Long-term variation of atmospheric beryllium-7 in Taiwan

Taiwan Radiation Monitoring Center (TRMC) has measured the concentration of atmospheric 7Be at tile four stations on Taiwan for almost twenty years. Gamma emitting nuclides have been collected by air samplers and measured by gamma spectrometry. Cosmogenic 7Be and other man-made radionuclides produced by Chinese nuclear weapon testings have been detected. Compared with 7Be, man-made nuclides vanished quickly because of their short half life. The behaviour of 7Be in long-term concentration variation is different between northern and southern Taiwan because of local meteorological conditions. Tile results of Fourier analysis show that washout effect of rainfalls and transportation from stratosphere to troposphere are closely related to tile variation of 7Be concentration in near surface air. All the measured data of 7Be show that tile characteristic of yearly data coincides with tile 11-year solar cycle. (author)