湖沼環境での物質循環に関する研究 : 琵琶湖における天然放射性核種^<210>Pbと^<210>Poの挙動

概要

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The behavior of ^<210>Pb and ^<210>Po in Lake Biwa, a large mesotorophic lake situated in the Kinki district of Japan, was investigated by analyzing lake water at various depths and precipitation at approximately monthly intervals for a period of 1.5 years, and sediments, streams flowing into and out of the lake. Flux balance calculation indicated that atmospheric deposition was the major source (97% of total) of ^<210>Pb to the lake, and for ^<210>Po growth in-situ from the decay of ^<210>Pb contributed about 75% of the total ^<210>Po supply to the lake. Most (about 90%) of all the ^<210>Pb inputs to this lake was found to be incorporated into sediment. Residence times via sedimentation in the epilimnion and hypoliminion were estimated to be 27 (6-40) and 22 (5-45) days, respectively, for ^<210>Pb and 95 (47-146) and 32 (7-109) days for ^<210>Po. These residence times suggest that there is a difference between ^<210>Pb and ^<210>Po in the extent of their cycling in the water column, with a more rapid removal of ^<210>Pb than ^<210>Po. Overall, ^<210>Pb and ^<210>Po were, furthermore, found to be removed more efficiently during the transit periods of high biological productivity, such as plankton blooms.
日本地球化学会の論文
2001-06-20