Highly Time-Resolved Measurements of Airborne Radionuclides by Extremely Low Background ^|^gamma;-ray Spectrometry

Abstract

In order to investigate variation of concentrations of airborne radionuclides, 214 Pb, 212 Pb, 7 Be, and 210 Pb, accompanied with a typical meteorological event, such as passage of cold front, approach of typhoon, and Asian dust (Kosa), highly time-resolved (2-6 hours) measurements of natural radionuclides were performed by ultra low background γ-ray spectrometry. Surface air concentrations of these nuclides showed characteristic temporal changes by each meteorological phenomenon. In addition, variation patterns were found to be obviously different between short-lived 214 Pb and 212 Pb and long-lived 7 Be and 210 Pb. One of causes of the difference might be explained by difference of their sources: local for short-lived nuclides and regional for long-lived ones.

Relationship between variations of 7Be, 210Pb and 212Pb concentrations and sub-regional atmospheric transport: Simultaneous observation at distant locations

“…On the figure, passages of two cold fronts near Japan are visible. Rapid decreases of 210 Pb and 7 Be concentrations resulting from passage of cold fronts have been reported by Abe et al (2007). Therefore, the drop in radionuclide concentrations in this observation is also considered to be caused by frontal passages.…”

“…The difference of the supply rate between them could be observed in the low concentration event. Abe et al (2007) reported that such a rapid increase of 210 Pb/ 7 Be ratio was also observed during the approach of a typhoon, when concentrations of the both nuclides were extremely low.…”