Digital economy exhibits varying degrees of mitigation of air pollution in China: Total cities-economic subdivisions-urban agglomerations.

Air pollution is a challenge for many cities. The digital economy enhances support for environmental pollution management, while the mechanisms and scaling heterogeneity remain unclear. This study explored the contribution of digital economy development to PM2.5 concentrations control in China and driving mechanisms in different economic subregions and urban agglomerations. Results show that the spillover transfer effect on air pollution mitigation far exceeded the direct effect at different scales. At the national scale, the air pollution mitigation effect of digital economy was mainly through empowering industrial structure optimization and green technology innovation, while it also affected economic subregions and urban agglomerations through varying scenario combinations of pathways with structural optimization, green production, resource allocation, and technology innovation. Research findings provide support for cross-regional joint management strategies of digital economy and air quality and designing regionally differentiated pollution control pathways in the digital economy dimension.

Removal effect of pollutants from stormwater runoff in shallow bioretention system with gramineous plants.

The bioretention system is one of the most widely used low impact development (LID) facilities with efficient purification capacity for stormwater, and its planting design has been a hot spot for research at home and abroad. In this paper, ryegrass (Lolium perenne L.), bermuda (Cynodon dactylon Linn.), bahiagrass (Paspalum notatum Flugge), and green grass (Cynodon dactylon × C .transadlensis 'Tifdwarf') were chosen as plant species to construct a shallow bioretention system. The growth traits and nutrient absorption ability of four gramineous plants were analyzed. Their tolerance, enrichment, and transportation capacity were also evaluated to compare plant species and their absorptive capacity of heavy metals (Cu, Pb, and Zn). Results showed that the maximum absorption rate (Imax) ranged from 22.1 to 42.4 µg/(g·h) for P and ranged from 65.4 to 104.8 µg/(g·h) for NH4+-N; ryegrass had the strongest absorption capacity for heavy metals and the maximum removal rates of Cu, Pb, and Zn by four grasses were 78.4, 59.4, and 51.3%, respectively; the bioretention cell with ryegrass (3#) was significantly more effective in purifying than the unplanted bioretention cell (1#) during the simulated rainfall test. Overall, the system parameters were optimized to improve the technical application of gramineous plants in the bioretention system.

Assessment of vertical cooling performance of trees over different surface covers.

Tree-induced cooling benefits are associated with various factors, such as canopy morphology, surface cover, and environmental configuration. However, limited studies have analyzed the sensitivity of tree-induced cooling effects to the combination of such factors. Most studies have focused on 1.5-m cooling performance, and few studies on the variability of the under-tree vertical cooling performance. Therefore, this study aims to investigate the vertical cooling performance of different combinations of trees and surface covers. The study was completed in Chongqing, China, with field experiments capturing vertical air temperature and wind speed at 0.5, 1.0, 1.5, 2.0 and 2.5 m under two typical combinations of "tree + grass" (ComA) and "tree + shrubs" (ComB), and capturing 1.5 m microclimatic environments of a control group with hard pavement without tree shade (REF). The results show that at an average ambient temperature of 33 °C, the maximum air-cooling temperatures for ComA and ComB were 2.46 °C and 1.78 °C, respectively. An increase in the ambient temperature corresponded to a decrease in the cooling effect difference between ComA and ComB. ComA had a maximum vertical temperature difference of 1.01 °C between H1.5m and H2.0m. Between H2.5m and H2.0m, the maximum vertical temperature difference for ComB was 1.64 °C. This study explored the changing patterns of under-tree vertical temperatures under different tree and surface cover combinations, conducive to clarifying the key elements affecting tree cooling performance. The results have implications for accurate thermal comfort assessments and provide a theoretical basis for fine-tuning the design of under-tree spaces.

Public responses to urban heat and payment for heat-resilient infrastructure: implications for heat action plan formulation.

