Measurements of PM_(2.5) in megacity

摘要

Air pollution in megacities has become a serious problem. Fine particles called PM_(2.5), with a diameter of 2.5 micrometres or less, are particularly problematic. Our observation site, located in eastern Osaka, is home to many small-and medium-scale manufacturing enterprises. A clear atmosphere is rare in this area, and the air is usually polluted with suspended particles emitted from diesel vehicles and industries. Furthermore, pollutants carried by winds from China add to the levels of pollution in the atmosphere. In this work, we investigate the size and composition of particulate matter with a scanning electron microscope (SEM) coupled with an energy-dispersive X-ray analyser (EDX). We use sampling data from an PM sampler mounted on the roof of a building at Kinki University at a height of about 50 m above sea level. It is evident that aerosol properties such as the amount, size, shape, and composition, change when anthropogenic or dust aerosol is transported. The level of sulphate and the percentage of fine particle increase in severe air pollution. In contrast, it is clear that silicon, which is possibly derived from soil particles, becomes dominant and that the number of large particles increase during the dust event.