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Hong Kong is a typical high-density city in a subtropical climate region, and deep street canyons are among the main features of its urban planning. How the urban geometry influences the urban thermal environment in this city has become a hot topic these days. The height-to-width ratio (H/W) and sky view factor (SVF) are commonly used to indicate the outdoor thermal environment performance, while previous studies in Hong Kong rarely analysed the importance bias of these two influencing factors systematically in this context. To fill this research gap, in this paper, we chose four typical sites in Hong Kong as research objects. Firstly, we conducted a field investigation to calculate the main influencing factors of urban street geometry (H/W and SVF) and then used field measurements to collect climatic data, including air temperature, wind speed, and relative humidity, and finally used regression to analyse the correlation between H/W, SVF, and temperature. The results indicate the following: (1) There is a greater correlation between H/W and air temperature than between SVF and air temperature by regression analysis, and H/W is more effective at improving the thermal environment within urban street canyons. (2) After field measurements, it was found that H/W at the measurement sites was 0.60 to 6.02, with an average of 2.13. (3) In the study area, H/W of 2.31–2.48 and 3.35–3.60 had a positive correlation with air temperature, and H/W had a dominant influence on outdoor air temperature, and H/W of 2.09–2.31 and H/W > 3.60 was inversely related to air temperature. The conclusions can provide support for urban planning in Hong Kong. [ABSTRACT FROM AUTHOR]

Spartina alterniflora is an invasive plant from coastal wetlands, and its use in applications has garnered much interest. In this study, a composite photocatalyst (ZnO@BC) was synthesized by preparing zinc oxide (ZnO) nanoparticles with S. alterniflora extracts, S. alterniflora, and one-step carbonization, which was characterized using scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), Raman, X-ray photoelectron spectroscopy, ultraviolet–visible spectroscopy (UV–vis DRS), photoluminescence (PL) and N2 adsorption–desorption isotherm. The degradation capacity and mechanism of malachite green (MG) using ZnO@BC were analyzed under visible irradiation, and the degradation products of malachite green were detected by LC–MS. The results show that ZnO@BC has a larger surface area (83.2 m2/g) and various reactive groups, which enhance its photocatalytic efficiency, with the presence of oxygen vacancy further improving the photocatalytic activity. The total removal rate of malachite green (400 mg/L) using ZnO@BC is up to 98.38%. From the LC–MS analysis, it could be concluded that malachite green is degraded by demethylation, deamination, conjugate structure and benzene ring structure destruction. This study provides a novel idea for the high-value utilization of S. alterniflora. [ABSTRACT FROM AUTHOR]