Subtropical City Research Articles

Response of soil moisture and vegetation conditions in seasonal variation of land surface temperature and surface urban heat island intensity in sub-tropical semi-arid cities

Response of soil moisture and vegetation conditions in seasonal variation of land surface temperature and surface urban heat island intensity in sub-tropical semi-arid cities

A UV-Reflective Organic-Inorganic Tandem Structure for Efficient and Durable Daytime Radiative Cooling in Harsh Climates.

Radiative cooling shows great promise in eco-friendly space cooling due to its zero-energy consumption. For subambient cooling in hot humid subtropical/tropical climates, achieving ultrahigh solar reflectance (≥96%), durable ultraviolet (UV) resistance, and surface superhydrophobicity simultaneously is critical, which, however, is challenging for most state-of-the-art scalable polymer-based coolers. Here an organic-inorganic tandem structure is reported to address this challenge, which comprises a bottom high-refractive-index polyethersulfone (PES) cooling layer with bimodal honeycomb pores, an alumina (Al2 O3 ) nanoparticle UV reflecting layer with superhydrophobicity, and a middle UV absorption layer of titanium dioxide (TiO2 ) nanoparticles, thus providing thorough protection from UV and self-cleaning capability together with outstanding cooling performance. The PES-TiO2 -Al2 O3 cooler demonstrates a record-high solar reflectance of over 0.97 and high mid-infrared emissivity of 0.92, which can maintain their optical properties intact even after equivalent 280-day UV exposure despite the UV-sensitivity of PES. This cooler achieves a subambient cooling temperature up to 3 °C at summer noontime and 5 °C at autumn noontime without solar shading or convection cover in a subtropical coastal city, Hong Kong. This tandem structure can be extended to other polymer-based designs, offering a UV-resist but reliable radiative cooling solution in hot humid climates.

Influence of rooftop mitigation strategies on the thermal environment in a subtropical city

As one of the most promising climate adaptation measures, rooftop mitigation strategies (RMSs) have been studied and practiced in many cities. However, the cooling potential of RMSs may be controversial under different climates. This study establishes city-scale numerical simulations of RMSs, including green roofs (GRs), cool roofs (CRs), rooftop photovoltaic panels (RPVPs), and photovoltaic panels plus green roofs (PVPs+GRs) in Guangzhou, a subtropical city in China, to explore the impact of RMSs on the urban thermal environment during the clear-sky meteorological conditions. The results indicate that RPVPs and PVPs+GRs can cool the city throughout the day, especially from 12 to 17 LST, reaching 0.3–0.7 K, while GRs have the weakest cooling potential, only 0.1 K. The order of cooling space range is PVPs+GRs (the entire city) > RPVPs > CRs (urban and downwind areas) > GRs (urban area). RPVPs and PVPs+GRs mitigate the urban heat island (UHI) effect, reaching 0.5–0.6 K, and increase relative humidity (RH) by 8.5% and 9.6%, respectively. PVPs+GRs and GRs could increase specific humidity (SH) by 0.35 g/kg and 0.23 g/kg, respectively. RPVPs and PVPs+GRs reduce the universal apparent temperature (UAT) throughout the day, especially at night, reaching 0.8 °C (PVPs+GRs) to 0.9 °C (RPVPs), and hence improve human thermal comfort.

The Degradation Process of Typical Neonicotinoid Insecticides in Tidal Streams in Subtropical Cities: A Case Study of the Wuchong Stream, South China.

Neonicotinoid insecticides (NEOs) are commonly used to prevent unwanted insects in urban fields. Degradation processes have been one of the important environmental behaviors of NEOs in an aquatic environment. In this research, hydrolysis, biodegradation, and photolysis processes of four typical NEOs (i.e., thiacloprid (THA), clothianidin (CLO), acetamiprid (ACE), and imidacloprid (IMI)) were examined through the adoption of response surface methodology-central composite design (RSM-CCD) for an urban tidal stream in South China. The influences of multiple environmental parameters and concentration levels on the three degradation processes of these NEOs were then evaluated. The results indicated that the three degradation processes of the typical NEOs followed a pseudo-first-order reaction kinetics model. The primary degradation process of the NEOs were hydrolysis and photolysis processes in the urban stream. The hydrolysis degradation rate of THA was the highest (1.97 × 10-5 s-1), and that of CLO was the lowest (1.28 × 10-5 s-1). The temperature of water samples was the main environmental factor influencing the degradation processes of these NEOs in the urban tidal stream. Salinity and humic acids could inhibit the degradation processes of the NEOs. Under the influence of extreme climate events, the biodegradation processes of these typical NEOs could be suppressed, and other degradation processes could be further accelerated. In addition, extreme climate events could pose severe challenges to the migration and degradation process simulation of NEOs.

