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Since the earthquake and tsunami event in Japan on March 11, the Hong Kong Observatory has strengthened the monitoring of concentration of radioactive substances in the air. The frequency of sample collection from the air samplers at King's Park and Yuen Ng Fan has increased from once weekly to once daily so as to operate round-the-clock for radioactivity measurement. Owing to the very low radiation dose, the Hong Kong Observatory needs to extend the measurement time from normally a few hours to 22 hours to meet the reliability requirement. After 22 hours of measurement, a very minute amount of radioactive iodine was detected on March 28 for the air sample collected at King's Park from March 26 to March 27 (noon to noon). However, the measurement result was not certain and the data needed to be re-checked for another 22 hours. After the measurement result was confirmed, it was announced to public in the media briefing yesterday (March 29).
The concentration of radionuclide Iodine-131 measured from the air samples collected at King's Park from March 26 to 27 (noon to noon), March 27 to 28 (noon to noon) and March 28 to 29 (noon to noon) were 0.0000625 Bq/m3, 0.0001869 Bq/m3 and 0.000296 Bq/m3 respectively. Although the concentration has increased, it remained very low.
Furthermore, after analysing and confirming the measurement data on the evening today (March 30), a very minute amount of artificial radionuclide Iodine-131 with concentration of 0.000274 Bq/m3 was detected in the air sample collected at Yuen Ng Fan from March 28 to 29 (noon to noon). In the routine weekly air sample collected at Sha Tau Kok (March 22 to 29), a concentration of 0.000132 Bq/m3 was also detected. Since the amount of radioactive iodine detected is very minute, it will not affect public health.
Ends/Wednesday, March 30, 2011
Issued at HKT 23:54
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