetic and traditional fibers. When a uniform magnetic field is applied along the X -axis, this weaving method makes the capturing performance of orthogonal magnetic fiber best. Moreover, the magnetic characteristics, flow characteristics, and combination sequence of magnetic fields should be considered. This study provides scientific researchers with new insights for the development of novel high-efficiency fibrous filters to reduce particulate pollutants emissions. [ABSTRACT FROM AUTHOR]

• Real-time vehicle-specific ratio power distribution of the fleet in Yan'an tunnel. • Change in Particulate Matter and Carbon Monoxide Emission Rates over years. • Model of motor vehicle emissions simulator in predicting the pollutant emission factors. • Human Health Damages indicate hazardous pollutants in the tunnel ventilation flow. • Complementary ventilation in pollution reduction and energy efficiency operation. Underground road tunnels are becoming increasingly prevalent in cities as a means to alleviate ground traffic congestion, which in turn leads to air pollution near tunnel exits and an increase in the power consumption of ventilation systems. To investigate the characteristics of vehicle exhaust pollutants and human health damages (HHDs), we conducted tests in a typical Shanghai underground tunnel, in which real-time wind speeds, traffic volume rates, vehicle velocities, and traffic distribution were recorded. The prediction model of emission factors with motor vehicle emissions simulator (MOVES) was verified by comparing test results, the UNEP/SETAC toxicity (USEtox) Life Cycle model was adopted to assess the HHDs due to CO, PM 2.5 , and PM 10 , and the air-exchanging ventilation was analysed for potential pollution reduction. Results showed emission rates were reducing yearly and could be predicted with MOVES, PM 10 had a greater impact on human health than PM 2.5 in the tunnel ventilation, and complementary ventilation could improve the tunnel ventilation effects. The survey findings can be used to conduct a new quantitative assessment and an efficient control method for air pollution in city tunnel systems, and in turn improve the energy efficiency of existing underground tunnels. [ABSTRACT FROM AUTHOR]

• Four influencing factors on the transport of high-temperature particles are investigated. • Motion mechanism is well revealed by analyzing dynamic variations of particle forces. • The maximum horizontal diffusion distance (Δ R max) is adopted to evaluate exposure risk. • Δ R max and movement of particles are dependent on heat exchange amount and particle size. The motion feature of particulate pollutants in industrial buildings, has a significant impact on the indoor environment and workers' health. In this study, the numerical simulations are performed to investigate the transport characteristics of high-temperature fine particles generated during the welding processes, influenced by four different factors (i.e, release temperature (T 0), release velocity (v 0), operation time (t 0), and particle diameter (d p)). Specifically, the movement mechanism of particles is clarified through the conservation of energy and Newton's second law. The maximum horizontal diffusion distance of particles (Δ R max) has been proposed to assess the exposure risk of particles. Results show that the transformation between heat energy and kinetic energy drives the two-phase flow to move up. The temperature of particles drops sharply and reaches the environmental temperature at 3.0 s approximately, while their velocity increases first before decreasing slowly. The gravity acting on particles and vortex interaction of airflow result in different motion behaviors of particles in both vertical and horizontal directions. Moreover, Δ R max is positively correlated with T 0 , v 0, and t 0 , but negatively correlated with d p , and has a maximum value of 6.4 m. Generally, the motion and exposure risk of particles are dependent on the heat exchange amount and particle size. The results can contribute to health risk assessment and ventilation system design in the industrial plants. [ABSTRACT FROM AUTHOR]