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Dissolution of sulfide phases: sulfuricization
When oxic conditions predominate, oxidative dissolution of sulfides occur, and new minerals form; this is known as sulfuricization (Carson et al., 1982; Fanning and Fanning, 1989a). The idealized stages of sulfuricization encompass three steps, which are i. pre-sulfuricization, ii. actively sulfuricizing and iii. post-sulfuricization (Fanning and Fanning, 1989a). In oxygen free matrices (as submerged sediments), sulfides are quite stable. Those stable metal sulfides encompass the pre-sulfuricization step. Upon shifting to sub-oxic or oxic conditions, oxidative dissolution of metal sulfides occurs, and sulfuric acid is produced (actively sulfuricization). Unless carbonates buffer the medium and sulfuric acid reacts with silicates, pH will drop drastically. The capacity to buffer the medium depends, indirectly, on the oxygen supply and the rate of sulfuric acid formation. Thus silicates may partly or completely be decomposed by sulfuric acid, while other minerals might precipitate (Fanning and Fanning, 1989a; Lowery and Wagner, 2012). Moreover, microbial activity accelerates the oxidation rate by up to 34-fold, in comparison to abiotic reactions (Lu and Wang, 2012). Some of the genera that are involved in the oxidation of metal sulfides are Acidithiobacillus, Acidiphilium, Acidiferrobacter, Ferrovum, Leptospirillum, Alicyclobacillus, Sulfobacillus, Ferrimicrobium, Acidimicrobium AND Ferrithrix (Vera et al., 2013). Despite the fact that those genera are predominantly acidophilic, some are mesophilic and moderately thermophilic (Clark and Norris, 1996; Norris et al., 2000). In addition, amorphous, freshly precipitated and particularly fine metal sulfides are more prone to oxidative dissolution in comparison to crystalline, aged and coarse metal sulfides. Studies have shown that oxidative dissolution of freshly formed Fe mono-sulfides, and consequent adsorbed metal release, could happen at a minute scale (Eggleton and Thomas, 2004; Whiteley and Pearce, 2003). When sulfides are completely oxidized, the post-sulfuricization stage is reached. At that point, the pH of the
mediumKFe+ SOis normallyOH superior to 4,CaSOand . sulfateHO minerals are formed, such as jarosite cases, the pH of the medium may be alkaline due to the presence of secondary carbonates. Nonetheless, during the last stage, an acidic pH is usually associated, especially if jarosite minerals were present. AMD due to oxidative dissolution of metal sulfides is also considered as a main metal release (this issue was discussed in section 4.3).
The fate of metals after anoxic sediments are re-oxidized
The oxidation of sediments might happen due to partial or complete resuspension caused by natural events and man-made activities. Natural events include pore water drainage or evaporation, which might be the case of winterbournexvii, ephemeralxviii and intermittentxix rivers, biotic disturbances (bioturbation) of surface sediments, which might be caused by benthic organisms (e.g. amphipods and fish) (Amato et al., 2016), and increase in water flow during flooding events. As for man-made activities, they include sediment dredging, land disposal, possible drainage of wetlands and boat activities (e.g. Calmano et al., 1993b; Du Laing et al., 2009; Simpson et al., 1998; Superville et al., 2014). However, metal sulfide dissolution is pH dependent. For example, oxidation of sulfides was found to be mainly a chemical process at elevated pH (~8), while it was a faster process at much lower pH values (~6.2), since the latter was mediated by microbes (Salomons et al., 1987). In addition, time of oxidation prevailing in the matrix plays a role in the metal sulfide dissolution processes. Some metal sulfides might be more stable than others and have different oxidation kinetics. For example, CuS and FeS2 are less likely to be dissolved during short term resuspension, since they have slow oxidation kinetics (Caetano et al., 2003). Nevertheless, when metal sulfides dissolve, the Fe might be rapidly re-precipitated as Fe oxy-hydroxides (Du Laing et al., 2009), and other dissolved metals might (co)-precipitate as well (Caetano et al., 2003; Eggleton and Thomas, 2004).
