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In urban environments, diachronic evolution of water quality can be reconstructed using geochemical analysis of urban secondary carbonate deposits (USCDs), from urban underground structures, similar to speleothems from natural caves. The use of the radiocarbon bomb peak to build their precise chronology was recently tested in two Paris-area urban sites (France). In this study, new samples from contrasted environments in the Paris region were sampled in order to test the sites’ effects on the radiocarbon signal recorded: under wood, under a fountain, in underground aqueducts, in the south and north of Paris. We compared the post-bomb atmospheric radiocarbon record with the one measured at the top of USCDs, and estimated the dead carbon proportion (DCP), between 0 and 40%. USCDs fed by water with a rapid transfer through thin soil (Versailles fountain) had the lowest DCP (14C very close to atmospheric one). Highest DCP were found for USCD from deep underground quarry under urban wood, and intermediate ones for USCDs fed by the waters of perched aquifers. These data support the use of radiocarbon as chronometer for USCDs in contrasted urban contexts, and show that it can be used to determine carbon transport and sources, an important parameter for pollution reconstruction.

International audience; AbstractPurposeUrban soil contamination by heavy metals is one of the foremost challenges for urban soil quality, especially in the urban agriculture context. Urban gardening is a common practice in many industrialized and developing countries. How sources of soil contamination relate to inputs and influence the heavy metal content in soils, however, is not established yet.Materials and methodsThis study aims to assess the potential of pesticide applications (such as Bordeaux mixture) on soil quality. A set of 104 allotment gardens was selected in three cities in France, and topsoil was sampled and analyzed.Results and discussionThe four most abundant metals in urban vegetable garden topsoils were Zn, Pb, Cu, and Cr. The past and/or present industrial and urban activities are not the only cause of the metal contamination in urban vegetable garden soils. Gardens, where pesticides such as the Bordeaux mixture are being used showed significantly higher total Cu values in soils (78 mg kg−1 compared with 49 mg kg−1 for untreated gardens).ConclusionsEven though the risk of metal contamination through vegetable consumption is usually considered low, we clearly identified indicators of anthropogenic Cd, Cu, Pb, and Zn pollution due to pesticides inputs. This link was particularly strong between the use of Bordeaux mixture and increases Cu levels.

International audience; Road runoff is contaminated by various micropollutants and may be treated using low impact development techniques, such as stormwater biofilters. Better understanding the processes, such as filtration, sorption and leaching, which affect pollutants in these systems is essential to reliably predicting treatment performance and optimizing system design. Field data from an in situ monitoring campaign, wherein dissolved and particulate concentrations of a wide range of micropollutants (trace metals, polycyclic aromatic hydrocarbons, bisphenol-A, alkylphenols and phthalates) were characterized in untreated road runoff and biofilter outlets for 19 rain events, are used to explore transport and retention processes. Although retention of the particulate phase of pollutants was generally quite effective, unusually high particle concentrations were observed at biofilter outlets for three winter events. Particle characterization in road runoff and outlet waters revealed that this degraded performance was due to poor filtration rather than particle erosion, which was attributed to the relative abundance of small (

Urban planning historically considers soils as a support for infrastructures. Hopefully, awareness is increasing on the fact that soils offer many more services than just this one, thanks to their various functions. It is therefore necessary to develop methodologies and tools that allow the urban planners to take into account the opportunities and constraints associated to soils. Considering the existing quality indexes already developed by the researchers, we faced within the MUSE project various difficulties and in particular the lack of knowledge on urban soils in France. We therefore developed a methodology to deal with limited knowledge on urban soils and tested it first on the Nantes metropolis territory (France). Our aim was to map each soil function as well as a soil multifunctionality in such a way that urban planning documents may refer to them.The aim of the multifunction map is to help protecting soils that show various functions, including patrimonial functions. We therefore considered the following functions: carbon storage, water storage and infiltration, storage and filtration of contaminants, agronomic potential, biodiversity reservoir. We did not consider the support and natural resources provision functions. According to the level of knowledge on soils (local/regional/national scales, direct/indirect), we considered three mapping approaches (statistical, global, and calculation) to build function maps, and interpreted them in terms of soil function index (SFI) map. To build the soil multifunctionality quality index (SMQI) map, we crossed the various function index maps using a ponderation according to the territorial issues. These issues derive from discussions with the urban planners of the local authority and the number of functions assessed on each part of the territory (some functions not mapped in the city center). We carried out discussions with the urban planners all along the methodological development process to ensure applicability of the index map produced.The results obtained are very satisfying considering the level of knowledge on soils. The urban planners of the local authority clearly imagine how to use both the soil function maps as well as the soil multifunctionality quality index map. We are nevertheless aware of the limits due to the use of data with different scales of validity (eg. 1 / 250 000 for pedological map; 1/10 000 for soil land-use model; statistical data on C and biodiversity at pedoclimatic scale vs national scale). The comparison with local punctual data helps verifying the degree of confidence of the maps. The methodological development is currently being adjusted and tested on other cities (in particular Marseilles and Châteauroux, France) and further discussed with urban planners at national scale. Efforts are necessary to build a wider and more precise knowledge on urban soils by gathering and sharing existing data. This implies building reference knowledge and by defining the most useful properties to acquire in a systematic way to characterize soils so as to optimise urban planning and development.

