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Sin CH, Cui PY, Jon KS, Luo Y, Huang YD. Effects of building envelope features on airflow and pollutant dispersion within a symmetric street canyon. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024; 31:31818-31842. [PMID: 38639909 DOI: 10.1007/s11356-024-33343-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 04/11/2024] [Indexed: 04/20/2024]
Abstract
Building envelope features (BEFs) have attracted more and more attention as they have a significant impact on flow structure and pollutant dispersion within street canyons. This paper conducted CFD numerical models validated by wind-tunnel experiments, to explore the effects of the BEFs on characteristics of the airflow and pollutant distribution inside a symmetric street canyon under perpendicular incoming flow. Three different BEFs (balconies, overhangs, and wing walls) and their locations and continuity/discontinuity structures were considered. For each canyon with various BEFs, the air exchange rate (ACH), airflow patterns, and pollutant distributions were evaluated and compared in detail. The results show that compared to the regular canyon, the BEFs will reduce the ACH of the canyon, but increase the disturbances (the proportion of ACH') inside the canyon. The BEFs on the leeward wall have the least influence on the in-canyon airflow and pollutant distributions, followed by that on the windward wall. Then when the BEFs are on both walls, the ventilation capacity of the canyon is weakened greatly, and the pollutant concentration in the ground center is increased significantly, especially near the windward side. Moreover, the discontinuity BEFs will weaken the effect of the continuity BEFs on the in-canyon flow and dispersion, specifically, the discontinuity BEFs reduced the region of high pollutant concentration distributions. These findings can help optimize the BEFs design to enhance ventilation and mitigate traffic pollution.
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Affiliation(s)
- Chung Hyok Sin
- School of Environment and Architecture, University of Shanghai for Science and Technology, No. 516, Jungong Road, Yangpu District, Shanghai, 200093, China
- Natural Science Center, Kim Il Sung University, Taesong District, Pyongyang, Democratic People's Republic of Korea
| | - Peng-Yi Cui
- School of Environment and Architecture, University of Shanghai for Science and Technology, No. 516, Jungong Road, Yangpu District, Shanghai, 200093, China
| | - Kwang Song Jon
- School of Environment and Architecture, University of Shanghai for Science and Technology, No. 516, Jungong Road, Yangpu District, Shanghai, 200093, China
| | - Yang Luo
- School of Environment and Architecture, University of Shanghai for Science and Technology, No. 516, Jungong Road, Yangpu District, Shanghai, 200093, China
| | - Yuan-Dong Huang
- School of Environment and Architecture, University of Shanghai for Science and Technology, No. 516, Jungong Road, Yangpu District, Shanghai, 200093, China.
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Xiao X, Kuang K, Tang Z, Yang X, Wu H, Wang Y, Fang P. Emission and spatial variation characteristics of odorous pollutants in the aerobic tank of an underground wastewater treatment plant (UWWTP) in southern China. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 346:123631. [PMID: 38395135 DOI: 10.1016/j.envpol.2024.123631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 02/09/2024] [Accepted: 02/20/2024] [Indexed: 02/25/2024]
Abstract
In this study, the spatial concentration of odorous pollutants in the aerobic tank of an underground wastewater treatment plant (UWWTP) in southern China is monitored. The odour activity value, odour contribution rate, and chemical concentration contribution rate are used to evaluate the degree of contribution of odorous substances. Computational fluid dynamics (CFD) simulations of odorous pollutant diffusion are also established. The study shows that the odorous substances detected in the aerobic tank mainly included ammonia (NH3), hydrogen sulfide (H2S), trimethylamine (C3H9N), and methanethiol (CH3SH), and their concentrations are 1.160, 0.778, 0.022, and 0.0006 mg/m3, respectively. The total odour activity value of the aerobic tank is 450.72 (dimensionless), of which the odour activity value of H2S is 432.22, and the contribution rate reaches 95.9%. H2S is the main contributor to odour and a key controlled substance. The air inlets and exhaust outlets in the aerobic tank are cross-arranged at the top of the space, and the CFD model of odorous pollutant diffusion shows that the gas flow organization determines the odorous pollutant diffusion. The spatial distribution of gas flow and odorous substances in the aerobic tank is relatively uniform, and the odour collection efficiency is higher. The production flux and production coefficient of H2S in the aerobic tank are calculated as 25.831 mg/(m2·h) and 14.149 mg/t, respectively. This study determines the reasonable air supply and exhaust design of the aerobic tank, the number of odour pollutants, and the key controlled substances. These findings offer guidance and serve as useful references for the prevention and control of odour pollution in aerobic tanks of the same type of UWWTPs.
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Affiliation(s)
- Xiang Xiao
- South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou, 510655, China; The Key Laboratory of Water and Air Pollution Control of Guangdong Province, Guangzhou, 510655, China; Guangdong Province Engineering Laboratory for Air Pollution Control, Guangzhou, 510655, China
| | - Ke Kuang
- Guangzhou Sewage Purification Co., Ltd., Guangzhou, 510655, China
| | - Zijun Tang
- South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou, 510655, China; The Key Laboratory of Water and Air Pollution Control of Guangdong Province, Guangzhou, 510655, China; Guangdong Province Engineering Laboratory for Air Pollution Control, Guangzhou, 510655, China
| | - Xia Yang
- South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou, 510655, China; The Key Laboratory of Water and Air Pollution Control of Guangdong Province, Guangzhou, 510655, China; Guangdong Province Engineering Laboratory for Air Pollution Control, Guangzhou, 510655, China
| | - Haiwen Wu
- South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou, 510655, China; The Key Laboratory of Water and Air Pollution Control of Guangdong Province, Guangzhou, 510655, China; Guangdong Province Engineering Laboratory for Air Pollution Control, Guangzhou, 510655, China
| | - Yunqing Wang
- South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou, 510655, China; The Key Laboratory of Water and Air Pollution Control of Guangdong Province, Guangzhou, 510655, China; Guangdong Province Engineering Laboratory for Air Pollution Control, Guangzhou, 510655, China
| | - Ping Fang
- South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou, 510655, China; The Key Laboratory of Water and Air Pollution Control of Guangdong Province, Guangzhou, 510655, China; Guangdong Province Engineering Laboratory for Air Pollution Control, Guangzhou, 510655, China.
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Liao HT, Yen CM, Chen YR, Wu JD, Tsai SW, Wu CF. Vertical variation of source-apportioned PM 2.5 and selected volatile organic compounds near an elevated expressway in an urban area. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024; 31:20477-20487. [PMID: 38376777 DOI: 10.1007/s11356-024-32480-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Accepted: 02/10/2024] [Indexed: 02/21/2024]
Abstract
Fine particulate matter (PM2.5) and volatile organic compounds (VOCs) are associated with adverse health effects and show spatial variation in three dimensions. The present study attempted to evaluate source contributions of PM2.5 and toxic VOCs in a metropolitan area focusing on the associated vertical variations. A special emphasis is put on the effects of the elevated expressway on the vertical variability of contribution estimates of the identified sources. Nine source factors, i.e., soil dust, sea salt/oil combustion, secondary nitrate, industrial emission, aged VOCs/secondary aerosol, traffic-related I, solvent use/industrial process, secondary sulfate, and traffic-related II, were identified using positive matrix factorization (PMF). The main contributors to PM2.5 were secondary sulfate (19.1%) and traffic-related emissions (traffic-related I and II, 16.1%), whereas the largest contributors to VOCs were traffic-related emissions (37.6%). The influence of the elevated expressway is suggested to be particularly critical on vertical variations of traffic-related emissions, including aging and secondary formation of locally accumulated air pollutants near roads. Increasing the building porosity under the viaduct could reduce the accumulation of air pollutants caused by the shelter effect. Additionally, in-street barriers would be beneficial in reducing population exposure to traffic-related emissions by altering the airflows near roads.
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Affiliation(s)
- Ho-Tang Liao
- Institute of Environmental and Occupational Health Sciences, College of Public Health, National Taiwan University, No. 17 Xu-Zhou Road, Taipei, 10055, Taiwan
| | - Chien-Mei Yen
- Institute of Environmental and Occupational Health Sciences, College of Public Health, National Taiwan University, No. 17 Xu-Zhou Road, Taipei, 10055, Taiwan
| | - Yu-Rui Chen
- Institute of Environmental and Occupational Health Sciences, College of Public Health, National Taiwan University, No. 17 Xu-Zhou Road, Taipei, 10055, Taiwan
| | - Jyun-De Wu
- Department of Occupational Safety and Health, School of Safety and Health Sciences, Chang-Jung Christian University, Tainan, Taiwan
| | - Shih-Wei Tsai
- Institute of Environmental and Occupational Health Sciences, College of Public Health, National Taiwan University, No. 17 Xu-Zhou Road, Taipei, 10055, Taiwan
| | - Chang-Fu Wu
- Institute of Environmental and Occupational Health Sciences, College of Public Health, National Taiwan University, No. 17 Xu-Zhou Road, Taipei, 10055, Taiwan.
- Department of Public Health, College of Public Health, National Taiwan University, Taipei, Taiwan.
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Lu DN, He HD, Zhao HM, Lu KF, Peng ZR, Li J. Quantifying traffic-related carbon emissions on elevated roads through on-road measurements. ENVIRONMENTAL RESEARCH 2023; 231:116200. [PMID: 37209989 DOI: 10.1016/j.envres.2023.116200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Revised: 04/30/2023] [Accepted: 05/17/2023] [Indexed: 05/22/2023]
Abstract
Vehicles generally move smoothly and with high speeds on elevated roads, thereby producing specific traffic-related carbon emissions in contrast to ground roads. Hence, a portable emission measurement system was adopted to determine traffic-related carbon emissions. The on-road measurement results revealed that the instantaneous emissions of CO2 and CO from elevated vehicles were 17.8% and 21.9% higher than those from ground vehicles, respectively. Based on it, the vehicle specific power was confirmed to exhibit a positive exponential relationship with instantaneous CO2 and CO emissions. In addition to carbon emissions, carbon concentrations on roads were simultaneously measured. The average CO2 and CO emissions on elevated roads in urban areas were 1.2% and 6.9% higher than those on ground roads, individually. Finally, a numerical simulation was performed, and the results verified that elevated roads could deteriorate the air quality on ground roads but improve the air quality above them. What ought to be paid attention to is that the elevated roads present varied traffic behaviour and cause particular carbon emissions, indicating that comprehensive consideration and further balance among the traffic-related carbon emissions are necessary when building elevated roads to alleviate the traffic congestion in urban areas.
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Affiliation(s)
- Dan-Ni Lu
- Center for Intelligent Transportation Systems and Unmanned Aerial Systems Applications, State-Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Hong-Di He
- Center for Intelligent Transportation Systems and Unmanned Aerial Systems Applications, State-Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
| | - Hong-Mei Zhao
- Center for Intelligent Transportation Systems and Unmanned Aerial Systems Applications, State-Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Kai-Fa Lu
- International Center for Adaptation Planning and Design, College of Design, Construction and Planning, University of Florida, PO Box 115706, Gainesville, FL 32611-5706, USA
| | - Zhong-Ren Peng
- International Center for Adaptation Planning and Design, College of Design, Construction and Planning, University of Florida, PO Box 115706, Gainesville, FL 32611-5706, USA
| | - Jian Li
- Key Laboratory of Road and Traffic Engineering of the Ministry of Education, College of Transportation Engineering, Tongji University, 4800 Cao'an Road, Shanghai 201804, China.
