Study of the factors influence on variation of Be-7 concentration in surface air at Osaka, Japan

Abstract

The concentration of 7Be in surface air and rainwater at Daito, Osaka (34.71 N, 135.64 E) has been measured during the period from January 8 to October 29, 2018 and April 1 to October 31, 2018, respectively. The weekly concentration of 7Be in surface air in the range of 8.92 ± 0.08 to 1.03 ± 0.02 mBq/m3 showing seasonal trend with maxima in spring and autumn and minima in summer, which can be ascribed to the transport of air masses from low latitudes carrying low 7Be concentration into the middle latitude region. The factors influences on the concentration of 7Be were examined. It was shown that the positive and negative correlation was found in PM2.5 (cc = 0.62) and relative humidity (cc = –0.57), respectively. The weak positive correlation was found in cosmic ray intensity (cc = 0.23), the weak negative correlation was found in precipitation (cc = –0.14) and sunspot number (cc = –0.05). The deposition rate was analyzed by using the rainwater samples. It shown negative correlation between deposition rate and precipitation (cc = –0.53). High volumes of precipitation can reduce the 7Be concentration of air by wash-out.