Validated by experimental data, this paper performs computational fluid dynamics (CFD) simulations to investigate the influence of tree plantings on urban airflow and vehicular CO exposure in ...two-dimensional (2D) street canyons with various aspect ratios (building height/street width, AR = H/W = 0.5, 1, 3, 5) and ground-level source. The impacts of tree canopy bottom height (Htb = 2 m, 6 m), tree stand density (y-density = 0.33, 0.67, 1) and leaf area density (LAD = 0.5, 1, 2 m2/m3) are considered. Personal intake fraction (P_IF) and its spatial mean value in leeward and windward sides ( lee, wind) and for entire streets (street intake fraction, ) are adopted to assess overall pollutant exposure.
For cases without trees, only one main vortex exists in shallow streets with AR = 0.5-3 and as AR = 3 (5.80 ppm) slightly exceeds AR = 0.5-1 (3.98-3.84 ppm). However, two counter-rotating vortexes appear in deep streets (AR = 5), inducing 1-2 orders smaller pedestrian-level velocity (U/Uref~10−4-10−3) and one-order greater (46.80 ppm) than shallow streets. Trees always weaken wind in streets and raise more in shallower streets by 46.0% as AR = 0.5 (3.98 ppm-5.81 ppm), 26.0-45.9% as AR = 1 (3.84 ppm to 4.84-5.60 ppm), 16.2-50.3% as AR = 3 (5.80 ppm to 6.74-8.72 ppm), but only 8.5-23.4% as AR = 5 (46.80 ppm to 50.78-57.73 ppm). Particularly, as AR = 1, trees raise lee (5.87 ppm) by 27.1-57.2%, while wind (1.80 ppm) only by 0%-23.3%. Higher Htb, smaller y-density or LAD produce less increase of . As AR = 3, vegetation increases lee (8.84 ppm) by 21.2%-66.4% but little affects wind (2.76 ppm). Lower Htb produces smaller differing from AR = 1. As AR = 5, vegetation increases wind (63.97 ppm) by 15.1-36.6% but reduces lee (29.63 ppm) by 5.2-8.5%. Although further investigations are still required for design purpose, this paper provides effective methodologies to quantify how vegetation influences street-scale pollutant exposure.
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•Personal intake fraction (P_IF) quantifies pollutant exposure with various H/Ws.•As H/W = 5, (~50 ppm) is 1-order larger than H/W = 0.5, 1, 3 (~4–6 ppm).•Trees weaken ventilation and raise by 16–50% as H/W = 0.5–3, 9–23% as H/W = 5.•Trees raise leeward-side C more than windward as H/W = 0.5–3 but opposite as H/W = 5.•Trees affect the whole canyon as H/W = 1 but area below 16th, 7th floor as H/W = 3, 5.
This street participatory action research (Street PAR) study organized 15 residents to document streetidentified Black youth and adult's negative experiences with police in Wilmington, Delaware. Data ...were collected on mostly street-identified Black men and women aged 18—35 in the forms of (1) 520 surveys, (2) 24 individual interviews, (3) four dual interviews, (4) three group interviews, and (5) extensive field observations. Forty-two percent of survey participants reported being stopped by police in the last year. However, with the exception of being "stopped," participants overall reported little negative contact with police at least within the past year. Chi-square and ANOVA analyses suggest an interactional relationship exists between race, gender, and age on experiences with police. Younger Black men (18–21) were found to have the most negative contact with police. Analysis suggests a smaller, more hardened mostly male variant of the larger street community has had repeated contact with police. Qualitative analysis reveals at least two major themes: (1) disrespect and disdain for residents and (2) low motivation for working with police. Street PAR methodology was also found to be instrumental in working with local residents and the Wilmington Police Department to improve conditions between residents and police.