Heat action plans should be urgently formulated to enable urban managers, planners, and designers to take appropriate actions for mitigation and adaptation. However, few studies have been conducted to investigate the societal needs and knowledge gaps regarding heat mitigation and adaptation. To address such research gaps, this paper presents an empirical study of 574 questionnaires in Chengdu, China, to explore heat-related impacts, public responses, and driving mechanisms. The results indicated that outdoor activities and work/study were more sensitive to extreme heat than transportation, sleep/rest, and diet. Heat-related impacts on physiological health were at the same level as those on psychological health, where digestive system illness and emotional irritability were the most prevalent physiological and psychological symptoms. Respondents' knowledge of heat-related threats, adaptation awareness, and adaptation knowledge were insufficient, compared with heat severity. The payment willingness among the respondents was not strong and payment amount was not high. Poorer, healthier, and the less affected in outdoor activities were positive groups in payment willingness, while the group which experienced heat-related impacts on outdoor activities could pay more compared with other groups. Overall, these results help to shape the main contents of heat action plans.

Exploring the potential of roof greening for low-carbon landscapes.

As one type of urban artificial ecosystems, roof greening exhibits carbon source/sink characteristics during their life cycle. The carbon cycle mechanism is complex. The lack of exhaustive carbon performance quantification methods and assessment indicators hinders the promotion and implementation of green roof urban decarboni-zation. Focusing on the quantification of roof greening low-carbon landscape potential, we analyzed the internal carbon cycle mechanism of green roof systems and explored four carbon reduction and sink pathways (P1-P4): biogenic carbon sink, embodied carbon, operational carbon, and bioenergy supply. Based on the dual performance indicators of normalized value of carbon emissions and carbon payback time, we summarized the normalized value measurement method of each pathway. The potential and characteristics of each pathway were quantified by extracting data from the literature. The results showed that the quantified potential values for P1 to P4 were 9.54, -2.26, 2.96 and 0.35 kg CO2·m-2·a-1, respectively, and that the potential values for each pathway were strongly influenced by plant types, climate, and other factors. The imperfect base database and the heterogeneity of assessment scenarios impacted the accuracy of the measurements. The integrated low carbon landscape potential of extensive green roofs was discussed in sub-scenarios, with the 40-year-life cycle integrated carbon reduction ranging from 92.24 to 433.42 kg CO2·m-2 and the carbon payback period ranging from 5 to 14 years. Finally, we summarized the problems in the assessment to facilitate future updates and improvements.

Removal effect of typical pollutants from stormwater runoff in ecological ditches.

Ecological ditches are a typical ecological facility for controlling road stormwater runoff pollution; they mainly remove harmful pollutants from runoff through plant absorption, retention and sedimentation, ecological adsorption, and microbial action. In this paper, according to the transport form of rainwater in the ditches, the removal effects of two different types of ditches on nitrogen, phosphorus, heavy metals, and other pollutants were simulated under three conditions of rainfall, slow flow, and still water, respectively, and their operating characteristics were analyzed. The results showed that the removal rate of TN in the two ecological ditches under slow flow conditions showed a downward trend as a whole with the increase of hydraulic load, and the suitable hydraulic load for TN removal should be selected as 0.3 m3/(m2 day). Under the simulated rainfall conditions, the TN removal rates of no. 1 and no. 2 ditches were 26.1-37.2% and 24.9 ~ 52.5%, respectively, and the TP removal rates were 44.6 ~ 63.3% and 36.1 ~ 62.1%. After 19.4 h and 22.1 h in the static state, the TP concentration in no. 1 ditch and no. 2 ditch reached the surface V water standard, and the average removal rate of TP was 74.7% and 53.7%, respectively. This paper provides a reference for selecting suitable parameters and optimizing the operational performance of ecological ditches to reduce runoff pollutants more effectively.

Government is expected to lead the payment of heat-resilient infrastructure.

