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An experiment was carried out using a scale model of a tall building, with the goal of investigating the role of individual buildings in the dispersion of air pollution. Pollutant dispersion around an isolated building with a height-to-length aspect ratio of 1.4 is investigated using simultaneous particle image velocimetry and planar laser induced fluorescence. Dye is released from a ground-level point source five building heights upstream of the tall building. It was found that in this case the scalar plume was dispersed laterally strongly by the building, but only slightly vertically. It is hypothesized that this is due to 94% of the plume impinging below the stagnation point on the front of the building and being drawn into the horseshoe vortex. We expect this fraction would be lower in a case in which the building is in an array of smaller buildings, and that this would lead to more vertical dispersion.

Time-varying characteristics of particulate matter (PM) pollution play a crucial role in shaping atmospheric dynamics, which impact the health and welfare of urban commuters. Previously published studies on the diurnal patterns of PMs are not consistent, especially in the context of field experiments in central China, and most field studies have only focused on particles with a single particle size. This study conducted regional-scale studies across 72 street canyon sets in Wuhan, China, investigated diurnal and seasonal PM concentration variations while also evaluating various PM size and the key driving factors. During summer (July, August, and September), evergreen tree-lined street canyons maintained a stable linear trend for smaller d p particulates (i.e., PM 1 , PM 2.5 , and PM 4 ), while deciduous street canyons exhibited a bimodal distribution. In winter (January and February), fine particulates (i.e., PM 1 and PM 2.5 ) remained a linear trend in evergreen street canyons, while deciduous street canyons show a slightly wavy fluctuating pattern. Meanwhile, it exhibited quadrimodal-peak and triple-trough patterns in both PM 7 , PM 10 , and TSP concentrations. The lowest PM concentrations were observed between 14:00 and 16:00 for all particle sizes, with decreased summer pollution (7.81% lower in PM 2.5 , 53.47% lower in PM 10 , and 50.3% lower in TSP) noted in our seasonal analysis. Among the various meteorological factors, relative humidity (RH) was identified as the dominant influencing PM factor in both summer and winter. Results from this study will help us better understand field-based air pollutant dispersion processes within pedestrian spaces while laying the groundwork for future research into street PM experiments. Graphical Abstract

Air quality in dense urban environments is a growing concern, especially in rapidly developing cities. In the face of growing traffic associated with urbanisation, there is evidence for high levels of pollutant concentration at street level which is influenced by building forms. In this paper, we examine the potential effects of high-rise, cluster developments permitted by the local planning authorities in the newly established Port City development in Colombo, Sri Lanka. We designed possible building forms based on specific guidelines for the development in terms of plot coverage, floor area ratio, and maximum height. The three-dimensional building clusters were simulated using the RANS RNG k-epsilon turbulence model, to determine pollutant dispersion of a complex street formation in a high-dense high-rise building cluster, within the development and the surrounding context (existing Colombo). Results show that while increased porosity within the built fabric facilitates better pollution dispersion, a low correlation was seen between wind velocity and pollution concentration, especially in deep narrow high-rise canyons. Dispersion patterns at street level and at the urban canopy differed with each built form and are dependent on each canyon geometry. Thus, the study highlights the need for building regulations to take a holistic approach to capture the various elements of a complex urban cluster rather than the current two-dimensional parameters proposed for Port City, Colombo.

To solve the problem of dust production by the caving coal seam on the weather side of a fully mechanized coal face with a large mining height, this study proposes coal cutter onboard dust removal technology for the first time. In this work, taking the 12511 fully mechanized coal face of the Bulianta Coal Mine with a large mining height as an example, a mathematical model was built to study the influence of the onboard dust collector on airflow–dust dispersion pollution and the key technological parameters of the dust collector, and field tests were performed for verification. The results of numerical simulation showed that the dust-carrying airflow, after being blocked by the coal cutter, dispersed in the lateral direction, leading to an increase of airflow velocity on the walkway side to 1.75 m s −1 , and a dust concentration as high as 2500 mg m −3 . At the same time, an airflow vortex area with the largest diameter of 3 m was formed near the surface of the coal cutter body, which attracted dust to gather there. However, after the application of the onboard dust removal technology, the lateral dispersion of dust-carrying airflow weakened, and the dust concentration on the walkway side was reduced to below 600 mg m −3 . In addition, this technology also obviously reduced the influence scope of the vortex and the dust concentration area. It was also found that the installation height of the suction inlet of the dust collector and the air capacity had a large impact on the dust suppression efficiency. The optimum dust suppression efficiency was reached at an installation height of 1.15 m and air capacity of 120 m 3 min −1 . Field test verification demonstrated that the dust concentration on the walkway side could be reduced by as much as 49.3% with the application of the proposed onboard dust removal technology.

Accurate measurement and inference of phase difference between two time series are critical across several fields, including signal processing, economic dynamics, and air pollution research. Wavelet methods offer advantages over traditional approaches by allowing time–frequency localization and adaptability to non-stationary signals, which makes them widely used for phase difference estimation. However, existing methods do not provide a statistical test to determine whether a measured phase difference reflects a true underlying relationship between the signals or is merely an artifact of measurement errors or randomness. In this paper, we propose a bootstrap method to fill this gap. Our method is particularly suited to the analysis of non-standard data distributions and complex temporal dependencies. Extensive simulations demonstrate its desirable power and control of type-I error. Furthermore, we apply the method to study air pollution dispersion in China and elucidate the factors influencing phase differences.

