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The Observatory announces the latest radiation monitoring information (30 March 2011)

 
     
 

Since the earthquake and tsunami event in Japan on 11 March, the 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 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 28 March for the air sample collected at Kings Park from 26 March to 27 March (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 on 29 March.

 
     
 

The concentration of radionuclide Iodine-131 measured from the air samples collected at Kings Park from 26 to 27 March (noon to noon), 27 to 28 March (noon to noon) and 28 to 29 March (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 of 30 March, 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 28 to 29 March (noon to noon).  In the routine weekly air sample collected at Sha Tau Kok (22 to 29 March), 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.

 
     

Activity of Iodine-131 in King's Park Air Sample

 

Activity of Iodine-131 in King's Park Air Sample

 
     

Activity of Iodine-131 in Yuen Ng Fan Air Sample

 

Activity of Iodine-131 in Yuen Ng Fan Air Sample

 
     

Activity of Iodine-131 in Sha Tau Kok Air Sample

 

Activity of Iodine-131 in Sha Tau Kok Air Sample

 

Last revision date: <21 Dec 2012>