By 2017, the book "Soils within cities" (Levin et al., 2017) is moving away from the pedologist's description of urban soils to a broader understanding of urban soils, including the functions and the services they provide. This approach, which complements the naturalistic description of the soil, corresponds to the approach derived from the millennium ecosystems assessment (Morel et al., 2015; Walter et al., 2015). It is considered to be relatively anthropocentric and thus favours the integration of the soil in the urban socio-ecosystem.Considering the soil by both its pedogenesis and functioning in ecosystems induces taking into account the dynamics of this system, but raises, with regard to the literature on urban soils, the existing lack to qualify and quantify the processes of genesis and evolution, especially in relation to ongoing climate change (Baveye et al., 2016). On the other hand, the description of soil ecosystem services (regulation, provisioning, cultural services) immediately reveals the interdependence of soil biophysicochemical processes with those occurring in the hydrosphere, the atmosphere and the biosphere (Adhikari and Hartemink, 2016). In this respect, the soil plays an interface role, but is deeply disturbed in urban areas.The objective of the communication will be to review the status of urban soil in the "urban critical zone" concept. Through methodologies and results from projects implemented in French major cities that have enabled the development of databases, we will review the classification of these atypical soils and the changes in their properties and functions. Through the definition of the services they provide, we will propose a more integrated vision of this compartment of the urban ecosystem, by specifying the forcing caused by its interface position, but also the opportunities of improvement foreseen by the development of solutions for revegetation and de-sealing. We will see how the timeframe of soil evolution in urban zones can influence the data collection of soil parameters and mapping.

International audience; Decentralized stormwater management generally involves the use of infiltration systems, the comportment of which is not always correctly understood. Incorrect assumptions about the hydrologic behavior of such systems can undermine their roles in both the quantitative and qualitative management of runoff, especially in systems designed to treat pollution at the source. Given the technical difficulty of directly measuring water fluxes in already existing systems, this paper discusses the utility of two indirect methods, applied to a real site made up of a vegetative filter strip followed by a biofiltration swale: the use of a hydrologic model and the characterization of soil pollution.The hydrologic model involves uncertainties due to its simplifying hypotheses and the variability of soil hydraulic conductivity measurements. Still, it can provide a rough estimation of the relative frequency of infiltration in different parts of the system. The cartography of contaminants, which shows that the majority of pollution is accumulated close to the roadside, indirectly provides time-integrated information as to the repartition of infiltration fluxes and the processes of sedimentation and filtration at the study site. The high spatial resolution of soil contamination data also provides evidence of heterogeneous surface runoff and infiltration flows.Despite the limits of each approach, both methods lead to the conclusion that the majority of runoff volumes - and as a consequence, the majority of pollutant loads - is infiltrated in the part of the system nearest to the system inlet: the vegetative filter strip. Therefore, the biofiltration swale does not fulfill its initially intended role of depolluting runoff water, as most pollutants do not reach it but rather are retained in the surface soil close to the roadside.; La mise en œuvre d'une gestion décentralisée des eaux pluviales implique généralement le recours à des systèmes d'infiltration, dont le fonctionnement n'est pas toujours correctement appréhendé. Une mauvaise évaluation de l'hydrologie peut s'avérer préjudiciable pour la gestion quantitative et qualitative du ruissellement, notamment dans des dispositifs conçus pour une maîtrise " à la source " des flux de polluants. Face aux difficultés associées à la mesure directe des flux d'eau et de polluants sur des ouvrages en place, on discute les apports de deux méthodes indirectes, appliquées à un site réel constitué d'une bande enherbée suivi d'un fossé filtrant: l'utilisation d'un modèle hydrologique et l'étude de la pollution du sol.Le modèle hydrologique présente des incertitudes dues à ses hypothèses simplificatrices, ainsi qu'à la variabilité des mesures de conductivité hydraulique. Il fournit toutefois un ordre de grandeur de la sollicitation relative des différentes parties de l'ouvrage. La cartographie des contaminants, qui montre que la majeure partie de la pollution s'accumule à proximité de la chaussée, renseigne indirectement sur la répartition " intégrée dans le temps " des flux d'infiltration et des processus de sédimentation/filtration sur le site d'étude. L'utilisation d'une résolution spatiale suffisamment fine permet de mettre en évidence des hétérogénéités dans l'infiltration et les écoulements superficiels.Malgré des limites propres à chaque approche, les deux méthodes mènent à la conclusion qu'une grande partie des volumes ruisselés - et, de facto, du flux polluant - est gérée par infiltration dans la bande enherbée, la partie de l'ouvrage à proximité immédiate de la zone d'arrivée de l'eau dans l'ouvrage. Ainsi, le fossé filtrant ne joue pas son rôle épuratoire de manière optimale, dans la mesure où les contaminants seraient retenus en bordure de chaussée dans le sol de surface.

On assiste aujourd’hui à un véritable paradoxe : les jardins collectifs urbains se développent en ville alors que les sols urbains sont peu connus. La localisation de ces jardins suscite des interrogations en termes de risques sanitaires puisque nombre d’entre eux ont été (et sont encore) implantés sur des délaissés urbains. Des controverses apparaissent sur la capacité du sol urbain à accueillir ou non des cultures à vocation alimentaire, ce que nous analysons à travers deux documents d’expertise. Nous mettrons ces deux guides techniques à l’épreuve de la notion de « science impliquée » pour expliciter d’abord les intentions et les valeurs qui constituent la démarche d’expertise ; il s’agit ensuite de comprendre ce qui distingue ces différentes formes d’expertise sur la question des cultures en ville à savoir : le rapport à la connaissance et à l’incertitude, le rapport au temps, le rapport au public et aux choix de sociétés., Today we are faced with a true paradox: collective urban gardens are growing in cities whereas so little is known about urban soils. The localization of such gardens raises questions in terms of health risks since many of them have been (and still are) implanted on abandoned land. Some points in controversy are growing to know whether urban soils can or cannot receive cultures designed for food, which we analyze through two expertise reports. We will confront the technical guidelines with the notion of « involved science ,» first in order to clarify the intentions and values underlying the expertise process. After that our purpose is to understand what distinguishes these different forms of expertise on the question of urban cultures, which means the relation to knowledge and uncertainty, the relation to time, the relation to the public and the options for society.

