Excess polonium-210 in the coastal atmosphere originating from marine biogenic material

The depositional fluxes of atmospheric polonium-210 were measured at one site in Xiamen from August 2001 to March 2002.With predominant marine air mass, the depositional fluxes of atmospheric polonium-210 ranged from 0.01 to 0.09 Bq/(m²·d), with an average of 0.04 Bq/(m²·d).The seasonal pattern showed elevated polonium-210 fluxes in summer and autumn rather than in winter.Atmospheric depositional fluxes of polonium-210 showed a good correlation with beryllium-7 (r²=0.85) and lead-210 fluxes (r²=0.71), indicating their similar removal mechanism from atmosphere.The relationship between the polonium-210 depositional fluxes and the precipitation amount demonstrated that the precipitation dominates the polonium-210 removal from the atmosphere.The observed high activity ratios of polonium-210 to lead-210 indicated the occurrence of excess polonium-210 in coastal atmosphere, which may originate from marine surface waters either by indirect (foam), or more likely, direct (air-sea exchange) input of marine biogenic material into the atmosphere.This source is even more important than the in situ decay of lead-210.