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PM2.5 air pollution is a critical global health issue. This paper introduces an innovative framework to explore the multi-scale relationship between urban morphology and PM2.5 concentrations. An enhanced Land Use Regression (LUR) model integrates geographic, architectural, and visual factors, enabling analysis from neighborhood to regional scales. A stratified sampling strategy, combined with standardized mobile monitoring and fixed-site data, establishes a robust and verifiable data collection methodology. Cross-validation (CV R2 > 0.70) further confirms the model's reliability and robustness. The nested buffer analysis reveals scale-dependent effects of urban morphology on PM2.5 concentrations, providing quantitative evidence for planning interventions. Quantitative analysis shows land use (β = 0.42, p < 0.01), visual factors (β = 0.38, p < 0.01), and building density (β = 0.35, p < 0.01) in descending order of influence. Geographic factors are significant at the regional scale (2000–3000 m) while architectural parameters dominate at the neighborhood scale (50–500 m), informing both macro-scale spatial optimization and micro-scale design. This framework, through standardized parameters and reproducible procedures, supports cross-regional and cross-scale air quality assessments, providing quantitative metrics for urban planning, neighborhood optimization, and public space design. [ABSTRACT FROM AUTHOR]

We are motivated by the field of air quality control, where one goal is to quantify the impact of uncertain inputs such as meteorological conditions and traffic parameters on pollutant dispersion maps. Sensitivity analysis is one answer, but the majority of sensitivity analysis methods are designed to deal with scalar or vector outputs and are badly suited to an output space of maps. To address this problem, we propose a generic approach to sensitivity analysis of set‐valued models. This approach can be applied to the case of maps. We propose and study three different types of sensitivity indices. The first ones are inspired by Sobol' indices but adapted to sets based on the theory of random sets. The second ones adapt universal indices defined for a general metric output space. The last set of indices uses kernel‐based sensitivity indices adapted to sets. The proposed methods are implemented and tested to perform an uncertainty analysis for a toy excursion set problem and for time‐averaged concentration maps of pollutants in an urban environment. [ABSTRACT FROM AUTHOR]

Atmospheric boundary layer (ABL) structure and dynamics are important aspects to consider in human health. The ABL is characterized by a high degree of spatial and temporal variability that hinders their understanding. This paper aims to provide a comprehensive overview of machine learning (ML) methodologies, encompassing deep learning and ensemble approaches, within the scope of ABL research. The goal is to highlight the challenges and opportunities of using ML in turbulence modeling and parameterization in areas such as atmospheric pollution, meteorology, and renewable energy. The review emphasizes the validation of results to ensure their reliability and applicability. ML has proven to be a valuable tool for understanding and predicting how ABL spatial and seasonal variability affects pollutant dispersion and public health. In addition, it has been demonstrated that ML can be used to estimate several variables and parameters, such as ABL height, making it a promising approach to enhance air quality management and urban planning. [ABSTRACT FROM AUTHOR]

Understanding hydrodynamic processes is crucial for examining the transport of living biomass and contaminants, including nutrients, metals, persistent organic pollutants, plastics, and suspended particles in aquatic systems. This study investigates pollution transport and influence times in the Altata-Ensenada del Pabellón (ALENPA) coastal lagoon in northwest Mexico using a vertically integrated hydrodynamic model and advection-diffusion equations. When tidal forces, freshwater discharge, and wind effects were taken into account in numerical simulations of a passive tracer release, the effect times ranged from a few weeks near the inlet to over four months in the eastern lagoon. The Culiacan River discharge and prevailing northwest winds significantly impacted these times and their spatial distribution, with areas in the southern lagoon showing slower tracer dispersion, suggesting higher vulnerability to pollution. This investigation provides insights into the hydrodynamic environment of the ALENPA lagoon, identifying regions with long and short influence times based on specific meteorological and hydrological conditions. More broadly, it enhances our understanding of pollutant transport in coastal environments, offering a valuable tool--the numerical assessment of ITD--for selecting suitable, less vulnerable sites for aquaculture or waste disposal across diverse coastal lagoons. [ABSTRACT FROM AUTHOR]