In order to determine the relative importance of a vegetative filter strip and a biofiltration swale in a treatment train for road runoff, US EPA SWMM was used to model infiltration and runoff from the filter strip. The model consists of a series of subcatchments representing the road, the filter strip and the side slopes of the swale. Simulations were carried out for different rain scenarios representing a variety of climatic conditions. In addition, a sensitivity analysis was conducted for the model's different parameters (soil characteristics and initial humidity, roughness, geometry…). This exercise showed that for the system studied, the majority of road runoff is managed by the filter strip rather than the biofiltration swale, an effect observed especially during periods of low-intensity rainfall. Additionally, it was observed that the combination of infiltration of road runoff in the filter strip and direct rainfall on the system leads to a significant and variable dilution of the runoff reaching the swale. This result has important implications for evaluating the treatment efficiency of the system., Afin de déterminer l'importance relative d'une bande enherbée dans un ouvrage combiné bande enherbée-fossé de biofiltration de traitement des eaux de ruissellement de voirie, le ruissellement et l'infiltration au niveau de la bande enherbée ont été modélisés avec US EPA SWMM. Le modèle consiste en une série de sous-bassins versants représentant la route, la bande enherbée et le talus du fossé. Des simulations ont été menées pour différents scenarios de pluies représentant une variété de conditions climatiques et en menant une analyse de sensibilité sur les différents paramètres du modèle (nature du sol, humidité initiale, rugosité, géométrie…). Cet exercice a montré que pour le système étudié, la grande majorité de l'eau est gérée par la bande enherbée et non pas par le fossé de biofiltration dans lequel peu d'eau arrive, notamment quand l'intensité de la pluie est faible. De plus, il a été observé que la combinaison de l'infiltration de l'eau de voirie sur la bande enherbée et de l'apport en précipitation directe sur l'ouvrage conduit à une dilution significative et variable de l'eau atteignant le fossé. Ces résultats ont des implications importantes pour l'évaluation de l'efficacité épuratoire du système.

International audience; Surfactants based on polyfluoroalkyl ethers are commonly used in fire-fighting foams on airport platforms, including for training sessions. Because of their persistence into the environment, their toxicity and their bioaccumulation, abnormal amounts can be found in ground and surface water following the operations of airport platforms. As with many other anthropogenic, organic compounds, some concerns are raised about their biodegradation. That is why the Organization for Economic Cooperation and Development (OECD) 301 F protocol was implemented to monitor the oxygen consumption during the biodegradation of a commercial fire-fighting foam. However, a Raman spectroscopic monitoring of the process was also attached to this experimental procedure to evaluate to what extent a polyfluoroalkyl ether disappeared from the environmental matrix. Our approach relies on the use of chemometrics, such as Principal Component Analysis (PCA) and Partial Least Squares (PLS), in order to monitor the kinetics of the biodegradation reaction of one fire-fighting foam, Tridol S3B, containing a polyfluoroalkyl ether. This study provided a better appreciation of the partial biodegradation of some polyfluoroalkyl ethers by coupling Raman spectroscopy and chemometrics. This will ultimately facilitate the design of future purification and remediation devices for airport platforms.; Surfactants based on polyfluoroalkyl ethers are commonly used in fire-fighting foams on airport platforms, including for training sessions. Because of their persistence into the environment, their toxicity and their bioaccumulation, abnormal amounts can be found in ground and surface water following the operations of airport platforms. As with many other anthropogenic, organic compounds, some concerns are raised about their biodegradation. That is why the Organization for Economic Co-operation and Development (OECD) 301 F protocol was implemented to monitor the oxygen consumption during the biodegradation of a commercial fire-fighting foam. However, a Raman spectroscopic monitoring of the process was also attached to this experimental procedure to evaluate to what extent a polyfluoroalkyl ether disappeared from the environmental matrix. Our approach relies on the use of chemometrics, such as Principal Component Analysis (PCA) and Partial Least Squares (PLS), in order to monitor the kinetics of the biodegradation reaction of one fire-fighting foam, Tridol S3B, containing a polyfluoroalkyl ether. This study provided a better appreciation of the partial biodegradation of some polyfluoroalkyl ethers by coupling Raman spectroscopy and chemometrics. This will ultimately facilitate the design of future purification and remediation devices for airport platforms

Evaluating the performance of sustainable drainage systems (SuDS) in a field context presents a number of methodological problems. For this reason, as a part of three French research projects focused on this type of evaluation, Matriochkas, Micromegas and Roulepur, a working group on methodological harmonisation was established in order to facilitate the inter-comparison of results between the projects and propose a methodological guideline for practitioners carrying out such evaluations. The guideline proposes an approach where performance is evaluated with respect to a service function that the SuDS aims to achieve, itself identified from local issues. Its first section presents the various service functions which may be assigned to these devices. Next, performance indicators are defined for a selection of the identified service functions, common within the French context and studied as a part of the three projects. Three categories of indicators are identified: hydrologic indicators (relative to water flows), pollutant indicators and socio-technical indicators. Examples of instrumentation and of the application of the proposed indicators drawn from the experience of the three projects are also presented., L'évaluation in situ des performances des ouvrages de maîtrise à la source des eaux pluviales pose un grand nombre de questions d'ordre méthodologique. Ainsi, dans le cadre de trois projets de recherche français dédiés à ce type d'évaluation, Matriochkas, Micromegas et Roulépur, un groupe de travail sur l'harmonisation des méthodes a été constitué afin de faciliter l'inter-comparaison des résultats issus des projets, mais aussi de rédiger un guide méthodologique à destination des acteurs opérationnels pouvant être amenés à faire ce type d'étude. Ce guide propose une démarche où la performance est évaluée pour chaque fonction de service visée pour l'ouvrage, en réponse à des enjeux locaux. La première partie du guide détaille les fonctions de service pouvant être attendues de ce type d'ouvrage. Ensuite, des indicateurs de performance sont déclinés pour une sélection de fonctions de service couramment rencontrées dans le contexte français et qui ont pu être abordées au cours des projets. Ces indicateurs se regroupent en trois catégories : les indicateurs hydrologiques (relatifs aux flux d'eau), les indicateurs pollutifs (relatifs aux polluants) et les indicateurs sociotechniques. Le guide s'appuie sur des exemples issus des trois projets pour présenter des cas pratiques de dispositifs métrologiques et d'application des indicateurs proposés.

