Lead-210 and Polonium-210 Across the frontal Region Between the Kuroshio and the East China Sea, Northeast of Taiwan


Concentration profiles of Pb-210, Po-210 were measured on several KEEP (Kuroshio Edge Exchange Process) program stations. Results of both Pb-210 and Po-210 of surface water along B transect (from station 6115 to station 4531) showed an increasing trend toward deeper water. This reflected the more efficient removal of Pb-210, Po-210 from the shelf water. Vertical profiles of deep water station (i.e. 4531, 5131) did show Po-210 deficiencies, Po-210/Pb-210 < 1, at upper layer ( < 100m); and Po-210 excess in the middle layer (200m-500m).
With Box Model calculation, the recycling effciency of Pb-210 and Po- 210 in the middle layer is found to be 2.9% and 85.4%. Vertical profile of the near shelf-break station S12A, where upwelling or intrusion of Kuroshio water occurred, showed the feature of richness in Po-210. The profile of the station 5323, located at a very steep upper slope region, showed the feature of Pb-210 excess all over the water column. Some sediment particles which contains excess Pb-210 might re-export from the outer shelf to slope water. The shelf water station was characterized with Po-210 excess in most of the water column except the very top layer ( < 20m).

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