Seasonal variations of atmospheric 210Pb and 7Be concentrations at Kumamoto, Japan and their removal from the atmosphere as wet and dry depositions

Atmospheric concentrations, dry and total depositions of 7Be and 210Pb were analyzed at Kumamoto, Japan from December 2001 to November 2003. Meteorologically derived change of air masses in Kumamoto resulted in lower atmospheric concentrations in summer than other seasons. The deposition of 7Be and 210Pb was large in winter and spring, however, the values of precipitation-normalized deposition indicated a clearer peak in winter than in spring, though the stratosphere-troposphere exchange supplies 7Be at mid latitude in spring. The deposition velocity suggested that the wet deposition process functioned almost equally for both nuclides but the dry deposition process was much effective for 210Pb. (author)