An in-situ measurement and assessment of evaporative cooling effects of low impact development facilities in a subtropical city

The urban green infrastructure such as the low impact development (LID) facility and traditional garden that are relatively small and characterized by decentralized distributions has been proposed as the most effective way to mitigate urban heat through its evaporative cooling effect. Recently, there have been increasing studies on its temperature reduction and evapotranspiration (ET) rate, but few of them correlate ET with external surface temperature reductions. Therefore, this study investigated the evaporative cooling effects, ET rates, and their relationships by the three-temperature (3T) model and ground-based thermal infrared remote sensing. Results show that the cooling effect of both vegetated LID facilities and traditional gardens is significantly stronger than that of non-vegetated LID facilities. Due to a thinner soil layer and lower water connectivity of LID facilities, their ET rates are significantly reduced in the dry period while the evaporative cooling effect of traditional gardens covered by the same vegetation can maintain high. The dependency of their cooling effect can be largely explained by the ET rates. When ET < 0.6 mm h–1, an increase in ET of 0.1 mm h–1 can enhance the cooling effect by 3.66 °C. When ET exceeds 0.6 mm h–1, the evaporative cooling effect saturates. Vegetation types and soil water conditions are two main factors that govern evaporative cooling effect. Specifically, shrubs with higher ET rates are more efficient in urban heat mitigation than herbs. The responses of the evaporative cooling effect to soil water availability vary among species, which may require species-specific irrigation regime. These results may have implications on the best management practices for urban heat mitigation by the small widely-distributed green spaces.

Study on water cooling island effects under different climatic conditions

Water bodies are regarded as effective tools to improve urban thermal environment. However, there is little information regarding the impacts of the water bodies under different climatic conditions. In this study, the thermal effects of similar water bodies were investigated in a temperate monsoon climate city (Xi’an) and a humid subtropical climate city (Chengdu) in summer. Results showed that both the water bodies reduced the air temperature and increase the humidity in their vicinity, and the closer to the water body the more obvious the effects. However, the water body in Xi’an could provide cooling to its surroundings all day, while the one in Chengdu had warming effect at night. In this study, the universal thermal climate index (UTCI) around the water bodies was also investigated. It was found that both water bodies would improve the thermal comfort in their vicinity, and the thermal comfort achieved by the cooling effect was not cancelled out by the humidity change. In addition, it was found that the actual thermal sensation of the human body can be different for same UTCI values in Xi’an and Chengdu, which indicated the necessity to modify the thermal benchmarks before investigating the thermal comfort in different cities.

Investigating the Impact of Weather Conditions on Urban Heat Island Development in the Subtropical City of Hong Kong

Subtropical monsoon climates, high-density and heterogeneous urban built environments, as well as coastal–mountainous geographical environments influence the development of urban heat island (UHI) effects in Hong Kong. For better weather control of in situ observations and spatial analysis of UHI effects, it is necessary to quantitatively understand the influence of weather conditions on UHI development in Hong Kong and establish weather-based UHI estimation models. Meteorological records of four urban stations, one rural reference station, and one wind reference station at an hourly interval during the period of 2002–2012 were collected from Hong Kong observatory. A frequency analysis of the mean values of multiple meteorological elements and UHI parameters in urban stations was conducted to examine the prevailing and critical weather conditions, as well as the associated UHI conditions in Hong Kong. Multiple Linear Regression (MLR) was used to estimate the daily maximum UHI intensity (UHImax) based on a set of meteorological elements including cloud amount, wind speed, wind direction, relative humidity, and air temperature, as well as a UHI parameter of the daily maximum UHI intensity of the previous day (UHIpre-max). The results showed that MLR-based models can explain 33% and 56% variations of the UHImax in the summer and the whole year, respectively. The relative importance of each meteorological element on UHI development differed in the summer and annual periods, and the UHImax tended to be intensified under high temperature conditions in the summer.

