Suspended Materials in River Waters Differentially Enrich Class 1 Integron- and IncP-1 Plasmid-Carrying Bacteria in Sediments

International audienc

Les fantômes remontent la Meuse… Observations préliminaires à propos d'un fantôme de roche en forêt de Jaulnay (Lorraine, France)

International audienc

Investigation of using Ni isotopes as anthropogenic source tracer in river sediments: a preliminary study

International audienceIn the past decade, high precision Ni stable isotopes of continental rocks and sediments, river and seawater have been studied and significant isotope variation has been reported [1-4]. Recently, Ni isotope fractionation during ore smelting and refining have been demonstrated, showing that slag holds isotopically heavier Ni than the feeding material and fly ash [5]. These studies showed the potential of using Ni isotopes for anthropogenic source tracing in the environment.As metal pollution in riverine systems poses a serious threat to water and sediment quality, it is of key importance to understand the pollution sources and their fate. Therefore, this study aims to (i) determine the Ni isotopic compositions of two river sediment cores from an industrial surrounded river in northern France and their origin; (ii) assess the movement of the anthropogenic sources in the riverine systems.We observed that 1) the δ60/58NiNIST986 values of the surface river sediments and suspended particles ranged from -0.15 ±0.04‰ to -0.04 ±0.04‰. 2) In the sediment cores, significantly different isotope signatures were measured (from -0.09‰ to -0.53‰ with a cluster around -0.36‰). Nearby natural soil dust, slag tailings could explain the excessive Ni of the river sediments. However, further studies of the isotope fractionation mechanisms in the riverine system are needed to better evaluate the anthropogenic source movements by using Ni isotope signatures as tracers.[1]Cameron et al.,2009,PNAS 106,10944-10948; [2]Cameron and Vance,2014,GCA 128,195-211; [3]Gall et al., 2013, EPSL 375,148-155; [4]Estrade et al.,2015,EPSL 423,24-35; [5]Ratié et al.,2016,APPL GEOCHEM 64, 136-145

Ni isotopic fractionation due to interaction with small organic acids and purified humic acids

International audienceThe biogeochemical cycle of metals in the environment can be considerably influenced by the role of vegetation. Several Ni accumulating plants are able to enrich Ni composition up to 5% in dry leaf matter [1]. Some recent studies have reported a significant Ni isotopic fractionation in hyperaccumulating plants between roots and storage organs, until the maximum absorption is reached (-0.18‰) [2], therefore, the use of stable isotopes can allow to understand the dynamics of trace elements and tracing Ni fate in the soil-plant system and in the environment.Several organic acids are present in plant roots, such as citric or malic, that are involved in soil-plant processes, including metal mobilization and uptake, and plant detoxification [3]. However, up to now, no specific investigations were performed about the potential Ni isotopic fractionation due to complexation with organic acids present in plant roots, or due to adsorption to organic matter in soils. To investigate the potential mechanisms responsible for Ni isotopic fractionation in the soil-plant system, the complexation by two different organic acids, citric and oxalic, with increasing complexation constants, was studied at pH=5 and pH=7. In addition, Ni adsorption onto purified humic acid (PHA) [4] from peats collected in São Paulo State, Brazil, an analog of organic matter, was investigated at pH=7 with PHA concentration of 40mg L-1 and 80mg L-1. According to Visual-MinteQ modeling, in these conditions, free Ni2+ in solution represents 63% and 40% of the total Ni, respectively, which is coherent with the measurements. The Donnan Membrane device (DMT) was used to separate complexed Ni from free Ni2+ after reaching equilibrium. The obtained results revealed that Ni complexation with citric and oxalic acids did not induce any significant isotopic fractionation, whatever the pH considered. On the contrary, in both PHA experiments, Ni complexed with PHA is slightly enriched in heavier isotopes compared to free Ni2+, inducing a Δ60 Nicomplexed-free ranging from 0.1 to 0.2 ‰. [1] Baker A.J.M. (2000), Phytoremediation of contaminated soil and water, Lewis Publishers, 85-107. [2] Estrade et al. (2015), EPSL, 423, 24-35. [3] Jones D.L. (1998), Plant and Soil, 205, 25-44. [4] Swift, R.S. (1996) Methods of soil analysis. D.L. Sparks et al. (eds), 35, 1018-1020

