•55% biosorption of chromium ions was achieved under optimum conditions.•After bioremediation by S. macrogoltabida only Cr(III) present in bulk solution.•XPS studies confirmed the presence of Cr(III) ...on the bacterial cell surface.•Extracellular bioreduction of Cr(VI) validated by chromate reductase assay tests.•Biosorption and bioreduction processes govern Cr(VI) bioremediation mechanism.
Bioremediation studies of toxic hexavalent chromium (Cr(VI)) were investigated using an indigenous bacterial strain namely, Sphingopyxis macrogoltabida SUK2c, isolated from water samples collected from the Sukinda Valley in Odisha, India. A maximum Cr(VI) biosorption of about 55% could be achieved using the isolate for an initial Cr(VI) concentration of 4 mg L−1. The Cr(VI) biosorption isotherm was found to follow a typical Langmuirian behaviour. The Gibbs free energy value of Cr(VI) biosorption obtained was -25.6 kJ/mol, indicative of the involvement of chemical binding forces. The Cr(VI) biosorption process followed pseudo second order kinetics. FTIR spectral studies revealed that carboxyl, hydroxyl, amino and phosphate groups present on bacterial surface were involved in the complexation process. XPS studies confirmed the involvement of Cr(III) in addition to Cr(VI) ions with the bacterial cell surface. Zeta potential studies showed that the bacterial cells became less negative after interaction with Cr(VI), which further corroborated the binding of positively charged Cr(III) on the cell surface. The marginal shift in iso-electric point for Cr(VI) interacted bacteria further testified to the involvement of chemical binding forces in the bioremediation process. The results of the chromate reductase and Bradford protein assay tests performed on the extracellular component of the isolate also confirmed the involvement of extracellular protein in the reduction of Cr(VI) to Cr(III).
Correct characterization of metal speciation and reactivity is a prerequisite for the risk assessment and remedial activity management of contaminated soil. To better understand the intrinsic ...reactivity of Pb and Zn, nine heavily and poorly contaminated soils were investigated using the combined approaches of chemical extractions, multi-element stable isotopic dilution (ID) method, and multi-surface modelling. The ID results show that 0.1–38% of total Pb and 3–45% of total Zn in the studied soils are isotopically exchangeable after a 3-day equilibration. The intercomparison between experimental and modelling results evidences that single extraction with 0.43 M HNO3 solubilizes part of non-isotopically exchangeable fraction of Pb and Zn in the studied soils, and cannot be used as a surrogate for ID to assess labile Pb and Zn pools in soil. Both selective sequential extraction (SSE) and modelling reveal that Mn oxides are the predominant sorption surface for Pb in the studied soils; while Zn is predicted to be mainly associated with soil organic matter in the soil with low pH and Fe/Mn oxides in the soils with high pH. Multi-surface modelling can provide a reasonable prediction of Pb and Zn adsorption onto different soil constituents for the most of the studied soils. The modelling could be a promising tool to decipher the underlying mechanism that controls metal reactivity in soil, but the submodel for Mn oxides should be incorporated and the model parameters, especially for the 2-pK diffuse layer model for Mn oxides, should be updated in the further studies.
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•0.1–38% of total Pb and 3–45% of total Zn are isotopically exchangeable in the studied soils.•Selective sequential extraction could not assess the ‘real’ metal speciation.•Mn oxides are the major sorption surface for Pb in the studied soils and should be incorporated into multi-surface model.•The parameters in the 2-pK diffuse layer model for metal binding to Mn oxides should be updated.
Pb and Zn have different affinities during sorption to soil constituents, multi-surface modelling is a useful tool to decipher the intrinsic metal reactivity and speciation in soil.
The natural river water certified reference material SLRS‐5 (NRC‐CNRC) was routinely analysed in this study for major and trace elements by ten French laboratories. Most of the measurements were made ...using ICP‐MS. Because no certified values are assigned by NRC‐CNRC for silicon and 35 trace element concentrations (rare earth elements, Ag, B, Bi, Cs, Ga, Ge, Li, Nb, P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl, W, Y and Zr), or for isotopic ratios, we provide a compilation of the concentrations and related uncertainties obtained by the participating laboratories. Strontium isotopic ratios are also given.
Le matériau de référence certifié d'eau de rivière naturelle SLRS‐5 (NRC‐CNRC) est analysé régulièrement comme contrôle qualité par dix laboratoires français étudiant les éléments majeurs et en trace dans les solutions naturelles. La plupart des mesures sont réalisées par ICP‐MS. Le silicium et 35 éléments en trace (terres rares, Ag, B, Bi, Cs, Ga, Ge, Li, Nb, P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl, W, Y et Zr) ne sont pas certifiés par NRC‐CNRC. Aucun rapport isotopique n'est disponible. Nous proposons, pour ces éléments, des valeurs moyennes et leurs incertitudes associées obtenues par les différents laboratoires participants. Le rapport isotopique de Sr est aussi mesuré.