Urban heat is severe in numerous cities, but the urgency of heat action and support for the development of heat-resilient infrastructure is unclear. To address these research gaps, this study investigated the perceived urgency of developing heat-resilient infrastructure and associated payment issues in eight megacities, in China using a questionnaire survey of 3758 respondents in August 2020. Overall, the respondents thought it was moderately urgent to take actions to address heat-related challenges. The development of mitigation and adaptation infrastructure is urgent. About 86.4% of the 3758 respondents expected the government to be involved in paying for heat-resilient infrastructure, but 41.2% supported cost-sharing among the government, developers, and owners. There were 1299 respondents willing to pay, resulting in an average annual payment of 44.06 RMB in a conservative scenario. This study is important for decision-makers to formulate plans on heat-resilient infrastructure and to release financial strategies for collecting investments and funds.

Co-occurrence of urban heat and the COVID-19: Impacts, drivers, methods, and implications for the post-pandemic era.

Cities, the main place of human settlements, are under various mega challenges such as climate change, population increase, economic growth, urbanization, and pandemic diseases, and such challenges are mostly interlinked. Urban heat, due to heatwaves and heat islands, is the combined effect of climate change and urbanization. The COVID-19 is found to be a critical intervention of urban heat. However, the interrelationship between COVID-19 and urban heat has not been fully understood, constraining urban planning and design actions for improving the resilience to the dual impacts of heat and the pandemic. To close this research gap, this paper conducted a review on the co-occurrence of urban heat and the COVID-19 pandemic for a better understanding of their synergies, conflicts or trade-offs. The research involves a systematic review of urban temperature anomalies, variations in air pollutant concentrations, unbalanced energy development, and thermal health risks during the pandemic lockdown. In addition, this paper further explored data sources and analytical methods adopted to screen and identify the interventions of COVID-19 to urban heat. Overall, this paper is of significance for understanding the impact of COVID-19 on urban heat and provides a reference for coping with urban heat and the pandemic simultaneously. The world is witnessing the co-existence of heat and the pandemic, even in the post-pandemic era. This study can enlighten city managers, planners, the public, and researchers to collaborate for constructing a robust and resilient urban system for dealing with more than one challenges.

Assessment of walkability and walkable routes of a 15-min city for heat adaptation: Development of a dynamic attenuation model of heat stress.

Actively addressing urban heat challenges is an urgent task for numerous cities. Existing studies have primarily developed heat mitigation strategies and analyzed their cooling performance, while the adaptation strategies are far from comprehensive to protect citizens from heat-related illnesses and deaths. To address this research gap, this paper aims to enhance people's adaptation capacity by investigating walkability within fifteen-minute cities (FMC). Taking cognizance of thermal comfort, health, and safety, this paper developed a dynamic attenuation model (DAM) of heat stress, along with heat stress aggravation, continuance, and alleviation. An indicator of remaining tolerant heat discomfort (R t ) was proposed with the integration of the Universal Thermal Climate Index (UTCI) to assess heat-related walkability. Following an empirical study among 128 residents in Mianyang, China, and assessing four levels of heat stress, the maximum tolerant heat discomfort was determined to be 60 min. Furthermore, the DAM was applied to an FMC with 12 neighborhoods in Fucheng, Mianyang, China. The results indicate that for each neighborhood, the street was generally walkable with an R t ranging between 15 and 30 min, after walking for 900 m. A population-based FMC walkability was further determined, finding that the core area of the FMC was favorable for walking with an R t of 45-46 min, and the perpetual areas were also walkable with an R t of 15-30 min. Based on these results, suggestions on the frequency of public services (frequently used, often used, and occasionally used) planning were presented. Overall, this paper provides a theoretical model for analyzing walkability and outlines meaningful implications for planning heat adaptation in resilient, safe, comfortable, and livable FMCs.

Heat-induced health impacts and the drivers: implications on accurate heat-health plans and guidelines.