In recent years, with the rapid growth in the number of cars, the safe and convenient street pedestrian traffic network in cities has been broken by motor vehicle lanes. The pedestrian traffic ...function of streets as an important urban public space has been lost, and the pedestrian friendliness of streets needs urgent improvement. However, the existing pedestrian-friendly street space assessment has not yet formed a set of full-factor quantitative evaluation systems, making the construction of pedestrian-friendly streets still in the conceptual stage and lacking practical significance. The complete streets design concept clarifies the goal of street pedestrian space construction and proposes the full elements of street pedestrian space design, which provides important support for the construction of the street pedestrian friendliness evaluation system. Based on the complete streets design concept, this study constructs a complete set of quantitative evaluation systems of street walkability from three aspects of street space: traffic, environment and function. Meanwhile, a street pedestrian usability evaluation method is proposed to further explore the actual demand of streets. Combined with the comprehensive evaluation matrix of street pedestrian friendliness and usability, the areas where the planning of street pedestrian space does not match with the actual space are explored. The case study in Wuhan found that the overall pedestrian friendliness was high in the area, but there was significant variability. The study area is dominated by streets in need of improvement, with medium demand–low friendliness, and both the pedestrian friendliness and usability of the streets need to be improved.
A large number of emerging contaminants (ECs) are known to persist in surface waters, and create pressure on wastewater treatment works (WWTW) for their effective removal. Although a large database ...for the levels of these pollutants in water systems exist globally, there is still a lack in the correlation of the levels of these pollutants with possible long-term adverse health effects in wildlife and humans, such as endocrine disruption. The current study detected a total of 55 ECs in WWTW influent surface water, 41 ECs in effluent, and 40 ECs in environmental waters located upstream and downstream of the plant. A list of ECs persisted through the WWTW process, with 28% of all detected ECs removed by less than 50%, and 18% of all ECs were removed by less than 25%. Negative mass balances of some pharmaceuticals and metabolites were observed within the WWTW, suggesting possible back-transformation of ECs during wastewater treatment. Three parental illicit drug compounds were detected within the influent of the WWTW, with concentrations ranging between 27.6 and 147.0 ng L−1 for cocaine, 35.6–120.6 ng L−1 for mephedrone, and 270.9–450.2 ng L−1 for methamphetamine. The related environmental risks are also discussed for some ECs, with particular reference to their ability to disrupt endocrine systems. The current study propose the potential of the pharmaceuticals carbamazepine, naproxen, diclofenac and ibuprofen to be regarded as priority ECs for environmental monitoring due to their regular detection and persistence in environmental waters and their possible contribution towards adverse health effects in humans and wildlife.
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•A list of ECs and metabolites persist in the aqueous phase of surface waters.•High levels of illicit drugs in wastewater indicates drug abuse within the area of study.•Conjugate or metabolites of PPCPs might be back-transformed during WWTW processes.•Persistent ECs may accumulate in WWTW effluent, leading to environmental risk.•Concentrations of ECs in surface waters provide a link towards possible endocrine disruption within aquatic vertebrates.
Reducing airborne particulate matter (PM), especially PM2.5 (PM with aerodynamic diameters of 2.5 μm or less), in urban street canyons is critical to the health of central city population. ...Tree-planting in urban street canyons is a double-edged sword, providing landscape benefits while inevitably resulting in PM2.5 concentrating at street level, thus showing negative environmental effects. Thereby, it is necessary to quantify the impact of trees on PM2.5 dispersion and obtain the optimum structure of street trees for minimizing the PM2.5 concentration in street canyons. However, most of the previous findings in this field were derived from wind tunnel or numerical simulation rather than on-site measuring data. In this study, a seasonal investigation was performed in six typical street canyons in the residential area of central Shanghai, which has been suffering from haze pollution while having large numbers of green streets. We monitored and measured PM2.5 concentrations at five heights, structural parameters of street trees and weather. For tree-free street canyons, declining PM2.5 concentrations were found with increasing height. However, in presence of trees the reduction rate of PM2.5 concentrations was less pronounced, and for some cases, the concentrations even increased at the top of street canyons, indicating tree canopies are trapping PM2.5. To quantify the decrease of PM2.5 reduction rate, we developed the attenuation coefficient of PM2.5 (PMAC). The wind speed was significantly lower in street canyons with trees than in tree-free ones. A mixed-effects model indicated that canopy density (CD), leaf area index (LAI), rate of change of wind speed were the most significant predictors influencing PMAC. Further regression analysis showed that in order to balance both environmental and landscape benefits of green streets, the optimum range of CD and LAI was 50%–60% and 1.5–2.0 respectively. We concluded by suggesting an optimized tree-planting pattern and discussing strategies for a better green streets planning and pruning.
•PM2.5 concentrations in urban street canyons with or without trees were compared.•The decrease of PM2.5 reduction rates was quantified.•Canopy density and leaf area index were identified as key predictors for PM2.5.•An optimized tree-planting strategy was suggested for a minimum PM2.5 accumulation.
