Analysis of airborne particulate matter (pm₂.₅) over Hong Kong using remote sensing and GIS

Abstract

Airborne fine particulates (PM₂.₅; particulate matter with diameter less than 2.5 µm) are receiving increasing attention for their potential toxicities and roles in visibility and health. In this study, we interpreted the behavior of PM₂.₅ and its correlation with meteorological parameters in Hong Kong, during 2007–2008. Significant diurnal variations of PM₂.₅ concentrations were observed and showed a distinctive bimodal pattern with two marked peaks during the morning and evening rush hour times, due to dense traffic. The study observed higher PM₂.₅ concentrations in winter when the northerly and northeasterly winds bring pollutants from the Chinese mainland, whereas southerly monsoon winds from the sea bring fresh air to the city in summer. In addition, higher concentrations of PM₂.₅ were observed in rush hours on weekdays compared to weekends, suggesting the influence of anthropogenic activities on fine particulate levels, e.g., traffic-related local PM₂.₅ emissions. To understand the spatial pattern of PM₂.₅ concentrations in the context of the built-up environment of Hong Kong, we utilized MODerate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Thickness (AOT) 500 m data and visibility data to derive aerosol extinction profile, then converted to aerosol and PM₂.₅ vertical profiles. A Geographic Information Systems (GIS) prototype was developed to integrate atmospheric PM₂.₅ vertical profiles with 3D GIS data. An example of the query function in GIS prototype is given. The resulting 3D database of PM₂.₅ concentrations provides crucial information to air quality regulators and decision makers to comply with air quality standards and in devising control strategies.