Pb-210 in precipitation in Japan and its implication for the transport of continental aerosols across the ocean

Total precipitation including rain or snow and dry fallout was collected once a month from February 1970 to March 1972 at five sampling stations in Hokkaido located from the coast of the Sea of Japan to inland. The monthly deposition rate of Pb-210 was determined together with other chemical constituents. The results are summarized as follows: (1) The deposition rate and the concentration of Pb-210 are remarkably high in winter. (2) A linear relation between the deposition rate of Pb-210 and the amount of rainfall is found in both summer and winter respectively. (3) As compared with the production rate of Pb-210, namely the exhalation rate of Rn-222 from the continent, the deposition rate of Pb-210 to the unit area at the coast of the Sea of Japan in winter is 2–4 times the exhalation rate of Rn-222 from the continent. (4) The budget calculation of Pb-210 in the atmosphere shows that about 40% of aerosols transported from the continent are caught by snow and deposited over the Sea of Japan and the Japan Islands in winter. Therefore, it is concluded that the Japan Islands play an important role as a collector of the continental aerosols in winter.