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Mong Kok reported the highest NO2 and dust concentrations, which is to be expected from that street level site. RSP levels were about 50% of the total dust burden at all stations.
The most noteworthy event in the month was the effect that Severe Tropical Storm 'Gary' produced on Hong Kong's air quality when its centre was 300 to 600 km away from the territory.
The warm air rising up the centre of the storm, cooled, and descended around it. Air below that was trapped and emissions into that lower air could not disperse vertically. For this reason, NO2 and RSP levels peaked in the afternoons at all three sites. At Mong Kok, NO2 levels reached 60% of the 1-hour AQO.
The gases and particles described originated from various sources. SO2 is mostly produced when fuels that contain sulphur are burned. NO2 is formed during combustion by the combination of nitrogen and oxygen, and by the atmospheric oxidation of nitric oxide (NO), also a product of combustion.
Vehicle exhaust is an important source of NO and NO2 in terms of impact on local air quality. It is also a major source of airborne particulate matter, especially the smaller respirable particles.
Diesel-engined vehicles such as taxis, public light buses, passenger coaches, franchised buses and light and heavy goods vehicles are the greatest contributor of particulate matter. Other sources include industry, furnaces and boilers, construction activities, the sea and the soil.
It is worth noting that while the weather and climate always affect the concentrations of pollutants in the air, the only sure way of reducing the levels is to reduce emissions from the man-made sources.
Attention News Editors:
For further information on this air quality report, please contact Mr S W Pang on 2594 6413.
End/Friday, August 11, 1995