The increase in urban building density will have a significant impact on pedestrian wind environments, especially in high-density urban building environments. Architectural designers should consider the impact of the urban microclimate through reasonable architectural designs and layouts, effectively improve the pedestrian wind environment, and enhance the comfort of urban dwellers and the sustainable development of cities. Therefore, on the basis of the Reynolds number average Navier–Stokes (RANS) method, a standard k-ε turbulence model was adopted to simulate the effects of high-rise buildings with different rotation angles on the flow and dispersion of pollutants. The results showed that the rotation angle has an obvious influence on the flow structure, turbulent kinetic energy, and near-ground concentration, and the effect is more significant with the increase in building height. When the building is rotated by a certain angle (10°, 20°, and 30°), the whole flow is deflected and no longer symmetrical. When the rotation angles are 20° and 30°, it is found that two large vortices are formed in the wake region of the entire building array, as if the building array can be regarded as a whole. Because the pollution source is located in the recirculation zone or the reverse-flow zone, the high-concentration area is mainly concentrated upwind of the source. As the building is rotated counterclockwise (10°, 20°, and 30°), the pollutant plume is also deflected counterclockwise, presenting an asymmetry. [ABSTRACT FROM AUTHOR]

This study presents an assessment of the levels of air pollution emanating from natural gas combustion at the Rumaila Combined Cycle Power Plant (CCPP) in Basrah City by using a Gaussian dispersion model, with results at distance of 100, 500 and 1000 m for the pollutants CO, SO2, NO, and particulate matters (PM). Data on atmospheric stability assessments were taken from meteorological stations in Basrah Governorate that belong to the Iraqi Ministry of Agriculture. The study determined the emission rates from the five stacks of the plant and the wind speed, wind direction at stack height, and Turner-Pasquill stability classes for the wet conditions of 2023/2024. The following are the maximum pollutant concentrations emanating from the stacks: CO was 186 µg.m-3 at 100 m, 6 µg.m-3 at 500 m, and 2.5 µg.m-3 at 1000 m; SO2 was 0.5 µg.m-3 at 100 m, 0.05 µg.m-3 at 500 m, and 0.01 µg.m-3 at 1000 m; NO was 0.07 µg.m-3 at 500 m and 0.03 µg.m-3 at 1000 m; PM was 11 µg.m-3 at 100 m, 0.4 µg.m-3 at 500 m, and 0.15 µg.m-3 at 1000 m. All of these measurements are well below national ambient air quality standards, which means that the Rumaila power plant is not locally deleterious to the air quality. [ABSTRACT FROM AUTHOR]

Abstract This study systematically examines how the urban heat island (UHI) and urban breeze circulation (UBC) respond to an increase in roof albedo (α r) and its influence on urban air pollutant dispersion. For this, idealized ensemble simulations are performed using the Weather Research and Forecasting (WRF) model. The increase in α r from 0.20 to 0.65 decreases the UHI intensity, UBC intensity, and urban planetary boundary layer (PBL) height in the daytime (from 1200 to 1700 LST) by 47%, 36%, and 6%, respectively. As both UBC intensity and urban PBL height decrease, the daytime urban near-surface passive tracer concentration increases by 115%. The daytime UHI intensity, UBC intensity, and urban tracer concentration nonlinearly change with α r: For 0.10 ≤ α r

This study addresses the need to investigate footprint function features in urban areas and establish a validation database for numerical methods. Concentration and its flux footprints of a block-arrayed urban model were measured in a wind tunnel with a neutrally stratified boundary layer. The velocity and concentration were simultaneously measured by an X-probe hot wire anemometer and a fast-response flame ionization detector to evaluate the vertical flux. Experimental results highlighted the influence of the measurement heights on footprint distributions. Because the sensors were immersed in the roughness sublayer, their footprints showed strong heterogeneity across horizontal positions caused by building configurations. It was found that turbulent flux contributes up to 70% of total flux footprints, emphasizing the importance of accurate turbulent dispersion estimation in numerical methods. Furthermore, measured footprints were compared to those modeled by a widely used analytical method (Kormann and Meixner in Boundary-Layer Meteorol 99:207–224, 2001, https://doi.org/10.1023/ A:1018991015119). The measured footprints extended further along the streamwise direction and their spanwise dispersions were constrained by the rows of blocks, which failed to be reproduced in the analytical method. This indicates the significant effects of building configurations on footprint functions in urban areas. [ABSTRACT FROM AUTHOR]