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Liu Y, Liu CH, Brasseur GP, Chao CYH. Empirical mode decomposition of the atmospheric flows and pollutant transport over real urban morphology. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023:121858. [PMID: 37244537 DOI: 10.1016/j.envpol.2023.121858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 05/13/2023] [Accepted: 05/19/2023] [Indexed: 05/29/2023]
Abstract
The momentum transport and pollutant dispersion in the atmospheric surface layer (ASL) are governed by a broad spectrum of turbulence structures. Whereas, their contributions have not been explicitly investigated in the context of real urban morphology. This paper aims to elucidate the contributions from different types of eddies in the ASL over a dense city to provide the reference of urban planning, realizing more favorable ventilation and pollutant dispersion. The building-resolved large-eddy simulation dataset of winds and pollutants over the Kowloon downtown, Hong Kong, is decomposed into a few intrinsic mode functions (IMFs) via empirical mode decomposition (EMD). EMD is a data-driven algorithm that has been successfully implemented in many research fields. The results show that four IMFs are generally enough to capture most of the turbulence structures in real urban ASL. In particular, the first two IMFs, which are initiated by individual buildings, capture the small-scale vortex packets that populate within the irregular building clusters. On the other hand, the third and fourth IMFs capture the large-scale motions (LSMs) detached to the ground surface that are highly efficient in transport. They collectively contribute to nearly 40% of vertical momentum transport even with relatively low vertical turbulence kinetic energy (TKE). LSMs are long, streaky structures that mainly consist of streamwise TKE components. It is found that the open areas and regular streets promote the portion of streamwise TKE in LSMs, improving the vertical momentum transport and pollutant dispersion. In addition, these streaky LSMs are found to play a crucial role in pollutant dilution in the near field after the pollutant source, while the small-scale vortex packets are more efficient in transport in the mid-field and far-field.
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Affiliation(s)
- Yixun Liu
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong
| | - Chun-Ho Liu
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong. https://aplhk.tech
| | - Guy P Brasseur
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong; National Center for Atmospheric Research, Boulder, CO, USA; Max Planck Institute for Meteorology, Hamburg, Germany
| | - Christopher Y H Chao
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong; Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
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Liu Z, Cao H, Hu C, Wu M, Zhang S, He J, Jiang C. Modeling the infection risk and emergency evacuation from bioaerosol leakage around an urban vaccine factory. NPJ CLIMATE AND ATMOSPHERIC SCIENCE 2023; 6:6. [PMID: 36846520 PMCID: PMC9937520 DOI: 10.1038/s41612-023-00342-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 02/08/2023] [Indexed: 06/18/2023]
Abstract
Mounting interest in modeling outdoor diffusion and transmission of bioaerosols due to the prevalence of COVID-19 in the urban environment has led to better knowledge of the issues concerning exposure risk and evacuation planning. In this study, the dispersion and deposition dynamics of bioaerosols around a vaccine factory were numerically investigated under various thermal conditions and leakage rates. To assess infection risk at the pedestrian level, the improved Wells-Riley equation was used. To predict the evacuation path, Dijkstra's algorithm, a derived greedy algorithm based on the improved Wells-Riley equation, was applied. The results show that, driven by buoyancy force, the deposition of bioaerosols can reach 80 m on the windward sidewall of high-rise buildings. Compared with stable thermal stratification, the infection risk of unstable thermal stratification in the upstream portion of the study area can increase by 5.53% and 9.92% under a low and high leakage rate, respectively. A greater leakage rate leads to higher infection risk but a similar distribution of high-risk regions. The present work provides a promising approach for infection risk assessment and evacuation planning for the emergency response to urban bioaerosol leakage.
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Affiliation(s)
- Zhijian Liu
- School of Energy and Power Engineering, North China Electric Power University, Baoding, 071003 China
| | - Hongwei Cao
- School of Energy and Power Engineering, North China Electric Power University, Baoding, 071003 China
| | - Chenxing Hu
- School of Mechanical Engineering, Beijing Institute of Technology, Beijing, 100081 China
| | - Minnan Wu
- School of Energy and Power Engineering, North China Electric Power University, Baoding, 071003 China
| | - Siqi Zhang
- School of Energy and Power Engineering, North China Electric Power University, Baoding, 071003 China
| | - Junzhou He
- School of Energy and Power Engineering, North China Electric Power University, Baoding, 071003 China
| | - Chuan Jiang
- School of Energy and Power Engineering, North China Electric Power University, Baoding, 071003 China
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Lu KF, Peng ZR. Impacts of viaduct and geometry configurations on the distribution of traffic-related particulate matter in urban street canyon. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 858:159902. [PMID: 36328259 DOI: 10.1016/j.scitotenv.2022.159902] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 10/15/2022] [Accepted: 10/29/2022] [Indexed: 06/16/2023]
Abstract
Viaduct is a ubiquitous transportation infrastructure in the congested megacities worldwide to improve the accessibility and capacity of urban transportation network. However, there is a lack of understanding of the impacts of the interplay between viaduct-ground emissions and viaduct-canyon configurations on the particle distribution in urban street canyon. To fill the research gap, we conducted vertical measurements of particle number concentrations (PNCs) at different heights of "street canyon along a viaduct" to reveal effect of viaduct on the vertical distribution of PNCs in street canyon. Observation results indicated that the vertical profiles of PNCs exhibited bimodal distribution patterns, which were more significant for coarse particles than fine particles. The one peak appeared at ground level and the other at the viaduct height, indicating the impacts of "double" emission sources (i.e., the emissions on the ground and viaduct) and the hindrance of viaduct to particle diffusion. We further modelled the role of viaduct in street canyon through Computational Fluid Dynamics (CFD) simulations to reveal the vertical distribution of particles under different viaduct-canyon configurations and discern the contributions of viaduct and ground emissions to the particle distribution. Simulation results showed that viaduct changed airflow field and turbulence structure and elevated particle concentrations in street canyon while the optimized viaduct-canyon configurations including higher viaduct height (12 > 10 > 8 m), smaller aspect ratio (0.5 > 0.67 > 1), and shorter centerline distance (0 > 1 > 2 m) between canyon and viaduct could bring better dispersion conditions and lower particle concentrations. Additionally, ground emissions contributed more to the vertical distribution of particles on the leeward side of street canyon than viaduct emissions while the windward side displayed the opposite characteristics to the leeward side. These findings revealed the general patterns of particle diffusion in viaduct-canyon configurations and provided implications into viaduct design and traffic management to alleviate local particulate pollution.
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Affiliation(s)
- Kai-Fa Lu
- iAdapt: International Center for Adaptation Planning and Design, College of Design, Construction and Planning, University of Florida, PO Box 115706, Gainesville, FL 32611-5706, USA
| | - Zhong-Ren Peng
- iAdapt: International Center for Adaptation Planning and Design, College of Design, Construction and Planning, University of Florida, PO Box 115706, Gainesville, FL 32611-5706, USA.
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Issakhov A, Omarova P, Abylkassymova A. Determination of optimal height of barriers to reduce the amount of pollution in the viaduct settings in an idealized urban canyon: a numerical study. ENVIRONMENTAL MONITORING AND ASSESSMENT 2022; 195:178. [PMID: 36471175 DOI: 10.1007/s10661-022-10751-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 09/08/2022] [Indexed: 06/17/2023]
Abstract
In this work, we numerically investigate the process of atmospheric air pollution in idealized urban canyons along the road in the presence of a viaduct, taking into account different height of barriers. To solve this problem, the 3D Reynolds-averaged Navier-Stokes equations (RANS) were used. The closure of this system of equations was achieved by using various turbulent models. The verification of the mathematical model and the numerical algorithm was carried out using a test problem. The obtained results using various turbulent models were compared with experimental data and calculated results of other authors. The main problem considered in this work is characterized as follows: assessment of emissions of pollutants between buildings using barriers of various types in the presence of a viaduct. Computational results have shown that the barrier viaduct plays a large role in improving air quality in urban canyons. So, for example, a barrier erected on a viaduct with a height of 2 m reduces the concentration value to a cross-section x = 84 by more than 2 times in comparison with the case of a complete absence of protective barriers. A similar situation was observed with barriers erected above the earth's surface: located along the road, they also significantly reduce the value of the concentration of pollutants. Thus, the presence of barriers in both cases is necessary to prevent the dispersion and deposition of pollutants.
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Affiliation(s)
- Alibek Issakhov
- Al-Farabi Kazakh National University, Almaty, Republic of Kazakhstan.
- Kazakh British Technical University, Almaty, Republic of Kazakhstan.
- International Information Technology University, Almaty, Republic of Kazakhstan.
| | - Perizat Omarova
- Al-Farabi Kazakh National University, Almaty, Republic of Kazakhstan
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Wu M, Zhang G, Wang L, Liu X, Wu Z. Influencing Factors on Airflow and Pollutant Dispersion around Buildings under the Combined Effect of Wind and Buoyancy-A Review. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:12895. [PMID: 36232193 PMCID: PMC9566737 DOI: 10.3390/ijerph191912895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 10/07/2022] [Accepted: 10/07/2022] [Indexed: 06/16/2023]
Abstract
With the rapid growth of populations worldwide, air quality has become an increasingly important issue related to the health and safety of city inhabitants. There are quite a few factors that contribute to urban air pollution; the majority of studies examining the issue are concerned with environmental conditions, building geometries, source characteristics and other factors and have used a variety of approaches, from theoretical modelling to experimental measurements and numerical simulations. Among the environmental conditions, solar-radiation-induced buoyancy plays an important role in realistic conditions. The thermal conditions of the ground and building façades directly affect the wind field and pollutant dispersion patterns in the microclimate. The coupling effect of wind and buoyancy on the urban environment are currently hot and attractive research topics. Extensive studies have been devoted to this field, some focused on the street canyon scale, and have found that thermal effects do not significantly affect the main airflow structure in the interior of the street canyon but strongly affect the wind velocity and pollutant concentration at the pedestrian level. Others revealed that the pollutant dispersion routes can be obviously different under various Richardson numbers at the scale of the isolated building. The purpose of this review is therefore to systematically articulate the approaches and research outcomes under the combined effect of wind and buoyancy from the street canyon scale to an isolated building, which should provide some insights into future modelling directions in environmental studies.
