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Title: Rare earth element fractionation and concentration variations along a groundwater flow path within a shallow, basin-fill aquifer, southern Nevada, USA

Abstract

Rare earth element (REE) concentrations were measured in 5 well water samples and 3 springs located along a groundwater flow path in a shallow, tuffaceous alluvial aquifer from southern Nevada, USA. The REE concentrations in these groundwaters decrease in the direction of groundwater flow. A previous investigation demonstrated that REE solid-liquid phase partitioning coefficients (i.e., K{sub d}'s) for groundwaters from tuffaceous alluvial aquifers in southern Nevada are relatively high (mean K{sub d} = 10{sup 2.6}). The groundwater REE data, in conjunction with these K{sub d}'s support strong sorption of aqueous REEs to aquifer surface sites as the primary removal mechanism of REEs from these groundwaters. In addition, relatively high aqueous REE concentrations occur at distinct locations along the groundwater flow path. The elevated REE concentrations are explained by addition of deeper groundwaters, influx of geothermal waters from a hot spring system, differences in solution complexation, and/or mixtures of regional and local recharge sources. Solution complexation modeling of REEs in the groundwaters indicate that carbonate complexes account for more than 99% of each REEs in solution. Moreover, groundwater Yb/Nd ratios (a measure of REE fractionation) are associated with alkalinity (HCO{sub 3}{sup {minus}} + CO{sub 3}{sup 2{minus}}; r = 0.71). The datamore » and speciation model results indicate that REE fractionation (i.e., the observed heavy REE, HREE, enrichments compared to rock-sources) is controlled by formation of progressively stronger carbonate complexes in solution with increasing atomic number, which inhibits HREE sorption compared to light REEs (LREE); and a greater affinity for the LREEs to sorb to surface sites in the local tuffaceous alluvial aquifers compared to the HREEs.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Old Dominion Univ., Norfolk, VA (US)
Sponsoring Org.:
USDOE
OSTI Identifier:
20000932
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 63; Journal Issue: 18; Other Information: PBD: Sep 1999; Journal ID: ISSN 0016-7037
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 05 NUCLEAR FUELS; NEVADA; AQUIFERS; GROUND WATER; GEOCHEMISTRY; RARE EARTHS; CONCENTRATION RATIO; LIQUID FLOW; GEOTHERMAL FLUIDS; HOT SPRINGS; MATHEMATICAL MODELS

Citation Formats

Johannesson, K H, Farnham, I M, Guo, C, and Stetzenbach, K J. Rare earth element fractionation and concentration variations along a groundwater flow path within a shallow, basin-fill aquifer, southern Nevada, USA. United States: N. p., 1999. Web. doi:10.1016/S0016-7037(99)00184-2.
Johannesson, K H, Farnham, I M, Guo, C, & Stetzenbach, K J. Rare earth element fractionation and concentration variations along a groundwater flow path within a shallow, basin-fill aquifer, southern Nevada, USA. United States. doi:10.1016/S0016-7037(99)00184-2.
Johannesson, K H, Farnham, I M, Guo, C, and Stetzenbach, K J. Wed . "Rare earth element fractionation and concentration variations along a groundwater flow path within a shallow, basin-fill aquifer, southern Nevada, USA". United States. doi:10.1016/S0016-7037(99)00184-2.
@article{osti_20000932,
title = {Rare earth element fractionation and concentration variations along a groundwater flow path within a shallow, basin-fill aquifer, southern Nevada, USA},
author = {Johannesson, K H and Farnham, I M and Guo, C and Stetzenbach, K J},
abstractNote = {Rare earth element (REE) concentrations were measured in 5 well water samples and 3 springs located along a groundwater flow path in a shallow, tuffaceous alluvial aquifer from southern Nevada, USA. The REE concentrations in these groundwaters decrease in the direction of groundwater flow. A previous investigation demonstrated that REE solid-liquid phase partitioning coefficients (i.e., K{sub d}'s) for groundwaters from tuffaceous alluvial aquifers in southern Nevada are relatively high (mean K{sub d} = 10{sup 2.6}). The groundwater REE data, in conjunction with these K{sub d}'s support strong sorption of aqueous REEs to aquifer surface sites as the primary removal mechanism of REEs from these groundwaters. In addition, relatively high aqueous REE concentrations occur at distinct locations along the groundwater flow path. The elevated REE concentrations are explained by addition of deeper groundwaters, influx of geothermal waters from a hot spring system, differences in solution complexation, and/or mixtures of regional and local recharge sources. Solution complexation modeling of REEs in the groundwaters indicate that carbonate complexes account for more than 99% of each REEs in solution. Moreover, groundwater Yb/Nd ratios (a measure of REE fractionation) are associated with alkalinity (HCO{sub 3}{sup {minus}} + CO{sub 3}{sup 2{minus}}; r = 0.71). The data and speciation model results indicate that REE fractionation (i.e., the observed heavy REE, HREE, enrichments compared to rock-sources) is controlled by formation of progressively stronger carbonate complexes in solution with increasing atomic number, which inhibits HREE sorption compared to light REEs (LREE); and a greater affinity for the LREEs to sorb to surface sites in the local tuffaceous alluvial aquifers compared to the HREEs.},
doi = {10.1016/S0016-7037(99)00184-2},
journal = {Geochimica et Cosmochimica Acta},
issn = {0016-7037},
number = 18,
volume = 63,
place = {United States},
year = {1999},
month = {9}
}