Resuspension of metal-laden anoxic sediments
Numerous studies focused on the effect of resuspension of anoxic metal enriched sediments and revealed metal fate (e.g. Caetano et al., 2003; Calmano et al., 1993a, 1993b; Hirst and Aston, 1λ8γ; Simpson et al., β000a, 1λλ8; Vdović et al., β006). The common findings were that sulfides are dissolved and metals are released upon oxidation, which are dependent on several factors, mainly pH and metal species, but also dissolved oxygen, biotic activity, redox potential, salinity, time of resuspension, temperature, sediment:water ratio, carbonate content (buffering capacity), shear stress and initial mineral phases and their stabilities. In some of those studies, metals, such as Cd, Cu, Pb and Zn, were found to change from sulfide phases to weaker bound carbonates and exchangeable fractions upon resuspension (Calmano et al., 1993b; Zoumis et al., 2001). In other studies, oxidation lead to increased metal release (Cu, Cd, Pb and Zn), especially since the sediments did not have a high acid neutralizing capacity (ANC) (or high buffering capacity). However, part of the released metals were re-(co)-precipitated after some time (> 4 – 5 days), depending on the metal (Calmano et al., 1993a, 1993b). On the ANC, it was seen as one of the major parameters that influenced metal release in a resuspension study. Indeed, ANC can control pH variation upon disturbance of anoxic sediments, as seen with higher ANC of clay rich samples (chlorites, smectites, and other phyllosilicates) over sandy ones (Cappuyns and Swennen, 2010). Finally, the main processes that are related to metal speciation in anoxic sediments are reductive precipitation of sulfides and reductive dissolution of metal oxy-hydroxides. On the contrary, oxidative sulfide dissolution and oxidative metal oxy-hydroxide precipitation are the main players in determining metal speciation in oxic conditions.
The importance of the fate of iron and iron bearing minerals is due to its natural abundance in the environment, its role as metal holding phases, and its significant release from mineral and mining industries (e.g. Cummings et al., 2000, 1999). Iron is the forth abundant element on the Earth’s crust (Marshak, 2011b). Some of the common iron minerals existing in sediments and soils are amorphous ferrihydrite and Fe oxy-hydroxides, crystalline oxides, such as hematite (Fe2O3), magnetite (Fe3O4) and wuestite (FeO), oxy-hydroxides, such as goethite (α-FeOOH), lepidocrocite ( -FeOOH), akaganeite ( -FeOOH) and limonite (FeO(OH).n(H2O)), and carbonates, such a siderite (FeCO3). Moreover, iron sulfides (pyrite FeS2) are common in anoxic conditions (Cornell and Schwertmann, 2003). The focus of the following sections will be on the precipitation and dissolution of iron species, namely Fe sulfides and Fe oxy-hydroxides.
The formation of iron sulfides under anoxic conditions
Even though various metal sulfides might form in anoxic conditions (section 7.1), iron sulfides are the major ones, due to the reactivity of sulfides towards iron (Canfield et al., 1992). In addition, ferric iron is considered as the terminal electron acceptor for bacterial decomposition of organic matter (Tugel et al., 1986), microbial Fe reduction is an important metabolism in freshwater sediments (Jones et al., 1984), and iron is found in contents higher than other metals that might form sulfides (e.g. Mn, Cu, Zn and Pb). Iron sulfides form according to the simplified equation below (Eq. I-9).
As a result, mono- and di-sulfides are formed (FeS and FeS2, respectively). The reactions previously mentioned are not independent ones (Eq. I-1 to Eq. I-9), rather they represent individual reactions of a complex process that depends on the microbial communities, available elements, oxic/anoxic state and other aspects related to the matrix. A traditional idealized chemical reaction representing iron sulfide formation in highly anoxic conditions is shown in Eq. I-10 (Fanning and Fanning, 1989a; Pons et al., 1982).
The case of Fe and Fe bearing minerals
(cubic Fe3S4), marcasite (orthorhombic FeS2) and pyrite (isometric FeS2); pyrite being the most abundant species (Billon et al., 2001; Fanning et al., 2010; Kurek, 2002; Rickard and Morse, 2005). The first two are quiet labile, and are considered as part of the acid volatile sulfides (AVS), which are dissolved very rapidly upon oxidation, while the latter two are relatively more stable. Furthermore, iron sulfide may initially be formed as mackinawite, and subsequent reactions give rise to greigite and pyrite (Billon et al., 2001; El Samrani et al., 2004; Fanning and Fanning, 1989a; Rickard, 1973). Iron sulfides might form from the reduction of several Fe species, such as iron oxides and oxy-hydroxides. Furthermore, freshly formed, poorly crystalline and fine-grained ferrihydrite phases are favorably reduced over aged and crystalline (older) iron oxides, such as hematite, goethite and magnetite (Brennan and Lindsay, 1998; Du Laing et al., 2009; Lynch et al., 2014).
