Concentrations of REEs, Th and U in river waters collected in Japan

Fifteen major rivers were selected for determination of concentration levels in order to understand behaviors of the rare earth elements (REEs), Th and U in Japanese rivers under normal conditions. Ten samples were collected in each river from the upper stream region to the river mouth and the concentrations in the samples were measured by inductively coupled plasma mass spectrometry (ICP-MS). The geometric mean concentrations of REEs except for La, Cc and Nd in the 15 rivers were < 0.5-20 ng L-1 (ppt), while those of La, Ce and Nd were at 80-200 ppt. These values are close to those reported previously for Japanese river waters and for average river water. The concentration pattern of REEs followed the Oddo-Harkins rule in each river and the concentration range of each element was usually narrow. The concentration range of U was wider than that of Th, probably because of application of phosphatic fertilizer to agricultural fields near the rivers. (c) 2005 Elsevier B.V. All rights reserved.