Bismuth in the Atlantic and North Pacific: a natural analogue to plutonium and lead?

Bismuth has been analysed on samples from a vertical section from California to VERTEX IV, north of Hawaii, from a profile in the western Sargasso Sea and from an extensive suite of surface stations in the North and South Atlantic. Taken together with data from samples of Bermuda rain and from the Mississippi, Amazon and the Orinoco and its tributaries, a general outline of the processes controlling the Bi distribution in the ocean can be worked out. The dominant source in the open ocean is aeolian with the fluvial inputs being very small. Most of the aeolian input is probably derived from volcanoes; an anthropogenic flux may be important in the northwest Atlantic. Bismuth is scavenged in the mixed layer and regenerated at shallow depth to give a distribution in the northwest Pacific similar to that of^239,240Pu and anthropogenic Pb. Below 2 km the values are extremely low, in the range 20–50 fM, lower than the coexisting levels for²³²Th. The residence time of the element in the water column is sufficiently short that there are large concentration decreases between the Deep Waters of the Atlantic and Pacific. In the latter ocean, the element appears to reflect essentially one-dimensional processes.