Speciation of rare earth elements in natural terrestrial waters: assessing the role of dissolved organic matter from the modeling approach

Tang, Jianwu; Johannesson, Karen H.

doi:10.1016/s0016-7037(02)01413-8

Cited by 261 publications

(210 citation statements)

References 73 publications

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“…The chemical equilibrium modeling revealed that in the presence of humic substance a considerable part of the La got complexed with the humic substance. This is fully in line with several studies that have shown humic substance to be a strong complexing agent for lanthanides [42,70,71]. The modeling indicated that in the presence of humic acids La was complexed and otherwise would have precipitated with either hydroxyls or carbonate.…”

Section: Discussionsupporting

confidence: 90%

“…The evaluation was performed without and with organic complexation. In the latter case, the models V/WHAM-W [38,39] Humic Ion-Binding Model VI [40] and Humic Ion-Binding Model VII [41] allow for the calculation of equilibrium chemical speciation for waters in which natural organic matter plays a significant role [42]. Hence, the models allow an evaluation of whether humic substance in the enclosures could have formed complexes with the lanthanum from the LMB, thereby lowering the La available for binding P. The input in the model was the mean pH at the start of the experiment (pH = 7.57), a phosphate concentration of 173.5 µg L −1 , and a mean total La concentration (as measured during the first two days of the experiment) of 2846.5 µg L −1 .…”

Section: Chemical Equilibrium Modelingmentioning

confidence: 99%

“…Hence, the models allow an evaluation of whether humic substance in the enclosures could have formed complexes with the lanthanum from the LMB, thereby lowering the La available for binding P. The input in the model was the mean pH at the start of the experiment (pH = 7.57), a phosphate concentration of 173.5 µg L −1 , and a mean total La concentration (as measured during the first two days of the experiment) of 2846.5 µg L −1 . One series also included carbonate (50 mg L −1 ) as, in the pH range of this study, a significant portion of La could be complexed with carbonates [42,43]. The input concentration of humic substances was determined to be 5.05 mg DOC L −1 , which was the mean of the three LMD-treated enclosures.…”

Section: Chemical Equilibrium Modelingmentioning

confidence: 99%

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Effects of Dredging and Lanthanum-Modified Clay on Water Quality Variables in an Enclosure Study in a Hypertrophic Pond

Waajen

Engels²,

Oosterhout

2017

Water

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An enclosure experiment was conducted between July and September 2009 to compare the effectiveness of a phosphate fixative, the lanthanum-modified bentonite clay Phoslock ® (LMB), dredging, and their combination in controlling eutrophication in a hypertrophic urban pond in Heesch, The Netherlands. In total, 25 water quality variables were monitored. Multivariate analysis revealed that the combination LMB-treated and dredged enclosures deviated most from the pond (reference) and the controls, and showed the strongest eutrophication reduction. Overall, dredging significantly increased transparency, lowered turbidity, and improved the oxygen conditions in the enclosures compared to non-dredged ones. Nonetheless, one dredged enclosure deviated dramatically from the others, which might reflect methodological issues with dredging. The LMB treatment appeared to be less effective at mitigating eutrophication than dredging, and phosphate concentrations even increased during the experiment in the LMB-treated enclosures. Chemical equilibrium modeling suggested that humic substances could have formed complexes with lanthanum (La) from the LMB, rendering it unavailable for intercepting P over the course of the enclosure experiment. Residual lanthanum concentrations in combination dredging and LMB treatments exceeded the Dutch standard 10-fold. Total zooplankton abundance, and particularly Cladocera, increased in all enclosures over the course of the experiment. The limited effect of LMB in the enclosure experiment and the violation of the Dutch La standard when combined with dredging disqualify LMB as an intervention agent in the restoration of the pond.

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Section: Discussionsupporting

confidence: 90%

Section: Chemical Equilibrium Modelingmentioning

confidence: 99%

Section: Chemical Equilibrium Modelingmentioning

confidence: 99%

See 1 more Smart Citation

Effects of Dredging and Lanthanum-Modified Clay on Water Quality Variables in an Enclosure Study in a Hypertrophic Pond

Waajen

Engels²,

Oosterhout

2017

Water

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“…We also included Al in these experiments as the presence of trivalent metals is known to affect the speciation and binding of other trace metals (Pinheiro et al 2000;Tang and Johannesson 2003). Note, however, that Al was precluded from more general study since it was prone to interferences from the C18 columns.…”

Section: Resultsmentioning

confidence: 99%

Hydrophobicity and reactivity of trace metals in the low‐salinity zone of a turbid estuary

