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In the last decades, the amount of dredged sediments (DS) increased in France harbours. Dredged sediments consist of fine soil collected from the deepening, broadening and maintaining of public waterways. The present study reports the investigation of the beneficial reuse of dredged sediments collected from Le Havre (France) harbour as fired material for sustainability requirements. The main challenge is the use of untreated dredged sediments from land deposit of the Seine estuary and port areas as building material, especially for fired bricks manufacture. The chemical, mineralogical and particle size compositions of the raw material were assessed using X-ray fluorescence (XRF), X-ray diffraction (XRD) and laser particle sizer, respectively. The results indicate that the main oxide components are SiO2 and CaO3, while quartz and calcite are the main mineral phases. Lesser amounts of feldspar, chlorite, kaolinite, muscovite and halite were also determined. The physical properties of the raw clay material, including plasticity, organic content and salinity, were investigated in order to assess the product suitability as building material. Ceramic properties such as linear shrinkage, water absorption, bending strength and mineral neo-formations were also investigated in fired bricks at temperatures ranging from 700 to 1000 °C. A high mechanical strength has been obtained at a temperature of 900 °C. The use of ternary diagrams indicates that the raw material falls inside the industrial domain, and ceramic tests show that the raw material could be used in brick making because of its firing behaviour and mechanical resistance. As regards environment sustainability, chemical analysis reveals that the levels of metal traces from leaching tests remain low and within regulatory limits.

In order to maintain a required water depth and to allow waterways navigable, dredging operations are of a great importance. So, large volumes of sediments are annually dredged in the ports over the world. In Le Havre harbor the annual dredged volume of sediments is close to 1.5 Mm3, which are mainly dumped at sea. Because of its perpetual availability and mineralogical characteristics, the sediment is regarded as a suitable raw material for terracotta production. The aim of this work, assessed in laboratory, is to investigate how dredged and deposited sediments from the Seine estuary and port basins can be used as alternative raw material for the heavy clay industry. The chemical and mineralogical composition of dredged sediments were addressed using X-ray fluorescence (XRF) and X-ray diffraction (XRD), respectively. The physical properties, including plasticity index (PI), organic content, and salinity were investigated. The results from all tested sediments in their raw state showed that their chemical and mineralogical compositions are fairly close. However, their low clay minerals content (6.6%) and their high carbonate content (25.2%) constitute a limitation to their use in ceramic industry. The grain size distribution was appraised on a diagram involving three range sizes (clay, silt, sand), and the results indicated that the raw material falls inside the suitable domain of fired-clay products. Additional ceramic tests performed showed that the raw material can be used as bricks making owing to provided interesting properties, such as firing behavior and mechanical resistance. Leaching test was performed on fired bricks in order to assess the environmental suitability of the construction material. In this framework, The SEDIBRIC project is part of the concern of the “sober management of resources” and aims a sustainable remediation with a low impact on the environment and recovery of dredged sediments.

(IF 2.42; Q2); International audience; Geochemical studies are becoming more and more frequent in the context of the increasing pressure of human activities on marine coastal ecosystems and represent an appropriate tool to assess anthropogenic disturbances. Moreover, it is difficult to find discriminant markers. The eastern part of the Bay of Seine (English Channel) is highly impacted by the presence of harbour activities, fishing and sediment extraction. Dredged sediment from the Grand Port Maritime du Havre (GPMH) are deposited at the subtidal Octeville site, in the north-eastern part of the mouth of the Seine estuary (mixed sediment area). To understand natural and anthropogenic sedimentary mechanisms in this area, a geochemical and sedimentological study was conducted at the beginning of 2016. A dense sampling campaign including 179 stations was carried out between Cap de La Hève and Cap d’Antifer. For comparison, sampling was carried out in the harbour (13 samples in basins strongly or very weakly dredged), in the dredged grab itself and in the Seine estuary sediment (one station in the brackish zone and two stations in the river freshwater zone). Elemental compositions were determined by X-Ray Fluorescence spectrometry and infrared spectrometry. Using PCA (Principal Component Analysis), seven constituents were selected (Si, As, S, Pb, Rb, organic Br and TOC) to determine the area influenced by dumped spoil and the sediment transport directions. Sediment areas in dynamic equilibrium display a TOC gradient perpendicular to the coastline, linked to granulometric variations due to a combination of the swell and tidal currents. In the study area, dredged sediment are finer grained and have undergone changes due to the influence of diagenetic processes characteristic of the harbour environment. As a result, these sediment are enriched in sulphides, Pb, TOC and Rb, which allows us to highlight the in-situ deposited sediment spoil. Dumped sediment and the area subject to their influence are clearly identified since they locally disrupt the natural dynamic equilibrium state.

