- 6.
districts close to industrial areas.
The reported air pollutants include sulphur dioxide (SO2), nitrogen dioxide (NO2), total suspended particulates (TSP) which comprise all sizes of dust particles, and the respirable fraction of the dust (RSP). All these pollutants can affect respiratory health in sufficient concentration.
The levels of all pollutants at the three sites were low in June, with no exceedances of the 24-hour Air Quality Objectives.
There was rain on most days of the month which washed sulphur dioxide, nitrogen dioxide and dust from the atmosphere, as well as dampened road surfaces and thereby preventing the release of surface dust.
Winds were from the South China Sea most of the time and brought in cleaner marine air. Also, wind speeds were relatively high, causing local emissions to be blown away.
SO2 is
The gases and particles described originated from various sources. 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. Note to Editors:
For further information on this air quality report, please contact Mr S W Pang on 2594 6413.
End/Wednesday, July 12, 1995
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