Biofuel-driven trigeneration systems for non-residential building applications: A holistic assessment from the energy, environmental and economic perspectives.

In the metropolises, it is unlikely to use merely solar and wind energy to pursue zero carbon building design. However, it would become possible if biofuel-driven trigeneration systems (BDTS) are adopted. It is thus essential to assess the application opportunity of BDTS in a holistic way. In this study, BDTS offered definite primary energy saving of up to 15% and carbon emissions reduction of at least 86% in different types of non-residential buildings as compared to the conventional systems. With 24/7 operation for the hotel and hospital buildings, the corresponding BDTS could even achieve zero carbon emissions. All the BDTS primed with compression-ignition internal combustion engine were not economically viable even in running cost due to the high local biodiesel price level. The BDTS primed with spark-ignition engine and fueled by biogas, however, would have economic merit when carbon price was considered for the conventional systems that fully utilize fossil fuels. Adoption of carbon tax and social cost could have the payback ceilings of 8 years and 2 years respectively for most of building types. Consequently, the results could reflect the application potential of BDTS for non-residential buildings, leading the pathway to carbon neutrality for sustainable sub-tropical cities.

Linking urban park cool island effects to the landscape patterns inside and outside the park: A simultaneous equation modeling approach

Urban parks have significant cooling effects that alleviate the urban heat island (UHI). The park cool island intensity (PCII), the temperature difference between outside and inside a park, is a widely used indicator of a park’s cooling ability. Understanding the driving factors of the PCII is crucial for better urban park planning and management. Taking the subtropical city of Changsha, China, as a case study, factors such as the landscape patterns inside and outside a park and the geometric morphology of a park were investigated, based on 153 urban parks. A novel simultaneous equation modeling (SEM) approach was used to account for the mutual interactions between the temperatures of a park and its buffer. The results show that: (1) Park geometric morphology and landscape patterns inside and outside the park all significantly impact the PCII. Specifically, doubling the park size can increase the PCII by 0.8 K. Increasing by ten percent the tree cover and water cover in the park can enhance the PCII by 0.12 K and 0.41 K, respectively. Increasing the mean tree patch size by 1 ha can increase the PCII by 0.43 K. Decreasing by one unit the mean tree patch shape index can increase the PCII by 0.31 K. (2) An elasticity analysis, which measures the PCII percent change resulting from one percent change in a driving factor, indicates the relative importance ranking of these driving factors: percent cover of impervious surface outside the park (0.77), park size (0.72), percent cover of tree within the park (0.51), percent cover of water within the park (0.12), and mean patch size of tree cover within the park (0.086). To enhance the PCII, we recommend building parks in the hot areas of the city, increasing their size, increasing the percentages of tree cover and water cover in the park, and optimizing the spatial configuration of the tree cover in the park (i.e., aggregating trees in a smaller number of large patches and reducing the irregularity of tree patches).

Urbanization alters soil bacterial communities in southern China coastal cities

Urbanization carries essential influences to ecosystem of soil bacteria in coastal cities. Comprehending the patterns and drivers of bacterial diversity are essential to understanding how soil ecosystems respond to environmental change. This study aimed to explore how soil bacterial community (SBC) response to distinct urbanization of coastal cities on composition, assembly process and potential function in Guangdong province, south China. 72 samples from 24 sample sites within 3 cities were included in the study. Soil chemical properties were analyzed, and the bacterial community were investigated by high-throughout sequencing. Proteobacteria and Acidobacteria were the main phyla. Assembly processes remained in stochastic processes and co-occurrence network of SBC kept stable, while urbanization altered SBC by influencing the dominant phyla. The indicators of communities in coastal city soils were the genera gamma_proteobacterium and beta_proteobacterium. Urbanized extent was the non-negligible factor which affected soil bacterial community, despite the total carbon was still the most vital. The impact of urbanization on bacterial communities might follow a non-linear pattern. Faprotax function prediction showed different urbanized coastal city soils share similar metabolic potential. Our study improved our understanding of the response of soil bacterial communities to urbanization in subtropical coastal cities and offered a useful strategy to monitor the ecology risk toward the soil under urbanization.