The mechanisms underlying the effects of wind and buoyancy on ventilation in urban street canyons are unclear. This study investigated the effects of facade heating on ventilation and pollutant transport in an idealized street canyon with a 1.67 aspect ratio through computational fluid dynamics simulations. The dispersion pattern of discharged hot pollutants was also studied. A primary recirculation was observed when facade heating was not applied; this recirculation was promoted in leeward-wall and ground heating cases. However, the recirculation was bifurcated into two recirculations in windward-wall heating cases, restricting ventilation. Enhanced recirculation increased the ventilation and decreased the pollution level; by contrast, air pollution increased considerably when the recirculation was bifurcated and ventilation was restricted. In the hot-pollutant case, similar results to those in the ground-heating case were observed. The hot discharged pollutant enhanced ventilation, reducing pollution. The pollutant transport mechanism was determined through an analysis of pollutant fluxes. For the one-recirculation pattern, air convection transported the pollutant from the ground level to the top boundary, and turbulent diffusion then caused pollutant removal. For the two-recirculation pattern, turbulent diffusion contributed substantially to pollutant transport both in the junction between the recirculations and through the top boundary of the street canyon. [ABSTRACT FROM AUTHOR]

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This study numerically investigates the effects of different riverbed forms (flat, ripple, and dune) on pollutant dispersion in open channels using the Flow-3D model and computational fluid dynamics (CFD). The numerical simulations were operated using the Reynolds-averaged Navier-Stokes (RANS) equations which was coupled with an advection-dispersion model for three distinct bed forms. Sodium chloride is used as a tracer material to track pollutant transport. The results reveal that bed forms profoundly influence pollutant dispersion rates in open channels. Ripple beds exhibited the fastest dispersion due to enhanced turbulence and mixing, promoting the breakdown and transport of pollutant particles throughout the water column. In contrast, flat beds displayed the slowest dispersion owing to minimal turbulence and mixing, resulting in higher pollutant concentrations near the source. Dune beds exhibited intermediate dispersion rates compared to ripple and flat beds, with complex flow patterns inducing both turbulence and stratification, leading to variations in dispersion based on flow conditions and pollutant properties. In addition, flow characteristics like velocity, and surface roughness played crucial roles, with higher velocities and rougher beds generally promoting faster dispersion through increased turbulence and mixing. However, excessively high velocities could also hinder dispersion by forming flow separation zones that trap pollutants. [ABSTRACT FROM AUTHOR]

This study presents an assessment of the levels of air pollution emanating from natural gas combustion at the Rumaila Combined Cycle Power Plant (CCPP) in Basrah City by using a Gaussian dispersion model, with results at distance of 100, 500 and 1000 m for the pollutants CO, SO2, NO, and particulate matters (PM). Data on atmospheric stability assessments were taken from meteorological stations in Basrah Governorate that belong to the Iraqi Ministry of Agriculture. The study determined the emission rates from the five stacks of the plant and the wind speed, wind direction at stack height, and Turner-Pasquill stability classes for the wet conditions of 2023/2024. The following are the maximum pollutant concentrations emanating from the stacks: CO was 186 μg.m-3 at 100 m, 6 μg.m-3 at 500 m, and 2.5 μg.m-3 at 1000 m; SO₂ was 0.5 μg.m-3 at 100 m, 0.05 μg.m-3 at 500 m, and 0.01 μg.m-3 at 1000 m; NO was 0.07 μg.m-3 at 500 m and 0.03 μg.m-3 at 1000 m; PM was 11 μg.m-3 at 100 m, 0.4 μg.m-3 at 500 m, and 0.15 μg.m-3 at 1000 m. All of these measurements are well below national ambient air quality standards, which means that the Rumaila power plant is not locally deleterious to the air quality.