Table ronde sur les aspects "utilisateurs" : intérêts et retours d’expériences de chercheurs et enseignants-chercheurs du site

National audienc

Sediment transport modelling in riverine environments: on the importance of grain-size distribution, sediment density, and suspended sediment concentrations at the upstream boundary

International audienc

Identifying the Anthropogenic Sources in River Sediments with Zn and Pb Isotope Signatures: A Case Study in Northeast France

International audienceThe Orne River is a tributary of Moselle River in the northeastern part of France, which has been strongly modified by steel-making facilities and associated urbanization. As a heritage of the past steel activities, the river displays several dams that were built for blast furnace cooling purpose. Those dams enhance the deposition of highly contaminated material in the riverbed and despite a river dredging in late 1980’s, several spots of steel-making waste are still present in the vicinity of the dams. Those sediment deposits, as deep as 1.3 m in some places, contain high content of Fe, Zn and Pb. In order to follow the eventual re-suspension of those sediments in the water column, a multi-marker study was performed, including the determination of Zn and Pb isotopic fingerprints. This study aims to (i) determine the Zn and Pb isotopic signatures of two dam front river sediment cores and suspended particles (SPM) along the river; (ii) establish the Zn and Pb isotope signatures of local anthropogenic and natural sources; (iii) assess the anthropogenic input sources with the isotope signatures as indicators.The δ66ZnIRMM-3702 values of the river sediments and SPM were shown to range from -0.12 to 1.36 ‰ and -0.12 to -0.05 ‰, respectively, while the 206Pb/204Pb ratio ranges between 18.326 and 18.690 for river sediments and from 18.370 to 18.609 for SPM. Within both cores, the isotope signatures suggest different source origins, including mining tailings, slag and atmospheric deposition. In the bottom 50 cm of the down stream core, the distinctive isotope signatures highlight one more source coming from past activities. Comparing the SPM signatures to the surface sediments show the potential of using isotopic tools to follow sediment re-suspension in the river

Long term behavior of iron and zinc in steelmaking wastes

International audienceBlast Furnace Sludges (BFS), by-products of iron pig making, are characterized by relatively high contents of trace metals (Zn, Pb, Co, Cr) and iron (20-30%) [1, 2]. During the last century, such wastes were released in the environment (soils and aquatic media), and underwent various weathering conditions (anoxic or oxic conditions). Since iron bearing phases are widely reported to readily scavenge trace metals, specific investigations were perfomed to unravel the evolution of both iron and zinc speciation in those various physico-chemical conditions. A set of BFS was collected on ancient sites and from an active iron pig plant, including freshly produced and weathered BFS samples. A multi-scale analysis was performed using the combination of microscopic and microspectroscopic techniques (XRD, TEM, microXRF, and bulk and micro-XAS at the Fe and Zn K-edges). In anoxic conditions, besides the predominance of zinc sulfides, TEM and XAS data evidenced supplementary Zn bearing phases, including Zn adsorbed onto iron oxyhydroxides and Zn inserted in neoformed iron rich phyllosilicates. The neoformed Fe-rich clay minerals appear to be related to the oxidation of metallic iron spheres and/or iron oxides (mainly wustite and magnetite). The latter Fe bearing minerals are ubiquitous in BFS as evidenced by XRD patterns and XAS spectra at the Fe K-edge. Furthermore, TEM investigations strongly suggest a link between the formation of Fe-rich clays and Zn sulfides. In oxic conditions, Zn was shown to be mainly included in double lamellar hydroxydes for high Zn contents (15-20%), or in the neoformed phyllosilicates for lower Zn contents (about 0.1%). [1] Kanbar et al. (2017) Sci. Total Environ. 599–600, 540–553. [2] Kretzschmar et al. (2012) Environ. Sci Technol. 46, 12381-1239