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Affiliation(s)
- Mei Wu
- School of Civil Engineering, Hefei University of Technology, Hefei 230009, China
| | - Guangwei Zhang
- School of Civil Engineering, Hefei University of Technology, Hefei 230009, China
| | - Liping Wang
- School of Civil Engineering, Hefei University of Technology, Hefei 230009, China
| | - Xiaoping Liu
- School of Civil Engineering, Hefei University of Technology, Hefei 230009, China
| | - Zhengwei Wu
- School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026, China
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10
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He R, Qiu Z. Exposure characteristics of ultrafine particles on urban streets and its impact on pedestrians. ENVIRONMENTAL MONITORING AND ASSESSMENT 2022; 194:735. [PMID: 36068351 DOI: 10.1007/s10661-022-10453-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 08/30/2022] [Indexed: 06/15/2023]
Abstract
In order to investigate the pedestrian exposure characteristics of ultrafine particles (UFPs) on urban streets, both mobile and fixed-point monitoring experiments were conducted. A generalized additive model and a respiratory deposition dose model were used to quantify the influencing factors and potential harm of UFPs, respectively. The results showed that UFPs' hotspots were more likely to manifest at places where vehicles tend to cluster, namely at road intersections and bus stops. The pedestrian bridge had the lowest number concentration of UFPs in comparison with the pedestrian crossing and underground passage at the same intersection. Aboveground, a "weekend effect" acting upon urban streets and evidence for periodicity at the intersections were found. The UFPs' number concentration was comprehensively explained-about 62.7% of its variation-by traffic volume, wind speed, temperature, and relative humidity. The UFPs were mainly deposited in the alveolar region of the respiratory system, but the deposition doses of males exceeded those of females under the same conditions. Based on these findings, the study also provides appropriate suggestions for better managing traffic pollution sources, traffic infrastructure, and traffic organization.
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Affiliation(s)
- Rong He
- School of Transportation Engineering, Chang'an University, Yucai Road, Xi'an, 710064, Shaanxi, People's Republic of China
| | - Zhaowen Qiu
- School of Automobile, Chang'an University, Chang'an Road, Xi'an, 710064, Shaanxi, People's Republic of China.
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11
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Wang W, Tian P, Zhang J, Agathokleous E, Xiao L, Koike T, Wang H, He X. Big data-based urban greenness in Chinese megalopolises and possible contribution to air quality control. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 824:153834. [PMID: 35157858 DOI: 10.1016/j.scitotenv.2022.153834] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Revised: 02/08/2022] [Accepted: 02/08/2022] [Indexed: 06/14/2023]
Abstract
Urban greenness is essential for people's daily lives, while its contribution to air quality control is unclear. In this study, Streetview big data of urban greenness and air quality data (Air Quality Index, PM2.5, PM10, SO2, NO2, O3, CO) from 206 monitoring stations from 27 provincial capital cities in China were analyzed. The national averages for the sky, ground and middle-level (shrub and short trees) view greenness were 5.4%, 5.5%, and 15.4%, respectively, and the sky:ground:middle ratio was 2:2:6. Street-view/bird-view greenness ratio averaged at 1.1. Large inter-city variations were observed in all the greenness parameters, and the weak associations between all street-view parameters and bird-eye greenspace percentage (21%-73%) indicate their representatives of different aspects of green infrastructures. All air quality parameters were higher in winter than in summer, except O3. Over 90% of air quality variation could be explained by socioeconomics and geoclimates, suggesting that air quality control in China should first reduce efflux from social economics, while geoclimatic-oriented ventilation facilitation design is also critical. For different air quality components, greenness had most significant associations with NO2, O3 and CO, and street-view/bird-view ratio was the most powerful indicator of all greenness parameters. Pooled-data analysis at national level showed that street-view greenness was responsible for 2.3% of the air quality variations in the summer and 3.6% in the winter; however, when separated into different regions (North-South China; East-West China), the explaining power increased up to 16.2%. Increased NO2 was accompanied with decreased O3, indicating NO titration effect. The higher O3 aligned with the higher street-view greenness, showing the greenness-related precursor risk for O3 pollution. Our study manifested that big internet data could identify the association of greenness and air pollution from street view scale, which can favor urban greenness management and evaluation in other regions where street-view data are available.
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Affiliation(s)
- Wenjie Wang
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou, China; Northeast Institute of Geography and Agroecology, Chinese Acadamy of Science, Changchun, China.
| | - Panli Tian
- Key Lab. of Forest Plant Ecology (Ministry of Education), Key Lab. of Forest Active Substance Ecological Utilization (Heilongjiang Province), Northeast Forestry University, Harbin, China
| | - Jinghua Zhang
- Key Lab. of Forest Plant Ecology (Ministry of Education), Key Lab. of Forest Active Substance Ecological Utilization (Heilongjiang Province), Northeast Forestry University, Harbin, China
| | - Evgenios Agathokleous
- Department of Ecology, School of Applied Meteorology, Nanjing University of Information Science & Technology (NUIST), Nanjing, China
| | - Lu Xiao
- Northeast Institute of Geography and Agroecology, Chinese Acadamy of Science, Changchun, China
| | - Takayoshi Koike
- Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
| | - Huimei Wang
- Key Lab. of Forest Plant Ecology (Ministry of Education), Key Lab. of Forest Active Substance Ecological Utilization (Heilongjiang Province), Northeast Forestry University, Harbin, China
| | - Xingyuan He
- Northeast Institute of Geography and Agroecology, Chinese Acadamy of Science, Changchun, China; University of Chinese Academy of Sciences, Beijing, China
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12
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Zeng L, Hang J, Wang X, Shao M. Influence of urban spatial and socioeconomic parameters on PM 2.5 at subdistrict level: A land use regression study in Shenzhen, China. J Environ Sci (China) 2022; 114:485-502. [PMID: 35459511 DOI: 10.1016/j.jes.2021.12.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 11/21/2021] [Accepted: 12/08/2021] [Indexed: 06/14/2023]
Abstract
The intraurban distribution of PM2.5 concentration is influenced by various spatial, socioeconomic, and meteorological parameters. This study investigated the influence of 37 parameters on monthly average PM2.5 concentration at the subdistrict level with Pearson correlation analysis and land-use regression (LUR) using data from a subdistrict-level air pollution monitoring network in Shenzhen, China. Performance of LUR models is evaluated with leave-one-out-cross-validation (LOOCV) and holdout cross-validation (holdout CV). Pearson correlation analysis revealed that Normalized Difference Built-up Index, artificial land fraction, land surface temperature, and point-of-interest (POI) numbers of factories and industrial parks are significantly positively correlated with monthly average PM2.5 concentrations, while Normalized Difference Vegetation Index and Green View Factor show significant negative correlations. For the sparse national stations, robust LUR modelling may rely on a priori assumptions in direction of influence during the predictor selection process. The month-by-month spatial regression shows that RF models for both national stations and all stations show significantly inflated mean values of R2 compared with cross-validation results. For MLR models, inflation of both R2 and R2CV was detected when using only national stations and may indicate the restricted ability to predict spatial distribution of PM2.5 levels. Inflated within-sample R2 also exist in the spatiotemporal LUR models developed with only national stations, although not as significant as spatial LUR models. Our results suggest that a denser subdistrict level air pollutant monitoring network may improve the accuracy and robustness in intraurban spatial/spatiotemporal prediction of PM2.5 concentrations.
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Affiliation(s)
- Liyue Zeng
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China; Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai 519000, China; Guangdong Provincial Field Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary, Guangzhou 510275, China
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China; Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai 519000, China; Guangdong Provincial Field Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary, Guangzhou 510275, China.
| | - Xuemei Wang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 510632, China
| | - Min Shao
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 510632, China
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13
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Li Q, Liang J, Wang Q, Chen Y, Yang H, Ling H, Luo Z, Hang J. Numerical Investigations of Urban Pollutant Dispersion and Building Intake Fraction with Various 3D Building Configurations and Tree Plantings. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph19063524. [PMID: 35329210 PMCID: PMC8951778 DOI: 10.3390/ijerph19063524] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 03/11/2022] [Accepted: 03/12/2022] [Indexed: 11/21/2022]
Abstract
Rapid urbanisation and rising vehicular emissions aggravate urban air pollution. Outdoor pollutants could diffuse indoors through infiltration or ventilation, leading to residents’ exposure. This study performed CFD simulations with a standard k-ε model to investigate the impacts of building configurations and tree planting on airflows, pollutant (CO) dispersion, and personal exposure in 3D urban micro-environments (aspect ratio = H/W = 30 m, building packing density λp = λf = 0.25) under neutral atmospheric conditions. The numerical models are well validated by wind tunnel data. The impacts of open space, central high-rise building and tree planting (leaf area density LAD= 1 m2/m3) with four approaching wind directions (parallel 0° and non-parallel 15°, 30°, 45°) are explored. Building intake fraction <P_IF> is adopted for exposure assessment. The change rates of <P_IF> demonstrate the impacts of different urban layouts on the traffic exhaust exposure on residents. The results show that open space increases the spatially-averaged velocity ratio (VR) for the whole area by 0.40−2.27%. Central high-rise building (2H) can increase wind speed by 4.73−23.36% and decrease the CO concentration by 4.39−23.00%. Central open space and high-rise building decrease <P_IF> under all four wind directions, by 6.56−16.08% and 9.59−24.70%, respectively. Tree planting reduces wind speed in all cases, raising <P_IF> by 14.89−50.19%. This work could provide helpful scientific references for public health and sustainable urban planning.
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Affiliation(s)
- Qingman Li
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai 519082, China; (Q.L.); (J.L.); (Y.C.); (H.Y.); (J.H.)
- Key Laboratory of Tropical Atmosphere-Ocean System, Ministry of Education, Sun Yat-sen University, Zhuhai 519000, China
| | - Jie Liang
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai 519082, China; (Q.L.); (J.L.); (Y.C.); (H.Y.); (J.H.)
- Key Laboratory of Tropical Atmosphere-Ocean System, Ministry of Education, Sun Yat-sen University, Zhuhai 519000, China
| | - Qun Wang
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China;
| | - Yuntong Chen
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai 519082, China; (Q.L.); (J.L.); (Y.C.); (H.Y.); (J.H.)
| | - Hongyu Yang
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai 519082, China; (Q.L.); (J.L.); (Y.C.); (H.Y.); (J.H.)
- Key Laboratory of Tropical Atmosphere-Ocean System, Ministry of Education, Sun Yat-sen University, Zhuhai 519000, China
| | - Hong Ling
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai 519082, China; (Q.L.); (J.L.); (Y.C.); (H.Y.); (J.H.)
- Key Laboratory of Tropical Atmosphere-Ocean System, Ministry of Education, Sun Yat-sen University, Zhuhai 519000, China
- Correspondence: ; Tel.: +86-20-84112436
| | - Zhiwen Luo
- School of Construction Management and Engineering, University of Reading, Whiteknights, Reading RG6 6AH, UK;
| | - Jian Hang
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai 519082, China; (Q.L.); (J.L.); (Y.C.); (H.Y.); (J.H.)
