Beryllium-7 in near-surface atmospheric aerosols in mid-latitude (40°N) city Beijing, China

A high-volume air sampler and a high-resolution gamma-ray spectrometer have been used to measure the activity of 7Be in near-surface atmospheric aerosols at sampling frequency of 3 days week for 1 year from August 2009 to July 2010 at Beijing in the mid-latitude region of East Asia monsoon. The measurements indicate that the average concentration of 7Be was 8.39 ± 0.49 mBq m−3, which was significantly higher than values reported for other cities in the East Asia monsoon region and in the world during the same period. The maximum and minimum of the weekly means of 7Be concentration were observed in September and May, respectively. The 7Be concentrations varied in accordance with the monsoon phases. Low but frequent wet precipitation may have caused lower 7Be observed in July when southeasterly was prevailing. Higher seasonal mean of 7Be concentrations in autumn could be attributed to the abnormal atmospheric circulation in autumn 2009.