Street photography is perhaps the best-loved and most widely known of all photographic genres, with names like Cartier-Bresson, Brassai and Doisneau familiar even to those with a fleeting knowledge ...of the medium. Yet, what exactly is street photography? From what viewpoint does it present its subjects, and how does this viewpoint differ from that of documentary photography? Looking closely at the work of Atget, Kertesz, Bovis, Rene-Jacques, Brassai, Doisneau, Cartier- Bresson and more, this elegantly written book, extensively illustrated with both well-known and neglected works, unpicks Parisian street photography's affinity with Impressionist art, as well as its complex relationship with parallel literary trends and authors from Baudelaire to Philippe Soupault. Clive Scott traces street photography's origins, asking what really what happened to photography when it first abandoned the studio, and brings to the fore fascinating questions about the way the street photographer captures or frames those subjects - traders, lovers, entertainers - so beloved of the genre.In doing so, Scott reveals street photography to be a poetic, even 'picturesque' form, looking not to the individual but to the type; not to the 'reality' of the street but to its 'romance'.
Many previous studies have investigated the role of urban greening (especially trees) on thermal comfort condition of open spaces while its influence in street canyons has, however, received ...relatively lower research attention. In this study, numerical experiments involving street canyons of varying aspect ratio (ARB) with embedded trees of varying aspect ratio (ART), leaf area index (LAI), leaf area density (LAD) distribution and trunk height under different wind conditions were conducted using a micro-meteorological model, ENVI-met. Employing physiological equivalent temperature (PET), the in-canyon thermal comfort was characterized. Results show variable magnitude of PET reduction (ΔPET) with trees of different vertical LAD distribution even though they are of similar LAI. While larger tree-covered area (TCA) ensures improved thermal comfort, the magnitude varies with tree-planting pattern. Between the tree-planting patterns in TCA = 0.6, ΔPET with double-rows is higher than centre tree-planting. Between eastern and western side tree-planting (TCA = 0.3), the former is more temporally effective than the latter. Furthermore, strong oblique wind condition (“without trees”) was found to be more efficient in improving thermal comfort than trees under calm perpendicular wind, reinstating the importance of desirable ventilation in achieving a thermally comfortable environment. However, vegetation offers improved PET reduction under calmer perpendicular than stronger oblique wind condition. Finally, recommendations on applications of our key findings were presented.
•Numerical experiments involving street canyons with trees of varying configuration were conducted.•Apart from LAI, vertical LAD distribution influences ΔPET while trunk height is less influential.•Variable temporal ΔPET was observed with similar tree-covered area but different planting pattern.
Urban canyon classification plays an important role in analyzing the impact of urban canyon geometry on urban morphology and microclimates. Existing classification methods using aspect ratios require ...a large number of field surveys, which are often expensive and laborious. Moreover, it is difficult for these methods to handle the complex geometry of street canyons, which is often required by specific applications. To overcome these difficulties, we develop a street canyon classification approach using publicly available Google Street View (GSV) images. Our method is inspired by the latest advances in deep multitask learning based on densely connected convolutional networks (DenseNets) and tailored for multiple street canyon classification, i.e., H/W-based (Level 1), symmetry-based (Level 2), and complex-geometry-based (Level 3) classifications. We conducted a series of experiments to verify the proposed method. First, taking the Hong Kong area as an example, the method achieved an accuracy of 89.3%, 86.6%, and 86.1%, respectively for the three levels. Even using the field survey data as the ground truth, it gained approximately 80% for different levels. Then, we tested our pretrained model in five other cities and compared the results with traditional methods. The transferability and effectiveness of the scheme were demonstrated. Finally, to enrich the representation of more complicated street geometry, the approach can separately generate thematic maps of street canyons at multiple levels to better facilitate microclimatic studies in high-density built environments. The developed techniques for the classification and mapping of street canyons provide a cost-effective tool for studying the impact of complex and evolving urban canyon geometry on microclimate changes.
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•A multi-level classification hierarchy for urban canyon geometry based on Google Street View (GSV) images is proposed.•A multitask deep learning model is proposed to accurately classify urban canyons based on the classification hierarchy.•The urban canyons in Hong Kong are mapped and analyzed from multiple levels.
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