- Key Laboratory of Tropical Atmosphere-Ocean System, Ministry of Education, Sun Yat-sen University, Zhuhai 519000, China
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14
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Numerical Simulations of Air Flow and Traffic–Related Air Pollution Distribution in a Real Urban Area. ENERGIES 2022. [DOI: 10.3390/en15030840] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
With increasing urbanization, urban air pollutants are becoming more and more relevant to human health. Here, combined with meteorological observation data, a numerical simulation of typical urban blocks in Shanghai was carried out to understand the spread of air pollutants caused by road traffic sources (ground–level and viaduct–level). Firstly, we analyzed the wind environment characteristics. Then, we quantitatively analyzed the pollutant distribution profiles and the contributions of two pollutant sources (PSV). Finally, we analyzed seven urban morphological parameters based on ventilation efficiency indices. Results revealed the following. (1) Ventilation patterns within the architectural complex are determined by local geometry; (2) Pollutants released at ground level were dominant when the Z–plane < 8 m high, and pollutants released from the viaduct source were 0.8–6.1% higher when the Z–plane ≥ 8 m high; (3) From ground level to a height of 60 m, the spatially–averaged normalized concentration (C*) tended to decrease gradually with distance from the source. C* increased irregularly with an increase in distance between 60 m and 86 m. Above 86 m, C* tended to increase linearly; (4) Vertical profiles of C* around buildings were building–specific, and their rate of change was inconsistent with height increases. In general, the correlations between C* and VRw, and between C* and KEturb were larger on the windward side of PSV upstream buildings than on the leeward side. Buildings downstream of the PSV showed the opposite situation; (5) At pedestrian level, the seven urban morphological parameters had no significant correlation with VRw, Cir*, and Czs*.
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15
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Impact of Indoor-Outdoor Temperature Difference on Building Ventilation and Pollutant Dispersion within Urban Communities. ATMOSPHERE 2021. [DOI: 10.3390/atmos13010028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mechanical ventilation consumes a huge amount of global energy. Natural ventilation is a crucial solution for reducing energy consumption and enhancing the capacity of atmospheric self-purification. This paper evaluates the impacts of indoor-outdoor temperature differences on building ventilation and indoor-outdoor air pollutant dispersion in urban areas. The Computational Fluid Dynamics (CFD) method is employed to simulate the flow fields in the street canyon and indoor environment. Ventilation conditions of single-side ventilation mode and cross-ventilation mode are investigated. Air change rate, normalized concentration of traffic-related air pollutant (CO), intake fraction and exposure concentration are calculated to for ventilation efficiency investigation and exposure assessment. The results show that cross ventilation increases the air change rate for residential buildings under isothermal conditions. With the indoor-outdoor temperature difference, heating could increase the air change rate of the single-side ventilation mode but restrain the capability of the cross-ventilation mode in part of the floors. Heavier polluted areas appear in the upstream areas of single-side ventilation modes, and the pollutant can diffuse to middle-upper floors in cross-ventilation modes. Cross ventilation mitigates the environmental health stress for the indoor environment when indoor-outdoor temperature difference exits and the personal intake fraction is decreased by about 66% compared to the single-side ventilation. Moreover, the existence of indoor-outdoor temperature differences can clearly decrease the risk of indoor personal exposure under both two natural ventilation modes. The study numerically investigates the building ventilation and pollutant dispersion in the urban community with natural ventilation. The method and the results are helpful references for optimizing the building ventilation plan and improving indoor air quality.
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16
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Intelligent Mining of Urban Ventilation Corridors Based on High-Precision Oblique Photographic Images. SENSORS 2021; 21:s21227537. [PMID: 34833612 PMCID: PMC8622167 DOI: 10.3390/s21227537] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 11/04/2021] [Accepted: 11/09/2021] [Indexed: 12/01/2022]
Abstract
With the advancement of urbanization and the impact of industrial pollution, the issue of urban ventilation has attracted increasing attention. Research on urban ventilation corridors is a hotspot in the field of urban planning. Traditional studies on ventilation corridors mostly focus on qualitative or simulated research on urban climate issues such as the intensified urban heat island effect, serious environmental pollution, and insufficient climate adaptability. Based on the high-precision urban remote sensing image data obtained by aeromagnetic oblique photography, this paper calculates the frontal area density of the city with reference to the urban wind statistics. Based on the existing urban patterns, template matching technology was used to automatically excavate urban ventilation corridors, which provides scientific and reasonable algorithmic support for the rapid construction of potential urban ventilation corridor paths. It also provides technical methods and decision basis for low-carbon urban planning, ecological planning and microclimate optimization design. This method was proved to be effective through experiments in Deqing city, Zhejiang Province, China.
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17
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Zhang M, Gao Z, Guo X, Shen J. Ventilation and Pollutant Concentration for the Pedestrian Zone, the Near-Wall Zone, and the Canopy Layer at Urban Intersections. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph182111080. [PMID: 34769599 PMCID: PMC8583701 DOI: 10.3390/ijerph182111080] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2021] [Revised: 10/07/2021] [Accepted: 10/19/2021] [Indexed: 11/16/2022]
Abstract
To gain further insight into the ventilation at urban street intersections, this study conducted 3D simulations of the ventilation at right- and oblique-angled intersections under eight wind directions by using the Reynolds-averaged Navier–Stokes (RANS) κ-ε turbulence model. The divergent responses of ventilation and pollution concentration for the pedestrian zone (ped), the near-wall zone (nwz), and the canopy layer to the change in intersection typology and wind direction were investigated. The flow characteristics of the intersections, taken as the air flow hub, were explored by employing indices such as the minimum flow ratio (β) between horizontal openings. The results show that oblique wind directions lead to a lower total volumetric flow rate (Qtotal) but a higher β value for right-angled intersections. For T-shaped intersections, a larger cross-sectional area for the outflow helps to increase Qtotal. Oblique-angled intersections, for example, the X-shaped intersection, experience a more significant difference in Qtotal but a steady value of β when the wind direction changes. The vertical air-exchange rate for the intersection was particularly significant when the wind directions were parallel to the street orientation or when there was no opening in the inflow direction. The spatially averaged normalized pollutant concentration and age of air (τ*¯) for the pedestrian zone and the canopy layer showed similar changing trends for most of the cases, while in some cases, only the τped*¯ or τnwz*¯ changed obviously. These findings reveal the impact mechanism of intersection configuration on urban local ventilation and pollutant diffusion.
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Affiliation(s)
- Mingjie Zhang
- School of Architecture and Urban Planning, Nanjing University, 22 Hankou Road, Nanjing 210093, China; (M.Z.); (X.G.)
| | - Zhi Gao
- School of Architecture and Urban Planning, Nanjing University, 22 Hankou Road, Nanjing 210093, China; (M.Z.); (X.G.)
- Joint International Research Laboratory of Eco-Urban Design, Tongji University, Ministry of Education, 1239 Siping Road, Shanghai 200092, China
- Correspondence: ; Tel.: +86-025-8359-7332
| | - Xin Guo
- School of Architecture and Urban Planning, Nanjing University, 22 Hankou Road, Nanjing 210093, China; (M.Z.); (X.G.)
| | - Jialei Shen
- Department of Mechanical and Aerospace Engineering, Syracuse University, Syracuse, NY 13210, USA;
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18
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Huang Y, Lei C, Liu CH, Perez P, Forehead H, Kong S, Zhou JL. A review of strategies for mitigating roadside air pollution in urban street canyons. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 280:116971. [PMID: 33774541 DOI: 10.1016/j.envpol.2021.116971] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 03/02/2021] [Accepted: 03/16/2021] [Indexed: 06/12/2023]
Abstract
Urban street canyons formed by high-rise buildings restrict the dispersion of vehicle emissions, which pose severe health risks to the public by aggravating roadside air quality. However, this issue is often overlooked in city planning. This paper reviews the mechanisms controlling vehicle emission dispersion in urban street canyons and the strategies for managing roadside air pollution. Studies have shown that air pollution hotspots are not all attributed to heavy traffic and proper urban design can mitigate air pollution. The key factors include traffic conditions, canyon geometry, weather conditions and chemical reactions. Two categories of mitigation strategies are identified, namely traffic interventions and city planning. Popular traffic interventions for street canyons include low emission zones and congestion charges which can moderately improve roadside air quality. In comparison, city planning in terms of building geometry can significantly promote pollutant dispersion in street canyons. General design guidelines, such as lower canyon aspect ratio, alignment between streets and prevailing winds, non-uniform building heights and ground-level building porosity, may be encompassed in new development. Concurrently, in-street barriers are widely applicable to rectify the poor roadside air quality in existing street canyons. They are broadly classified into porous (e.g. trees and hedges) and solid (e.g. kerbside parked cars, noise fences and viaducts) barriers that utilize their aerodynamic advantages to ease roadside air pollution. Post-evaluations are needed to review these strategies by real-world field experiments and more detailed modelling in the practical perspective.
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Affiliation(s)
- Yuhan Huang
- Centre for Green Technology, School of Civil and Environmental Engineering, University of Technology Sydney, NSW, 2007, Australia
| | - Chengwang Lei
- Centre for Wind, Waves and Water, School of Civil Engineering, The University of Sydney, NSW, 2006, Australia
| | - Chun-Ho Liu
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Pascal Perez
- SMART Infrastructure Facility, University of Wollongong, NSW, 2522, Australia
| | - Hugh Forehead
- SMART Infrastructure Facility, University of Wollongong, NSW, 2522, Australia
| | - Shaofei Kong
- Department of Atmospheric Sciences, School of Environmental Sciences, China University of Geosciences, Wuhan, 430074, China
| | - John L Zhou
- Centre for Green Technology, School of Civil and Environmental Engineering, University of Technology Sydney, NSW, 2007, Australia.
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19
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Chen T, Yang H, Chen G, Lam CKC, Hang J, Wang X, Liu Y, Ling H. Integrated impacts of tree planting and aspect ratios on thermal environment in street canyons by scaled outdoor experiments. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 764:142920. [PMID: 33172638 DOI: 10.1016/j.scitotenv.2020.142920] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 09/25/2020] [Accepted: 10/04/2020] [Indexed: 06/11/2023]
Abstract
Urban tree planting has the potential to reduce urban heat island intensity and building energy consumption. However, the heterogeneity of cities makes it difficult to quantitatively assess the integrated impacts of tree planting and street layouts. Scaled outdoor experiments were conducted to investigate the influence of tree plantings on wind and thermal environments in two-dimensional (2D) north-south oriented street canyons with various aspect ratios (building height/street width, AR = H/W = 1, 2, 3; H = 1.2 m). The effects of tree species with similar leaf area index (C. kotoense, big crown; C. macrocarpa, small crown), tree planting densities (ρ = 1, 0.5), and arrangements (double-row, single-row) were considered. Vegetation reduces pedestrian-level wind speed by 29%-70%. For ρ = 1 and single-row arrangement, C. kotoense (big crown) has a better shading effect and decreases wall and air temperature during the daytime by up to 9.4 °C and 1.2 °C, respectively. In contrast, C. macrocarpa (small crown) leads to a temperature increase at the pedestrian level. Moreover, C. kotoense raises the air and wall temperature of the upper urban canopy layer and increases the street albedo during the daytime because of the solar radiation reflected by trees. C. kotoense/C. macrocarpa produces the maximum daytime cooling/warming and nighttime warming of air temperature when H/W = 2 owing to its weaker convective heat transfer. When H/W = 3, the building shade dominates the shading cooling and tree cooling is less significant. When ρ = 1, double-row trees (C. kotoense) reduce wall and air temperatures by up to 10.0 °C and 1.0 °C during the daytime. However, reducing ρ from 1 to 0.5 weakens the capacity of daytime cooling by C. kotoense and the warming effect by C. macrocarpa. Our study quantifies the influence of tree planting and aspect ratios on the thermal environment, which can provide meaningful references for urban tree planting and produce high-quality validation data for numerical modeling.