Impact of synoptic condition on urban microclimate variation: A measurement study in a humid subtropical city during summer season

The urban microclimate is not only predominated by synoptic weather features but also closely related to heterogeneous characteristics of urban morphology. This study conducted an on-site field measurement campaign in Guangzhou, China from July to August 2021 to investigate the urban microclimate variation under typical synoptic conditions according to the Spatial Synoptic Classification (SSC) scheme. The climatic data were collected from eight locations installed in three residential neighborhoods. Cooperating with the statistical test, the results of deviation analysis demonstrate inconsistent urban microclimate variations among different SSC weather types. Under the moist moderate and moist tropical synoptic conditions, the urban microclimate variations between locations are insignificant. According to the results of the correlation analysis, the associations between morphological factors relating to building density and thermal environment are negative at noon but positive in the afternoon and night. The highest correlation coefficient is found between the ground coverage ratio and mean radiant temperature during nighttime under the extreme moist tropical weather types (0.58), but it turns out to be −0.29 at noon. These findings suggest that the application of the SSC benefits understanding reasons for microclimate variation within urban areas and detecting critical urban morphological indicators for achieving better thermal environments.

Effects of vertical greenery systems on the spatiotemporal thermal environment in street canyons with different aspect ratios: A scaled experiment study

Many studies have focused mainly on the thermal and energy performance of VGSs on a building scale; however, little is known about the cooling effect of VGSs in street canyons and its response to different aspect ratios (building height/street width, H/W). Therefore, a scaled outdoor experiment was conducted to investigate the spatiotemporal variation of the urban wind and thermal environment caused by west-facing vertical greenery systems (VGSs) in street canyons with H/W = 1 and 2 in the subtropical city of Guangzhou, China. On a typical hot day (26th Oct. 2021), VGSs reduced wind speed by 38.0 % and 21.0 % in street canyons with H/W = 1 and 2, respectively. Compared with the reference cases, the temperature regimes of VGS cases (H/W = 1 and 2), including west-facing wall temperature (Tw-west), east-facing wall temperature (Tw-east), ground temperature (Tg), and air temperature (Ta), were all significantly decreased. Because of the cooling effect of VGSs, the maximum reduction of Tw-west in the upper level of street canyons with H/W = 1 and 2 was 20.3 and 16.8 °C, respectively. The maximum reduction of Tg in the center of the VGS case with H/W = 2 was 4.6 °C, which was more pronounced than in the VGS case with H/W = 1 (1.8 °C). The maximum reduction of Ta at the pedestrian level along the central axis of street canyons with H/W = 1 and 2 was 0.8 and 1.6 °C, respectively, which was more pronounced than at the upper level. The reduction of Tw-west in the upper level and of Tg and Ta in the VGS case with H/W = 2 was greater than that in the VGS case with H/W = 1 due to lower wind speed and albedo.

Source tracing and health risk assessment of phthalate esters in household tap-water: A case study of the urban area of Quanzhou, Southeast China

The occurrence of phthalate esters (PAEs) in household tap water has been investigated via the presence of their geochemical characteristics in the pretreatment and transfer processes of water plants in the urban and suburban areas of the subtropical medium-sized city of Quanzhou, southeast China. The results for all approximately 300 tap water samples collected from 6 sampling stations at household kitchens from Nov. 30, 2017, to Dec. 6, 2018, showed that dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutylphthaate (DIBP), di-n-butyl phthalate (DBP), and di(2-ethylhexyl) phthalate (DEHP) could be identified and quantified among the 16 PAE congeners with the developed gas chromatographymass spectrometry method. The levels of the sum of 5 PAE congeners (Σ5PAEs) for all tap water ranged from 780.0 ng/L to 9180 ng/L, while DIBP and DEHP were the most abundant congeners, accounting for 82.2% in the dry season, 89.9% in the normal season, and 89.3% in the wet season. Factors of the transferring process, such as the spatial distance from the sampling station to the water plant, the material of pipelines, and the storage time of tap water in the pipeline, affected the levels of PAE congeners in tap water from the correlation of Σ5PAEs levels and transferring distance according to hierarchical cluster analysis. The seasonal variations in Σ5PAEs and each congener had good agreement with the temperature, suggesting that PAEs in tap water mainly come from raw water, which should be further explored in future work. Health risk assessment of PAEs in tap water with the HQ method showed that the occurrence of DEP and DBP has no noncarcinogenic risk for adults and children, while the concentration of DEHP might cause potential noncarcinogenic risk for adults and children, which should be given considerably more attention.

