The distributions of 210Po and 210Pb in the intermediate layer (400–2000 m) of the northwestern North Pacific were determined to elucidate the export flux of
particulate matter. 210Po generally showed depletion relative to 210Pb in the intermediate layer, suggesting that 210Po was scavenged by particles. Because the removal rate constants of 210Po in the western region were higher than those in the eastern region and this trend coincided with that of the particle fluxes
in the surface layer, the export production in the surface layer was assumed to influence the particle flux in the intermediate
layer of the northwestern North Pacific.