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Institut de minéralogie, de physique des matériaux et de cosmochimie

Biomineralization and natural attenuation of pollution at redox interfaces

Importance of biogenic sulfides (FJ, GO, GM, MB, JB, CM). The mechanisms of metal sulfides formation in low temperature environments and their role in trace metal biogeochemistry remain incompletely understood. During the CIFRE thesis of Vincent Noël (2011-2014) with Koniambo Nickel SAS, we showed by electron microscopy and EXAFS spectroscopy that nickel co-precipitates with pyrite in the mangrove sediments of New Caledonia [Noël et al. 2014, 2015] (Figure 2). Such a formation of nickel-bearing pyrite in mangrove sediments naturally contributes to the protection of the lagoon, classified as a World Heritage Site by UNESCO, against metal inputs related to the erosion of lateritic nickel deposits. However, the oxidation of these pyrites by the tidal cycles mobilizes aqueous nickel to the pore water, which could facilitate its transfer to the lagoon [Noël et al. 2015]. This remobilization may also contribute to bioaccumulation of nickel, which is observed up to exceptionally high concentrations in some mangrove leaves, although the roots seem to limit the translocation of metals [Marchand et al., 2016].


Figure 1

Nickel-bearing pyrites in mangrove sediments of New Caledonia. The microcrystalline Ni-rich pyrites are the most sensitive to re-oxidation by oxygen rich-water brought by the rising tide. Their oxidation causes partial remobilization of nickel toward the sediment pore water, and ultimately, toward the lagoon [Noël et al. 2015].



In this context, we have also investigated the role of sulfate-reducing bacteria in the formation of metal sulfides with model microorganisms as Desulfovibrio sp. or native bacterial consortia isolated from mangrove sediments. In this work conducted during the thesis of Maya Ikogou (2013-2016) granted by ANBG (Agence Nationale des Bourses du Gabon), we have highlighted some key steps of a sustainable nickel sequestration in biogenic iron sulfides [Ikogou et al. 2016]. These results open particularly interesting perspectives for future studies that are scheduled by the MinEnv team in that field and that will help to elucidate the mechanisms involved in the formation of metal sulfides in low temperature sedimentary environments.

Downstream of the nuclear cycle (TA, GM, JB, SL). The nuclear fuel cycle generates large quantities of mine tailings in which it is important to identify the speciation and mobility of residual radionuclides, in order to evaluate the environmental impact of this industrial heritage. In the framework of the thesis of Guillaume Othmane (2009-2012) under the direction of T. Allard, N. Menguy (PR UPMC IMPMC) and M. Fayek (Manitoba Univ.) we have determined the chemical forms of uranium in tailings from the Uranium City site in Canada [Othmane et al. 2013a], as well as in the opals of the Nopal deposit in Mexico [Othmane et al. 2013b; 2016].

At Uranium City, uranium is present mainly as uranyl groups adsorbed at the surface of ferrihydrite and  chlorites. Uranium trapping therefore relies on sorption processes in these fine-grained tailings (Figure 3). In Nopal, we have demonstrated the presence of a rare mineral, vorlanite (CaUO4), and uranyl in the form of phosphate or hydroxo-polynuclear complexes, all trapped in silica. Luminescence, often used for prospecting, is here proposed as a pH probe for the formation of opals, with reference to various synthesis conditions explored in parallel at the laboratory.

With IRSN, we analyze the speciation and mobility of uranium in lake sediments impacted by old mining activities. This research has been especially conducted within the framework of the NEEDS-USEDIM project 2013-2015. We have shown that uranium is essentially present in the form of U(IV) sorbed complexes and as nanocrystalline U(IV) phosphates in these sediments [Morin et al. 2016]. This result calls into question the classical view of the immobilization of uranium in the form of insoluble UO2, with implications for the behavior of uranium during change of redox conditions, especially after sediment removal. This latter issue is studied in the NEEDS-RUMBA project 2016-2017, in which U contaminated sediments are subjected to oxic or anoxic incubations in order to mimic surface storage scenarios.


Figure 2

Uranyl sorption complexes on amorphous hydrated iron oxyhydroxides (HFO) and chlorite, identified by EXAFS in the tailings of Gunnar, Uranium City, Canada. TEM-EDXS directly shows the association of U with HFO [Othmane et al. 2013a].


