Johannesson,K.H., Chevis,D.A., Burdige,D.J., Cable,J.E., Martin,J.B. and Roy,M.(2011): Submarine groundwater discharge is an important net source of light and middle REEs to coastal waters of the Indian River Lagoon, Florida, USA. Geochimica et Cosmochimica Acta, 75, 825-843.

『米国フロリダ州のインディアンリバーラグーンの沿岸水への希土類元素（軽と中）の重要な正味の源は海底地下水流出である』

『Abstract
　Porewater (i.e., groundwater) samples were collected from multi-level piezometers across the freshwater-saltwater seepage face within the Indian River Lagoon subterranean estuary along Florida's (USA) Atlantic coast for analysis of the rare earth elements (REE). Surface water samples for REE analysis were also collected from the water column of the Indian River Lagoon as well as two local rivers (Eau Gallie River, Crane Creek) that flow into the lagoon within the study area. Concentrations of REEs in porewaters from the subterranean estuary are 10-100 times higher than typical seawater values (e.g., Nd ranges from 217 to 2409 pmol kg-1), with submarine groundwater discharges (SGD) at the freshwater-saltwater seepage face exhibiting the highest REE concentrations. The elevated REE concentrations for SGD at the seepage face are too high to be the result of simple, binary mixing between a seawater end-member and local terrestrial SGD. Instead, the high REE concentrations indicate that geochemical reactions occurring within the subterranean estuary contribute substantially to the REE cycle. A simple mass balance model is used to investigate the cycling of REEs in the Indian River Lagoon and its underlying subterranean estuary. Mass balance modeling reveals the Indian River Lagoon is approximately at steady-state with respect to the REE fluxes into and out of the lagoon. However, the subterranean estuary is not at steady-state with respect to the REE fluxes. Specifically, the model suggests that the SGD Nd flux, for example, exported from the subterranean estuary to the overlying lagoon waters exceeds the combined input to the subterranean estuary from terrestrial SGD and recirculating marine SGD by, on average, 〜100 mmol day-1. The mass balance model also reveals that the subterranean estuary is a net source of light REEs (LREE) and middle REEs (MREE) to the overlying lagoon waters, but acts as a sink for the heavy REEs (FREE). Geochemical modeling and statistical analysis further suggests that this fractionation occurs, in part, due to the coupling between REE cycling and iron redox cycling within the Indian River Lagoon subterranean estuary. The net SGD flux of Nd to the Indian River Lagoon is 〜7-fold larger than the local effective river flux to these coastal waters. This previously unrecognized source of Nd to the coastal ocean could conceivably be important to the global oceanic Nd budget, and help to resolve the oceanic “Nd paradox” by accounting for a substantial fraction of the hypothesized missing Nd flux to the ocean.』

1. Introduction
2. Study site
3. Methods
　3.1. Sample collection
　3.2. Sample analysis
　3.3. REE solution complexation modeling
　3.4. Mass balance model
4. Results
　4.1. Rare earth element concentrations
　4.2. REE solution complexation
　4.3. Hydrologic and chloride mass balance model
　4.4. REE mass balance
5. Discussion
　5.1. SGD fluxes of REEs in the Indian River Lagoon subterranean estuary
　5.2. REE cycling in the Indian River Lagoon subterranean estuary
　5.3. Global implications
6. Conclusions
Acknowledgements
References

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