Table of contents :
I. Chapter 1: State of the Art
1. Interests of sediments in environmental studies
2. Sediment formation processes
3. Particle transport and settling in rivers
3.1. Effects of dams on sedimentation
3.2. Transformations of suspended matter and surface sediments
4. Origin of metallic elements in sediments
4.1. Geochemical background of metals
4.2. Atmospheric deposition of metals
4.2.1. Natural sources of atmospheric depositions
4.2.2. Anthropogenic sources of metals
4.3. Metal release due to mining activities
4.4. Metal input resulting from agricultural activities
5. Sediments: a reservoir of deposited materials and a record of industrial activities
5.1. Contribution of grain sizes on the mineralogical and chemical composition
6. Assessing the age of sediments using 210Pbxs and 137Cs
7. Fate of metals and minerals in river sediments
7.1. Precipitation of metal sulfides in anoxic conditions: sulfidization
7.2. Dissolution of sulfide phases: sulfuricization
7.3. The fate of metals after anoxic sediments are re-oxidized
7.3.1. Resuspension of metal-laden anoxic sediments
8. The case of Fe and Fe bearing minerals
8.1. The formation of iron sulfides under anoxic conditions
8.1.1. The emergence and detection of framboïdal pyrites
8.2. Dissolution of iron sulfides upon oxidation of anoxic sediments
8.3. On the dissolution of sulfides and precipitation of Fe oxy-hydroxides
8.4. Precipitation of Fe oxy-hydroxides
8.5. Iron in the context of mining and steelmaking
9. The case of Zn and Zn bearing minerals
9.1. The fate of zinc in submerged sediments
9.2. The fate of Zn under oxic conditions
9.3. Fate of zinc released from steel industries
10. How to distinguish natural sediments from those that have been impacted by anthropogenic activities?
10.1. Geochemical composition and metal contents in sediments
10.2. Using factors and indices compared to the geochemical background to determine the degree of contaminated sediments
10.2.1. Contamination factor
10.2.2. Enrichment factor
10.2.3. Geoaccumulation index
10.2.4. Pollution load index
10.3. Crystalline minerals as a criterion for lithogenic and anthropogenic matter differentiation
10.4. Microscopic tools used in the investigation of sediment mineralogy at a sub-micrometric scale
10.4.1. Complementarity between various techniques for mineral characterization
11. The parameters to follow to understand metal speciation in remobilized sediments
11.1. Carbonates, period of flooding and pH
11.2. Carbonates, pH and sulfides
11.3. Microbial communities, pH and redox potential
11.4. Redox potential, salinity and sulfur
11.5. Period of resuspension, redox potential and salinity
11.6. Organic matter and size of complex
References
II. Chapter 2: A Review on the Orne Watershed and Steelmaking Processes: Past Activities and Sampling Sites
1. Geology of the Orne Watershed, a tributary of the Moselle River
2. Hydrology and physico-chemical parameters of the Orne River
3. The evolution of iron and steelmaking
4. Industrial development near the Orne River
4.1. Steelmaking facilities and outcome on the Orne River area
5. The production of pig or cast iron
5.1. Coal combustion, coke production, and mineralogical and chemical composition
5.2. Iron ore used in Lorraine steelmaking facilities
6. Processes occurring in blast furnaces
7. Steelmaking: production of steel from pig iron
8. Sources and fate of metals inside the blast furnace
8.1. Iron fate in blast furnaces
8.2. Zinc cycle in blast furnaces
8.3. Lead cycle in blast furnaces
9. The output materials of blast furnaces: composition and fate
9.1. Slag composition and usage
9.2. Dust particles emitted from blast furnaces
9.3. Sludge composition and fate
10. Locations of the sampling sites along the course of the Orne River
11. Context of the study
12. Objectives of the study
References
III. Chapter 3: Chemical and Mineralogical Composition of Surface Sediments: Variation Accounted by Lithology, Land Use and Former Industrial Activities
Abstract
1. Introduction
2. Materials and Methods
2.1. Study area and sampling sites
2.2. Sediment preparation for analyses
2.3. Particle size distribution, water content and pH
