How Outdoor Trees Affect Indoor Particulate Matter Dispersion: CFD Simulations in a Naturally Ventilated Auditorium

Research on compound pollution characteristics and health risk evaluation of particulate matter and heavy metals in waste glass recycling process

Owing to the large amount of waste glass generated, the waste glass recycling base is an indispensable municipal supporting facility of a sustainable city. However, waste glass recycling is a complex process involving stages such as multiple-stage crushing and material sorting. Consequently, waste glass recycling base has a considerable impact on the surrounding environment, such as health risk of particulate matter on workers. In this study, we aimed to perform a comprehensive investigation and analysis of compound pollution characteristics and health risk evaluation of particulate matter and heavy metals generated from waste glass recycling process. Soil, particulate fallout, and glass samples were collected from inside and outside a recycling plant in eastern China. Our findings showed that the waste glass treatment process produces a large amount of air particulate matter, and the PM2.5 and PM10 concentrations can reach 3725 and 4055 μg/m3, respectively, in the production workshop during working hours. Meanwhile, the monitoring results show that the concentration of heavy metals on fine particles is higher compared to coarse particles. The high Zn and Pb concentrations detected in the soil and dustfall were proved to be derived from the glass raw materials. However, health risk assessment and particle deposition modeling in the human respiratory system revealed that heavy metals from the air particulate matter have no significant carcinogenicity or non-carcinogenic risk. The Gaussian dispersion model showed that the impact of particulate matter on the surrounding environment and health of the surrounding residents is minimal. Furthermore, transportation is the major emission link according to the particulate emission calculation, indicating that it is imperative to upgrade and reform the existing processes of waste glass recycling. Taken together, this study provides a scientific basis for the green development of waste glass recycling process and further environmental information regarding waste glass recycling plants.

Coupling CFD Simulation and Field Experiments in Summer to Prove Feng Shui Optimizes Courtyard Wind Environments: A Case Study of Prince Kung’s Mansion in Beijing

Feng shui in ancient China was harmonized with the natural environment. The layout of houses following feng shui is conducive to a comfortable wind environment. To explore the positive influence of feng shui on ventilation, this study takes Prince Kung’s Mansion, which has the characteristics of a feng shui layout, as the research object. In parallel, the study assumes a dissimilation layout that has lost the feng shui layout characteristics. Comparing the ventilation of courtyards in the summer for both the feng shui layout and the dissimilation layout through CFD simulation, the results were as follows: (1) the wind speed values in the summer, taken from 60 points in Prince Kung’s Mansion by way of CFD simulation and field experiments, were well coupled, which proves that PHOENICS is suitable for the courtyard wind environments simulation in this study. (2) The CFD simulation results show that the average wind speed and the comfortable wind speed zone ratio in the courtyards of the feng shui layout were higher than those of the dissimilation layout during the summer, and the courtyard wind speeds of the two layouts were linearly related. Therefore, the feng shui layout is more conducive to the comfort of courtyards’ wind environment than the dissimilation layout. (3) The front and rear wind pressure differences of the main houses in the feng shui layout can optimize the indoor ventilation better than those of dissimilation layout in the summer. (4) According to the evaluation criteria for the wind environment, the wind speed and wind pressure of the feng shui layout are superior to those of dissimilation layout in the summer. In summary, this study verifies that the layout of feng shui optimizes the courtyard wind environment in the summer, which embodies the ecological concept of the Chinese ancients in the layout of houses.

Modeling and Validation of the Cool Summer Microclimate Formed by Passive Cooling Elements in a Semi-Outdoor Building Space

Previous measurements (Del Rio et al. 2019) have confirmed the formation of cool summer microclimates through a combination of passive cooling elements (i.e., evaporative cooling louver, vegetation, and sunscreen) in semi-outdoor building spaces in Japan. Computational fluid dynamics (CFD) simulation is useful to understand the contribution of each element to semi-outdoor and indoor microclimates with natural ventilation, and to determine their effective combination. To date, there have not been sufficient studies on the modeling and validation for the CFD simulation of microclimates by such elements. This study demonstrates the modeling method using literature-based values and field measurements. It also demonstrates model validity by comparing the obtained results with field measurements. The results show that CFD simulation with detailed modeling of these elements can replicate vertical temperature distributions at four different positions across the semi-outdoor space and indoor space. The maximum difference in air temperature between the measurements and simulation results was 0.7–1 °C. The sensitivities of each passive cooling element on the microclimates formed in both spaces were confirmed. The watered louver condition and shorter louver–window distance were most effective in cooling both spaces. These results indicate that the modeling method could be effectively applied to assess cool microclimates and formulate a passive cooling design.

The Effect of Vegetation Enhancement on Particulate Pollution Reduction: CFD Simulations in an Urban Park

Vegetation in parks is regarded as a valuable way to reduce particulate pollution in urban environments but there is little quantitative information on its effectiveness. The aim of this study was to conduct on-site measurements and computational fluid dynamic (CFD) simulations to determine the aerodynamic and deposition effects of vegetation enhancement on particulate matter (PM) dispersions in an urban park in Xi’an, China. Initially, the airflow characteristics and deposition effects of vegetation were predicted and compared with measured air velocities and particulate pollution data to validate the numerical modeling. Then, associated coverage ratios and supplementary green areas (tree coverage ratio, crown volume coverage (CVC), and roof greening) were added to numerical simulations. After a series of numerical simulations and comparisons, results indicated that: (1) Numerical models with simplified vegetation method could reproduce the distribution of particulate matter concentrations in the real park environment; (2) with a tree coverage ratio >37.8% (or CVC > 1.8 m3/m2), the pedestrian-level PM2.5 could meet the World Health Organization’s air quality guidelines (IT-1) standards in the park; (3) roof greening on leeward buildings produced greater PM removal effects compared with windward buildings; and (4) the most economical and reasonable tree coverage ratio and CVC to reduce atmospheric PM in urban parks should be 30% and 1.8 m3/m2, respectively. These results are useful guidelines for urban planners towards a sustainable design of vegetation in urban parks.