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MONDAY, FEBRUARY 14, 1994
THE ANNOUNCEMENT CONTAINS MONITORING RESULTS FROM MONG кок, CENTRAL/WESTERN AND KWAI CHUNG. THESE LOCATIONS ARE TYPICAL OF THREE OF THE IMPORTANT LAND USE TYPES FOUND IN THE TERRITORY:
* LOCATIONS CLOSE TO ROAD TRAFFIC IN BUILT-UP URBAN AREAS;
*
COMBINED COMMERCIAL AND RESIDENTIAL DISTRICTS; AND
DISTRICTS CLOSE TO INDUSTRIAL AREAS.
THE DEPARTMENT CURRENTLY MONITORS AIR QUALITY CONTINUOUSLY AT EIGHT STATIONS, INCLUDING THE THREE MENTIONED.
SHORT-TERM MEASUREMENT CAMPAIGNS ARE ALSO UNDERTAKEN AS AND WHERE THE NEED ARISES.
THE REPORTED AIR POLLUTANTS INCLUDE SULPHUR DIOXIDE (SO2), NITROGEN DIOXIDE (NO2), TOTAL SUSPENDED PARTICULATES (TSP) WHICH COMPRISE ALL SIZES OF DUST PARTICLES, AND RESPIRABLE SUSPENDED PARTICULATES (RSP) WHICH ARE THE RESPIRABLE FRACTION OF THE DUST.
ALL THESE POLLUTANTS CAN AFFECT SUFFICIENT CONCENTRATION.
RESPIRATORY HEALTH
IN
IN JANUARY, POLLUTION CONCENTRATIONS FOLLOWED SIMILAR TRENDS AT ALL THREE REPORTED SITES SHOWING THAT METEOROLOGY WAS THE OVERRIDING FACTOR AFFECTING POLLUTANT LEVELS THIS MONTH.
AT THE STREET LEVEL SITE IN MONG KOK ON JANUARY 6 AND 26, THE 24-HOUR AIR QUALITY OBJECTIVE FOR NOZ WAS EXCEEDED.
DURING THOSE PERIODS THERE WERE BOTH LOW WINDSPEEDS AND HIGH
SUNSHINE LEVELS.
THE LOW WINDSPEEDS MADE IT DIFFICULT FOR LOCALLY EMITTED POLLUTANTS TO DISPERSE.
APART FROM THOSE TWO DAYS, LEVELS OF NO2 WERE HIGH AT MONG KOK FOR THE REST OF THE MONTH.
THE MINIMAL RAINFALL IN JANUARY AND RESULTING DRY CONDITIONS MEANT THAT DUST LEVELS WERE HIGH, UP TO 40 PER CENT MORE THAN IN JANUARY 1993.
AT THE ROOFTOP SITES, MOST OF THE DUST WAS IN THE RESPIRABLE RANGE BECAUSE THE LARGER, HEAVIER PARTICLES HAD SETTLED OUT.
THE GASES AND PARTICLES DESCRIBED ORIGINATE 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.
HOWEVER, THE MAJORITY OF IT IS FORMED IN THE ATMOSPHERE BY THE OXIDATION OF NITRIC OXIDE (NO), ALSO A PRODUCT OF COMBUSTION.
VEHICLE EXHAUSTS ARE IMPORTANT SOURCES OF NO AND NO2 IN TERMS OF IMPACT ON LOCAL AIR QUALITY.
/THESE EXHAUSTS