Comparative investigation on performance of single-stage and double-stage desiccant dehumidification boxes under hot-humid climatic conditions

Desiccant fixed bed is a prospective alternative for conventional vapor compression refrigeration system. In this paper, a novel structure of fixed bed, desiccant dehumidification box, was constructed and experimented at a sub-tropical city, Guangzhou. Dehumidification performance of the new structure was evaluated by several indicators. Mathematical models were established concerning moisture adsorption rate and moisture ratio. The adsorption heat generated was analyzed by testing sensible heat gain of the process air and heat storage of the desiccant. The result shows that the double-stage desiccant dehumidification box could perform better generally. The maximum dehumidification capacity could reach 3.9 g•kg−1 and 1.6 g•kg−1 on average in condition 4. Maximum dehumidification efficiency (27.8%) was obtained in the same condition when applying the double-stage box. The desiccant saturated at about 6 h in experiments, of which variation in the double-stage box was more stable and lasting, though moisture adsorption rate presents only a little difference in comparison boxes. Exponential models fit the practical curves within 10% relative error. Maximum average temperature rise of the desiccant and process air was 4.3 °C and 3.8 °C respectively in the double-stage box, which was 0.4 °C and 0.9 °C higher than the single-stage box. Around 97% of the adsorption heat was directed to heat storage of the desiccant and only left 3% directed to sensible heat gain of the process air.

Metagenomic and viromic analysis reveal the anthropogenic impacts on the plasmid and phage borne transferable resistome in soil

Anthropogenic land use changes have been recognized with significant effects on the abundance and diversity of antibiotic resistance genes (ARGs) in soil, but their impacts on ARGs with potential health risk remained poorly understood. In this study, paired metagenomes and viromes were obtained from soils (Anthrosols and Nitisols) with different land uses including urban parks, road verge, forests, vegetable and paddy in a subtropical city, Xiamen, and soils (Anthrosols) with various long-term fertilization treatments in Dezhou located in temperate region, respectively, to explore the influence of anthropogenic activity on soil resistome. The diversity and abundance of antibiotic resistance genes (ARGs) were profiled, and the risk associated factors of ARGs, i.e., genetic location, host, and co-existence with virulence factors (VFs), were systematically investigated at reads and contigs level. We observed that agricultural areas significantly enriched human-related ARGs and viruses, and positively related with clinical ARGs. Most of the ARG-carrying contigs were chromosomes (∼85 %), while, human-related ARGs presented a higher odds ratio to locate on plasmids. Soil VFs exhibited land use pattern and distinct distribution between chromosome and plasmids, but less mobile than ARGs. Analysis of 131,014 soil viral genomes indicated that they barely encoded ARGs, nevertheless, transduction of VLPs was implicated in the spread of ARGs. The results can be mutually verified in Xiamen and Dezhou datasets. Overall, the agricultural soils with dry-farming are hotspots for the clinical ARGs, and the transmission of clinical ARGs between human dominated environments and soil is primarily mediated by plasmids, rather than bacterial chromosomes, and the transduction of human-gut related viruses could participate the process. These results highlight the importance of tracking the fate of clinical ARGs for better evaluating the impacts of human activities on soil resistome.

Microfibers shed from synthetic textiles during laundry: Flow to wastewater treatment plants or release to receiving waters through storm drains?

