In response to the development of the nuclear accident in Fukushima, Japan, the Observatory enhanced radiation monitoring of soil. The Observatory collected soil samples at various locations in Hong Kong from 6 to 12 May to find out if they contained any artificial radioactive materials. The samples were taken at two different layers - the upper layer from the surface to 15 cm deep and the lower layer from 15 cm to 30 cm deep. The sample weighed 1 kilogram each.

Radiation measurement results indicated that minute amount of caesium-137 was detected in some samples.  Since the amount of radioactive caesium-137 detected is well within the background range detected in the Background Radiation Monitoring Programme*, the background radiation level in Hong Kong remains unchanged after the Fukushima nuclear accident.  The very minute amount of caesium-137 will have practically no impact on public health.

Detailed radiation measurement results are summarized in the following table:

Soil Sampling Location/Date	Activity of Radioactive Caesium-137 (Bq/kg)	Background Range* of Activity of Radioactive Caesium-137 (Bq/kg)
High Island West (Upper Layer)/6 May 2011	0.6	≤10
High Island West (Lower Layer)/6 May 2011	Not Detected	≤4
Ping Chau (Upper Layer)/7 May 2011	0.8	≤10
Ping Chau (Lower Layer)/7 May 2011	0.6	≤4
Happy Valley (Upper Layer)/7 May 2011	Not Detected	≤10
Happy Valley (Lower Layer)/7 May 2011	Not Detected	≤4
Shatin (Upper Layer)/9 May 2011	Not Detected	≤10
Shatin (Lower Layer)/9 May 2011	Not Detected	≤4
King's Park (Upper Layer)/11 May 2011	2.1	≤10
King's Park (Lower Layer)/11 May 2011	2.2	≤4
Sha Tau Kok (Upper Layer)/11 May 2011	1.2	≤10
Sha Tau Kok (Lower Layer)/11 May 2011	0.4	≤4
Tap Mun (Upper Layer)/12 May 2011	2.1	≤10
Tap Mun (Lower Layer)/12 May 2011	2.6	≤4

* A Background Radiation Monitoring Programme was conducted from 1987 to 1991 to establish the baseline radiation levels in Hong Kong prior to the operation of the Guangdong Nuclear Power Station (GNPS) in 1994. These baseline levels would enable the detection of changes arising from the operation of GNPS, if any.  The background value of caesium-137 in upper and lower layer soil samples is within 10 and 4 Bq/kg respectively.