Novatech 2019, LYON, FRANCE, 01-/07/2019 - 05/07/2019; Evaluating the performance of sustainable drainage systems (SuDS) in a field context presents a number of methodological problems. For this reason, as a part of three French research projects focused on this type of evaluation, Matriochkas, Micromegas and Roulepur, a working group on methodological harmonisation was established in order to facilitate the inter-comparison of results between the projects and propose a methodological guideline for practitioners carrying out such evaluations. The guideline proposes an approach where performance is evaluated with respect to a service function that the SuDS aims to achieve, itself identified from local issues. Its first section presents the various service functions which may be assigned to these devices. Next, performance indicators are defined for a selection of the identified service functions, common within the French context and studied as a part of the three projects. Three categories of indicators are identified: hydrologic indicators (relative to water flows), pollutant indicators and socio-technical indicators. Examples of instrumentation and of the application of the proposed indicators drawn from the experience of the three projects are also presented.; L'évaluation in situ des performances des ouvrages de maîtrise à la source des eaux pluviales pose un grand nombre de questions d'ordre méthodologique. Ainsi, dans le cadre de trois projets de recherche français dédiés à ce type d'évaluation, Matriochkas, Micromegas et Roulépur, un groupe de travail sur l'harmonisation des méthodes a été constitué afin de faciliter l'inter-comparaison des résultats issus des projets, mais aussi de rédiger un guide méthodologique à destination des acteurs opérationnels pouvant être amenés à faire ce type d'étude. Ce guide propose une démarche où la performance est évaluée pour chaque fonction de service visée pour l'ouvrage, en réponse à des enjeux locaux. La première partie du guide détaille les fonctions de service pouvant être attendues de ce type d'ouvrage. Ensuite, des indicateurs de performance sont déclinés pour une sélection de fonctions de service couramment rencontrées dans le contexte français et qui ont pu être abordées au cours des projets. Ces indicateurs se regroupent en trois catégories: les indicateurs hydrologiques (relatifs aux flux d'eau), les indicateurs pollutifs (relatifs aux polluants) et les indicateurs sociotechniques. Le guide s'appuie sur des exemples issus des trois projets pour présenter des cas pratiques de dispositifs métrologiques et d'application des indicateurs proposés.

Runoff infiltration in Sustainable Drainage Systems enables the interception of a part of urban contaminant fluxes owing to several processes. The soil's ability to retain dissolved pollutants is generally assessed via sorption isotherms obtained from batch studies; however, the experimental points are not always in the same range as runoff concentrations. The present work (i) explores the consequences of modelling runoff–soil interactions from out-of-range equilibrium concentrations and (ii) proposes an improved method to ensure that experimental points fall within the desired range. Uncertainty analysis demonstrates that for a non-linear isotherm, using an extrapolated relationship may introduce significant biases in the ensuing estimations. Therefore, the proposed method consists of anticipating the equilibrium state of batch tests to accurately set the experimental conditions and reach appropriate concentrations. It is successfully applied to the determination of the sorption properties of copper and zinc onto three soils with different electrolyte solutions, as well as those of bisphenol A and three alkylphenols onto one soil. The contrasting affinities between the studied species and the soil materials could be related to their intrinsic properties and the soils' pedological parameters, as well as the presence of salt or dissolved organic ligands which partially inhibited metal sorption.

Afin de repondre durablement a la demande croissante des citoyens pour des jardins potagers urbains, la ville de Paris a realise un projet de potagers experimentaux - POTEX - avec l’objectif de reduire l’exposition des usagers aux polluants. Plusieurs solutions d’amenagement, de contextes environnementaux et de voies d’exposition (ingestion des vegetaux autoproduits et de sol) ont ete testes. La methodologie pluridisciplinaire developpee pour gerer les pollutions est exposee : etude historique, enquete des pratiques de jardinage, echantillonnage, prelevement, pretraitement des vegetaux, caracterisation des sols et vegetaux, mesures de bioaccessibilite et evaluation des risques sanitaires.