Urban heat challenges are increasingly severe, along with climate change and urbanisation. Despite significant environmental, economic, and social consequences, limited actions have been conducted to address urban heat challenges. To support the formulation of heat-health plans and guidelines at the city and community scale, this study presented results, through a questionnaire survey among 584 respondents in Shanghai, China, on heat-induced physiological and psychological impacts and analysed the variability of them with demographic characteristics. The results indicate that psychological impacts were more severe than physiological impacts in severity and susceptible people. Skin heat damage and digestive system diseases were ignored in previous studies, compared with fatal cardiovascular and respiratory diseases. Emotional irritability and difficulty in controlling temper were the two most prominent psychological symptoms. The elderly and health-vulnerable groups were more susceptible to heat-induced physiological and psychological impacts than other groups. Among different demographic groups, the most critical physiological and psychological symptoms could vary significantly. Afterwards, suggestions for heat-health plans or guidelines have been proposed. Overall, this study provides a reference for the understanding of heat-induced impacts and enhancing the capacity to cope with urban heat challenges.

Performance synergism of pervious pavement on stormwater management and urban heat island mitigation: A review of its benefits, key parameters, and co-benefits approach.

Pervious pavement system (PPS) is a suitable alternative technique for mitigating urban flooding and urban heat island (UHI) simultaneously. However, existing literature has revealed that PPSs cannot achieve the expected permeability and evaporation. To overcome this gap, this study presents an elaborate review of problems associated with PPSs and highlights its benefits to stormwater management and UHI mitigation. We determined key parameters of PPSs that could influence urban flooding and UHI mitigation, including hydrological properties, thermal physical properties, structure design, and clogging resistance. We identified the co-benefits approach of PPS towards performance synergism on stormwater management and UHI mitigation from quality controlled design and fabrication, periodic maintenance, and effective evaluation system based on practice environments. The results indicate that existing studies of PPSs primarily focus on permeability, while little emphasis is given to the evaporative cooling performance, leading to a biased development with a loss of test standards and regulations that cannot control the cooling potential of the system. The performance synergism of permeability and evaporative cooling in PPS should be studied further, while considering quality control of the materials and in-situ practice design. Parameter controls (with commonly used standards) during fabrication, periodic maintenance (during operation), and pre- and post-evaluation processes of PPSs should work collectively to achieve optimal benefits and reduced costs.

Influence of climates and materials on the moisture buffering in office buildings: a comprehensive numerical study in China.

In recent years, moisture buffering materials for interior finishing have received much attention for their ability to regulate indoor humidity passively. It is necessary to investigate the potential of such materials' moisture buffering performance before application because the effect is highly climate and material dependent. However, existing studies in China lack a comprehensive overview of the moisture buffering potential of different interior finishing materials throughout the large country with a wide spectrum of climates. This paper aims to outline the moisture buffering potential for office buildings in various climates in China through numerical methods. Specifically, simulations in 15 representative Chinese cities are conducted with five interior finishing materials under two heating, ventilation, and air conditioning (HVAC) scenarios. The results show that the moisture buffering materials hold a general potential to regulate indoor humidity conditions and reduce buildings' HVAC load. Such benefits are evident in the mild climate but weak in humid areas. The moisture buffering effect also displays significant seasonal variations and could worsen indoor humidity conditions in some cases, indicating the importance of utilizing moisture buffering materials properly. In addition, although moisture buffering materials can reduce the HVAC load, the reduction is limited, within 3 kWh/m2, in most simulated cases. The energy-saving benefits of moisture buffering materials should thus not be over-emphasized. Finally, suggestions are put forward to instruct the choice of interior finishing material according to climate and buildings' HVAC scenarios.

Variation of rooftop thermal environment with roof typology: a field experiment in Kitakyushu, Japan.