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Affiliation(s)
- Taihan Chen
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, China 510275
| | - Hongyu Yang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, China 510275
| | - Guanwen Chen
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, China 510275
| | - Cho Kwong Charlie Lam
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, China 510275; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China; Guangdong Provincial Field Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary, 510275 Guangzhou, China
| | - Jian Hang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, China 510275; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China; Guangdong Provincial Field Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary, 510275 Guangzhou, China.
| | - Xuemei Wang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou, China
| | - Yonglin Liu
- Institute for Environmental and Climate Research, Jinan University, Guangzhou, China
| | - Hong Ling
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, China 510275; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China; Guangdong Provincial Field Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary, 510275 Guangzhou, China
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20
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Liu J, Cui S, Chen G, Zhang Y, Wang X, Wang Q, Gao P, Hang J. The influence of solar natural heating and NO x-O 3 photochemistry on flow and reactive pollutant exposure in 2D street canyons. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 759:143527. [PMID: 33261867 DOI: 10.1016/j.scitotenv.2020.143527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Revised: 10/21/2020] [Accepted: 10/28/2020] [Indexed: 06/12/2023]
Abstract
This study incorporates solar radiation model and NOx-O3 photochemistry into computational fluid dynamics (CFD) simulations with the standard k-ε model to quantify the integrated impacts of turbulent mixing, solar heating and chemical processes on vehicular passive (CO) and reactive (NOx, O3) pollutant dispersion within two-dimensional (2D) street canyons. Various street aspect ratios (H/W = 1, 3, 5) and solar-radiative scenarios (LST 0900, 1200, 1500) are considered. The initial source ratio of NO2 to NO is 1:10 and the background O3 concentration is 100 ppb (mole fraction). The reference Reynolds numbers are ~106-107 and Froude number ranges from 0.23 to 1.14. Personal intake fraction (P_IF) and its spatially-averaged values at the leeward-side (⟨P_IF⟩lee), windward-side (⟨P_IF⟩wind) and both street sides (⟨P_IF⟩) are adopted to evaluate pollutant exposure in near-road buildings. As H/W = 1 and 3, the clockwise single vortex is formed under neutral condition. Leeward/ground solar heating at LST 0900/1200 slightly enhance such vortex and reduce ⟨P_IF⟩. However, as H/W = 3, the single dominant vortex is separated into two counter-rotating vortices by windward solar heating at LST 1500, thus this ⟨P_IF⟩wind is significantly larger than the neutral case. As H/W = 5, the lower-level secondary anticlockwise vortex appears under neutral condition inducing much weaker wind and extremely higher pedestrian-level concentration. This two-main-vortex structure is destroyed by leeward/ground heating into single-main-vortex pattern, but dissociates into three counter-rotating vortices by windward heating. These three radiative scenarios raise pedestrian-level velocity in neutral case by about two orders, and reduce overall ⟨P_IF⟩ by two times to one order. For all cases, NO2 exposure is generally about 40%-380% larger than passive CO exposure, which indicates the conversion of NO into NO2 by depleting O3 is dominant in present NOx-O3 titration interactions. Finally, solar heating only raises air temperature by up to 2-3 K and influences chemical rate slightly, thus this impact on reactive pollutant dispersion is less significant than its effect by the enhanced turbulent mixing.
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Affiliation(s)
- Jiarui Liu
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China
| | - Shuhang Cui
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China; Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, 519000 Zhuhai, PR China
| | - Guanwen Chen
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China; Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, 519000 Zhuhai, PR China
| | - Yong Zhang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China; Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, 519000 Zhuhai, PR China
| | - Xuemei Wang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou, PR China
| | - Qun Wang
- Department of Mechanical Engineering, University of Hong Kong, Hong Kong, China
| | - Peng Gao
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China; Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, 519000 Zhuhai, PR China.
| | - Jian Hang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China; Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, 519000 Zhuhai, PR China.
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21
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Zhang X, Wang C, Liu X, Zhou T, Tao C, Shi Q. Effect of triangular roof angle on dispersion of gaseous pollutants and particulate matter. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:15537-15550. [PMID: 33241499 DOI: 10.1007/s11356-020-11512-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 11/02/2020] [Indexed: 06/11/2023]
Abstract
The Euler-Lagrangian method is adopted to simulate the dispersion of gaseous pollutants and particulate matter (PM) in isolated street canyons, and the influences of the roof angle on the flow structures and distributions of gaseous pollutants and PM are analyzed in detail. Numerical simulation results indicate that gaseous pollutants and PM in the canyons present three typical single main clockwise vortex, transition vortex, and double vortex structures, which are identified at increasing roof slopes. Gaseous pollutants and PM demonstrate the lowest concentration of pollutants when a single vortex structure exists. The concentration of gaseous pollutants and PM reaches the highest value in pedestrian-level areas when the flow field is in a transitional vortex structure. Unlike gaseous pollutants, the concentration of PM does not always decrease with increasing altitude, and higher PM concentrations sometimes occur in the mid-level areas of the canyon. A small roof incline angle is generally recommended for discharging gaseous pollutants and PM.
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Affiliation(s)
- Xiaoxiao Zhang
- School of Automotive and Transportation Engineering, Hefei University of Technology, Hefei, 230009, Anhui, China
| | - Chunmei Wang
- School of Automotive and Transportation Engineering, Hefei University of Technology, Hefei, 230009, Anhui, China
| | - Xiaoping Liu
- School of Civil Engineering, Hefei University of Technology, No. 193, Tunxi Road, Hefei, 230009, Anhui, China
| | - Taotao Zhou
- School of Automotive and Transportation Engineering, Hefei University of Technology, Hefei, 230009, Anhui, China.
| | - Changfa Tao
- School of Automotive and Transportation Engineering, Hefei University of Technology, Hefei, 230009, Anhui, China.
- Intelligent Vehicle Labs of Anhui Province, Hefei University of Technology, No. 193, Tunxi Road, Hefei, 230009, Anhui, China.
| | - Qin Shi
- School of Automotive and Transportation Engineering, Hefei University of Technology, Hefei, 230009, Anhui, China
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22
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Huang YD, Xu N, Ren SQ, Qian LB, Cui PY. Numerical investigation of the thermal effect on flow and dispersion of rooftop stack emissions with wind tunnel experimental validations. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:11618-11636. [PMID: 33128145 DOI: 10.1007/s11356-020-11304-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Accepted: 10/18/2020] [Indexed: 06/11/2023]
Abstract
The thermal effect on the flow and dispersion of pollutants emitted from a rooftop stack is investigated by means of CFD (computational fluid dynamics) models with wind tunnel experimental validations. The leeward wall and its nearby ground are heated simultaneously to mimic solar radiation. Seventeen Ri (Richardson number) cases with four inflow wind speeds (1, 3, 6, and 9 m/s) and five temperature differences (0, 60, 120, 180, and 240 K) between the heated surface and ambient air are considered to represent the interaction between thermal buoyancy force and inertia force. The results reveal that (1) the steady RANS (Reynolds Averaged Navier-Stokes) computations with Boussinesq approximation can generally reproduce the effect of thermal buoyancy on the wake flow and pollutant distribution in wind tunnel experiments; (2) the wake vortex flow is less affected by the thermal buoyancy force at small Ri (e.g., Ri ≤ 0.26) while an upward flow rather than a clockwise vortex structure is developed in the near wake at Ri ≥ 0.58; (3) it is inappropriate to place fresh air intakes on the leeward wall of the emitting building, but natural ventilation through windows on the leeward wall can be implemented at higher Ri (e.g., Ri = 2.33); (4) at the pedestrian respiration height downstream of the building, the distance between the location of maximum pollutant concentration and the leeward wall increases linearly with Ri while the maximum dimensionless concentration decreases exponentially with increasing Ri; (5) the air temperature is rapidly reduced away from the heated wall/ground and a heat accumulation zone is formed at the ground corner next to the leeward wall. This study can be helpful for determining the strategy for natural ventilation through windows and for evaluating the impacts of rooftop stack exhaust on air quality downstream of emitting buildings.
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Affiliation(s)
- Yuan-Dong Huang
- School of Environment and Architecture, University of Shanghai for Science and Technology, No.516, Jungong Road, Yangpu District, Shanghai, 200093, China
| | - Nuo Xu
- School of Environment and Architecture, University of Shanghai for Science and Technology, No.516, Jungong Road, Yangpu District, Shanghai, 200093, China
| | - Su-Qi Ren
- School of Environment and Architecture, University of Shanghai for Science and Technology, No.516, Jungong Road, Yangpu District, Shanghai, 200093, China
| | - Li-Bing Qian
- School of Environment and Architecture, University of Shanghai for Science and Technology, No.516, Jungong Road, Yangpu District, Shanghai, 200093, China
| | - Peng-Yi Cui
- School of Environment and Architecture, University of Shanghai for Science and Technology, No.516, Jungong Road, Yangpu District, Shanghai, 200093, China.
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23
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Lee SH, Kwak KH. Assessing 3-D Spatial Extent of Near-Road Air Pollution around a Signalized Intersection Using Drone Monitoring and WRF-CFD Modeling. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:ijerph17186915. [PMID: 32971859 PMCID: PMC7559155 DOI: 10.3390/ijerph17186915] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 09/17/2020] [Accepted: 09/19/2020] [Indexed: 01/10/2023]
Abstract
In this study, we have assessed the three-dimensional (3-D) spatial extent of near-road air pollution around a signalized intersection in a densely populated area using collaborating methodologies of stationary measurements, drone monitoring, and atmospheric dispersion modeling. Stationary measurement data collected in the roadside apartment building showed a substantial effect of emitted pollutants, such as nitrogen oxides (NOx), black carbon (BC), and ultrafine particles (UFPs), especially during the morning rush hours. Vertical drone monitoring near the road intersection exhibited a steeper decreasing trend with increasing altitude for BC concentration rather than for fine particulate matter (PM2.5) concentration below the apartment building height. Atmospheric NOx dispersion was simulated using the weather research and forecasting (WRF) and computational fluid dynamics (CFD) models for the drone measurement periods. Based on the agreement between the measured BC and simulated NOx concentrations, we concluded that the air pollution around the road intersection has adverse effects on the health of residents living within the 3-D spatial extent within at least 120 m horizontally and a half of building height vertically during the morning rush hours. The comparability between drone monitoring and WRF-CFD modeling can further guarantee the identification of air pollution hotspots using the methods.
