A novel approach for assessing the spatiotemporal trend of health risk from ambient particulate matter components: Case of Hong Kong

The spatiotemporal assessment of health risk due to exposure to particulate matter (PM) components should be well studied because of the different toxicity among PM components. However, this research topic has long been overlooked. This study aimed to examine the spatiotemporal variability in ambient respirable PM (PM₁₀) components associated inhalation carcinogenic and non-carcinogenic risk (ICR and INCR) in Hong Kong over 2015-2019. The land-use regression (LUR) approach was adopted to predict the spatial distribution of PM₁₀ component concentrations for the period of 2015-2019, whereas the ICR and INCR values of PM₁₀ components were also estimated using the classic health risk assessment method. Both concentration of PM₁₀ and INCR of PM₁₀ components showed a general decreasing trend, while ICR of PM₁₀ components increased slightly over the study period. LUR-model-based spatial maps at 500 m × 500 m resolution revealed the important spatial variability in PM₁₀ and its eleven components, and their associated ICR and INCR values. High pollution levels and high ICR and INCR of studied PM₁₀ components were generally found in developed urban areas and along the road network. Despite the fact that the PM₁₀ concentrations met the Hong Kong annual PM₁₀ air quality objective of 50 μg/m³, there was still significant potential health risk from the studied PM₁₀ components. This study highlights the importance of taking PM component concentrations and associated inhalation health risk as well as PM mass concentrations into account for the perspective of air quality management and protecting public health.

Development of a 3D Real-Time Atmospheric Monitoring System (3DREAMS) Using Doppler LiDARs and Applications for Long-Term Analysis and Hot-and-Polluted Episodes

Heatwaves and air pollution are serious environmental problems that adversely affect human health. While related studies have typically employed ground-level data, the long-term and episodic characteristics of meteorology and air quality at higher altitudes have yet to be fully understood. This study developed a 3-Dimensional Real-timE Atmospheric Monitoring System (3DREAMS) to measure and analyze the vertical profiles of horizontal wind speed and direction, vertical wind velocity as well as aerosol backscatter. The system was applied to Hong Kong, a highly dense city with complex topography, during each season and including hot-and-polluted episodes (HPEs) in 2019. The results reveal that the high spatial wind variability and wind characteristics in the lower atmosphere in Hong Kong can extend upwards by up to 0.66 km, thus highlighting the importance of mountains for the wind environment in the city. Both upslope and downslope winds were observed at one site, whereas downward air motions predominated at another site. The high temperature and high concentration of fine particulate matter during HPEs were caused by a significant reduction in both horizontal and vertical wind speeds that established conditions favorable for heat and air pollutant accumulation, and by the prevailing westerly wind promoting transboundary air pollution. The findings of this study are anticipated to provide valuable insight for weather forecasting and air quality studies. The 3DREAMS will be further developed to monitor upper atmosphere wind and air quality over the Greater Bay Area of China.

The effect of urbanization and climate change on the mosquito population in the Pearl River Delta region of China

The rising incidence of mosquito-borne diseases is a global concern. Changes in regional climate, due to urbanization and global greenhouse gas concentrations, may affect the ecology of mosquitoes and mosquito-transmitted pathogens. The effects of changes in climate on mosquito population dynamics are complex but critical and urgent for implementing more effective public health policies. This study quantified the impact of urbanization and global climate change on the population of the mosquito species, Culex quinquefasciatus, in the Pearl River Delta region in southern China-an area that has undergone substantial urbanization and is expected to experience changes in climate. This study employed a mechanistic model to simulate mosquito population dynamics under various greenhouse gas emission and land-cover change scenarios based on climate data provided by a state-of-the-art regional climate model. Our results show a 12.6% decrease in the annual mosquito population in newly urbanized areas and a 5.9% increase in the annual mosquito population in existing urban areas. Furthermore, changing climate conditions are projected to cause a 15-17% reduction in the total annual mosquito population; however, the change will not be uniform throughout the year. Peak months exhibit a reduction in population, whereas non-peak months show a significant increase. These findings suggest mosquito control strategies may need to be adjusted to respond to the impacts of urbanization and climate change on mosquito population dynamics to maximize effectiveness. Region specific, quantitative analyses of environmental impacts on mosquito-borne disease ecology, like this study, are needed to provide policy makers with a scientific reference to guide the formation of effective transmission intervention strategies.

Spatial assessment of air resources in China from 2013 to 2017

The concept of air resource management originated in the United States and subsequently became the foundation of most air quality control programs in developed countries. However, little is known about its validity and quantitative assessment methods in regional atmospheric environment management. The aim of this study was to construct an air resource endowment (ARE) index and apply it in a case study for assessing the distribution of ARE across mainland China from 2013 to 2017. The quantification of the ARE index includes two terms: the atmospheric diffusion coefficient (A value) and self-purification ability (B value), which can be calculated via Weather Research and Forecasting modeling (WRF-CALMET). The results indicated that about 15% of China's land area enjoys high ARE, around 20-25% of China's land area was considered to have relatively high or relatively low ARE indices, and ARE in the rest of China's land area (40%) was considered to be low. Further, a complex network correlation model was created and used to demarcate highly inter-correlated regions based on the data mining of the ARE index. Six key Joint Prevention and Control of Atmospheric Pollution (JPCAP) regions with strong synchronicity in the ARE index were identified, which suggests that JPCAP could be implemented separately within each of these demarcated regions. The concepts and analysis methods proposed in this study for determining ARE and regional divisions can have broad significance for JPCAP implementation in China.