The present study investigated the buoyant wind-driven pollutant plume dispersion and recirculation behaviour inside urban street canyons formed by buildings with wedge-shaped roofs. Numerical modelling was performed using a computational fluid dynamics (CFD) large eddy simulation (LES). Street canyon models with a strongly buoyant fire source located on the street and environmental winds perpendicular to the canyon were developed using the fire dynamics simulator (FDS). The complex interaction of buoyancy and wind, as well as their combined effects on the pollutant plume dispersion, was simulated inside the urban street canyon. The results showed that the flow pattern of pollutant plume dispersion inside the street canyon with increasing wind speed for different roof inclination angles could be divided into three regimes, including a recirculation regime, a quasi-recirculation regime and a non-recirculation regime. The pollutant levels in the street canyon, as indexed by carbon monoxide (CO) concentration, increased under the recirculation regime. For the quasi-recirculation regime, however, the leeward buildings primarily suffered from the higher pollutant levels. The critical wind speed needed to trigger recirculation was analysed for various roof inclination angles. A correlation was proposed to predict the critical wind speed of various wedge-shaped roof angles for recirculation regime and quasi-recirculation regimes.

Urban population growth has led to increased air pollution, influenced by disrupted wind patterns and the heterogeneous distribution of pollutants. Although the relationship between urban form and air quality is well recognized, it is often examined in isolation and through simplified urban geometries. This study addresses these limitations by numerically analyzing pollutant dispersion in densely populated hillside areas using idealized but topographically representative building geometries. A three-dimensional microclimatic simulation is conducted with ENVI-met software, incorporating parametric slope angles and building height variations. The results demonstrate that both slope steepness and building height significantly affect local pollutant concentrations: steeper slopes and taller buildings are associated with higher peak pollution values in the environment. Additionally, the simulation results show that vegetation is critical in mitigating pollution, acting as a natural barrier that enhances dispersion. These findings highlight the need for slope-sensitive urban planning and strategically integrating vegetation in hillside developments to improve air quality in complex urban terrains.

The emission control in adverse meteorological conditions is one of the ways to reduce a negative impact of air pollution. A complex meteorological pollution dispersion index (MPDI) based on the numerical model data is proposed for early forecasting of such conditions. An algorithm for calculating the hourly and periodic MPDI is presented. The results of the method verification according to ground-based and high-altitude observations in the layer of 2–250 m and with the use of average urban pollution data are analyzed. A method for probabilistic forecasting of the MPDI is proposed to increase the reliability of the deterministic forecasting of adverse meteorological conditions. An automated technology for preparing and transmitting an information package of forecast products to the Roshydromet operational and production divisions is described. The package contains the forecasts of vertical temperature profiles, wind in the lower atmospheric layer, precipitation, and the height of the mixing layer with a time step of 3 hours, as well as the forecasts of two kinds of the MPDI with a lead time of two days.

Atmospheric pollution is a critical issue in public health systems. The simulation of atmospheric pollution dispersion in urban blocks, using CFD, faces several challenges, including the complexity and inefficiency of existing CFD software, time-consuming construction of CFD urban block geometry, and limited visualization and analysis capabilities of simulation outputs. To address these challenges, we have developed a prototype system that couples 3DGIS and CFD for simulating, visualizing, and analyzing atmospheric pollution dispersion. Specifically, a parallel algorithm for coordinate transformation was designed, and the relevant commands were encapsulated to automate the construction of geometry and meshing required for CFD simulations of urban blocks. Additionally, the Fluent-based command flow was parameterized and encapsulated, enabling the automatic generation of model calculation command flow files to simulate atmospheric pollution dispersion. Moreover, multi-angle spatial partitioning and spatiotemporal multidimensional visualization analysis were introduced to achieve an intuitive expression and analysis of CFD simulation results. The result shows that the constructed geometry is correct, and the mesh quality meets requirements with all values above 0.45. CPU and GPU parallel algorithms are 13.3× and 25× faster than serial. Furthermore, our case study demonstrates the developed system’s effectiveness in simulating, visualizing, and analyzing atmospheric pollution dispersion in urban blocks.

The motivation for this work stems from the increased number of high-rise buildings/skyscrapers all over the world, and in London, UK, and hence the necessity to see their effect on the local environment. We concentrate on the mean velocities, Reynolds stresses, turbulent kinetic energies (TKEs) and tracer concentrations. We look at their variations with height at two main locations within the building area, and downstream the buildings. The pollution source is placed at the top of the central building, representing an emission from a Combined Heat and Power (CHP) plant. We see how a tall building may have a positive effect at the lower levels, but a negative one at the higher levels in terms of pollution levels. Mean velocities at the higher levels (over 60 m in real life) are reduced at both locations (within the building area and downstream it), whilst Reynolds stresses and TKEs increase. However, despite the observed enhanced turbulence at the higher levels, mean concentrations increase, indicating that the mean flow has a greater influence on the dispersion. At the lower levels (Z < 60 m), the presence of a tall building enhanced dispersion (hence lower concentrations) for many of the configurations.