Concentration of 210Pb and 7Be in the Air of Tsukuba, Japan

Concentration of 210Pb and 7Be in the surface air was measured in
Tsukuba Sience City (36deg. 03min. N, 140deg. 07min. E), Japan, during
the period of Nov. 1987 to May 1992. Aerosol samples were collected on
glass fiber filters using a high volume air sampler. Radioactivity was
determined by the gamma-ray spectrometry with an LEPS and an HPGe
spectrometer. The air concentration of 210Pb and 7Be ranged from 0.2
to 0.8mBq/m3 and from 1 to 6 mBq/m3, respectively. Seasonal variation
was observed: high concentration appeared in the spring and in the
fall. Unusual and temporal increase in the concentration observed in
the winter months of 1991-92 may be attributed partly to the 210Pb
fallout originated from the 1991 eruption of Pinatubo volcano,
Phillippines.