With the increasing integration of nanomaterials into daily life, the potential ecotoxicological impacts of nanoparticles (NPs) have attracted increased attention from the scientific community. This ...study assessed the ecotoxicity of ZnS quantum dots (QDs) doped with varying molar concentrations of Mn
on
. The ZnS:Mn QDs were synthesized using the polyol method. The size of the ZnS:Mn QDs ranged from approximately 1.1 nm to 2 nm, while the aggregation size in Seine River water was 341 nm at pH 6 and 8. The presence of ZnS:Mn (10%) NPs exhibited profound toxicity to
, with immediate reductions in viability (survival cells) from 71%, 60% to 51%, 52% in BG11 and Seine River water, respectively, at a concentration of 100 mg L
of ZnS:Mn (10%) NPs. Additionally, the ATP content in
significantly decreased in Seine River water (by 20%) after 3 h of exposure to ZnS:Mn (10%) NPs. Concurrently, SOD activity significantly increased in Seine River water, indicating that the ZnS:Mn (10%) NPs induced ROS production and triggered an oxidative stress response in microalgae cells.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The need to quantify engineered nanoparticles (ENPs) in the environment is due to the increasing incorporation of these particles in the daily products, which threatens human health and can possibly ...impact natural systems. Ceria NPs (CeO2NPs) and titanium dioxide NPs (TiO2NPs) are two of the most used ENPs in the world. In this study their occurrence was determined in river waters with accurate and relevant techniques such as single particle ICP-MS (spICPMS). In the Loire River (France), the variation of both CeO2NPs and TiO2NPs could be assessed locally, with an increase of the concentrations near a wastewater treatment plant (WWTP) outlet as well as in a lake connected to the river and dedicated to outdoor activities. In the upstream river water, supposedly less impacted by NPs, 6.4 ± 1.2 x 104 part mL-1 Ce-bearing and 13.4 ± 1.8 x 104 part mL-1 Ti-bearing particles were measured. These values increased to 33.9 ± 3.4 x 104 part mL-1 Ce-bearing and 80.3 ± 3.4 x 104 part mL-1 Ti-bearing particles near the WWTP outlet. Equivalent size for sphere distributions ranged from 24 nm to 70 nm for CeO2 and from 80 nm to 500 nm for TiO2 in the river water. In the lake, a raise of the concentrations has been observed with 38.3 ± 2.0 x 104 part mL-1 and 71.6 ± 2.1 x 104 part mL-1 containing Ce and Ti, respectively, with similar size distributions. FEG-SEM imaging confirms the occurrence of Ce- and Ti-bearing particles in the water samples. On the contrary, NPs seem to undergo strong heteroaggregation in the Loire river water. The Ce/La elemental ratios does not evolve from upstream to downstream the WWTP outlet, suggesting that a natural origin cannot be excluded to explain the increase observed in NPs number concentration. On the contrary, the Ce/La ratio increases in the outdoor activities center, which suggests the contribution of NPs potentially related to the cars parked nearby. Besides, elemental ratios Ti/V and Ti/Y have been assessed to highlight an anthropogenic source of Ti in both sampling sites, possibly to the sunscreens used during the summer.
Motivation for detecting engineered nanoparticles (ENPs) in the environment comes from a need to understand fate and behavior of these materials in natural matrices. The difficulty lies in the low ...expected ENP particle number concentration (PNC) and the presence of a large and variable background concentration of natural NPs. We report the PNCs and characteristics of cerium-bearing nanoparticles (Ce-NPs) and titanium-bearing nanoparticles (Ti-NPs) in an aquatic matrix (the Seine River and three of its tributaries) with the use of single particle ICP-MS (spICPMS) and electron microscopy (FEG-SEM). Ce-bearing and Ti-bearing particles were observed in suspended particulate matter collected onto 0.2 μm and 1 kDa filters, using FEG-SEM imaging. At Marnay-sur-Seine, the upstream point, PNCs for Ce-NPs and Ti-NPs were 0.47 ± 0.07 × 10
6
and 1.35 ± 0.17 × 10
6
particles as measured by spICPMS. The maximum PNC for both Ce-NPs and Ti-NPs, 1.59 ± 0.10 × 10
6
particles mL
−1
and 5.89 ± 0.10 × 10
6
particles mL
−1
, respectively, were found in the Marne River, a major tributary to the Seine. It was shown that downstream of each confluence, an increase in the PNC of the Seine is observed, suggesting a significant contribution of the different tributaries. Mass balance of particles flows and elemental ratios of Ce/La showed that in the Marne and the Oise River, a contribution of natural CeO
2
NPs exists. The anthropogenic contribution in TiO
2
ENPs for the Marne River was further assessed with Ti/Al, Ti/V, and Ti/Y elemental ratios. Near constant element ratios in the Seine below the Orge River and Paris city suggest neither contribute significantly to Ce or Ti NP concentrations. The study provides further investigation of the strengths and limitations of the application of spICPMS to natural samples and contributes data to the currently highly-limited dataset on natural NP backgrounds in rivers, information that is key to assessing the potential for quantifying the input of ENPs to surface waters. Of the total mass of Ce and Ti, 83 and 90%, respectively, could be detected as particles by spICPMS.