Biomineralization of metalloids and radionuclides in biofilms (GM, GO, JB, SL). Our insights into the mechanisms of biomineralization of iron have highlighted the importance of biogenic iron phosphates. We have shown, for example, that amorphous ferric phosphates, that are major constituents of bacterial ferritin, are precursors of the intracellular formation of magnetites [Baumgartner et al., 2013]. We have also contributed to show that microbial iron phosphates control the phosphorus cycle in some lake environments [Cosmidis et al. 2014]. In addition, nanocrystalline and amorphous iron phosphates are capable of trapping metalloids such as arsenic [Muehe et al. 2016] and radionuclides in biofilms [Seder Colomina et al. 2014, 2015a]. In the course of the thesis of Marina Seder Colomina (2011-2014) conducted with the University of Paris Est and IRSTEA, we have demonstrated the trapping of uranium by iron phosphates fixed on filamentous neutrophilic bacteria [Seder Colomina et al. 2015b].


Figure 3

EXAFS spectroscopy at the U LIII-edge showing uranyl UO22+ sorption complexes at the surface of amorphous iron phosphates. These amorphous mineral phases precipitated on the surface of filamentous bacteria of the Sphaerotilus natans type which can form fixed biofilms. [Seder-Colomina et al. 2015].

With Pierre le Pape (Post-Doc at IMPMC 2015-2016 granted by ANR project ECOTS INGECOST-DMA 2014-2016) we have contributed to the development of bioremediation processes based on the fixation of arsenic in biofilms, a promising route for the treatment of contaminated waters, especially mine-drainage waters. Under oxidizing conditions, arsenic is treated by sorption or incorporation in biogenic nanocrystalline iron hydroxysulfates, whose structure and solubility depends on arsenic oxidation state [Maillot et al. 2013]. This parameter is now followed in a simple way on the pilots and in the field [Resongles et al. 2016] and is mainly controlled by microbial diversity through iron- and arsenic-oxidizing activities [Volant et al. 2012]. In turn, the natural attenuation of arsenic in the mine drainage influences the diversity of eukaryotic microorganisms [Volant et al. 2016]. Under reducing conditions, Pierre Le Pape's work in collaboration with BRGM demonstrated the feasibility of treating arsenic acid mineral waters by a consortium of sulfate-reducing bacteria capable of precipitating arsenic sulfides: realgar and orpiment [Le Pape et al. 2016].

Nano-oxides for pollutants remediation (GO, GM, FJ). Ferrihydrite, the structure of which having been debated [Guyodo et al. 2012], is a poorly ordered nanocrystalline iron oxyhydroxide that has been recognized as a major phase controlling pollutant sorption in natural and engineered systems. The impurities present in natural ferrihydrites (Al, Si, P, S ...) can modify their structure, their formation and evolution [Miot et al. 2016] and their sorption properties with respect to contaminants. In the thesis of Areej Adra (2010-2014), we have demonstrated for the first time that aluminum substituted ferrihydrites scavenge arsenic in river sediments downstream from the heavily arsenic-impacted Carnoulès Mine, Gard [Adra et al. 2013]. We have also shown that the presence of iron-substituted aluminum in ferrihydrite significantly modifies the arsenic sorption efficiency, with different effects for As(III) and As(V) [Adra et al. 2016].

Meanwhile, a new direction of our work has been dedicated to the search for remarkable surface properties of natural and synthetic nanoparticles toward contaminants. For instance, nanomagnetites efficiently trap inorganic contaminants such as arsenic [Wang et al. 2014]. In addition to these sorption properties, we have recently shown that, nanomagnetite exhibits a particular surface reactivity under oxidizing conditions, which allows the production of reactive oxygen species (ROS) capable of oxidizing and degrading organic pollutants adsorbed at its surface [Ardo et al., 2015]. This new process, which does not require strong oxidants, was the subject of a declaration of invention at the UPMC / CNRS / INRA. This work was carried out during Sandy Ardo's PhD thesis (2011-2014) with Sylvie Nelieu (INRA) as part of a Technological Innovations project of the Ile-de-France Research Network on Sustainable Development (R2DS) in the IdF region.

Some biogenic nanoparticles can also behave as chemical reducers for a wide variety of pollutants, thus offering interesting prospects for alternative water treatment processes. In particular, we validated a new mechanism for reducing nitrate ions by means of a patent filed during the ANO ECOTECH (2010-2013) [Guerbois et al., Patent 2014 – CNRS/UPMC WO2014125217A2], conducted in collaboration with the LCPME in Nancy and several industrial partners (SAUR and Marion-Technology) [Guerbois et al. 2014 ; Ruby et al. 2016]. These themes will be pursued over the next years by promoting interaction with the partners of axis 3 "Interfaces, transport, reactivity in natural media" of LABEX MATISSE. 



Figure 4

Remarkable properties (A) of nanomagnetite able to oxidize organic contaminants via Fenton-like reactions [Ardo et al. ES & T 2015] and (B) of biogenic hydroxycarbonate green rust, a lamellar iron hydroxide mineral able to reduce nitrite ions to nitrogen gases [Guerbois et al. ES&T 2014].


Cécile Duflot - 21/11/17

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