Microplastic particles (MPs), which have been considered as emerging contaminants, are widely found in water environments. In southern China, many apartment owners place washing machines on their balconies, where the separated drain system usually leads to the storm-water pipes, resulting in releasing MPs directly into the environment. In the present study, we firstly obtained the laundry preference of residents in the study area based on a questionnaire survey and then designed a simulated laundry experiment to determine the MFs shed in the laundry process. The approximate amount of MFs discharged into the environment under various scenarios was estimated. The results showed that type of washing machine and detergent had a great influence on the MFs shedding. The use of a front-load machine and liquid laundry detergent pods (LDPs) can reduce MFs shed in the laundry process. If the laundry effluent generated by washing machines placed on apartment balconies flows into the municipal pipe network and is treated by wastewater treatment plants (Andrea Menéndez-Manjón), the environmental load of MFs can be reduced. Taking Nanning, the capital city of Guangxi Zhuang Autonomous Region, as a case study, the calculated result shows that the number of MFs discharged into the environment decreased by 93% at the optimized laundry mode. This study provides a reference for the control of MFs and the rational revision of the Architectural Design Guidelines in subtropical cities equipped with the diversion drainage system.

Numerical evaluation of enhanced green infrastructures for mitigating urban heat in a desert urban setting

The cities of desert climates are anticipated to recognize a synergy of urban heat island (UHI) and severe heat waves during summertime. To improve the urban thermal environment, the present study aims quantitatively explore a strategically designed network of vegetation patches called green infrastructure (GI) in subtropical desert cities such as Dubai. To achieve a more comfortable temperature environment, we built and simulated four GI situations with higher GI fractions, GI25, GI50, GI75, and GI100. Using a mesoscale urban model, the mosaic approach is utilized to test potential thermal improvement and urban climate impact, and a portion of each urban grid cell in the model domain is altered with various species of urban vegetation patches by 25%, 50%, 75%, and 100%. The daily peak reduction in ambient temperature at 17:00LT is similar to 0.0168 °C per unit of GI increase when compared to the untreated scenario; however, the maximum anticipated daytime summer temperature decline for GI25, GI50, GI75, and GI100 is 0.6 °C, 1.1 °C, 1.4 °C, and 1.7 °C, respectively. The associated reduction in nighttime ambient temperature per unit increase in the GI is 0.0432 °C, with a maximum temperature drop of around 2.4 °C for the GI100 scenario. Increased GI reduces the height of the planetary boundary layer (PBL) by up to 468 m, which might lead to greater pollution concentrations. While GI-based cooling has a significant influence on delayed sea breeze and humidity, it may raise the risk of heat discomfort in the indoor building environment. This study adds to our understanding of the potential for GI mitigation as well as the seasonal impact of developing GIs on the desert urban boundary layer.

The association of myocardial infarction hospitalizations and weather conditions in a private hospital in Brazil

Abstract Background The relationship between seasonal temperature peaks and the incidence of hospitalization for myocardial infarction has been reported in different countries. Despite increased interest in assessing the impact of temperature on hospitalization, few studies have used case-crossover designs to study non-linear and distributed delay effects temperature and thermal amplitude. In addition, is not clear how myocardial hospitalization is affected by temperature in subtropical climate cities. Objective We investigated the effects of climatic variables on the number of hospitalizations for myocardial infarctions at a private hospital at a city with a subtropical climate from 2017 to 2019. Methods Myocardial hospitalization records were extracted from database obtained through the Brazilian Information System on Hospitalization according to the municipality of residence and the CID-10 classification in elderly people. The temporal analysis of this study aimed at verifying the relationship between hospitalizations, climatic attributes, and the standard deviation of other descriptive statistics. To estimate the non-linear and time-interval effects, we used Distributed Lag Non-Linear Models (DLNM), which allowed us to observe their distributed delay effects. This model is suitable for studying the impact of environmental conditions on health, as it usually occurs a few days after exposure. The data were analyzed using the R software. Results In Figure 1, five descriptive graphs illustrate the study's primary data.Distribution of hospitalizations by gender (A), showing the predominance of males (65.81%), age group of 60 to 69 years (44.63%), followed by the group of 70 to 79 years (33.61%). Chart D shows that the medians representing hospitalization rates are higher in different bimesters throughout the year. Moreover, in chart E, the monthly averages of hospitalization rates per 100,000 elderly inhabitants, segmented by gender, show a prevalence of the male gender in all months.Based on the Poisson model for the variables combined, some lags were shown to be significant (17 and 20) at an α= 5% significance level, both for minimum temperature (p=0.00768) and relative humidity (p=0.03263). In addition to the other factors such as gender (p=4.14e-09) and all age levels (p=0.000), they can influence the number of hospitalizations. From the results shown in Table 1, we can interpret that when the Odds Ratio has a value between 0 and 1, the chance of hospitalization is reduced as the variable increases, or when the estimated value of the Odds Ratio is greater than 1, there is an increase in the chance of hospitalization as the respective variable increases. No significant results were found for maximum temperature and mean temperature. Conclusion Understanding the effects of temperature on cardiovascular risk factors over time in the elderly may help optimize prevention strategies and better organize care for elderly patients throughout the year. Funding Acknowledgement Type of funding sources: Private hospital(s). Main funding source(s): Constantini Cardiology Hospital