Turner

Mawji

2005

Limnology & Oceanography

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We chemically fractionated water samples from the low-salinity zone of a turbid estuary (Tamar, UK) using C18 columns to examine the controls on the complexation, hydrophobicity, and reactivity of dissolved trace metals (Co, Cu, Mn, and Pb). The hydrophobic (C18-retained) fraction of metal was related to the solubility of metal in the amphiphilic solvent, n-octanol, and in acid-base titrations and for all metals this fraction exhibited a peak centered around pH 7-8 in both freshwater and brackish water. In freshwater, hydrophobicity decreased in the order Pb Ͼ Cu Ͼ Mn Ͼ Co, and in brackish water, hydrophobicity was either reduced (Cu and Pb) or enhanced (Co and Mn) compared to freshwater, but in all cases peaks were more distinct. Salinity distributions of dissolved trace metals in the estuary indicated significant removal of Co, Cu, and Mn, and a source of Pb that was coincident with the onset of the turbidity maximum, and all distributions could be accounted for empirically by end-member water mixing and sediment resuspension. Salinity distributions of the hydrophobic fraction of metal were not consistent with any variation in water composition (including pH), but revealed that this fraction was preferentially removed from (Co, Cu, and Mn) or added to (Pb) the aqueous phase in the vicinity of the turbidity maximum. Removal implies that hydrophobic species are more reactive than hydrophilic species, and that either re-equilibration between these fractions is not attained within the hydrodynamic timescales of the upper estuary, or new equilibria are established by the buffering effects of additional anions and ligands in the water column. Addition of hydrophobic species of Pb coincided with minimum total and hydrophobic concentrations of Co, Cu, and Mn, and could, therefore, be explained in terms of reduced competition for nonspecific hydrophobic ligands from these and other (e.g., Al) metals in this region of the estuary.

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“…However, our samples were collected with special care to avoid anthropogenic pollutants and biogenic materials, which makes the contribution from organic materials minimal. Recently, Tang and Johannesson (2001) have shown that 1.4~6.2% of total dissolved REE are combined with organic materials for relatively lower level of organic material concentrations. These relatively low values are not serious for affecting REE patterns of the stream waters.…”

Section: Ce Anomalymentioning

confidence: 99%

Rare earth elements in stream waters from the Rokko granite area, Japan: Effect of weathering degree of watershed rocks.

Nakajima

Terakado

2003

Geochem. J.

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The concentrations of major elements and rare earth elements (REE) of the stream waters from the Rokko granite area, Japan, were analyzed to examine the relationship between the degree of weathering and chemistry of the waters. The clay minerals in the related soils from the watershed areas were also examined. It was found that the relative proportion of kaolinite to total clay minerals is a good measure for the degree of weathering of the area. The Ca concentrations of the stream waters are rather high in comparison with other cations such as Na, K and Mg, and are well correlated with HCO 3 -. These facts indicate that the Ca concentrations in the stream waters are largely controlled by dissolution of calcite that occurs as disseminated crystals in granites. The Ca/Na molar ratio in the waters decreases with increasing kaolinite/ clay ratio in the related soils. The high Ca waters tend to occur in the fresh or weakly weathered areas, which is attributed to abundant calcite in these granites. By contrast, in the strongly weathered areas, where calcite had already been consumed via previous weathering processes, low Ca waters occur. The REE abundances, especially light REE, of the stream waters tend to be high in the strongly weathered watershed areas, and low in the fresh or weakly weathered watershed areas. This is attributed to either enhanced REE leaching from rocks in strongly weathered watershed areas due to larger solid surface areas or increased weathering of accessory minerals such as apatite. Interestingly, the magnitude of negative Ce anomalies appears to be inversely related to the degree of weathering. We suggest that the magnitude of Ce anomalies in those waters is largely controlled by mechanical filtration of CeO 2 during infiltration in micro-cracks or pores rather than by Eh-pH conditions.

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Speciation of rare earth elements in natural terrestrial waters: assessing the role of dissolved organic matter from the modeling approach

Cited by 261 publications

References 73 publications

Effects of Dredging and Lanthanum-Modified Clay on Water Quality Variables in an Enclosure Study in a Hypertrophic Pond

Effects of Dredging and Lanthanum-Modified Clay on Water Quality Variables in an Enclosure Study in a Hypertrophic Pond

Hydrophobicity and reactivity of trace metals in the low‐salinity zone of a turbid estuary

Rare earth elements in stream waters from the Rokko granite area, Japan: Effect of weathering degree of watershed rocks.

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