Earth and Planetary Science Letters, 89 (1988) 35-47 35 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands [6] Rare earth elements in river waters Steven J. Goldstein * and Stein B. Jacobsen Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138 (U.S.A.) Received April 1, 1987; revised version received March 21, 1988 We measured rare earth element (REE) concentrations in river waters to characterize the suspended and dissolved river flux of the REE to the oceans. The REE pattern of river suspended materials is sensitive to drainage basin geology. A positive correlation is observed between La/Yb ratios and Nd model ages for the rivers studied. Major rivers have light REE enriched patterns relative to the North American Shale Composite (NASC), with (La/Yb)N = 1.6-2.7. River water dissolved material (< 0.2 #m) is heavy REE enriched relative to suspended material, and the most pronounced negative Ce anomalies occur in rivers of high pH. Light REE concentrations vary by approximately 3 orders of magnitude and are inversely related to pH and major cation concentrations. From these data, we estimate that typical major river runoff has heavy REE depleted suspended material with (La/Yb)N = 1.9. We conclude that the terrigenous input to the oceans from major rivers is heavy REE depleted relative to shales. From the available data, average river water dissolved material appears to be heavy REE enriched with (La/Yb)~ --- 0.4. Estuarine removal processes lower the dissolved REE river flux by approximately 60% and result in a flux that is more heavy REE enriched with (La/Yb)r ~ = 0.2. Calculated oceanic residence times with respect to river input range from 2300 to 21,000 years, are shortest for Ce, and greatest for the heavy REE and La. Such long residence times may suggest the presence of additional sources of REE in seawater. 1. Introduction Rare earth dement (REE) abundance patterns of river water dissolved and suspended material should provide insight into both the seawater cycle of REE and the abundances of these elements in the continental crust. Neutron activation data on the suspended load of 5 major rivers [1] suggest a flat or slightly light REE enriched pattern relative to shales. Dissolved load data are available for only a few rivers [1-3] and suggest a flat or slightly heavy REE enriched pattern relative to shales. On the basis of these sparse data, many authors have assumed that the river input to the oceans is characterized by a flat REE pattern relative to shales [4-7]. Clearly, more data are necessary to characterize the input to the oceans of REE in the dissolved and suspended load of rivers. In an attempt to * Present address: Los Alamos National Lab., Los Alamos, NM 87545, U.S.A. 0012-821X/88/$03.50 © 1988 Elsevier Science Publishers B.V. rectify this situation we have measured the REE abundances of dissolved (< 0.2 ~m) and sus- pended material from 9 rivers. From these data we estimate the typical REE pattern of the dissolved and suspended load of average river water. The implications of these data for the behavior of REE during weathering and river transport, the marine geochemical cycle of the REE, and the REE sys- tematics of the continental surface are briefly dis- cussed. 2. Samples and methods Samples of Amazon, Indus, Mississippi, Mur- ray-Darling, and Ohio rivers were selected be- cause they are all rivers with large drainage areas or discharges. In addition, a few samples of smaller rivers were selected to establish the REE pattern of rivers with more distinct drainage basin lith- ology and water chemistry. These samples include Lake Isua in West Greenland and the Great Whale River in northwest Quebec; two dilute waters of low pH which drain Archean metasediments and