Assessment of aerial thermography as a method of in situ measurement of radiant heat transfer in urban public spaces

Urban public spaces are an essential part of the urban environment, supporting social relationships and promoting a healthy lifestyle among citizens. However, the high value of urban land has led to an over-urbanisation of cities, increasing urban heat stress and decreasing the number and size of public spaces. Rising air temperatures in cities – known as the urban heat island effect (UHI) - combined with global warming, make public spaces less comfortable. For these reasons, there has been a growing concern to improve the thermal comfort of urban spaces. Thermal radiation is a determining factor in urban thermal comfort and is normally summarised in a value called mean radiant temperature (TMRT). In the past, conventional methods have been used to calculate it, such as net radiometers and globe thermometers. In recent years, the scientific community has used ground-based handheld thermal cameras for its quantification. However, there is a lack of literature on the use of aerial thermography for this purpose (i.e. an unmanned aerial vehicle (UAV) equipped with a thermal infrared device). Given this gap in the literature and the advantages in time, versatility and accuracy of these systems, this paper presents a new method for assessing the measurement of radiant heat transfer in a pedestrian urban space using aerial thermography. From the surface temperatures of the infrared imagery collected by the UAV, TMRT was estimated at multiple points in a pedestrian area of a subtropical city (Huelva, Spain) during a typical summer day. In order to verify accuracy of the proposed method to estimate the TMRT, a microclimate urban simulation was carried out using ENVI-met v5. The comparative analysis of the measured and simulated dataset verified the applicability of aerial thermography for the measurement of radiant heat transfer (with R2 values of 0.98 for the data set and 0.8 for the data of each time period). To conclude, new strategies were proposed to improve urban thermal comfort and to make cities more sustainable.

Backyard buzz: human population density modifies the value of vegetation cover for insect pollinators in a subtropical city

AbstractUrbanisation drives overall declines in insect pollinators. Although urban green spaces can provide suitable habitat for pollinators much remains to be learned about how urban landscapes either promote or negatively impact pollinators. We investigated how backyard design, local (100 m) and landscape (500 m) scale vegetation cover and human population density were associated with non-eusocial native bee species, eusocial bees (Apis melliferaandTetragonula spp.), and hoverflies, in residential green spaces of the subtropical city Brisbane, Australia. We found that associations between bee abundance and vegetation cover were moderated by human density, but the direction of this effect differed for non-eusocial and eusocial species. Non-eusocial bee abundance was positively associated with tree cover at local and landscape scales when human densities were low, but negatively so at high human population densities. We suggest this may be because the quality of vegetation for non-eusocial bees deteriorates as human density increases. In contrast, abundance of eusocial bees was negatively associated with increasing local cover of grass and shrubs at low levels of human density, but positively associated at high densities. This affinity to humans could partly be explained by domesticated “kept” hives. We found no effect of urban gradients on bee species richness. Hoverfly abundance was negatively related to human density and positively related to vegetation cover at local and landscape scales. At the backyard scale, both bee species richness and bee and hoverfly abundances were positively associated to flower abundance. Backyards with more vegetation cover had higher densities of non-eusocial bees. Our results thus support the idea that urban greening in densely populated areas at multiple spatial scales can benefit a range of insect pollinators.