2.4. Chemical composition of the sediments
2.5. Mineralogy of sediments
2.5.1. Major and crystalline minerals of bulk sediments and clay-sized particles
2.5.2. Sub-micrometric mineral analyses of Orne sediments
3. Results
3.1. Chemical composition as a function of grain size
3.2. Grain size variation, water content and pH of Orne sediments
3.3. Chemical composition of sediments
3.4. Mineralogy of Orne River sediments
3.4.1. Major crystalline minerals, bulk samples and clay fractions
3.4.2. Micrometric to sub-micrometric investigations of surface sediments (SEM and TEM)
4. Discussion
4.1. Influence of grain size on the chemical and mineralogical composition of sediments
4.2. Particle size properties and water content
4.3. Variation of chemical and mineralogical composition of Orne sediments and possible sources
4.3.1. Detrital elements and clay mineralogy
4.3.2. Carbonates and REEs
4.3.3. Metallic elements and contribution of anthropogenic deposits
4.3.4. Particularity of Fe and Fe bearing phases in Orne sediments
4.3.5. Phosphorous contents and land cover
5. Conclusion
6. Supplementary Material
References
IV. Appendix to Chapter 3: Chemical Composition of Sediments of the Moselle River and Tributaries
1. Introduction
2. Study area and sampling sites
3. Sediment preparation for analyses
4. Chemical composition of sediments of the Moselle River and tributaries
5. Conclusion
References
V. Chapter 4: Iron Mineralogy as a Fingerprint of Former Steelmaking Activities in River Sediments
Abstract
1. Introduction
2. Materials and Methods
2.1. Study area
2.2. Sediment coring
2.3. Sample preparation for analyses
2.4. Physical properties of sediments
2.5. Sediment dating, measurements of 137Cs and excess 210Pb
2.6. Chemical composition of sediments
2.7. Mineralogy of sediments
2.7.1. Bulk and major mineral phases detected by XRD
2.7.2. Millimetric to sub-micrometric analyses: light microscope, SEM and TEM
3. Results
3.1. Visual description, water content and grain size of the sediments
3.2. Dating of Beth sediments
3.3. Chemical composition of sediments as a function of depth
3.4. Mineralogy of sediments
3.4.1. Major crystalline minerals
3.4.2. Identification of main mineral phases using microscopic tools
3.4.3. Iron minerals: crystalline, poorly crystalline and amorphous phases
4. Discussion
4.1. Industrial and natural contributions to the sediment deposits
4.1.1. Natural contributions in Beth sediment deposits
4.1.2. Industrial contributions to the sediments, ferrous and non-ferrous materials
4.2. Evolution of the iron minerals
5. Conclusion
6. Supplementary Materials
References
VI. Appendix to Chapter 4: Sedimentation Upstream the Beth Dam
1. Introduction
2. Recapture of the sediments upstream the Beth dam
3. An insight about Beth deposits
4. Why didn’t 137Cs and 210Pb data provide the age of Beth sediments?
5. Conclusion
References
VII. Chapter 5: Zinc Speciation in Submerged River Sediments Mixed with Steelmaking Wastes in the Orne River, Northeastern France
Abstract
1. Introduction
2. Materials and Methods
2.1. Study area
2.2. Sediment Coring
2.3. Sample preparation for analyses
2.4. Chemical composition of sediments
2.5. Mineralogical composition of sediments
2.6. X ray absorption spectroscopy at the Zn K-edge
3. Results
3.1. Interstitial waters of BETH1402 sediments
3.2. Chemical composition of BETH1402 sediments
3.3. Zn bearing phases revealed by SEM and TEM
3.4. Zn solid speciation using X-ray absorption spectroscopy at the Zn K-edge
3.4.1. Introductory data about XANES spectra and references
3.4.2. XANES spectra of BETH1402 sediments revealing Zn speciation
4. Discussion
4.1. An insight about the sources and fate of Zn in blast furnaces
4.2. Origin and fate of Zn in BETH1402 sediments
4.3. Zn speciation in BETH1402 sediments
4.3.1. Clays as Zn bearing minerals, with focus on Fe-aluminosilicates
4.3.2. Sorption of Zn onto carbonates, ferrihydrite and oxy-hydroxide
4.3.3. Zn sulfides: the predominant Zn species
5. Conclusion
References
VIII. General Discussion, Conclusion and Perspectives
1. General discussion
2. General conclusion
3. Perspectives
3.1. Recommendations on the management of metal rich sediments
