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Displaying One Session

Session Type
Academic Sessions
Date
02/24/2022
Session Time
11:30 AM - 12:40 PM
Room

Hall C

MODELING THE EFFECTS OF NATURE-BASED SOLUTIONS (NBS) ON URBAN AIR QUALITY USING CFD MODEL PALM4U

Session Type
Academic Sessions
Date
02/24/2022
Session Time
11:30 AM - 12:40 PM
Room

Hall C

Lecture Time
11:30 AM - 11:40 AM

Abstract

Abstract Body

Nature-based solutions will play an essential role in urban planning because their potential to reduce the air pollution concentrations. This study investigates the effects of a green space in one of the most polluted areas of the Madrid (Spain) city for a week of June 2017, when contribution of biogenic VOC emissions to ozone formation is important. The PALM4U (BMBF, DE) computational fluid dynamics (CFD), which includes aerodynamics, energy fluxes, chemical and deposition effects, was used to simulate pollutant dispersion for different biogenic emissions scenarios from trees, under a real morphological and micrometeorological environment with very high spatial resolution (5 m). We have used a Large Eddy Simulation (LES) approach which requires high performance computational resources (400 cores in a supercomputer environment). The simulated scenarios are: 1. non emission from the trees to isolate the effect of the biogenic emissions; 2. change the tree species from deciduous broad leaf to evergreen needles and 3. remove trees to isolate the combined effects of the emissions and turbulence. The first two scenarios affects to fundamental processes in the atmospheric pollution, such as energy balance, emission rates and the deposition velocity. Meteorological and chemical boundary conditions are supplied by a WRF/Chem (NCAR, US) model simulation up to 1 km of spatial resolution. The analysis shows that there are non uniform effects (positive and negative) on the concentrations of pollutants (NO2 and O3) over all computational domain, 1 km by 1km. The simulations show that trees have direct effects on air pollution (emission and deposition) and indirect effects in the energy fluxes, temperature and ventilation processes. The performance analysis shows that this model (PALM$U) reproduce successfully pollutant dispersion with the boundary and top conditions supplied by the WRF/Chem simulation taking into account the real building morphology and water green areas. The comparison between observed concentrations in a local monitoring station and the model results shows an excellent performance. This study contributes to reduce knowledge gaps relating to the contribution of nature base solutions to improve air quality.

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LIGHT POLLUTION SPATIAL IMPACT ASSESSMENT IN HONG KONG: A CASE STUDY WITH MEASUREMENT AND NUMERICAL MODELLING

Session Type
Academic Sessions
Date
02/24/2022
Session Time
11:30 AM - 12:40 PM
Room

Hall C

Lecture Time
11:40 AM - 11:50 AM

Abstract

Abstract Body

Outdoor commercial lighting becomes an icon of urbanization. The excessive use of these commercial lighting in open space causes not only energy wastage, also the light trespass that impacts human health. More than 60% of the sky on earth is covered by light pollution, and about 80% of the world population suffers from its effect. Hence, many jurisdictions demand regulations and polices to control the light pollution. one of the most cities, Hong Kong, famed as Pearl of the Orient, is one of the most light affected cities.

This study aimed to assess light pollution quantitatively through measurement and numerical modelling. Site measurement protocols were developed and carried out in one of the busiest mixed commercial-residential area which also received the most complaints on the light nuisance) in Hong Kong. In this study, the illuminance level on the street was measured. In the shopping area (need to define), the average horizontal illuminance ranged from 44 to 1142 lux, with a mean of 223 lux. In the mixed-use area (need to define), a range from 14 to 556 lux and a mean of 130 lux were found. Findings showed illuminance levels are of 2.8-3.7 times (on average) in the shopping area and 1.6-2.2 times in the mixed-use one in excess of the International Commission on Illumination’s recommended levels.

