Earth and Planetary Science Letters, 88 (1988) 241-252 241 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands [6] REE in the Great Whale River estuary, northwest Quebec 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 February 4, 1988 We report rare earth element (REE) concentrations of a longitudinal profile within the estuary of the Great Whale River in northwest Quebec and in Hudson Bay. All of the measured REE have concentrations less than those predicted by conservative mixing of seawater and river water, demonstrating removal of the REE from solution. REE removal is rapid, occurring primarily at salinities less than 27~. Removal of the REE is greatest for the light REE, and ranges from about 70% for the light REE to no more than 40% for the heavy REE. Fe removal is essentially complete at low salinity. The shape of the Fe and REE vs. salinity profiles is not consistent with a simple model of destabilization and coagulation of iron and REE-bearing colloidal material. A linear relationship between the activity of free ion REE 3+ and pH is consistent with a simple ion-exchange model for REE removal. Surface and subsurface samples of Hudson Bay seawater are characterized by high REE concentrations and high La/Yb relative to average seawater. The subsurface sample has a Nd concentration of 100 pmol/kg and an CNa of -29.3 + 0.3. These characteristics are consistent with the high REE concentration, high La/Yb, and low crq d of river inputs into Hudson Bay. These results indicate that rivers draining the Canadian Shield are a major source of non-radiogenic Nd and REE to the Atlantic Ocean. We estimate that outflow of water from Hudson Bay to the Labrador Sea could supply = 30% of the non-radiogenic Nd in North Atlantic Deep Water. 1. Introduction Chemical processes in estuaries play an im- portant role in controlling the dissolved river in- put to the oceans for many trace metals. Many trace metals, including the rare earth elements (REE), are removed from the dissolved load of rivers in estuaries. Martin et al. [1] measured REE concentrations in waters filtered to 0.4/~m from a transect of the Gironde estuary in France. They found that the REE were removed from solution during estuarine mixing, with greater removal for the light REE (70%) than the heavy REE (50%). Laboratory mixing experiments [2] of seawater and water filtered to 18/~m from the organic-rich Luce River resulted in removal of REE and Fe from the river water, whereas similar experiments for the organic-poor Wharfe River resulted in no removal of REE and Fe. These initial studies suggest that estuarine removal of REE from the dissolved load of rivers may have two important * Present address: Los Alamos National Laboratory, Los Alamos, NM 87545, U.S.A. 0012-821x/88/$03.50 © 1988 Elsevier Science Publishers B.V. effects on the global oceanic REE budget: at- tenuation of the dissolved REE flux from rivers to the oceans by > 50%, and alteration of the REE pattern of the dissolved REE flux from rivers. Estuarine removal of the REE from the dis- solved load of rivers can also have an important effect on the global oceanic budget of a43Nd. Nd and Sm concentrations in rivers are sensitive to pH; the highest concentrations of Nd and Sm occur in low pH rivers draining silicate rocks [3]. Major rivers of pH > 7.5, such as the Mississippi, St. Lawrence, Columbia, and Colorado, have Nd concentrations < 170 pmol/kg, whereas rivers of pH < 7.5, such as the Amazon, Ottawa, and Great Whale, have Nd concentrations of 700-2100 pmol/kg. From these measurements we estimated that low pH rivers draining the Canadian Shield can contribute approximately 80% of the flux of Nd from North America toward the Atlantic Oce- an [3]. These rivers are expected to have highly negative end values (eNd = --25), and thus could be a major source of Nd in the 1OW-~Nd bottom waters found in the North Atlantic Ocean [4]. However, it is possible that removal of REE in the