Estimating the parameters of an unidentified toxic pollutant source is crucial for public safety, especially in densely populated urban areas. Implementing source term estimation methods in real-world urban environments is challenging due to complex phenomena and the absence of concentration observational data. This work combines a computational fluid dynamics numerical simulation with the Metropolis–Hastings MCMC algorithm to identify the location and quantify the release rate of an unknown source within the geometry of Augsburg city center. To address the lack of concentration measurements, synthetic observations are generated by a forward dispersion model. The methodology is tested using these datasets, both as directly calculated by the forward model and with added Gaussian noise under different source release and wind flow scenarios. The results indicate that in most cases, both the source location and the release rate are estimated accurately. Although a higher performance is achieved using synthetic datasets without additional noise, high accuracy predictions are also obtained in many applications of noisy measurement datasets. In general, the outcomes demonstrate that the presented methodology can be a useful tool for estimating unknown source parameters in real-world urban applications. [ABSTRACT FROM AUTHOR]

AbstractIn this paper, it was performed a numerical simulation of the spread of a pollutant - carbon dioxide from the chimneys of a thermal power plant. To determine the correctness of the models, a test problem was used, the results of which were compared with obtained numerical and experimental values. These models were used for a 3D model on a real scale of Ekibastuz SDP P, the largest thermal power station in Kazakhstan. A study on the spread of pollutants was performed within 24 hours. In addition, in the model, environmental conditions close to the real ones were used - a variable direction of the wind, a variable humidity of the ambient air, and different temperatures, which vary depending on the time of day. The results can be used in the future to study the problem of environmental pollution and reduce the consequences of the environmental situation as a whole. [ABSTRACT FROM AUTHOR]

Understanding hydrodynamic processes is crucial for examining the transport of living biomass and contaminants, including nutrients, metals, persistent organic pollutants, plastics, and suspended particles in aquatic systems. This study investigates pollution transport and influence times in the Altata-Ensenada del Pabellón (ALENPA) coastal lagoon in northwest Mexico using a vertically integrated hydrodynamic model and advection-diffusion equations. When tidal forces, freshwater discharge, and wind effects were taken into account in numerical simulations of a passive tracer release, the effect times ranged from a few weeks near the inlet to over four months in the eastern lagoon. The Culiacan River discharge and prevailing northwest winds significantly impacted these times and their spatial distribution, with areas in the southern lagoon showing slower tracer dispersion, suggesting higher vulnerability to pollution. This investigation provides insights into the hydrodynamic environment of the ALENPA lagoon, identifying regions with long and short influence times based on specific meteorological and hydrological conditions. More broadly, it enhances our understanding of pollutant transport in coastal environments, offering a valuable tool—the numerical assessment of ITD—for selecting suitable, less vulnerable sites for aquaculture or waste disposal across diverse coastal lagoons.

PM2.5 air pollution is a critical global health issue. This paper introduces an innovative framework to explore the multi-scale relationship between urban morphology and PM2.5 concentrations. An enhanced Land Use Regression (LUR) model integrates geographic, architectural, and visual factors, enabling analysis from neighborhood to regional scales. A stratified sampling strategy, combined with standardized mobile monitoring and fixed-site data, establishes a robust and verifiable data collection methodology. Cross-validation (CV R2 > 0.70) further confirms the model’s reliability and robustness. The nested buffer analysis reveals scale-dependent effects of urban morphology on PM2.5 concentrations, providing quantitative evidence for planning interventions. Quantitative analysis shows land use (β = 0.42, p < 0.01), visual factors (β = 0.38, p < 0.01), and building density (β = 0.35, p < 0.01) in descending order of influence. Geographic factors are significant at the regional scale (2000–3000 m) while architectural parameters dominate at the neighborhood scale (50–500 m), informing both macro-scale spatial optimization and micro-scale design. This framework, through standardized parameters and reproducible procedures, supports cross-regional and cross-scale air quality assessments, providing quantitative metrics for urban planning, neighborhood optimization, and public space design.