(Bio)leaching Behavior of Chromite Tailings Bolaños-Benítez, Viviana; Van Hullebusch, Eric D.; Lens, Piet N.L. ...
Minerals,
06/2018, Letnik:
8, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Chromite beneficiation operations in Sukinda valley (India) produce large amounts of tailings, which are stored in open air. In this study, bioleaching experiments were carried out in batch reactors ...with Acidithiobacillus thiooxidans or Pseudomonas putida in order to determine the potential leachability of metals contained in these tailings due to biological activity. Acidic and alkaline pH resulted from the incubation of tailings with A. thiooxidans and P. putida, respectively. Tailings were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM), and chemical extraction of Cr(VI) with KH2PO4 was performed. Mineralogical investigations showed that tailings are mainly composed of chromite, hematite, lizardite, chlorite, and goethite, which are all known as Cr-bearing phases. During the leaching with A. thiooxidans and P. putida, total Cr was initially extracted as Cr(VI) due to the presence of phosphates in the medium, and subsequently decreased because of Cr(VI) adsorption and reduction to Cr(III). Reduction was associated with bacterial activity, but also with the presence of ferrous iron. Despite the occurrence of siderophores in the tailings after incubation with P. putida, under acidic conditions, Fe extracted remained higher. Extracted Ni, Mn, and Al concentrations also increased over time. Given the significant amount of chromite tailings produced every year, this study shows that tailings storage and leachability represent a potential source of chromium. However, our findings suggest that the presence of bacterial communities, as well as physicochemical processes, favor Cr(VI) reduction.
The difficulties when studying the behavior of engineered nanoparticles (ENPs), and the subsequent metal speciation in aquatic ecosystems, at concentrations relevant of environment (i.e. ppt level) ...are often related to the occurrence of ENPs constitutive elements at high concentrations as a background in aquatic media (i.e.). In this study, the physico-chemical behavior of CdSe/ZnS quantum dots (QDs) when spread at very low concentration in surface waters was investigated. The above-mentioned issues were overcome with the use of isotopically labeled QDs, separated by centrifugal ultrafiltration (CU) and measured by HR-ICP-MS, combined with the detection of free and labile metal ions by Scanned Stripping ChronoPotentiometry (SSCP). They firmly provided a thorough comprehension regarding the transformation of QDs in surface waters. The physicochemical conditions of the medium including the presence of an analogue of natural organic matter and a mineral (i.e. fulvic acid, goethite), the manufactured coating of the QDs (here thioglycolic acid), and the occurrence of added Zn in the medium, were considered in the study. The overall results show that, in the absence of mineral/organic matter, the TGA ligands in solution detached from the QDs surface after dissolution control the metal ions speciation, especially for Cd. Conversely in a more representative aquatic ecosystem conditions (i.e. with Zn in the background media together with fulvic acid and goethite), almost no Zn nor Cd dissolution from the QDs is detected. SSCP measurements reveal that the Zn complexes formed with the organic/mineral material in the system are inert, whereas the speciation model calculations indicated that Cd2+ is bound to TGA ligands in solution and organic/inorganic matter – therefore suggesting that, under the studied conditions, aquatic organisms will be exposed to a very low concentration of free and labile metal ions issued from the QDs.
A microbial sensor, namely carbon paste electrode (CPE) modified with Citrobacter freundii (Cf–CPE) has been developed for the detection of hexavalent (Cr(VI)) and trivalent (Cr(III)) chromium ...present in aqueous samples using voltammetry, an electroanalytical technique. The biosensor developed, demonstrated about a twofold higher performance as compared to the bare CPE for the chosen ions. Using cyclic voltammetry and by employing the fabricated Cf–CPE, the lowest limit of detection (LLOD) of 1x10−4 M and 5x10−4 M for Cr(VI) and Cr(III) ions respectively could be achieved. By adopting the Differential Pulse Cathodic Stripping Voltammetric technique, the LLOD could be further improved to 1x10−9 M and 1x10−7 M for Cr(VI) and Cr(III) ions respectively using the biomodified electrodes. The reactions occurring at the electrode surface‐chromium solution interface and the mechanisms of biosorption of chromium species onto the biosensor are discussed. The stability and utility of the developed biosensor for the analysis of Cr(VI) and Cr(III) ions in chromite mine water samples has been evaluated.
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