Dans le cadre de la prévention du saturnisme infantile, le Haut Conseil de la Santé Publique (HCSP) a fixé en 2014 des seuils de gestion liés aux concentrations en plomb dans les sols. En effet, au regard des risques liés à l’ingestion de particules de terre liée au portée main-bouche pour les enfants de moins de 6 ans, un seuil de vigilance de 100 mg de plomb par kg de terre a été fixé dans les sols des espaces verts. Suite à la parution de ces nouveaux objectifs de gestion, la Ville de Paris a amorcé un travail de caractérisation des sols de ses 500 ha d’espaces verts (EV). Ainsi, des analyses d’éléments traces métalliques (ETM), d’hydrocarbures et de paramètres agronomiques ont été réalisées sur 102 premiers EV. Ces mesures de qualité des sols, confrontées à la reconstitution de l’histoire des espaces verts, ont permis de dresser un certain nombre d’hypothèses quant à l’origine des terres végétales qui ont été utilisées depuis 200 ans. Alors que les efforts pour passer à une économie circulaire aboutissent à privilégier les circuits courts et l’approvisionnement local, il s’agit de s’interroger sur les pollutions potentielles des terres d’apports qui ont transité et qui transitent encore de la proche banlieue vers les centres urbains pour l’aménagement des espaces verts accueillant de plus en plus des potagers urbains. Dans ce contexte, il n’est pas inutile de réinterroger les principes et les rouages complexes de l’économie circulaire appliquée aux flux de terres végétales dans une démarche à la fois historique et spatiale., As part of the measures taken to prevent infantile saturnism, the French Higher Council for Public Health (Haut Conseil de la Santé Publique – HCSP) set thresholds values in 2014 for lead concentrations in the soil. Considering the risks linked to the ingestion of particles of soil by children under the age of six, who tend to put their hands in their mouth, a vigilance threshold value of 100 mg of lead per kilogram of soil was set for green spaces. Following the publication of these new objectives, the City of Paris initiated a program intended to characterize the soil of its102 green spaces representing 500 ha. Analyses of metallic trace elements, of hydrocarbons and of agronomic parameters were carried out to assess soil quality. Related to the history of the green spaces, they provided the basis for several hypotheses on the origins of the topsoil that has been used in vegetable gardens over the past 200 years. Considering the efforts made to shift to a circular economy, that favour short circuits and local supplies, this paper critically examines the potential pollution of soils which move from the close suburbs to the green spaces of urban centres, where more and more vegetable gardens are developed. In this context, it is interesting to re-examine the principles and complex workings of the circular economy applied to the evolution of vegetable gardens from a historical and spatial point of view.

International audience; The treatment efficiency of a vegetative filter strip and a biofiltration swale treating heavily loaded road runoff are evaluated. Concentrations measured in water drained from the two systems are compared to those in untreated road runoff collected from a reference catchment for a wide range of contaminants including organic carbon, nutrients (N and P), metallic trace elements, and organic micropollutants (polycyclic aromatic hydrocarbons (PAH), total petroleum hydrocarbons (TPH), alkylphenols, bisphenol-A, phthalates), in both total and dissolved phases. Predominantly particulate pollutants, including Pb, Zn and PAH, were very efficiently removed (around 90%) for most events. However, poor particulate removal was observed during a winter period. Relatively few pollutants were significantly removed in the dissolved phase and observed concentration reductions tended to be lower than those of suspended solids and associated pollutants; as such, lower removals were observed for total concentrations of moderately particulate micropollutants, including bisphenol-A, alkylphenols and phthalates. In addition, some pollutants appear to be emitted from various biofilter components (filter media, drainage and lining materials), as low or negative concentration removals were observed during the first months of operation of the biofiltration swale.

International audience; Among the processes governing contaminant retention in soil-based Sustainable Urban Drainage Systems (SUDS), quantifying the relative contribution of particle settling and filtration requires a tracer of runoff-generated solids. Since zirconium (Zr) is a widely used geochemical invariant in pedological approaches, with few anthropogenic sources, the present investigation aims to assess whether its use may be extended to sediment identification in SUDS. High-resolution horizontal and vertical soil sampling was carried out in 11 infiltration systems, as well as in road-deposited sediment. Following elemental analysis via X-ray fluorescence spectrometry, the spatial distribution of both Zr and urban-derived metals could be determined. Zr content in sediment was found to be fairly stable and significantly lower than in soil. In most devices, Zr and metals exhibited "mirror" trends, both horizontally and vertically, i.e. a deficit of Zr could be observed in the most contaminated area. This indicated a "dilution-like" mixture of soil and sediment, the fraction of which could be calculated and appraised spatially. The vertical profiles proved the occurrence of bed filtration over 5 to 15 cm, and enabled the calibration of a simple filtration model. The uncertainties associated with the determined filter coefficient were found to be comparable to the other experimental methods – with the additional improvement that the present approach does not require water sampling.

International audience; Depuis quelques décennies, on observe le développement de systèmes végétalisés conçus pour stocker, filtrer et parfois infiltrer à la source les eaux de ruissellement urbaines. Dans le monde anglophone de nombreux guides ont été publiés afin d'encadrer la conception et la maintenance de ce type d'ouvrage, qualifiés de bioretention. Ces guides, issus de retour d'expérience dans ces pays, proposent des préconisations relatives à l'emplacement des ouvrages, leurs modes de vidange, les caractéristiques des couches du filtre, les critères et méthodes de dimensionnement, le choix des végétaux et l'entretien des ouvrages. Comme ces techniques sont encore relativement peu diffusées en France et ne font pas encore l'objet de tels guides, cet article a pour vocation de dresser une synthèse d'une sélection de ces guides. Abstract: Over the past few decades, vegetated systems designed for the on-site storage, filtration and sometimes infiltration of urban runoff have been developed and become increasingly popular. Across the English-speaking world, one can find a great many guides providing detailed information as to the design and maintenance of this type of system, referred to as bioretention. These guides, which present advice as to where to locate these systems, how to drain them, the characteristics of the filter media, sizing methods, plant choice and system maintenance, contain a wealth of valuable information and feedback from the experience in these countries. As this technique is relatively new in France and no such detailed guidelines yet exist, this article synthesizes the information from a selection of these guides. 2

Purpose Mainstreaming land use history into urban maps is of interest for many applications. In this study, it was seen as a way for introducing soil quality information in urban planning. The quality of urban soils is indeed assumed to be driven not only by the current land cover but also by the land use history. The purpose is to investigate this assumption by proposing two mapping processes of the land use history.