Studying the mechanism of pollutant transport around an isolated building is essential to address the environmental issue of air pollution around buildings and to understand the intricate process of pollutant dispersion in urban environments. In this paper, an effective numerical approach is used to study the effects of building heights and widths on airflow and pollutant dispersion around an isolated building. The source of pollutants is behind the building. The pollutant is confined to the lower areas as a result of small vortices behind the low-rise buildings, and transported to the wake area. Whereas high-rise buildings make the pollutant move to an upper region. At the pedestrian level, the wake area of the lower building stores more pollution. Therefore, the environment around the low-rise buildings may be more hazardous. The concentration of pollutants is greater at higher altitudes around wider buildings. Pollutants are transferred to the sides of wider buildings at the pedestrian level, leading to lower concentrations in the wake-central area. A wider building poses a greater lateral dangerous-area, while a narrower building results in a longer central wake area that is hazardous. [ABSTRACT FROM AUTHOR]

In recent years, the outbreak of infectious diseases has highlighted the need for improved planning of hospital buildings. Traditional planning for infectious disease hospitals only considers the impact of wind and pollutant diffusion, without analysing pollutant diffusion under different thermal conditions. To reveal the distribution of pollutants in infectious disease hospitals under different thermal conditions, this study conducted wind tunnel tests and numerical analyses of pollutant diffusion in the environment surrounding an infectious disease hospital in Changsha, China. The results show that the pollutant concentration mainly depends on the local wind speed. In the range of Rb = −1.25 to 1.25, the concentration of pollutants was mainly affected by the disturbance of the flow field in areas with rough surfaces, where the effect of the thermal stability of the atmosphere on pollutant diffusion was relatively small. However, in relatively flat regions, the thermal stability of the atmosphere played a significant role in pollutant diffusion around the buildings. [ABSTRACT FROM AUTHOR]

The mechanisms underlying the effects of wind and buoyancy on ventilation in urban street canyons are unclear. This study investigated the effects of facade heating on ventilation and pollutant transport in an idealized street canyon with a 1.67 aspect ratio through computational fluid dynamics simulations. The dispersion pattern of discharged hot pollutants was also studied. A primary recirculation was observed when facade heating was not applied; this recirculation was promoted in leeward-wall and ground heating cases. However, the recirculation was bifurcated into two recirculations in windward-wall heating cases, restricting ventilation. Enhanced recirculation increased the ventilation and decreased the pollution level; by contrast, air pollution increased considerably when the recirculation was bifurcated and ventilation was restricted. In the hot-pollutant case, similar results to those in the ground-heating case were observed. The hot discharged pollutant enhanced ventilation, reducing pollution. The pollutant transport mechanism was determined through an analysis of pollutant fluxes. For the one-recirculation pattern, air convection transported the pollutant from the ground level to the top boundary, and turbulent diffusion then caused pollutant removal. For the two-recirculation pattern, turbulent diffusion contributed substantially to pollutant transport both in the junction between the recirculations and through the top boundary of the street canyon.

Health factors concerning the well-being of the urban population urge us to better comprehend the impact of emissions in urban environments on the micro-scale. There is great necessity to depict and monitor pollutant concentrations with high precision in cities, by constructing an accurate and validated digital air quality network. This work concerns the development and application of a CFD model for the dispersion of particulate matter, CO, and NOx from traffic activity in a highly busy area of the city of Augsburg, Germany. Emissions were calculated based on traffic activity during September of 2018 with COPERT Street software version 2.4. The needed meteorological data for the simulations were taken from a sensor's network and the resulting concentrations were compared and validated with high-precision air quality station indications. The model's solver used the steady-state RANS approach to resolve the velocity field and the convection–diffusion equation to simulate the pollutant's dispersion, each one modelled with different molecular diffusion coefficients. A sensitivity analysis was performed to decide the most efficient computational mesh to be used in the modelling. A velocity profile for the atmospheric boundary layer (ABL) was implemented into the inlet boundary of each simulation. The cases concerned applications on the street level in steady-state conditions for one hour. The results were evaluated based on CFD validation metrics for urban applications. This approach provides a comprehensive state-of-the-art 3D digital pollution network for the area, capable of assessing contamination levels at the street scale, providing information for pollution reduction techniques in urban areas, and combining with existing sensor networks for a more thorough portrait of air quality. [ABSTRACT FROM AUTHOR]

