Search

Analyzing the distribution of air pollution and its influencing factors is critical for regional air pollution prevention and control. This study takes the Pearl River Delta (PRD) as a study area, analyzes the spatial-temporal changes in air pollution (including sulfur dioxide (SO 2), nitrogen dioxide (NO 2), ozone (O 3), carbon monoxide (CO), and particles with an aerodynamic diameter less than 10 μm (PM 10) and less than 2.5 μm (PM 2.5)) from 2006 to 2019, and explores the relationship between air pollution and meteorological factors. The results showed that (1) most air pollutant concentrations decreased from 2006 to 2019, with the most obvious change being the decrease in the SO 2 concentration from 52.4 μg/m3 to 7.8 μg/m3. The O 3 concentration increased, with a Sen's slope of 0.649 μg m−3·year−1. Air pollution was lower in coastal areas (Shenzhen and Huizhou) than in inland areas (Foshan and Zhaoqing), affected by ocean atmospheric transmission, and coastal areas had the cleanest air quality. (2) Air pollutants had high correlations with air pressure, relative humidity, precipitation, and temperature. The most serious air pollution was found in winter, which was partially due to the meteorological conditions in winter that were more unfavorable for pollutant dispersion and dilution than were the conditions in other seasons. (3) Through the wavelet coherence method, an interesting finding revealed that other air pollution and meteorological factors exhibited complex period-dependent characteristics that were significantly related to PM 2.5. Areas with less air pollution were more susceptible to meteorological factors. (4) The overlapping area of the PM 2.5 distribution hotspot and nighttime light hotspot was mainly in Foshan and Guangzhou, representing approximately 12.1% of the study area. Our work contributes to the literature by considering seasonal and timescale-dependent characteristics of meteorological factors affecting air pollutant emissions, and it provides new insights into recognizing regions that need to prioritize urban air pollution control based on hotspot analysis. [Display omitted] • The mean SO 2 concentration decreased from 52.4 μg/m3 in 2006 to 7.8 μg/m3 in 2019. • The O 3 concentration increased with a Sen's slope of 0.649 μg m−3·year−1. • The time-frequency relationship between PM 2.5 and meteorological factors was explored by wavelet coherence. • Higher air pollution was detected in regions with higher night-time brightness. [ABSTRACT FROM AUTHOR]

With the rapid economic development and tremendous urban expansion, cities frequently experience overheating problem. Urban green infrastructure (UGI) has proved effective in alleviating urban warming and enhancing thermal comfort. However, few research has been conducted to determine the proper UGI strategy across scales. Here, we propose a sustainable strategy for UGI planning by synthesizing the local climate zone (LCZ) concept and microclimate simulation, with the goal of ameliorating surface urban heat island (SUHI) and improving thermal comfort in cities. The LCZ map of Guangzhou showed that the major 'built-up land types' concentrated in the central area with high land surface temperature (LST) and intensities of SUHI. The circles (1-km diameter) identified as LCZ 2, 3, and 8 were recognized as planning areas by considering the intensities of SUHI and practicability. Afterward, the simulations of the UGI strategy scenarios at three randomly selected sample sites in LCZ 2, 3, and 8 were carried out using the ENVI-met model. The case study results in Guangzhou showed that increasing the green cover to 10% by adding grove and street trees could be the best adaptation strategy to ameliorate overheating, whereas adding extensive green roofs aggravated SUHI to a certain extent and showed minimal impacts on the thermal comfort at a pedestrian level. We show that it is promising to combine the LCZ concept and ENVI-met simulation in optimizing UGI toward urban overheating mitigation. • Multi-scale & discipline UGI strategy is needed to mitigate urban overheating. • A practical approach synthesizing LCZ concept and ENVI-met simulation was proposed. • Major built types concentrated in the central area with high intensities of SUHI. • Adding grove and street trees was the best adaptation strategy. • Application value of adopted approach was underlined for subsequent UGI studies. [ABSTRACT FROM AUTHOR]