Characteristics of Concentrations and Chemical Forms of Trace Elements in Deep Seawater near Kume Island in Okinawa Prefecture Studied by Multielement Profiling Analysis

Abstract

The dissolved and acid-soluble concentrations of major and trace elements in deep and surface seawater samples near Kume Island in Okinawa Prefecture were investigated by ICP-MS and ICP-AES with two types of preconcentration methods using chelating disk preconcentration and lanthanum hydroxide coprecipitation. As a result, 16 elements in each sample were determined over the concentration range from% to ng L⁻¹ (ppt). In addition, it was elucidated from multielement profiling analyses by using the obtained analytical results that the concentrations of Cd, Zn, Ni, Cu, and Co in deep seawater near Kume Island were higher than those at the surface. The acid-soluble particle fraction to the total concentration (P_acid) was calculated from dissolved and acid-soluble concentrations. The P_acid values for Cu, Co, Zn, and Ni in deep seawater were 10∼30%, and higher than those at the surface, while that for Cd was below 10%, and almost the same as those for the surface. The results suggested that portions of Cu, Co, Zn, and Ni exist as acid-soluble biogenic particles in deep seawater (water depth : 612 m), which were detritus and colloidal particles bound with organic matter, while most Cd exists as a dissolved form.