Wind flow around an isolated building is highly turbulent. Facade appurtenances can further increase the complexity of the flow, which strongly affects the gas dispersion around the building. This study investigated the turbulence and pollutant statistics around a high-rise building with large-eddy simulations and determined the influence of overhangs on the local wind flow and dispersion. Large-scale periodic vortex motion was detected. The results indicated that both the oncoming flow and the flow around the building followed a standard Gaussian distribution, whereas the occurrence frequencies of pollutant concentrations were far from Gaussian for pollutants discharged from both the rooftop and the ground behind the building. Near the pollutant sources, the positive concentration fluctuations occurred more frequently; occasionally, positive and negative fluctuations occurred equally. For the majority of areas far from the source, negative fluctuations were more common, but the maximum positive fluctuations were much larger. Overhangs changed the local flow structures near the building facade. Both the maximum concentration fluctuation and the maximum occurrence frequency decreased in the region between overhangs because turbulence was restricted. [ABSTRACT FROM AUTHOR]

The objective of the present study is to analyze the influence of various inflow turbulence generation techniques (ITGT) on the flow field and pollutant dispersion around a street canyon with perpendicular wind flow through the large eddy simulation approach. Vortex method (VM), internal mapping (IM), spectral method (SM) and no fluctuations (NF) are the four ITGTs under investigation. Results suggest that ventilation of the canyon is mainly due to corner eddies, canyon vortex and the flow passing over the top of the buildings. All ITGTs can capture the two important structures of canyon vortex and corner eddy, but IM underpredicts the corner eddies and SM and NF underpredict the canyon vortex. VM slightly overpredicts the canyon vortex. However, its accuracy in predicting the pollutant dispersion at both walls and low speed regions is higher than the other methods. The velocity fluctuation is also another important parameter for ventilating the low speed regions. The VM displays the most accurate results, and the NF shows the least accurate ones. In terms of relative error, computational cost, and the number of required input parameters, VM is the most optimized ITGT. [ABSTRACT FROM AUTHOR]

Urban surfaces exert profound influences on local wind patterns, turbulence dynamics, and the dispersion of air pollutants, underscoring the critical need for a thorough understanding of these processes in the realms of urban planning, design, construction, and air quality management. The advent of advanced computational capabilities has propelled the computational fluid dynamics model (CFD) into becoming a mature and widely adopted tool to investigate microscale meteorological phenomena in urban settings. This review provides a comprehensive overview of the current state of CFD-based microscale meteorological simulations, offering insights into their applications, influential factors, and challenges. Significant variables such as the aspect ratio of street canyons, building geometries, ambient wind directions, atmospheric boundary layer stabilities, and street tree configurations play crucial roles in influencing microscale physical processes and the dispersion of air pollutants. The integration of CFD with mesoscale meteorological models and cutting-edge machine learning techniques empowers high-resolution, precise simulations of urban meteorology, establishing a robust scientific basis for sustainable urban development, the mitigation of air pollution, and emergency response planning for hazardous substances. Nonetheless, the broader application of CFD in this domain introduces challenges in grid optimization, enhancing integration with mesoscale models, addressing data limitations, and simulating diverse weather conditions. [ABSTRACT FROM AUTHOR]

