Abstract: Air quality in Central Taiwan has improved grdually over the past decade, though the visibility has not changed much. This raises poor perception and great concerns from its citizens and NGOs. From a scientific view, visibility is related to air quality or more specifically the fine particulate matter (PM2.5), but not in a direct proportional relationship. With that in mind, this study proposes to evaluate the sources and formation mechanisms of PM2.5 to elucidate the likely causes to the aforementioned bottleneck in improving visibility. Data from ground-level measurements, satellite telemetry and mathematic models will be combined, while two independent methods: physical and chemical extinction efficiencies (bext) will be estimated based on the measured aerosol physicochemical properties. The estimated bext will then be used to assimilate the bext from satellite data, with which further being used to reconstruct the spatiotemporal distribution of past bext for evaluating the impact of land use and microenvironment meteorology on visibility. Meantime, the highly time-resolved aerosol physicochemical properties will be used for apportioning the contributions of sources and chemical-components on impaired visibility.
This two-year proposal aims to (1) evaluate the relationships between air pollution sources and the chemical components of PM2.5, (2) characterize the roles of aerosol size distribution, cloud condensation nuclei, hygroscopic growth and optical properties in regional visibility, and (3) analyze the impacts of urban developments on land cover changes, formation and emission of air pollutants, and the relationships among short-term weather changes, aerosol physicochemical properties and regional transport. The outputs are expected to provide new insights and strong evidences critically needed to elucidate the causes of the un-coupling phenomena of improved PM pollution but degraded visibility. Furthermore, they will serve as the basis for effective control strategies for improving both PM pollution and visibility.
fine particulate matter