Yann Sivry

Bio-alteration of metallurgical wastes by Pseudomonas aeruginosa in a semi flow-through reactor

Metallurgical activities can generate a huge amount of partially vitrified waste products which are either landfilled or recycled. Lead Blast Furnace (LBF) slags are often disposed of in the vicinity of metallurgical plants, and are prone to weathering, releasing potentially toxic chemical components into the local environment. To simulate natural weathering in a slag heap, bioweathering of these LBF slags was studied in the presence of a pure heterotrophic bacterial strain (Pseudomonas aeruginosa) and in a semi-flow through reactor with intermittent leachate renewal. The evolution of water chemistry, slag composition and texture were monitored during the experiments. The cumulative bulk release of dissolved Fe, Si, Ca and Mg doubled in the presence of bacteria, probably due to the release of soluble complexing organic molecules (e.g. siderophores). In addition, bacterial biomass served as the bioadsorbent for Pb, Fe and Zn as 70-80% of Pb and Fe, 40-60% of Zn released are attached to and immobilized by the bacterial biomass.

Metals in the Aquatic Environment—Interactions and Implications for the Speciation and Bioavailability: A Critical Overview

In most case scenarios, individual metals exist as components in mixtures with organic and inorganic substances and/or particulate matter. While the concepts encompassing mixture toxicity and modeling have been around for decades, only recently have new approaches (dynamic speciation techniques and fate and bioavailability models) been expanded to consider metal mixture scenarios. For example, the kinetic features of humic substances and inorganic colloids on the complexation of metals are generally considered. Although current environmental regulations rarely require an assessment of chemicals mixtures, research on these mixtures in the environment is essential for future regulatory demands and is vital for ensuring adequate environmental protection. Interpretation of speciation and bioavailability data from metal mixtures can be very complex and demanding, due to the existence of kinetic physicochemical transformations of the dynamic components. This kinetic effect largely affects metals’ dynamic speciation, culminating in different transformed metal-containing products with different contributions for the metal uptake by a consuming interface. This manuscript is focused on the environmental fate of metal mixtures, which determines how the mixture is biogeochemically processed and which receptors are most exposed (organisms and exposure route), with a special focus on their dynamic speciation, including a critical evaluation of the current challenges and available dynamic speciation techniques as well as computer codes and models.

Multielementary (Cd, Cu, Pb, Zn, Ni) Stable Isotopic Exchange Kinetic (SIEK) Method To Characterize Polymetallic Contaminations

A new method is proposed to precisely and simultaneously quantify the exchangeable pool of metals in soils and to describe its reactivity at short- and long-term. It is based on multielementary Stable Isotopic Exchange Kinetics (multi-SIEK), first validated by a comparison between two monoelementary radioactive ((109)Cd*, (65)Zn*) IEK experiments, a mono- ((106)Cd) and multi- ((62)Ni, (65)Cu, (67)Zn, (106)Cd, (204)Pb) SIEK. These experiments were performed on a polluted soil located near the Zn smelter plant of Viviez (Lot watershed, France). The IEK results obtained for Cd and Zn were consistent across the experiments. (109)Cd*, (65)Zn* IEK, and multi-SIEK were then applied on 3 non- and moderate impacted soils that also provided consistent results for Cd and Zn. Within these experimental conditions, it can be concluded that no competition occurs between Cd, Zn, and the other metals during SIEK. Multi-SIEK results indicate that the isotopically exchangeable pool of Ni, Zn, and Cu are small (E(Ni), E(Zn), and E(Cu) values up to 17%) whatever the pollution degree of the soils considered in this study and whatever the duration of the interaction. On the contrary, Cd displays the highest E values (from 35% to 61% after 1 week), and E(Pb) displays a maximum value of 26% after 1 week. The multi-SIEK provides useful information on metal sources and reactivity relationship. Ni would be located in stable pedogenic phases according to its very low enrichment factor. The low E(Zn) and E(Cu) are consistent with location of Zn and Cu in stable phases coming from tailings erosion. Though Pb enrichments in soils may also be attributed to tailings particles, its larger exchangeable pool suggests that the Pb-bearing phases are more labile than those containing Zn and Cu. The high mobility of Cd in upstream soils indicates that it has been mostly emitted as reactive atmospheric particles during high temperature ore-treatment.

Testing nanoeffect onto model bacteria: Impact of speciation and genotypes

Abstract The gram-negative bacteria Escherichia coli (E. coli) is a very useful prokaryotic model for testing the toxicity of ZnO nanoparticles (nano-ZnO). This toxicity is often linked to Zn2+ released from nanoparticles in the culture medium, and nano-ZnO dissolution in different media is clearly established. Here, two model E. coli strains MG1655 and W3110 both descendant from the original K-12 showing slight differences in their genome were submitted to nano-ZnO or Zn2+ in order 1 > to refine the nano-ZnO toxicity mechanisms to E. coli, and 2 > to investigate whether toxicity resulted from a real “nanoparticle” effect or from the release of Zn2+ in solution. To do so, both strains were submitted to various concentrations (i.e., 0.1–1 mM) of nano-ZnO or Zn2+ in Luria Bertani (LB) medium. These toxicity studies take into account the nano-ZnO solubility in the culture medium by specifically monitoring the Zn2+ release in our experimental systems. In our experimental conditions, differences in tolerance to nano-ZnO or Zn2+ between both strains were clearly evidenced. W3110 is generally more tolerant to metal than MG1655, the latter showing no real difference in its sensitivity to the two zinc added forms unlike W3110. The differences in behavior between both strains could be attributed to differences in the two genomes as a mutation named “amber” in W3110. Moreover, by using these two closely E. coli strains, a real “nano” effect is here clearly demonstrated providing a model to study the toxicity of ZnO nanoparticles.

Characterization of polymer-coated CdSe/ZnS quantum dots and investigation of their behaviour in soil solution at relevant concentration by asymmetric flow field-flow fractionation – multi angle light scattering – inductively coupled plasma - mass spectrometry

A careful separation, identification and characterization of polymer-coated quantum dots (P-QDs) in complex media such as soil solution is the key point to understand their behaviour and to accurately predict their fate in the environment. In the present study, a synthesized CdSe/ZnS core/shell P-QDs suspension, proved to be stable for at least six months, was investigated with respect to P-QDs dimension, structure and elemental composition. Separation of P-QDs and size distribution determination were carried out by Asymmetric Flow Field-Flow Fractionation (AF4) - Multi Angle Light Scattering (MALS). AF4 and MALS were coupled to Inductively Coupled Plasma-Mass Spectrometry (ICPMS) as a selective and sensitive technique for the detection and the characterization of metallic and metalloid analytes. The exploration of element-specific data obtained by ICPMS after AF4 separation enabled the signal to be deconvoluted reliably. Thus, 3 classes of size populations were identified from the whole population of P-QDs. Additionally, a soil solution and a mix of P-QDs suspension with soil solution were characterized by the same method. This strategy enabled the P-QD population, which interacted with the soil solution, to be determined, this interaction leading either to an aggregation or dissolution of the P-QDs. Reproducibility and recovery of the size distributions and element concentrations were examined for each sample. Complementarily, Dynamic Light Scattering (DLS) and Scanning Transmission Electron Microscopy (STEM) were used jointly with AF4-MALS-ICPMS in order to demonstrate all potentialities of this coupling technique.