International audience; Speleothem-like deposits that develop underground in urban areas are an archive of the environmental impact of anthropic activities that has been little studied so far. In this paper, the sulfate content in shallow groundwater from northern Paris (France) is compared with the sulfur content in two 300-year-old urban carbonate deposits that grew in a historical underground aqueduct. The present-day waters of the aqueduct have very high sulfur and calcium contents, suggesting pollution from gypsum dissolution. However, geological gypsum levels are located below the water table. Sulfur content was measured by micro-X-ray fluorescence in these very S-rich carbonate deposits (0.5 to 1% of S). A twofold S increase during the second half of the 1800s was found in both samples. These dates correspond to two major periods of urbanization above the site. We discus three possible S sources: anthropic sources (industries, fertilizers…), volcanic eruptions and input within the water through gypsum brought for urbanization above the studied site (backfill with quarry waste) since the middle of the 19th century. For the younger second half of the studied section, S input from gypsum brought during urbanization was confirmed by the study of isotopic sulfur composition (δ34S = + 15.2‰ at the top). For the oldest part, several sulfur peaks could be related to early industrial activity in Paris, that caused high local air pollution, as reported in historical archives but also to historical gypsum extraction. This study provides information on the origin and timing of the very high SO42 − levels measured nowadays within the shallow groundwater, thus demonstrating the interest in using carbonate deposits in urban areas as a proxy for the history of urbanization or human activities and their impact on water bodies.

Les premières démarches de suivi in situ en ANC résultent, en France, de la volonté des financeurs publics de s'assurer des performances des installations d'ANC soutenues dans le cadre d'une politique d'aide à la réhabilitation. Dans ce contexte, c'est créé le Groupe National Public (GNP) de suivi in situ. Cette structure regroupe les acteurs publics investis dans l'évaluation sur site des installations d'ANC et dont le but partagé est de s'assurer de la pérennité des installations dans leurs conditions réelles de vie. Á travers cette étude, le groupe national public « suivi in situ des installations d'assainissement non collectif » fournit des informations objectives sur la qualité des eaux usées traitées et l'entretien « curatif » de près d'une vingtaine de dispositifs d'ANC dans leurs conditions réelles de fonctionnement, qu'ils soient de type « agréé » ou « traditionnel ». Seuls 1 dispositif traditionnel et 4 dispositifs agréés suivis (soit 20 % des dispositifs agréés suivis) délivrent une eau usée traitée de qualité acceptable. Cet effectif se réduit à 1 dispositif traditionnel et 2 dispositifs agréés (soit un peu plus de 10 % des dispositifs agrées suivis) lorsque le qualificatif d'acceptable pour la fréquence d'entretien « curatif » s'ajoute aux exigences précédentes visant la qualité chimique des eaux usées traitées. Cette étude donne un éclairage scientifique et technique destiné à alimenter la réflexion des responsables des politiques publiques exerçant une action de soutien auprès des citoyens concernés par l'assainissement non collectif.

One of the environmental concerns for airport managers is stormwater management. Three kinds of contamination occur at airports: (1) chronic contamination, (2) seasonal contamination associated with de-icing procedures and (3) accidental pollution. At Orly Airport, a stormwater treatment plant (STEP) is devoted to removing chronic pollution. About 4 million m3 of water are processed yearly by the STEP, producing about 50–100 t of sludge. Mainly contaminated by petroleum hydrocarbons (Hc), it is removed as final wastes. During the winter, the STEP is unable to treat organic load associated with de-icers (formate and glycol). In order to improve onsite stormwater management, two experiments were carried out in real conditions between 2008 and 2010. The first one dealt with the ability of two vertical flow planted beds (VFPB) associated with two kinds of plant to treat waters contaminated by de-icers. Organic loads of up to 2,094 mg/L chemical oxygen demand (COD) were passed through sand filters in a closed-loop system. Organic degradation was characterized by a first-order kinetic constant driven by nutrient availability. Nutrient (N, P) addition was then necessary to reach treatment objectives (40 mg/L COD). The second system evaluated sludge Hc removal by four VFPB associated with several plant species. This experiment showed that the measured Hc removal rates of 70% for sludge and 95% for water did not depend on the choice of plant and that a rest time was necessary to allow Hc removal. Finally, a treatment system, based on VFPB, should be a good alternative which could optimize both sludge and contaminated water management.

Stormwater runoff infiltration brings about some concerns regarding its potential impact on both soil and groundwater quality; besides, the fate of contaminants in source-control devices somewhat suffers from a lack of documentation. The present study was dedicated to assessing the spatial distribution of three heavy metals (copper, lead, zinc) in the surface soil of ten small-scale infiltration facilities, along with several physical parameters (soil moisture, volatile matter, variable thickness of the upper horizon). High-resolution samplings and in-situ measurements were undertaken, followed by X-ray fluorescence analyses and spatial interpolation. Highest metal accumulation was found in a relatively narrow area near the water inflow zone, from which concentrations markedly decreased with increasing distance. Maximum enrichment ratios amounted to > 20 in the most contaminated sites. Heavy metal patterns give a time-integrated vision of the non-uniform infiltration fluxes, sedimentation processes and surface flow pathways within the devices. This element indicates that the lateral extent of contamination is mainly controlled by hydraulics. The evidenced spatial structure of soil concentrations restricts the area where remediation measures would be necessary in these systems, and suggests possible optimization of their hydraulic functioning towards an easier maintenance. Heterogeneous upper boundary conditions should be taken into account when studying the fate of micropollutants in infiltration facilities with either mathematical modeling or soil coring field surveys.