The measured areas were also modelled with DIALux. This effort complemented the measurements by providing a means to increase the resolution on the light variation and to visualize light pollution in a 3D environment. The simulation results were verified by correlating the numerical model with measurements. The correlated model was exercised in a subsequent sensitivity study to predict possible outcomes with changing lighting pattern and light sources’ luminance level. This study serves as a pilot study in quantifying the light pollution issue in an urbanized area in order to eventually develop effective pollution management and policy.

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MODELING THE RESILIENT SUPPLY OF ECOSYSTEM FUNCTION FOR ADAPTIVE MANAGEMENT OF WETLAND CITY

Session Type
Academic Sessions
Date
02/24/2022
Session Time
11:30 AM - 12:40 PM
Room

Hall C

Lecture Time
11:50 AM - 12:00 PM

Abstract

Abstract Body

The wetlands have suffered continuous damage in recent years. Ninety percent of the wetlands were, in particular, located in the cities and peri-urban areas, which caused a lack of a resilient supply of the desired set of ecosystem functions. To improve the resilience in wetlands, the International Union for Conservation of Nature suggested the new concept, Wetland City. However, the Wetland City is facing challenges, including the ecosystem function trade-offs, which lead to a decreased ability to maintain the ecosystem functions' production. Therefore, it is necessary to plan and manage Wetland City with an approach to resilience. However, few studies have dealt with ecosystem function trade-offs that lead to integrated urban planning and design. Moreover, it is hard to derive substantial strategies for enhancing the ecosystem functions and building the Wetland City's resilience. This study aimed to analyze climate change adaptive management strategy by simulating the resilient supply of ecosystem functions in Wetland City. First, we constructed Wetland City’s social-ecological system, which provides ecosystem functions that are traded off. Second, we simulated the resilient supply of ecosystem functions according to climate change adaptive management scenarios. The scenarios were selected by a scenario planning approach that allows us to integrate strategies to improve each ecosystem function. Finally, we determined an appropriate scenario that minimizes impacts of ecosystem function trade-offs reinforced by climate change and suggested adaptive management with resilience strategies for a sustainable Wetland City. This study can contribute to the guidelines for planning and managing Wetland City.

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HOW MUCH STORMWATER RUNOFF CAN BE GENERATED BY THE LOSS OF URBAN GREEN SPACES?

Session Type
Academic Sessions
Date
02/24/2022
Session Time
11:30 AM - 12:40 PM
Room

Hall C

Lecture Time
12:00 PM - 12:10 PM

Abstract

Abstract Body

Urban impervious surfaces alter the hydrological nature of surface runoffs, prevent the infiltration of surface water into the ground, and greatly increase storm runoffs in terms of volumes and peak flow. Stormwater drains through gutters, storm sewers, and other engineered collection systems and is discharged into nearby water bodies. Heavy rains may cause urban flooding which endangers life, private properties and public infrastructures, and may erode stream banks and channels. Stormwater runoff is also a major cause of water pollution in urban areas, carrying solid wastes, bacteria, heavy metals, and other pollutants from the urban landscape. Urban flooding risk may be intensified by climate change which may cause more frequent weather extremes. The study examines the case of Milan municipality where the 58% of the area is constituted by impervious surfaces and the green area per inhabitant is lower than 20 square meters, much lower than many other European cities. The stormwater runoff volume which generated in a subarea of the Milan municipality was estimated through the application of the SCS-CN method. Based on the runoff volume estimates in the current land cover scenario, different scenarios were simulated to evaluate the role of the existent green areas in mitigating the runoff generation and the potential application of mitigation measures, such as green roofs or permeable pavements. The study showed that the green areas have a remarkable role in mitigating the runoff generation. The mitigation measures considered, although proven as effective in reducing runoff volumes, were shown to be expensive and not sufficient to compensate the increase in runoff volumes which may be generated from the loss of the existing green areas. Permeable pavements, compared to extensive green roofs, were shown to have better results per square meter of installed surface, both in terms of reduction of runoff volumes and in terms of total costs.

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Q&A

Session Type
Academic Sessions
Date
02/24/2022
Session Time
11:30 AM - 12:40 PM
Room

Hall C

Lecture Time
12:10 PM - 12:40 PM