International audience; In the context of the increasing pressure of human activities on marine coastal ecosystems, the study of sedimentary disturbances remains a challenge. The eastern part of the Bay of Seine is very anthropized by the presence of harbour activities (heavy shipping, dredging and sediment dumped deposit …), fishing, sediment extraction… The dredging sediments of the Grand Port Maritime du Havre (GPMH) are deposited on the Octeville site, in the northeastern part of the Seine estuary mouth. The high hydrodynamics (swell and tide) associating with the constant supply of fines particles from both the Seine estuary and the English Channel combined with dumped sediment deposition create a mixed sedimentary zone. To understand sedimentary mechanism in this area, a geochemical and sedimentological study was conducted at the beginning of 2016. A sampling of 179 stations (distance of 500m between stations) was conducted between cape of La Hève and cape of Antifer. In addition, sampling in the harbour basins and in the dredge itself (13 samples in basins strongly or very weakly dredged) and in the Seine estuary (one station in the brackish zone and two stations in freshwater) were also studied. Geochemical elemental composition was obtained through X-Ray Fluorescence spectrometry (SPECTRO xSORT, 43 elements) and infrared spectrometry (LECO CS 744, Total Organic Carbon: TOC). Multiple PCA (Principal Component Analysis) had been conducted to reduce the large set of variables into a more concise one that retains most of the existing variations. Only seven elements had been conserved in the last PCA (Si, As, S, Pb, Rb, organic Br and TOC). Deposited sediments in the studied area have the same geochemical pattern irrespective of whether their originate from natural or dredged sources. The only difference is that dredged sediments are finer and have undergone changes under the influence of diagenetic processes which are characteristic of harbour environment. As a result, they are enriched in S, TOC, Rb and Pb, which allows to highlight in-situ the dredged deposits. To determine the area under dumped sediments influence and sediments transport directions, we sought if deposits were in a " dynamical equilibrium state ". To do that, TOC is the more accurate parameter. Area under dynamical equilibrium state display, a gradient perpendicular to the shoreline tied up to the granulometrical refinement gradients due to the swell and tide combined actions. Dumped sediments and area under their influence are clearly highlighted as they disrupt the natural dynamical equilibrium state.

International audience; Dans les études sédimentaires côtières, l'équilibre dynamique est défini, comme un équilibre entre le transport des particules, l'érosion et le dépôt, en fonction des processus physico-chimiques et hydrodynamiques associés, dont la marée et la houle. En baie de Seine et dans l'estuaire, les processus de dépôt et d'érosion des particules fines sont principalement étudiés sur la base d'études sédimentologiques, de calculs de taux de sédimentation, de modélisation et/ou de leur association avec la macrofaune benthique. Dans le présent travail, une autre approche est envisagée, sur la base de traceurs géochimiques, pour comprendre les mécanismes sédimentaires présents entre le cap de La Hève et celui d'Antifer (baie de Seine Orientale). L'étude a été menée sur des prélèvements sédimentaires réalisés début 2016 à l'aide d'une benne Shipeck. Un échantillonnage de 179 stations, disposées en lignes parallèles à la côte (espacées de 500 m), a été mené entre le cap de La Hève et le port d'Antifer, zone incluant le site de dépôt de dragage du Grand Port Maritime du Havre (Octeville). Pour caractériser les sources, des prélèvements ont été effectués dans les bassins portuaires fortement et faiblement dragués (13 stations) ainsi que dans l'estuaire de la Seine, en eau saumâtre et en eau douce (trois stations). La composition géochimique a été obtenue par XRF (X-ray fluorescence, Spectro xSORT) et par analyseur carbone/soufre (LECO CS 744), pour le dosage du carbone organique total (COT). La sélection des éléments porteurs d'information a été menée progressivement par la réalisation de plusieurs Analyses en Composantes Principales (ACP). Ces dernières ont permis de sélectionner sept éléments (Si, As, S, Pb, Rb, Br organique et COT).