Urban water is composed of a complex matrix of micropollutants produced by traffic and contributes to the degradation of the aquatic bodies without treatment before discharge toward the environment. Various solutions are available to manage or treat these pollutants loads. However, an in-situ evaluation of the efficiency of these solutions is still necessary. Within the framework of the ROULÉPUR project, four innovative source control solutions for the micropollutant loads stemming from runoff on urban streets are tested. These solutions are: i) a compact decantation/filtration/adsorption device, the STOPPOL ® 10CKF, Saint Dizier Environnement, ii) non-infiltrating stormwater biofilters, iii) vegetative filter strips and biofiltration/infiltration swales and iv) a vegetative pervious parking lot. Assessment of performance of these solutions requires measurement of both, quality and quantity of water at the inlet and outlet of each device over a period of at least one year. Continuous measurements that are also comparable between devices are quite difficult to achieve in the harsh urban environment. This paper seeks to present difficulties encountered and solutions in order to have accurate measurement for the four devices., Les eaux de voiries et parkings sont constituées d'une matrice complexe de micropolluants d'origines multiples (émissions liées au trafic et à l'environnement urbain – chauffage, usure du mobilier urbain, des bâtiments...), qui contribuent à la dégradation des milieux aquatiques lorsqu'elles ne sont pas traitées avant rejet. Diverses solutions techniques existent pour la maîtrise, voire un traitement à la source de ces flux polluants. Leur efficacité en termes d'abattement des micropolluants demande cependant à être évaluée in-situ. Dans le cadre du projet Roulépur, quatre solutions innovantes de maîtrise à la source des flux de micropolluants générés par le ruissellement sur les voiries urbaines sont testées. Ces quatre solutions sont : i) un dispositif compact de décantation/filtration/adsorption, le STOPPOL ® 10CKF de Saint Dizier Environnement, ii) des filtres plantés horizontaux non infiltrants, iii) des bandes enherbées et des fossés filtrants/infiltrants et iv) un parking perméable végétalisé Ecovégétal. L'évaluation de ces solutions nécessite des mesures combinées, de quantité et qualité des eaux, en entrée et en sortie de chaque dispositif, et ce pour des périodes de temps au moins annuelles. La nécessité d'avoir des mesures en continu et comparables entre les différentes solutions dans des environnements contraints complique la mise en oeuvre de l'instrumentation. L'objectif de cette communication est de présenter les difficultés liées à cette instrumentation et les solutions envisagées.

Le sol, régulateur de la quantité et de la qualité de l’eauLa gestion des sols agricoles pour réduire la contamination des milieux aquatiquesLa gestion des sols urbains et péri-urbains pour réguler les flux et épurer les eauxConclusionBibliographie

Soil quality is related to soil characteristics such as fertility and contamination. The aim of this study is to assess the effect of land use on these soil characteristics and to confirm the following anthropisation gradient: (i) forest, (ii) grassland, (iii) cultivated, (iv) orchard and vineyard, (v) urban vegetable garden, and (vi) SUITMA (urban, industrial, traffic, mining and military areas). A database comprising the characteristics of 2451 soils has been constituted. In order to compare the topsoils from six contrasting land uses, a principal components analysis (PCA) was performed on nine geochemical variables (C, N, pH, POlsen, total Cd, Cu, Ni, Pb, Zn). The first axis of the PCA is interpreted as a global increase of topsoil metallic elements along the anthropisation gradient. Axis 2 reflects the variability of fertility levels. Human activity increases the pressure on soils along the proposed gradient according to six different distribution patterns. This better knowledge of topsoil quality and its dependence on current land use should therefore help to manage and preserve the soil mantle.

The first record of urban speleothems used to reconstruct the history of heavy metal pollution of shallow groundwaters is presented. Two speleothems grew during the last 300 years in an underground aqueduct in the north-eastern part of Paris. They display high Pb, Mn V, Cu, Cd and Al concentrations since 1900 due to the urbanization of the site which triggered anthropogenic contamination of the water feeding the speleothems. Surprisingly, these heavy metal concentrations are also high in the oldest part. This early pollution could come from the use of Parisian waste as fertilizers in the orchards and vineyards cultivated above the aqueduct before urbanization. Lead isotopes were measured in these carbonates as well as in lead artifacts from the 17th–18th centuries (206Pb/207Pb = 1.180 +/− 0.003). The mean 206Pb/207Pb ratio, for one of the speleothems is 1.181 +/− 0.003 unvarying with time. These lead signatures are close to those of coal and old lead from northern European mines, lower than the natural background signature. It confirms that the high metal concentrations found come from anthropogenic pollution. Conversely, the lead isotopic composition of the second speleothem presents two temporal trends: for the oldest levels, the mean value (1.183 +/− 0.003) is similar to the first speleothem. For the youngest part, a lower value (1.172 +/− 0.005) is recorded, evidencing the contribution of a new lead source at the beginning of the industrial revolution. Pb isotopes were also measured in recent samples from a nearby superficial site. The first sample is a recent (AD 1975 +/− 15 years) deposit (206Pb/207Pb = 1.148 +/− 0.003), and the second, a thin subactual layer (206Pb/207Pb = 1.181 +/− 0.002). These data are compatible with the adding of anthropogenic sources (leaded gasoline and industrial lead from Rio Tinto ore).

