Modeling rare earth elements binding to humic acids with model VII

Marsac, Rémi; Catrouillet, Charlotte; Davranche, Mélanie; Coz, Martine Bouhnik‐Le; Briant, Nicolas; Janot, Noémie; Otero-Fariña, Alba; Groenenberg, J.E.; Pédrot, Mathieu; Dia, Aline

doi:10.1016/j.chemgeo.2021.120099

Cited by 32 publications

(39 citation statements)

References 54 publications

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“…6), although this is limited to a zone just below the SWI. This is in line with previous studies that have suggested the competition between PO4 3and other anions for complexation with La 3+ (aq), given that La-DOC is a thermodynamically favourable complex 61 .…”

Section: Coupling Of P Cycling To That Of Fe La and Docsupporting

confidence: 93%

“…It was assumed that DOM: (i) comprised 50% C, (ii) was 50% chemically active and (iii) was composed of humic acids (HA) only. The most recently optimized binding parameters for La and HA were taken from 61 . The PHREEQC-Model VII coupling is described elsewhere 62, 63 .…”

Section: Porewater Analysismentioning

confidence: 99%

“…Under oxygenated conditions, Fe 2+ is rapidly oxidized to Fe 3+ and precipitates as Fe oxyhydroxides 85 . In an oxic system dominated by Fe oxyhydroxides, DOC is available to bind La 3+ , with available PO4 3adsorbing on the freshly precipitated Fe 3+ oxyhydroxides 24,33,34,61 . Visual inspection of the profiles on Fig.…”

Section: Coupling Of P Cycling To That Of Fe La and Docmentioning

confidence: 99%

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Response of sediment phosphorus partitioning to lanthanum-modified clay amendment and porewater chemistry in a small eutrophic lake.

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Sustained eutrophication of the aquatic environment by the remobilization of legacy phosphorus (P) stored in soils and sediments is a prevailing issue worldwide. Fluxes of P from the sediments to the water column, referred to as internal P loading, often delays the recovery of water quality following a reduction in external P loads. Here, we report on the vertical distribution and geochemistry of P, lanthanum (La), iron (Fe) and carbon (C) in the culturally eutrophied Lake Bromont. This lake underwent remediation treatment using La- modified bentonite (LMB) commercially available as PhoslockTM. We investigated the effectiveness of LMB in decreasing soluble reactive phosphorus (SRP) availability in sediments and in reducing dissolved fluxes of P across the sediment-water interface. Sediment cores were retrieved before and after LMB treatment at three sites representing bottom sediment, sediment influenced by lakeside housing and finally littoral sediment influenced by the lake inflow. Sequential extractions were used to assess changes in P speciation. Depth profiles of dissolved porewater concentrations were obtained after LMB treatment at each site. Results indicate that SRP extracted from the sediments decreased at all sites, while total extracted P (PTOT) bound to redox-sensitive metal oxides increased. 31P NMR data on P extract reveals that 20-43% of total solid-phase P is in the form of organic P (Porg) susceptible to be released via microbial degradation. Geochemical modelling of porewater data provides evidence that LaPO4(s) mineral phases, such as rhabdophane and/or monazite, are likely forming. However, results also suggest that La3+ binding by dissolved organic carbon (DOC) hinders La-phosphate precipitation. We rely on thermodynamic modelling to suggest that high Fe2+ would bind to DOC instead of La3+, therefore promoting P sequestrations by LMB under anoxic conditions.

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Section: Coupling Of P Cycling To That Of Fe La and Docsupporting

confidence: 93%

Section: Porewater Analysismentioning

confidence: 99%

Section: Coupling Of P Cycling To That Of Fe La and Docmentioning

confidence: 99%

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Response of sediment phosphorus partitioning to lanthanum-modified clay amendment and porewater chemistry in a small eutrophic lake.

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“…Model simulations paired with field studies in terrestrial waters revealed that humic acids are able to complex dREEs. These organic REE complexes can occur in large quantities and in even higher abundances than inorganic carbonate complexes (Tang and Johannesson, 2003;Sonke and Salters, 2006;Pourret et al, 2007;Marsac et al, 2011;Marsac et al, 2021). However, terrestrial waters have lower carbonate concentrations than seawater, so that these findings of competition between carbonate and OM as dissolved ligands cannot be transferred directly to seawater.…”

Section: Introductionmentioning

confidence: 99%

Rare earth element behaviour in seawater under the influence of organic matter cycling during a phytoplankton spring bloom – A mesocosm study

et al. 2022

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Rare earth elements (REEs) are used as powerful proxies for a variety of oceanic processes. The understanding of their biogeochemical behaviour in the marine environment is therefore essential. While the influence of OM-cycling on REE patterns in seawater is considered as insignificant, it has been shown that algae and bacteria provide good sorption surfaces for REEs and that components of the dissolved OM pool are able to complex REEs, thus potentially altering their behaviour. To investigate the impact of bio-associated processes on REEs in the bio-productive marine environment, we conducted an indoor mesocosm experiment that mimicked a phytoplankton spring bloom in the neritic coastal North Sea. The incubation period of 38 days covered two distinct phytoplankton bloom phases (diatoms followed by Phaeocystis sp.) and an interjacent bacterioplankton maximum. All dissolved REEs (dREEs) except samarium showed similar temporal concentration patterns, which were closely connected to the bloom succession. The concentration patterns were shaped by the ‘phytoplankton-shuttle’, which summarizes adsorption processes on phytoplankton-derived particulate OM (POM) and resulted in decreasing dREE concentrations alongside chlorophyll-a and POM maxima. The ‘heterotrophic-shuttle’ resulted in increasing dREE concentrations likely linked to heterotrophically mediated regeneration of POM and associated desorption processes. The effect of these processes on dREEs resulted in enhanced fractionation of light REEs (LREEs) relative to heavy REEs (HREEs) during adsorption processes and decreased fractionation as a result of desorption. At times of high dissolved organic carbon (DOC) concentrations, we observed a stabilization of especially dHREEs likely in organic complexes. To test the potential influence of DOC on dREEs, we used a PHREEQC model approach that revealed dREE complexation with components of the DOC pool and an increase in complexation with atomic mass of the REEs. That is, at high DOC concentrations OM-dREE complexation leads to an effective and preferential buffering of dHREE against adsorption. Our findings reveal that OM-cycling influences concentration patterns of dREEs via ad- and desorption processes as well as organic complexation with parts of the OM pool, suggesting these processes can have a significant impact on dREE concentrations in the natural marine environment under high OM conditions.

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“…Dissolved organic matter (DOM) is ubiquitous in aquatic systems and plays a key role in the environment as it is at the crossroad of multiple biogeochemical cycles. In particular, because of its capacity to form complexes with metal contaminants, the quantification of chemical entities that drive DOM-metal ion interaction is highly required [5] , [6] , [7] , [8] , [9] , [10] . These are mainly acid-base functional groups, which can be determined by acid-base titrations.…”

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An easy spectrophotometric acid-base titration protocol for dissolved organic matter

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Modeling rare earth elements binding to humic acids with model VII

Cited by 32 publications

References 54 publications

Response of sediment phosphorus partitioning to lanthanum-modified clay amendment and porewater chemistry in a small eutrophic lake.

Response of sediment phosphorus partitioning to lanthanum-modified clay amendment and porewater chemistry in a small eutrophic lake.

Rare earth element behaviour in seawater under the influence of organic matter cycling during a phytoplankton spring bloom – A mesocosm study

An easy spectrophotometric acid-base titration protocol for dissolved organic matter

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