While urban open spaces have been shrinking with the rapid urbanization, rooftop space use is an alternative solution to such problems. Rooftop thermal environment is a critical consideration under global warming and local warming. Although there have been studies on rooftop thermal environment, variation of rooftop thermal environment with roof typology has not been fully revealed to support rooftop space design. To fill this gap, a field experiment was conducted over green roof (GR), wooden roof (WR), and shaded roof (SR) in a temperate city of Kitakyushu, Japan. Environmental parameters such as solar radiation, air temperature, and relative humidity at different heights of these three roofs were recorded, to understand rooftop thermal environment and daily heat stress variation with rooftop types and the height above roof surface. The results indicate that WR had the highest diurnal near-surface temperature and the worst heat stress, where the near-surface heat stress could even reach the danger level. GR exhibited the lowest diurnal near-surface temperature and heat stress, where the heat stress was only under caution and almost safe condition. SR exhibited the lowest diurnal 1-m temperature and SR had the weakest heat stress, indicating the significance of installing shading devices for rooftop thermal environment improvement and heat stress alleviation. GR exhibited excellent performance in reducing air temperature and heat stress at the pedestrian level, where its worst heat stress was only in caution condition. Compared with that at 1-m height, moreover, 1-cm temperature and heat stress of WR and SR were generally higher, indicating that people may undergo worse heat stress when kneeling or sitting compared with upright activities. Moreover, GR suppressed near-surface heat stress due to its excellent cooling performance.

Public Willingness to Pay for and Participate in Sanitation Infrastructure Improvement in Western China's Rural Areas.

The suitability and feasibility of public-private partnership (PPP) patterns in a rural context have not been well-documented and understood. To address this research gap and practical plight, this study aims to analyze the rural resident's willingness to pay for and participate in the improvement of rural sanitation facilities, and further explore the drivers and barriers affecting their decisions. This study was performed in rural areas of three western provinces, including Shaanxi, Ningxia, and Inner Mongolia, of western China's rural areas by conducting a survey on 1,248 rural residents. In Inner Mongolia, the proportion of respondents who were willing to pay was highest, while the proportion of respondents who may provide labor was lowest among the three provinces. Respondents from Ningxia had the least willing to pay, and respondents from Shaanxi had the highest willingness to participate. Overall, respondents' rural (living) duration time, personal interest in local government notice, and the latest time when the sanitation facilities were improved could significantly affect their willingness. In Inner Mongolia, occupation and water availability could significantly influence respondents' willingness, and both gender and health conditions had significant impacts. In Ningxia, respondents' personal interest in local government notice had a notable impact on willingness, and low-income respondents showed a more notable willingness to pay and participate. In Shaanxi, occupation and water availability could significantly influence respondents' willingness. Respondents' personal interest in local government notice had a notable impact on their willingness. This study is of significant importance to understand rural resident's participation in sanitation infrastructure improvement to support relevant PPP projects, and is important to solve poverty-caused dilemmas.

Localized synergies between heat waves and urban heat islands: Implications on human thermal comfort and urban heat management.

Heat waves (HWs) and urban heat islands (UHIs) can potentially interact. The mechanisms behind their synergy are not fully disclosed. Starting from the localized UHI phenomenon, this study aims i) to reveal their associated impacts on human thermal comfort through three different definitions of HW events, based on air temperature (airT), wet-bulb globe temperature (WBGT) and human-perceived temperature (AppT) respectively, and ii) to understand the role of air moisture and wind. The analysis was conducted in four districts (NH, JD, MH and XJH) with different urban development patterns and geographic conditions, in the megacity of Shanghai with a subtropical humid climate. Results evidenced the localized interplay between HWs and UHIs. The results indicate that less urbanized districts were generally more sensitive to the synergies. JD district recorded the highest urban heat island intensity (UHII) amplification, regardless of the specific HW definition. Notably, during AppT-HWs, the increment was observed in terms of maximum (1.3 °C), daily average (0.8 °C), diurnal (0.4 °C) and nocturnal UHII (1.0 °C). Nevertheless, localized synergies between HWs and UHIs at different stations also exhibited some commonalities. Under airT-HW, the UHII was amplified throughout the day at all stations. Under WBGT-HW, diurnal UHII (especially at 11:00-17:00 LST) was consistently amplified at all stations. Under AppT-HW conditions, the nocturnal UHII was slightly amplified at all stations. Air moisture and wind alleviated the synergistic heat exacerbation to the benefit of thermal comfort. The extent depended on geographic condition, diurnal and nocturnal scenarios, temperature type and HW/normal conditions. Stronger HW-UHI synergies indicate the necessity to develop specific urban heat emergency response plans, able to capture and intervene on the underlying mechanisms. This study paves to way to their identification.

