Strontium-90 and Caesium-137 in Columbia River Plume, July 1964

Abstract

OCEANOGRAPHERS informally term the extension of Columbia River outflow into the Pacific Ocean as the ‘Columbia River plume’. The plume can be identified by its low salinity even at a distance of several hundred kilometres from the mouth of the river (Fig. 1). The plume distributes dissolved and suspended substances in the river water over a wide surface area of the ocean and introduces annually to the euphotic zone over a billion moles of phosphorus and nitrogen fertilizers, as phosphate and nitrate. Equally significantly, the radionuclides contained in the river water are diffused over a wide region¹.