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Affiliation(s)
- Seung-Hyeop Lee
- Department of Environmental Science, Kangwon National University, Chuncheon 24341, Korea;
| | - Kyung-Hwan Kwak
- School of Natural Resources and Environmental Science, Kangwon National University, Chuncheon 24341, Korea
- Correspondence:
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24
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Fu X, Xiang S, Liu Y, Liu J, Yu J, Mauzerall DL, Tao S. High-resolution simulation of local traffic-related NO x dispersion and distribution in a complex urban terrain. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 263:114390. [PMID: 32203857 DOI: 10.1016/j.envpol.2020.114390] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 03/13/2020] [Accepted: 03/14/2020] [Indexed: 06/10/2023]
Abstract
Urban air pollution features large spatial and temporal variations due to the high heterogeneity in emissions and ventilation conditions, which render the pollutant distributions in complex urban terrains difficult to measure. Current urban air pollution models are not able to simulate pollutant dispersion and distribution at a low computational cost and high resolution. To address this limitation, we have developed the urban terrain air pollution (UTAP) dispersion model to investigate, at a spatial resolution of 5 m and a temporal resolution of 1 h, the distribution of the local traffic-related NOx concentration at the pedestrian level in a 1 × 1 km2 area in Baoding, Hebei, China. The UTAP model was shown to be capable of capturing the local pollution variations in a complex urban terrain at a low computational cost. We found that the local traffic-related NOx concentration along or near major roads (10-200 μg m-3) was 1-2 orders of magnitude higher than that in places far from roads (0.1-10 μg m-3). Considering the background pollution, the NO and NO2 concentrations exhibited similar patterns with higher concentrations in street canyons and lower concentrations away from streets, while the O3 concentration exhibited the opposite behavior. Sixty percent of the NOx concentration likely stemmed from local traffic when the background pollution level was low. Both the background wind speed and direction substantially impacted the overall pollution level and concentration variations, with a low wind speed and direction perpendicular to the axes of most streets identified as unfavorable pollutant dispersion conditions. Our results revealed a large variability in the local traffic-related air pollutant concentration at the pedestrian level in the complex urban terrain, indicating that high-resolution computationally efficient models such as the UTAP model are required to accurately estimate the pollutant exposure of urban residents.
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Affiliation(s)
- Xiangwen Fu
- Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China; Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ, 08544, USA
| | - Songlin Xiang
- Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China
| | - Ying Liu
- School of Statistics, University of International Business and Economics, Beijing, 100029, China
| | - Junfeng Liu
- Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.
| | - Jun Yu
- School of Resources and Environmental Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Denise L Mauzerall
- Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ, 08544, USA; Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Shu Tao
- Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China
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25
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Chen G, Wang D, Wang Q, Li Y, Wang X, Hang J, Gao P, Ou C, Wang K. Scaled outdoor experimental studies of urban thermal environment in street canyon models with various aspect ratios and thermal storage. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 726:138147. [PMID: 32305749 DOI: 10.1016/j.scitotenv.2020.138147] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 03/18/2020] [Accepted: 03/21/2020] [Indexed: 06/11/2023]
Abstract
Street aspect ratios and urban thermal storage largely determine the thermal environment in cities. By performing scaled outdoor measurements in summer of 2017 in Guangzhou, China, we investigate these impacts on spatial/temporal characteristics of urban thermal environment which are still unclear so far. Two types of street canyon models are investigated, i.e. the 'hollow' model resembling hollow concrete buildings and the 'sand' model consisting of buildings filled with sand attaining much greater thermal storage. For each model, three street aspect ratios (building height/street width, H/W = 1, 2, 3; H = 1.2 m) are considered. The diurnal variations of air-wall surface temperatures are observed and their characteristics are quantified for various cases. The daily average temperature and daily temperature range (DTR) of wall temperature vary significantly with different aspect ratios and thermal storage. During the daytime, wider street canyon (H/W = 1) with less shading area experiences higher temperature than narrower ones (H/W = 2, 3) as more solar radiation received by wall surfaces. At night, wider street canyon cools down quicker due to stronger upward longwave radiation and night ventilation. For hollow models, H/W = 1 attains DTR of 12.1 °C, which is 1.2 and 2.1 °C larger than that of H/W = 2, 3. Moreover, the sand models experience smaller DTR and a less changing rate of wall temperature than hollow models because larger thermal storage absorbs more heat in the daytime and releases more at night. DTR of hollow models with H/W = 1, 2, 3 is 4.5, 4.6 and 3.8 °C greater than sand models respectively. For both hollow and sand models, wider streets experience a little higher daily average temperature (0.3-0.6 °C) than narrower ones. Our study provides direct evidence in how man-made urban structures influence urban climate and also suggests the possibility to control outdoor thermal environment by optimize urban morphology and thermal storage.
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Affiliation(s)
- Guanwen Chen
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China 510275
| | - Dongyang Wang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China 510275
| | - Qun Wang
- Department of Mechanical Engineering, the University of Hong Kong, Pokfulam Road, Hong Kong
| | - Yuguo Li
- Department of Mechanical Engineering, the University of Hong Kong, Pokfulam Road, Hong Kong
| | - Xuemei Wang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou, PR China
| | - Jian Hang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China 510275; Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai), Zhuhai, China; Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University), Ministry of Education, Zhuhai (519000), China.
| | - Peng Gao
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China 510275
| | - Cuiyun Ou
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China 510275
| | - Kai Wang
- Department of Mechanical Engineering, the University of Hong Kong, Pokfulam Road, Hong Kong.
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26
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Xie X, Hao C, Huang Y, Huang Z. Influence of TiO 2-based photocatalytic coating road on traffic-related NO x pollutants in urban street canyon by CFD modeling. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 724:138059. [PMID: 32247975 DOI: 10.1016/j.scitotenv.2020.138059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 03/02/2020] [Accepted: 03/18/2020] [Indexed: 06/11/2023]
Abstract
The use of titanium dioxide (TiO2) photocatalytic nanoparticles as road coating to trap and decompose air pollutants provides a promising technology to mitigate the harmful effects of vehicle emissions. However, there are few studies on computational fluid dynamics (CFD) simulations of the effect of NOx photocatalytic oxidation in street canyon with TiO2 nanoparticles as pavement coating. This study develop a CFD model with photocatalytic oxidation (PCO) reaction implemented for numerical simulation of NOx abatement in an urban street canyon with TiO2 coating, considering the effects of relative humidity (RH) (10-90%), and irradiance (10-40W ⋅ m-2). Results show that TiO2 coating road can effectively reduce nitrogen oxide (NOx) concentration in the street canyon. The average nitric oxide (NO) and nitrogen dioxide (NO2) concentrations in street canyon with TiO2 coating road were reduced by 3.70% and 4.31%, respectively, comparing with street canyon without TiO2 coating. The irradiance and relative humidity had great effect on PCO reaction in street canyon with TiO2 coating road. When the irradiance increased from 10W ⋅ m-2 to 40W ⋅ m-2, average NO conversion rose from 1.35% to 3.70%, and average NO2 conversion rose from 2.43% to 4.31%. The average conversion of NO and NO2 decreased from 5.11% to 2.54% and from 5.60% to 3.25%, respectively, when the relative humidity is varied from 10% to 90%. Results are useful to transport planners and road engineers who need to reduce NOx concentrations in urban streets travelled by fossil fuel-powered vehicles. Method of the study can be considered by future research faced with different pavement construction and traffic environment.
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Affiliation(s)
- Xiaomin Xie
- Key Laboratory for Power machinery and Engineering of M. O. E., Shanghai Jiao Tong University, No. 800, Dongchuan Road, 200240 Shanghai, PR China.
| | - Chenrui Hao
- Key Laboratory for Power machinery and Engineering of M. O. E., Shanghai Jiao Tong University, No. 800, Dongchuan Road, 200240 Shanghai, PR China
| | - Yue Huang
- Institute for Transport Studies, University of Leeds, 34-40 University Road, Leeds LS2 9JT, UK
| | - Zhen Huang
- Key Laboratory for Power machinery and Engineering of M. O. E., Shanghai Jiao Tong University, No. 800, Dongchuan Road, 200240 Shanghai, PR China
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27
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Keshavarzian E, Jin R, Dong K, Kwok KCS, Zhang Y, Zhao M. Effect of pollutant source location on air pollutant dispersion around a high-rise building. APPLIED MATHEMATICAL MODELLING 2020; 81:582-602. [PMID: 32287944 PMCID: PMC7111480 DOI: 10.1016/j.apm.2020.01.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 12/20/2019] [Accepted: 01/09/2020] [Indexed: 05/25/2023]
Abstract
This article investigates the dispersion of airborne pollutants emitted from different locations near a high-rise building. A Computational Fluid Dynamics (CFD) model for simulating the wind flow field and the pollutant dispersion was developed and validated by wind tunnel data. Then the spreading of the pollutant emitted from different locations to a rectangular-shaped high-rise residential (HRR) building was numerically studied. The pollutant source location was set in a wide range of the position angle and distance between the source and the building. It was found that the pollutant concentration on the building decreases with an increase in the emission distance whereas the effect of the position angle is more complicated. Interestingly, there is a critical range of the position angle from which the emitted pollutants will not spread to the building in a significant way. The effect of the source location was linked to the wind flow field around the building, particularly with several major flows. The vertical distributions of the pollutant concentration on different faces were also investigated, and it was found that these are more affected by the vertical flow near each face. Finally, a mathematical model was developed to evaluate the pollutant concentration as a function of the emission distance and position angle. These findings are helpful to the understanding of the dispersion of airborne pollutants around high-rise buildings and the related hazard management in urban design.
