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WEDNESDAY, JANUARY 13, 1993
LOCATIONS CLOSE TO ROAD TRAFFIC IN BUILT-UP URBAN DISTRICTS,
X COMBINED COMMERCIAL, AND RESIDENTIAL DISTRICTS, AND
DISTRICTS CLOSE TO INDUSTRIAL AREAS.
THE REPORTED AIR POLLUTANTS INCLUDE SULPHUR DIOXIDE (SO2), NITROGEN DIOXIDE (NO2), RESPIRABLE SUSPENDED PARTICULATES (RSP) AND TOTAL SUSPENDED PARTICULATES (TSP).
THE GASEOUS POLLUTANTS ARE MONITORED CONTINUOUSLY WHILE PARTICLE SAMPLES ARE COLLECTED FOR 24 HOURS, ONCE EVERY SIX DAYS.
THE CONCENTRATIONS OF THE GASEOUS SPECIES
302 AND NO2 SHOWED SIGNIFICANT INCREASE ON DECEMBER 7 AND BETWEEN 26 AND 29.
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ON THESE DAYS THE LOW WINDSPEED CREATED STAGNANT CONDITIONS. THIS INHIBITED THE DISPERSION OF EMITTED S02 AND ALLOWED INCREASED FORMATION OF NO2.
ROSE To
THE CONCENTRATION OF NO2 AT MONG KOK ON DECEMBER JUST ABOVE THE 24-HOUR AIR QUALITY OBJECTIVE VALUE OF 150 UG PER CUBIC METER.
ONLY ONE EXCEEDANCE A YEAR IS ALLOWED BY THE AIR OBJECTIVES. THIS WAS THE THIRD REPORTED FOR THE SITE.
QUALITY
LEVELS OF RESPIRABLE SUSPENDED PARTICULATES MEASURED DURING THE MONTH REMAIN BELOW THE AIR QUALITY OBJECTIVE VALUE.
AT MONG KOK, THE LEVELS OF TOTAL SUSPENDED PARTICULATES EXCEEDED THE APPROPRIATE 24-HOUR AIR QUALITY LIMIT OF 260 CUBIC METER ON DECEMBER 23.
PER
ONLY ONE EXCEEDANCE A YEAR IS ALLOWED BY THE AIR QUALITY OBJECTIVES, THIS WAS THE FOURTH MEASURED.
THE FOUR POLLUTANTS DISCUSSED HAVE DIFFERENT ORIGINS. S02 MOSTLY ORIGINATES FROM THE COMBUSTION OF SULPHUR CONTAINING FOSSIL FUELS.
NO2 IS FORMED EITHER DIRECTLY DURING COMBUSTION OR, BY THE ATMOSPHERIC OXIDATION OF NITRIC OXIDE (NO) WHICH IS ALSO PRODUCED DURING COMBUSTION. VEHICLE EXHAUST IS A MAJOR SOURCE OF NO AND NO2.
VEHICLE EXHAUST IS ALSO A MAJOR SOURCE OF AIRBORNE PARTICLES: OTHER SOURCES INCLUDE INDUSTRY, FURNACES AND BOILERS, CONSTRUCTION ACTIVITIES, THE SEA AND SOJL DUST.
AT
THE DEPARTMENT AT PRESENT MONITORS AIR QUALITY CONTINUOUSLY 11 STATIONS, INCLUDING THE THREE MENTIONED ABOVE. SHORT-TERM MEASUREMENT CAMPAIGNS ARE
UNDERTAKEN AS AND WHERE THE NEED
ALSO
ARISES.
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