Dust accumulated fungi in air-conditioning system: Findings based on field and laboratory experiments.

This study analyzes the growth and reproduction of dust accumulated fungi (DAF) in an air-conditioning system based on field measurement and molecular biology, laboratory experiment and prediction modelling. The field measurement was conducted to collect dust in filter screen, surface cooler and air supply duct of two air handling units (AHUs). The results indicate that dust volume and fungal number in two AHUs generally met the hygienic specification of public buildings, but the cleansing did not fulfil requirements. High-throughput sequencing was conducted, revealing that the dominant fungal species were Alternaria_betae-kenyensis, Cladosporium_delicatulum, Aspergillus_sydowii, Verticillium_dahliae. Laboratory experiment was conducted to analyze the impact of several factors (e.g. growth time, temperature, relative humidity, duct material) and their combination on the DAF growth. The results indicate that fungal growth increased with time, peaking at 4 days or 5 days. Higher relative humidity or temperature was conducive to fungal growth. The orthogonal experiment revealed that the condition of "antibacterial composite, 22 ± 1 °C and 45%-55% RH" had the strongest inhibiting impact on fungal growth. Logistic model, Gompertz model and square-root model were further developed to predict the fungal growth under different conditions. The results show that the Logistic model had high feasibility and accuracy, the Gompertz model was feasible with lower accuracy and the square-root model was feasible with high accuracy. Overall, this study facilitates the understanding of the DAF growth in air-conditioning ducts, which is important for real-time prediction and timely control of the fungal contamination.

An experiment and numerical study of resuspension of fungal spore particles from HVAC ducts.

Fungal spore resuspension on the surfaces of the heating, ventilation and air-conditioning (HVAC) ducts have been verified as one of the most important factors causing indoor biological pollution. To effectively control indoor bioaerosols pollution, it is essential to understand the resuspension characteristics of fungal spores in HVAC ducts. Therefore, this study aims to investigate the movement behavior of particles and further the variation of particle resuspension with HVAC operation mode. Based on the experimental and numerical study, this study specifically investigated the micro-movement behavior of particles and impact of particle size (1, 4, 7 and 10 µm), air temperature (9, 15 and 30 °C), relative humidity (20, 50 and 80%), duct surface roughness (0.5 and 50 µm) and air velocity (0.3, 0.9, 1.5 and 2.5 m/s) on the short-term resuspension of particle in horizontal HVAC ducts. Results indicate that spore particles were dominantly rolling off rather than sliding or being lifted into the air. Compared with larger particles, smaller ones were more sensitive to the wall roughness. The resuspension rate of spores was mainly affected by airflow velocity and particle size, where the resuspension rate of particles increased by up to six times with the increase of airflow velocity from 0.9 to 2.5 m/s. In comparison, either air temperature or relative humidity made negligible difference to particle resuspension rate. Overall, this study provides the knowledge of fungal spore resuspension in HVAC ducts, laying the foundation for effectively controlling the indoor biological pollution.

Assessment of Landscape Ecological Health: A CaseStudy of a Mining City in a Semi-Arid Steppe.

