The fractionation between Y and Ho in the marine environment

New measurements of Y and Ho in seawater, rivers and rain are presented. Based on the data and a two-box model calculation, we suggest that fractionation between Y and Ho takes place during their removal by particulate matter from the surface ocean to the deep sea. The fractionation factor, K-D is calculated to be 0.50, implying that Ho is scavenged two times faster than Y. This presumably occurs due to differences between Y and Ho complexation behavior with respect to seawater inorganic ligands (mainly carbonate ions) and soft organic ligands (though unspecified) of the surface of particulate matter. Fractionation of Y and Ho during weathering and fluvial transport to the ocean appears to have minor influence on the relative abundance of Y and Ho in seawater. We also estimated the mean oceanic residence time to be 5100 years for Y and 2700 years for Ho. Y is less effectively scavenged from seawater than any of the trivalent rare earth elements and the Y/Ho ratio in seawater is higher than those in rain, rivers and estuarine waters.