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Affiliation(s)
- Erfan Keshavarzian
- Centre for Infrastructure Engineering, School of Computing, Engineering and Mathematics, Western Sydney University, Penrith, NSW 2751, Australia
| | - Ruizhi Jin
- Centre for Infrastructure Engineering, School of Computing, Engineering and Mathematics, Western Sydney University, Penrith, NSW 2751, Australia
| | - Kejun Dong
- Centre for Infrastructure Engineering, School of Computing, Engineering and Mathematics, Western Sydney University, Penrith, NSW 2751, Australia
| | - Kenny C S Kwok
- School of Civil Engineering, The University of Sydney, NSW 2006, Australia
| | - Yu Zhang
- School of Medicine, Tsinghua University, Beijing 100048, China
| | - Ming Zhao
- Centre for Infrastructure Engineering, School of Computing, Engineering and Mathematics, Western Sydney University, Penrith, NSW 2751, Australia
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28
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Zhang K, Chen G, Zhang Y, Liu S, Wang X, Wang B, Hang J. Integrated impacts of turbulent mixing and NO X-O 3 photochemistry on reactive pollutant dispersion and intake fraction in shallow and deep street canyons. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 712:135553. [PMID: 31787286 DOI: 10.1016/j.scitotenv.2019.135553] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 10/28/2019] [Accepted: 11/14/2019] [Indexed: 06/10/2023]
Abstract
We employ computational fluid dynamics (CFD) simulations with NO-NO2-O3 chemistry to investigate the impacts of aspect ratios (H/W = 1,3,5), elevated-building design, wind catchers and two background ozone concentrations ([O3]b = 100/20 ppb) on reactive pollutant dispersion in two-dimensional (2D) street canyons. Personal intake fraction of NO2 (P_IFNO2) and its spatial mean value in entire street (i.e. street intake fraction <P_IFNO2>) are calculated to quantify pollutant exposure in near-road buildings. Chemical reaction contribution of NO2 exposure (CRC<P_IF>), O3 depletion rate (dozone) and photostationary state defect (δps) are used to analyze the interplay of turbulent and chemical processes. As H/W increases from 1, 3 to 5 with [O3]b = 100 ppb, the flow pattern turns from single-main-vortex structure to two-counter-rotating-vortex structure, and pedestrian-level velocity becomes 1-2 orders smaller. The high-dozone regions and low-|δps| regions get larger with more complete chemical reactions. Consequently, passive <P_IFNO2> rises 1 order (4.09-5.71 ppm to 41.76 ppm), but reactive <P_IFNO2> only increases several times (17.80-21.28 ppm to 58.50 ppm) and the contribution of chemistry (CRC<P_IF>) decreases with higher H/W. Thus, chemistry raises <P_IFNO2 > more effectively in shallow street canyons (H/W = 1-3). In deep street canyons (H/W = 5), elevated-building design and wind catchers destroy two-counter-rotating-vortex structure, improve street ventilation and reduce passive <P_IFNO2> by 2 and 1 orders (41.76 ppm to 0.38-5.16 ppm), however they only reduce reactive <P_IFNO2> by about 97.5% and 75% (58.50 ppm to 1.61-14.48 ppm). Such building techniques induce lower O3 depletion rate but greater chemical contribution. Finally, raising [O3]b from 20 to 100 ppb causes greater O3 depletion rate and chemical contribution and produces larger <P_IFNO2>. For deep street canyons, the impact of higher [O3]b on <P_IFNO2> is weaker than that in shallow street canyons, while it becomes stronger when fixing elevated-building design and wind catchers. This study provides some innovative findings on reactive pollutant exposure in 2D street canyons and offers effective CFD methodologies to evaluate pollutant exposure with more complicated chemistry and urban configurations.
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Affiliation(s)
- Keer Zhang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China
| | - Guanwen Chen
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China
| | - Yong Zhang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China
| | - Shanhe Liu
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China
| | - Xuemei Wang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou, PR China
| | - Baoming Wang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China.
| | - Jian Hang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China.
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29
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Gao D, Xie M, Chen X, Wang T, Zhan C, Ren J, Liu Q. Modeling the Effects of Climate Change on Surface Ozone during Summer in the Yangtze River Delta Region, China. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2019; 16:E1528. [PMID: 31052196 PMCID: PMC6539038 DOI: 10.3390/ijerph16091528] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 04/22/2019] [Indexed: 11/17/2022]
Abstract
Future climate change can impact ozone concentrations by changing regional meteorological factors related to ozone (O3) pollution. To better understand the variations of meteorological factors and their effects on O3 formation processes under future climate conditions, we model the present and the future meteorology and air quality in summer over the Yangtze River Delta (YRD) region by using the Weather Research and Forecasting Model with Chemistry module (WRF/Chem), which is driven by the outputs of Community Climate System Model version 4 (CCSM4). The simulations predict that solar radiation, 2-m air temperature, and wind speed increase in the daytime over most of the YRD region. Absolute humidity and precipitation increase in the north and decrease in the south, while the planetary boundary layer height (PBLH) has an opposite change pattern displaying a decrease in the north and an increase in the south. The southerly wind will be strengthened in the daytime. At night, the change patterns of the meteorological factors are similar to the daytime but with small variations. Meanwhile, O3 and its precursors all increase in the north and decrease in the south. The increases of NOx, volatile organic compounds (VOC), and CO are related with the decreases of PBLH and the input effect of stronger southerly wind, while the decreases are attributed to the output effect of the stronger southerly wind. During the daytime, the increase of surface O3 in the north is dominated by the chemical processes related with the increases of solar radiation, air temperature, and O3 precursors. The decrease of surface O3 in the south is mainly caused by the transport process changing with the strengthened southerly wind. At night, the surface O3 changing the amplitude is less than the daytime. The less O3 variations at night can be attributed to an O3 titration reaction with NO, the changes in NOx concentrations, and the increases of nocturnal PBLH. With the aid of H2O2/HNO3, O3 formation in the YRD region is found to be easily affected by NOx in the future. The findings can help to understand the changing trend of O3 in the YRD region and can propose reasonable pollution control policies.
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Affiliation(s)
- Da Gao
- School of Atmospheric Sciences, Nanjing University, Nanjing 210023, China.
| | - Min Xie
- School of Atmospheric Sciences, Nanjing University, Nanjing 210023, China.
| | - Xing Chen
- School of Atmospheric Sciences, Nanjing University, Nanjing 210023, China.
| | - Tijian Wang
- School of Atmospheric Sciences, Nanjing University, Nanjing 210023, China.
| | - Chenchao Zhan
- School of Atmospheric Sciences, Nanjing University, Nanjing 210023, China.
| | - Junyu Ren
- School of Atmospheric Sciences, Nanjing University, Nanjing 210023, China.
| | - Qian Liu
- Jiangsu Provincial Academy of Environmental Science, Nanjing 210036, China.
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30
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Zhang K, Chen G, Wang X, Liu S, Mak CM, Fan Y, Hang J. Numerical evaluations of urban design technique to reduce vehicular personal intake fraction in deep street canyons. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 653:968-994. [PMID: 30759622 DOI: 10.1016/j.scitotenv.2018.10.333] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 10/04/2018] [Accepted: 10/24/2018] [Indexed: 05/21/2023]
Abstract
High-rise deep street canyons usually experience poor ventilation and large vehicular pollutant exposure to residents in near-road buildings. Investigations are still required to clarify the flow and dispersion mechanisms in deep street canyons and explore techniques to reduce such large pollutant exposure. By conducting computational fluid dynamics (CFD) simulations validated by wind tunnel data and scale-model outdoor field measurements, we investigate the integrated impacts of aspect ratios, first-floor and second-floor elevated building designs, viaduct settings, height variations and wind catchers on the flow, personal intake fraction (P_IF) of CO (carbon dioxide) and its spatial mean value 〈P_IF〉 in two-dimensional (2D) street canyons. Results show that cases with H/W = 5 experience two counter-rotating vortices, much poorer ventilation and 1-2 orders larger 〈P_IF〉 (43.6-120.8 ppm) than H/W = 1 and 3 (3.8-4.3 and 5.6-5.8 ppm). Moreover, in cases with H/W = 5 the height variation results in three vertically-aligned vortices and much weaker wind, subsequently produces greater 〈P_IF〉 (1402-2047 ppm). To reduce 〈P_IF〉 with H/W = 5, various urban designs are evaluated. The first-floor elevated building design creates more effective ventilation pathways than the second-floor elevated type does and reduces 〈P_IF〉 at H/W = 5 by five orders (1402 to ~0.01 ppm) or two orders (43.6 to ~0.1 ppm) in cases with or without the height variation. However, such reductions at H/W = 1 and 3 are only 76.8%-81.4% and 22.4%-36.2% respectively. Wind catchers destroy the multi-vortex flow pattern as H/W = 5, produce a contra-clockwise main vortex and reduce 〈P_IF〉 by 1-2 orders for cases with or without the height variation.
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Affiliation(s)
- Keer Zhang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China
| | - Guanwen Chen
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China
| | - Xuemei Wang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou, PR China
| | - Shanhe Liu
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China
| | - Cheuk Ming Mak
- Department of Building Services Engineering, Hong Kong Polytechnic University, Hong Kong
| | - Yifan Fan
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong.
| | - Jian Hang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, PR China.
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31
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Holnicki P, Kałuszko A, Nahorski Z, Tainio M. Intra-urban variability of the intake fraction from multiple emission sources. ATMOSPHERIC POLLUTION RESEARCH 2018; 9:1184-1193. [PMID: 30740016 PMCID: PMC6358147 DOI: 10.1016/j.apr.2018.05.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 04/30/2018] [Accepted: 05/11/2018] [Indexed: 05/31/2023]
Abstract
BACKGROUND Ambient air pollution and associated adverse health effects are among most acute environmental problems in many cities worldwide. The intake fraction (iF) approach can be applied for evaluating the health benefits of reducing emissions, especially when rapid decisions are needed. Intake fraction is a metric that represents emission-to-intake relationship and characterizes abatement of exposure potential attributed to specific emission sources. AIM In this study, the spatial variability of iF in Warsaw agglomeration, Poland, is discussed. METHODS The iF analysis is based on the earlier air quality modeling results, that include the main pollutants characterizing an urban atmospheric environment (SO2, NOx, PM10, PM2.5, CO, C6H6, B(a)P, heavy metals). The annual mean concentrations were computed by the CALPUFF modeling system (spatial resolution 0.5 × 0.5 km2) on the basis of the emission and meteorological data from year 2012. The emission field comprised 24 high (power generation) and 3880 low (industry) point sources, 7285 mobile (transport) sources, and 6962 area (housing) sources. RESULTS The aggregated iFs values are computed for each emission class and the related polluting compounds. Intra-urban variability maps of iFs are attributed to an emission sources by emission category and pollutant. CONCLUSIONS Intake fraction is shown as a decision support tool for implementing the cost-effective emission policy and reducing the health risk of air pollution.
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Affiliation(s)
- Piotr Holnicki
- Systems Research Institute, Polish Academy of Sciences, Warsaw, Poland
| | - Andrzej Kałuszko
- Systems Research Institute, Polish Academy of Sciences, Warsaw, Poland
| | - Zbigniew Nahorski
- Systems Research Institute, Polish Academy of Sciences, Warsaw, Poland
- Warsaw School of Information Technology (WIT), Warsaw, Poland
| | - Marko Tainio
- Systems Research Institute, Polish Academy of Sciences, Warsaw, Poland
- UKCRC Centre for Diet and Activity Research (CEDAR), MRC Epidemiology Unit, University of Cambridge, UK
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Natural Ventilation of a Small-Scale Road Tunnel by Wind Catchers: A CFD Simulation Study. ATMOSPHERE 2018. [DOI: 10.3390/atmos9100411] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Providing efficient ventilation in road tunnels is essential to prevent severe air pollution exposure for both drivers and pedestrians in such enclosed spaces with heavy vehicle emissions. Longitudinal ventilation methods like commercial jet fans have been widely applied and confirmed to be effective for introducing external fresh air into road tunnels that are shorter than 3 km. However, operating tunnel jet fans is energy consuming. Therefore, for small-scale (~100 m–1 km) road tunnels, mechanical ventilation methods might be highly energetically expensive and unaffordable. Many studies have found that the use of wind catchers could improve buildings’ natural ventilation, but their effect on improving natural ventilation in small-scale road tunnels has, hitherto, rarely been studied. This paper, therefore, aims to quantify the influence of style and arrangement of one-sided flat-roof wind catchers on ventilation performance in a road tunnel. The concept of intake fraction (IF) is applied for ventilation and pollutant exposure assessment in the overall tunnel and for pedestrian regions. Computational fluid dynamics (CFD) methodology with a standard k-epsilon turbulence model is used to perform a three-dimensional (3D) turbulent flow simulation, and CFD results have been validated by wind-tunnel experiments for building cross ventilation. Results show that the introduction of wind catchers would significantly enhance wind speed at pedestrian level, but a negative velocity reduction effect and a near-catcher recirculation zone can also be found. A special downstream vortex extending along the downstream tunnel is found, helping remove the accumulated pollutants away from the low-level pedestrian sides. Both wind catcher style and arrangement would significantly influence the ventilation performance in the tunnel. Compared to long-catcher designs, short-catchers would be more effective for providing fresh air to pedestrian sides due to a weaker upstream velocity reduction effect and smaller near-catcher recirculation zone. In long-catcher cases, IF increases to 1.13 ppm when the wind catcher is positioned 240 m away from the tunnel entrance, which is almost twice that in short-catcher cases. For the effects of catcher arrangements, single, short-catcher, span-wise, shifting would not help dilute pollutants effectively. Generally, a design involving a double short-catcher in a parallel arrangement is the most recommended, with the smallest IF, i.e., 61% of that in the tunnel without wind catchers (0.36 ppm).
