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Unusually large 210 Po deficiencies relative to 210 Pb in the Kuroshio Current of the East China and Philippine seas

1990; American Geophysical Union; Volume: 95; Issue: C4 Linguagem: Inglês

10.1029/jc095ic04p05321

2156-2202

Yoshiyuki Nozaki, Naoko Ikuta, Mayumi Yashima,

Groundwater and Isotope Geochemistry

Three vertical water profiles of 210 Pb and 210 Po have been measured in the East China and Philippine seas. All the profiles show a large 210 Po deficiency of ∼8 dpm cm −2 relative to 210 Pb in the top ∼1000 m of the water column. Based on the 210 Po deficiency, the steady state flux for 210 Po removal from the surface water is estimated to be 14 dpm cm −2 yr −1 . The 210 Po/ 210 Pb ratio of sinking particles will be too high unless an additional source of 210 Pb into the surface is accounted for. Thus the large 210 Po deficit is probably caused by the increased atmospheric input of 210 Pb without any significant 210 Po, which is focused in the Kuroshio region by isopycnal transport, and the preferential scavenging of 210 Po relative to 210 Pb by settling particles. The transient model calculations indicate that the model can account for the observed high excess 210 Pb inventory and large 210 Po deficiency in the water column if focusing of atmospherically derived 210 Pb in the Kuroshio water is a factor of 2–3 more than the local input. Such a lateral redistribution by the western North Pacific gyre circulation is not inconsistent with the deeper penetration and the high water column inventories of anthropogenic substances observed in this region.