Features of Urban Heat Island in Mountainous Chongqing from a Dense Surface Monitoring Network

The spatial and temporal features of urban heat island (UHI) intensity in complex urban terrain are barely investigated. This study examines the UHI intensity variations in mountainous Chongqing using a dense surface monitoring network. The results show that the UHI intensity is closely related to underlying surfaces, and the strongest UHI intensity is confined around the central urban areas. The UHI intensity is most prominent at night and in warm season, and the magnitude could reach ~4.5 °C on summer night. Our quantitative analysis shows a profound contribution of urbanization level to UHI intensity both at night and in summer, with regression coefficient b = 4.31 and 6.65, respectively. At night, the urban extra heat such as reflections of longwave radiation by buildings and release of daytime-stored heat from artificial materials, is added into the boundary layer, which compensates part of urban heat loss and thus leads to stronger UHI intensity. In summer, the urban areas are frequently controlled by oppressively hot weather. Due to increased usage of air conditioning, more anthropogenic heat is released. As a result, the urban temperatures are higher at night. The near-surface wind speed can serve as an indicator predicting UHI intensity variations only in the diurnal cycle. The rural cooling rate during early evening transition, however, is an appropriate factor to estimate the magnitude of UHI intensity both at night and in summer.

Trans-boundary air pollution in a city under various atmospheric conditions

Trans-boundary air pollution (TAP) is a crucial factor affecting air quality, and its contribution may vary over time and differ under various atmospheric conditions. This study firstly applies an integrated statistical scheme to estimate the contributions of TAP and local sources to air pollutants in a city, and then investigate the influences of tropical cyclones (TC) on TAP. Hong Kong is chosen as an example because of its significant and special TAP characteristics. This study focuses on four major air pollutants, namely, respirable and fine suspended particulates (RSP/PM₁₀ and FSP/PM_2.5), sulfur dioxide (SO₂), and nitrogen dioxide (NO₂), from 2002 to 2013. Our results show that, on average, TAP is the major contributor of the annual RSP, FSP, SO₂, and NO₂ in Hong Kong. We estimate that when a TC is approaching, the increase in pollutant concentration in Hong Kong is mainly due to the increase in TAP contribution by the strengthened northerly wind at higher level of atmosphere (≥900hPa). These changes are accompanied by decreases in precipitation and increases in northerly/north-easterly wind, which may prolong the lifetime of pollutants, enhancing pollutant transport from mainland China to Hong Kong.

China's adaptation to climate & urban climatic changes: A critical review

Since the conclusion of the 2014 Climate Summit in New York and the 21st Conference of the Parties (COP21) in Paris, China has been actively advancing its national policies on climate change mitigation and adaptation since more unpredictable extreme weather events are expected, which may incur a heavy cost in terms of economics and public health. Since China is still in the process of urbanisation, the greatest challenge it faces is finding a balance between economic growth and keeping carbon dioxide and greenhouse gas emission rates at a manageable level. Cities in China play a key role in the implementation of the central policies and make concrete actions in response to climate change. With reference to a series of recent policy papers and action plans as the background, this paper attempts to provide a critical overview of China's climate change action plans from the national to the city and urban level. It seeks to understand whether the proposed responses to climate change and strategies for actions on greening and air corridors for cities and urban areas are appropriate. It is found that for China to advance its urban climatic adaptation strategy there is a need for (1) urban data, (2) a cross-disciplinary impact assessment, and (3) the development of a market and policy transformation mechanism.

Practical application of CFD on environmentally sensitive architectural design at high density cities: A case study in Hong Kong

Concerns on negative effects of urbanization on the environment make the aerodynamic properties of urban areas increasingly important in architectural design, particularly at high density cities. Over the past few decades, a rapid development in Computational Fluid Dynamics (CFD) has resulted in the widespread use of this technique not only as an environmental research tool but also as an architectural design tool. However, given real building morphologies and particular architectural requirements for the modeling and data analysis, the frequently used methods in research work are unsuitable for practical application. Therefore, this study focuses on the practical application of CFD to bridge the gap between wind engineering and architectural design. This study aims to provide a framework to accurately predict the pedestrian level wind environment, and identify the wind-related design issues. The methods are provided to answer the questions encountered by wind consultants and architects, particularly those on the input boundary condition, simulation modeling, modeling verification, data collection and analysis. The hypothesis testing method is introduced in the framework to verify and evaluate the simulation results. A Hong Kong case study is presented to illustrate that the framework and methods can work well.

Improving the wind environment in high-density cities by understanding urban morphology and surface roughness: A study in Hong Kong

In this study, a high-resolution frontal area density (FAD) map that depicts the surface roughness of urban Hong Kong is produced using a mapping method that takes into account the dense urban morphology and the site wind availability of the territory. Using the MM5/CALMET model simulated wind data of Hong Kong, the FAD map of three urban zones are calculated: podium (0-15 m), building (15-60 m), and urban canopy (0-60 m). The wind tunnel test data is used to correlate the FAD understanding of the three zones. The grid sensitivity test indicates that 200 m × 200 m is the reasonable resolution for the FAD map; the test also establishes that the lower urban podium zone yields the best correlation with the experimental data. The study further establishes that the simpler two-dimensional ground coverage ratio (GCR), which is readily available in the planning circle, can be used to predict the area's average pedestrian level urban ventilation performance of the city. Working with their inhouse GIS team using available data, it allows the planners a way to understand the urban ventilation of the city for decisions related to air paths, urban permeability and site porosity.