It is challenging to investigate the transport and dispersion of contaminants in river confluence areas due to the complex flow dynamics. In recent studies on the flow dynamics in river confluence areas, it has been revealed that changes in inflow conditions (discharge ratio, width-depth ratio and concentration difference) can greatly influence pollutant diffusion. In this study, an asymmetric confluence-type river is modeled by a three-dimensional hydrodynamic water quality model, and three hydrodynamic scenarios are numerically simulated. The results show that a higher discharge ratio and width-depth ratio led to an increase in the lateral diffusion area of pollutants, deviation in the trajectory line of the mixing interface towards the opposite bank of the interchange, and an increase in the mixing rate of pollutants. For R = 0.267 and b/h = 3.75, the pollutants at the bottom are completely mixed in the exit end section. However, the difference in the pollutant concentration slightly affects the area, length and shape of the pollutant dispersion zone and notably affects only the concentration in each section. [ABSTRACT FROM AUTHOR]

Dredging of inland waterways may cause the spread of contaminants in the bed mud, thus polluting the river water. In order to hinder the spread of pollutants during dredging, a near -closed and semi -closed dredging auxiliary device for environmental protection was proposed, and three-dimensional numerical simulation method was used to study and analyze the different hindering effects of different design schemes against the pollutant dispersion, and to select a more suitable design scheme. The results of the study can provide a new idea for the design of dredging auxiliary facilities for environmental protection. [ABSTRACT FROM AUTHOR]

To improve the reliability of the computational fluid dynamics (CFD) models of wind-driven pollutant dispersion within urban settings, a re-calibration study is conducted to optimize the standard k − ε model. A modified optimization framework based on the genetic algorithm is adapted to alleviate the computational expenses and to further identify ranges for each empirical coefficient to achieve the most reliable and accurate predictions. A robust objective function is defined, incorporating both the flow parameters and pollutant concentration through several linear and logarithmic measures. The coefficients are trained using high-quality and full-scale tracer experiments in a mock urban arrangement simulating a building array. The proposed ranges are 0.14 ≤ C μ ≤ 0.15 , 1.30 ≤ C ε 1 ≤ 1.46 , 1.68 ≤ C ε 2 ≤ 1.80 , 1.12 ≤ σ ε ≤ 1.20 , and 0.87 ≤ σ k ≤ 1.00 . A thorough evaluation of the predicted flow and concentration fields indicates the modified closure is effective. The fraction of predictions within the acceptable ranges from measurements has increased by 8% for pollutant concentration and 27% for turbulence kinetic energy. The generality of the calibrated model is further tested by modeling additional cases with different meteorological conditions, in which the calculated validation metrics attest to the noteworthy improvements in predictions. [ABSTRACT FROM AUTHOR]

In this study, uneven urban streets are explored with different standard deviations (σH = 0–0.6) through numerical simulations. The ventilation and pollutant diffusion conditions are investigated under the combined action between the thermal buoyancy force and mechanical wind force. When the thermal buoyancy is uniformly distributed, the upstream vortex gradually occupies the most area of the flow unit with the increase in σH. Three configurations of green roof systems (roof, leeward, and windward cooling schemes) are assumed to represent different thermal buoyancy distributions in the street canyon. The average air exchange rate and pollutant retention time (τ) are proposed to evaluate the ventilation efficiency and pollutant dispersion condition. The "free airflow" phenomenon occurs and gradually expands with the increase in the standard deviation of each model. The flow structure and pollutant distribution inside the urban canopy are similar in the uniformly heated and leeward cooling scheme. The windward cooling scheme presents the least local retention time in most working conditions. The roof cooling scheme aggravates the pollutant accumulation conditions inside the street canyon. This study can provide some constructive guidelines in the urban planning process and benefit the design of urban greening with different building morphologies. [ABSTRACT FROM AUTHOR]