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Sha C, Wang X, Lin Y, Fan Y, Chen X, Hang J. The impact of urban open space and 'lift-up' building design on building intake fraction and daily pollutant exposure in idealized urban models. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 633:1314-1328. [PMID: 29758884 DOI: 10.1016/j.scitotenv.2018.03.194] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 03/14/2018] [Accepted: 03/17/2018] [Indexed: 06/08/2023]
Abstract
Sustainable urban design is an effective way to improve urban ventilation and reduce vehicular pollutant exposure to urban residents. This paper investigated the impacts of urban open space and 'lift-up' building design on vehicular CO (carbon monoxide) exposure in typical three-dimensional (3D) urban canopy layer (UCL) models under neutral atmospheric conditions. The building intake fraction (IF) represents the fraction of total vehicular pollutant emissions inhaled by residents when they stay at home. The building daily CO exposure (Et) means the extent of human beings' contact with CO within one day indoor at home. Computational fluid dynamics (CFD) simulations integrating with these two concepts were performed to solve turbulent flow and assess vehicular CO exposure to urban residents. CFD technique with the standard k-ε model was successfully validated by wind tunnel data. The initial numerical UCL model consists of 5-row and 5-column (5×5) cubic buildings (building height H=street width W=30m) with four approaching wind directions (θ=0°, 15°, 30°, 45°). In Group I, one of the 25 building models is removed to attain urban open space settings. In Group II, the first floor (Lift-up1), or second floor (Lift-up2), or third floor (Lift-up3) of all buildings is elevated respectively to create wind pathways through buildings. Compared to the initial case, urban open space can slightly or significantly reduce pollutant exposure for urban residents. As θ=30° and 45°, open space settings are more effective to reduce pollutant exposure than θ=0° and 15°.The pollutant dilution near or surrounding open space and in its adjacent downstream regions is usually enhanced. Lift-up1 and Lift-up2 experience much greater pollutant exposure reduction in all wind directions than Lift-up3 and open space. Although further investigations are still required to provide practical guidelines, this study is one of the first attempts for reducing urban pollutant exposure by improving urban design.
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Affiliation(s)
- Chenyuan Sha
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, PR China
| | - Xuemei Wang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou, PR China.
| | - Yuanyuan Lin
- School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou 510275, PR China
| | - Yifan Fan
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, PR China
| | - Xi Chen
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, PR China
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou 510275, PR China.
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Yang F, Zhong K, Chen Y, Kang Y. Simulations of the impacts of building height layout on air quality in natural-ventilated rooms around street canyons. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2017; 24:23620-23635. [PMID: 28856497 DOI: 10.1007/s11356-017-9934-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 08/08/2017] [Indexed: 06/07/2023]
Abstract
Numerical simulations were conducted to investigate the effects of building height ratio (i.e., HR, the height ratio of the upstream building to the downstream building) on the air quality in buildings beside street canyons, and both regular and staggered canyons were considered for the simulations. The results show that the building height ratio affects not only the ventilation fluxes of the rooms in the downstream building but also the pollutant concentrations around the building. The parameter, outdoor effective source intensity of a room, is then proposed to calculate the amount of vehicular pollutants that enters into building rooms. Smaller value of this parameter indicates less pollutant enters the room. The numerical results reveal that HRs from 2/7 to 7/2 are the favorable height ratios for the regular canyons, as they obtain smaller values than the other cases. While HR values of 5/7, 7/7, and 7/5 are appropriate for staggered canyons. In addition, in terms of improving indoor air quality by natural ventilation, the staggered canyons with favorable HR are better than those of the regular canyons.
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Affiliation(s)
- Fang Yang
- College of Mechanical Engineering, Shanghai University of Engineering Science, Shanghai, 201620, China
- School of Environmental Science and Engineering, Donghua University, Shanghai, 201620, China
| | - Ke Zhong
- School of Environmental Science and Engineering, Donghua University, Shanghai, 201620, China
| | - Yonghang Chen
- School of Environmental Science and Engineering, Donghua University, Shanghai, 201620, China
| | - Yanming Kang
- School of Environmental Science and Engineering, Donghua University, Shanghai, 201620, China.
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Impacts of Urban Layouts and Open Space on Urban Ventilation Evaluated by Concentration Decay Method. ATMOSPHERE 2017. [DOI: 10.3390/atmos8090169] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Zhang Z, Gong D, Mao R, Kim SJ, Xu J, Zhao X, Ma Z. Cause and predictability for the severe haze pollution in downtown Beijing in November-December 2015. THE SCIENCE OF THE TOTAL ENVIRONMENT 2017; 592:627-638. [PMID: 28341468 DOI: 10.1016/j.scitotenv.2017.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Revised: 01/31/2017] [Accepted: 03/02/2017] [Indexed: 06/06/2023]
Abstract
Based on the hourly PM2.5 concentrations, meteorological variable records and ERA-Interim reanalysis data, a series of diagnostic analyses were conducted to explore the possible meteorological causes for the severe haze pollution that occurred in Beijing in November-December 2015. Using the online-coupled WRF-Chem model and GFS data, the predictability of hourly and daily PM2.5 concentrations was evaluated. The results showed that, in the context of pollutant emission, the severe haze pollution in downtown Beijing in November-December 2015 was primarily attributed to anomalous local meteorological conditions, which were caused and strengthened by anomalous large-scale atmospheric circulations. The abnormal changes in the upper troposphere appeared to trigger the anomalies in the middle-lower troposphere and the local conditions. The numerical simulations can capture the spatial distribution patterns of the PM2.5 concentrations for predictions of 1 to 10days in advance. The PM2.5 concentration trends in downtown Beijing were generally consistent with the predictions on both daily and hourly time-scales, although the predictability decreased gradually as the lead times prolonged. The predictability of the daily mean PM2.5 concentration was slightly higher than that of the hourly concentration. The statistical indices suggested that the predictions of daily and hourly mean PM2.5 concentrations were generally skillful and reliable for maximum lead times of 8 and 5days, respectively.
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Affiliation(s)
- Ziyin Zhang
- Environmental Meteorology Forecast Center of Beijing-Tianjin-Hebei, Chinese Meteorological Administration, Beijing 100089, China; Institute of Urban Meteorology, Chinese Meteorological Administration, Beijing 100089, China.
| | - Daoyi Gong
- State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China
| | - Rui Mao
- State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China
| | - Seong-Joong Kim
- Korea Polar Research Institute, Incheon 406-840, Republic of Korea
| | - Jing Xu
- Institute of Urban Meteorology, Chinese Meteorological Administration, Beijing 100089, China
| | - Xiujuan Zhao
- Institute of Urban Meteorology, Chinese Meteorological Administration, Beijing 100089, China
| | - Zhiqiang Ma
- Environmental Meteorology Forecast Center of Beijing-Tianjin-Hebei, Chinese Meteorological Administration, Beijing 100089, China
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He L, Hang J, Wang X, Lin B, Li X, Lan G. Numerical investigations of flow and passive pollutant exposure in high-rise deep street canyons with various street aspect ratios and viaduct settings. THE SCIENCE OF THE TOTAL ENVIRONMENT 2017; 584-585:189-206. [PMID: 28152457 DOI: 10.1016/j.scitotenv.2017.01.138] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 01/18/2017] [Accepted: 01/20/2017] [Indexed: 05/21/2023]
Abstract
Vehicular pollutant exposure of residents and pedestrians in high-rise deep street canyons with viaducts and noise barriers requires special concerns because the ventilation capacity is weak and the literature reported inconsistent findings on flow patterns as aspect ratios (building height/street width, H/W) are larger than 2. By conducting computational fluid dynamics (CFD) simulations coupled with the intake fraction iF and the daily pollutant exposure Et, this paper investigates the impact of street aspect ratios, viaducts and noise barriers on the flow and vehicular passive pollutant exposure in full-scale street canyons (H/W=1-6, W=24m). iF represents the fraction of total emissions inhaled by a population (1ppm=10-6), while Et means the extent of human beings' contact with pollutants within one day. CFD methodologies of passive pollutant dispersion modeling are successfully validated by wind tunnel data in Meroney et al. (1996). As a novelty, the two-main-vortex pattern start appearing in full-scale street canyons as H/W changes from 4 to 5, however previous studies using wind-tunnel-scale models (H=6cm) reported two to five vortexes as H/W=2-5. This finding is validated by both smoke visualization in scale-model outdoor field experiments (H=1.2m, W=0.6m) and CFD simulations of Reynolds number independence. Cases with two main vortexes (H/W=5-6) experience much larger daily pollutant exposure (~103-104mg/m3/day) than those with single main vortex as H/W=1-4 (~101-102mg/m3/day). Moreover leeward-side pollutant exposures are much larger than windward-side as H/W=1-4 while oppositely as H/W=5-6. Assuming a general population density, the total iF is 485-803ppm as H/W=1, 2020-12051ppm as H/W=2-4, and 51112-794026ppm as H/W=5-6. With a single elevated pollutant source, cases with viaducts experience significantly smaller pollutant exposures than cases without viaducts. Road barriers slightly increase pollutant exposure in near-road buildings with H/W=1 while reduce a little as H/W=3 and 5. Two-source cases can experience 2.60-5.52 times pollutant exposure as great as single-source cases.
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Affiliation(s)
- Lejian He
- School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou, China
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou, China.
| | - Xuemei Wang
- School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou, China.
| | - Borong Lin
- Department of Building Science, School of Architecture, Tsinghua University, Beijing 100084, China
| | - Xiaohui Li
- Guangzhou Urban Planning Design & Survey Research Institute, Urban Planning Research Center, Guangzhou, China
| | - Guangdong Lan
- School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou, China
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38
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Seasonal Changing Effect on Airflow and Pollutant Dispersion Characteristics in Urban Street Canyons. ATMOSPHERE 2017. [DOI: 10.3390/atmos8030043] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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