The ecological status of the semi-arid steppes in China is fragile. Under the long-term and high-intensity development of mining, the ecological integrity and biodiversity of steppe landscapes have been destroyed, causing soil pollution, grassland degradation, landscape function defect, and so on. Previous studies have mainly focused on ecosystem health assessment in mining areas. Landscape ecological health (LEH) pays more attention to the interactions between different ecosystems. Therefore, the ecological assessment of mining cities is more suitable on a landscape scale. Meanwhile, the existing LEH assessment index systems are not applicable in ecologically fragile areas with sparse population, underdeveloped economy, and in relatively small research areas. The purpose of this study was to construct a LEH assessment index system and evaluate the LEH of a mining city located in a semi-arid steppe. Xilinhot is a typical semi-arid steppe mining city in China. The contradictions between the human, land and ecological environment are serious. A new model Condition, Vigor, Organization, Resilience, and Ecosystem (CVORE) model was constructed that integrated five subsystems (services) from the perspectives of ecology, landscape ecology, mining science, and geography. This study used the CVORE model to systematically evaluate the LEH in Xilinhot city in terms of five LEH levels, including very healthy, healthy, sub-healthy, unhealthy and morbid landscape. Research results show that the areas of the very healthy, healthy, sub-healthy, unhealthy and morbid landscapes are 13.23, 736.35, 184.5, 66.76 and 20.63 km², respectively. The healthy landscapes area accounts for 72.08% and most grasslands are healthy. The sub-healthy landscapes are mainly located around areas with higher disturbances due to human activities. The morbid or unhealthy landscapes are concentrated in the mining areas. The proposed CVORE model can enrich the foundations for the quantitative assessment of Landscape Ecological Health of Mining Cities in Semi-arid Steppe (LEHMCSS). This study provided a new LEH assessment approach (CVORE model), which can support landscape ecological restoration, ecological environmental protection and urban planning of the semi-arid steppe mining cities.

Impact of Morphological Characteristics of Green Roofs on Pedestrian Cooling in Subtropical Climates.

Growing and densifying cities set a challenge for preserving and enhancing green spaces to cool urban spaces. Green roofs, involving the planting of vegetation on rooftops, are regarded as an alternative approach to enhancing urban greenery and urban cooling. For better cooling performances, it is essential to reasonably configure green roofs, especially in real and complex neighborhoods. Therefore, the aim of this paper is to investigate the impact of morphological characteristics of green roofs on pedestrian cooling in real and complex neighborhoods. In specific, based on an ENVI-met model, we studied the effect of greening layout, coverage ratio, vegetation height, and building height on pedestrian air temperature reduction in the tropical city of Hangzhou, China. Results indicate green roofs could generate moderate effects on pedestrian air temperature reduction (around 0.10⁻0.30 °C), while achieving a cooling performance of 0.82 °C. Green roofs in upwind zones were able to generate the most favorable cooling performance, while green roofs in downwind zones made slight differences to pedestrian thermal environments. Green roofs with a low coverage ratio were not useful for lowering pedestrian temperature, and a greening coverage ratio of 25⁻75% in upwind zones was cost-effective in real neighborhoods. Locations that were horizontally close to green roofs enjoyed better cooling performances. Increasing vegetation height could strengthen cooling effects of green roofs, while an increase in building height weakened the cooling performance. Nevertheless, higher building height could enhance pedestrian cooling performances because of building shading effects. In addition, because of wind effects and building shading, building height limits for the cooling performance of green roofs could be higher than 60 m.

CFD simulation research on residential indoor air quality.

Nowadays people are excessively depending on air conditioning to create a comfortable indoor environment, but it could cause some health problems in a long run. In this paper, wind velocity field, temperature field and air age field in a bedroom with wall-hanging air conditioning running in summer are analyzed by CFD numerical simulation technology. The results show that wall-hanging air conditioning system can undertake indoor heat load and conduct good indoor thermal comfort. In terms of wind velocity, air speed in activity area where people sit and stand is moderate, most of which cannot feel wind flow and meet the summer indoor wind comfort requirement. However, for air quality, there are local areas without ventilation and toxic gases not discharged in time. Therefore it is necessary to take effective measures to improve air quality. Compared with the traditional measurement method, CFD software has many advantages in simulating indoor environment, so it is hopeful for humans to create a more comfortable, healthy living environment by CFD in the future.