Deposition of beryllium-7 in Hsinchu, Taiwan

Abstract

In the present study, factors that influence the distribution and variation of 7Be in Hsinchu, Taiwan were elucidated. The 7Be activity including the deposition flux and air concentration was continuously monitored and recorded throughout a 15-year period (1996–2010). To explain the observed variability in the 7Be activity over time, air concentration and deposition flux of 7Be were correlated to rainfall and solar activity. The monthly average deposition flux and air concentration of 7Be were inversely related to solar activity with the 11-year cycle and were not strongly correlated to rainfall. The highest seasonal deposition flux of 7Be occurred in March, which is commonly referred to as the spring maximum, due to air-mass mixing processes in the troposphere. The air concentration of 7Be was seasonally variable and was significantly affected by monsoons. The lowest deposition flux and air concentration of 7Be were observed in July and August due to the occurrence of southwest monsoons from low latitudes, which carry air masses with low concentrations of 7Be. The deposition flux was enhanced by precipitation, which increased the deposition velocity, transferring more 7Be from the troposphere to the ground. The fraction of dry to total deposition varied seasonally and was equal to 9.86%, on average.