In a context where air quality has become a global concern, modelling techniques are becoming very popular for analysing pollutant dispersion conditions. While models based on empirical formulations are most widely used for industrial scenarios, singular cases involving complex terrain or large obstacles in the vicinity of emission sources require a more robust approach to evaluate the dispersion conditions. In this research, a computational fluid dynamics (CFD) model is developed to analyse the dispersion of pollutants from an industrial facility whose location and characteristics suggest the occurrence of complex flow features that affect the dispersion patterns. In addition, the variation of the gas exit temperatures of waste heat recovery systems is proposed as a measure to mitigate the impact of the plume. The simulation results show unexpected deviations in the plume path affecting vulnerable areas in a nearby mountainside, but increasing the gas exit temperature is useful to prevent this event. Therefore, the proposed methodology can be considered a decision support tool to find a compromise between the environmental impact and the fuel consumption of the plant. [ABSTRACT FROM AUTHOR]

Based on the Reynolds-averaged Navier–Stokes (RANS) method, a modified standard k-ϵ turbulence model with a source term rooted on Monin–Obukhov similarity theory was used to investigate the effects of temperature stratifications on the flow field and pollutant dispersion in 3D street canyons. The results showed that airflow and pollutant transport was highly dependent on temperature stratifications. The vortex velocity in the canyon varied with temperature stratifications. With the more unstable conditions, the centre of the vortex was closer to the ground, and the intensity and turbulent kinetic energy of the eddy increased. Because the source of pollution was located on the ground, the pollutants migrated to the leeward side of the building with the eddy and then moved upstream or downstream with the airflow. Under neutral conditions, the pollutants migrated to the leeward side first with the eddy in the canyon and then mainly migrated downstream with the airflow but rarely migrated to the upstream street canyons. However, under unstable conditions, the pollutant concentration in the upstream street canyons also increased, mainly because the intensity of the vortex increased, which made the pollutant easier to transport upstream. According to the results of the pollutant flux analysis, the turbulent fluxes on the top plane of the buildings were positive and increased significantly with the more unstable conditions, indicating that turbulent fluxes play a positive leading role in the dispersion of pollutants. The transverse transport of the pollutants was mainly dominated by convective motion, and turbulent transport was relatively minor. [ABSTRACT FROM AUTHOR]

The main objective in this research is to determine the behavior of the dispersion of the criteria air pollutants in the city of Valledupar; In addition, establish the areas of greatest impact due to emissions from mobile sources from three of its main roads. To carry out this investigation, an analysis of the meteorology of the city of Valledupar was carried out for the days of the modeling, in which the variables of wind direction, wind speed, ambient temperature and relative humidity were taken into account, this Meteorological information was obtained from the Corpocesar and IDEAM meteorological stations, the WRF model was also simulated for October 14, 15 and 16, 2021 and January 13, 14 and 15, 2022 with a resolution of 3 kilometers. The emissions data from mobile sources are the product of the IVE model, finally, the modeling of the dispersion of the criteria pollutants was carried out with the HYSPLIT model, for which the daily meteorological data, product of the WRF model simulations, were used as input data; In addition, the emission rate for each pollutant resulting from the IVE model was established. It was observed that the behavior of the dispersion concentration of pollutants is more frequent towards the east of the city on the study days of October and on the study days of January the dispersion plumes were directed mainly towards the west area from the city, it was presented that the pollutant that obtained the maximum concentration in 10 hours of emission for each day was CO with a concentration of 980 ug/m³ in the month of October, likewise, in the month of January it was CO with a concentration of 790 ug/m³. [ABSTRACT FROM AUTHOR]

In recent years, the outbreak of infectious diseases has highlighted the need for improved planning of hospital buildings. Traditional planning for infectious disease hospitals only considers the impact of wind and pollutant diffusion, without analysing pollutant diffusion under different thermal conditions. To reveal the distribution of pollutants in infectious disease hospitals under different thermal conditions, this study conducted wind tunnel tests and numerical analyses of pollutant diffusion in the environment surrounding an infectious disease hospital in Changsha, China. The results show that the pollutant concentration mainly depends on the local wind speed. In the range of Rb = −1.25 to 1.25, the concentration of pollutants was mainly affected by the disturbance of the flow field in areas with rough surfaces, where the effect of the thermal stability of the atmosphere on pollutant diffusion was relatively small. However, in relatively flat regions, the thermal stability of the atmosphere played a significant role in pollutant diffusion around the buildings.