International audience; In order to be a relevant indicator of exposure towards teratogenic stressors, morphological defects should not be passed on to the next generation. In this study, we compare morphological variations in Chironomids collected from a contaminated river stretch with those of their progeny, reared in uncontaminated sediment under laboratory conditions. We focused on mentum defects (deformities, fluctuating asymmetry and mean shape change), measured by geometric morphometrics. We observed no significant variation in deformity rate between the parental generation and its progeny. On the contrary, we observed a significant increase in fluctuating asymmetry and a significant decrease in mentum centroid size in the offspring. Our results suggest that shape defects are not caused by direct exposure to teratogenic stressors alone. We propose four hypotheses to explain this: (a) teratogenic contaminants are present in egg-clutches, (b) contaminants at the sampling site have mutagenic effects, (c) costs of tolerance, and (d) contamination-induced genetic impoverishment.

In urban areas, the increasing use of infiltration devices for stormwater management raises some concerns about the potential for micropollutants' accumulation in soil and transport to groundwater. It is necessary to properly appraise the spatial variability of contamination, so as to optimize the number and representativeness of soil samplings. In this study, we determined the distribution of three trace metals in the surface soil of two infiltration basins. On each study site, we performed a series of high-resolution samplings and physical measurements (soil moisture, volatile matter, thickness of the dark upper soil horizon). Analyses show high Cu, Pb and Zn contents in the first centimetres of soil, but this accumulation is restricted to a relatively narrow area near the inflow point of the basins. This finding highlights the influence of heterogeneous infiltration on the distribution of trace metals. Moreover, their concentrations appear to be strongly correlated to the volatile matter content and thickness of the upper layer of soil., Si les systèmes favorisant l'infiltration des eaux de ruissellement connaissent un fort développement en zones urbaines et périurbaines, des interrogations demeurent quant à l'accumulation et au transfert éventuel de micropolluants dans le sol de ces dispositifs. En vue d'une étude d'impact ou d'une caractérisation systématique de ces ouvrages, il est essentiel d'appréhender convenablement la variabilité spatiale de la contamination, afin d'assurer une représentativité optimale de l'échantillonnage de sol. Ces travaux s'intéressent à la répartition de trois éléments traces métalliques dans le sol superficiel de deux bassins d'infiltration « amont ». Sur chaque site d'étude, on a prélevé une série d'échantillons avec une haute résolution spatiale, accompagnés de différentes mesures physiques (teneur en eau TDR, teneur en matières volatiles, épaisseur de l'horizon superficiel sombre). Les analyses montrent un enrichissement important en cuivre, plomb et zinc des premiers centimètres du sol, phénomène localisé autour du point d'arrivée de l'eau dans les bassins, ce qui confirme l'importance de la sollicitation hydrologique sur la distribution des contaminants métalliques. Par ailleurs, les teneurs en métaux traces apparaissent fortement corrélées au taux de matières volatiles du sol ainsi qu'à l'épaisseur de l'horizon superficiel.

Session 13; National audience

International audience; Two laminated carbonate deposits from the wall of an underground aqueduct, built between the 13 th and 15 th century, in Paris, France, were studied to provide historical information about nearby human occupation and urban development. To obtain a robust chronology for these small (29 and 45 mm thickness) and very young deposits< 800 a based on the probable date of aqueduct construction, we adopted two methods: laminae counting and U-Th analysis. For laminae, we tested the hypothesis that their deposition is biannual. Concerning U-Th dating, the influence of inherited 230 Th on calculated ages is discussed and detrital 230 Th/ 232 Th values for each speleothem was determined using stratigraphic constraints and found to be significantly different despite their close proximity. In these speleothems, that precipitated over approximately 300 a according to U-Th dating, the number of laminae is similar, and two laminae were deposited each year. A lamina-counting chronology was used to interpret the rare earth elements and yttrium content (REE + Y) variations measured by ICP-QMS as historical variations in water quality in relation with the anthropogenic use of these elements, with a marked increase in the REE + Y concentrations since the second half of the twentieth century. A marked negative Ce anomaly in the NASC-normalized REE trend is evidenced, and is more pronounced for post 1850s. This anomaly could be due to prior precipitation of Ce 4+ before the water reached the aqueduct, related to a high organic matter content of the water in oxidizing conditions. The increase in the Ce anomaly could indicate a second source of water, from a wastewater collection system or a modern water conveyance system. We thus demonstrate the interest of using these annual carbonate deposits in urban areas as a proxy for the history of urbanization or human activities. Keywords : urban speleothems, relative chronology, U-Th dating, urbanization impact on water quality, Rare Earth Elements, Yttrium. Highlights:  We test the potential of urban speleothems as a natural archive for the history of the impact of urbanization on water chemistry  We compare absolute (U-Th) and relative chronologies for young speleothems  We discuss corrections for detrital 230 Th for U-Th dating using stratigraphic constraints  We evidence a high REE and yttrium content in infiltration waters in Paris since the mid-twentieth century  We discuss the presence of a negative Ce anomaly in the urban speleothems

Laboratory studies have sometimes failed to detect a relationship between toxic stress and morphological defects in invertebrates. Several hypotheses have been proposed to account for this lack of effect. (1) It was suggested that only a combination of stressful conditions – rather than a single one – would affect the phenotype. (2) Phenotypic defects should be detected on adult individuals, rather than on juveniles. (3) Phenotypic abnormalities might mostly affect the progeny of the exposed individuals, some contaminants exhibiting trans-generational effects. In the present study, we test those three hypotheses. We first examined the effects of a multiple exposure by using laboratory Chironomus riparius larvae cultured on two sediments sampled in contaminated rivers and those containing a mixture of mineral and organic compounds. On the larvae, we investigated mentum phenotypes: the frequency of phenodeviants, the shape fluctuating asymmetry and the mean shape. To test whether adult's morphology was more sensitive than the larval's, we also measured asymmetry and mean shape of the adult wings. Finally, to test for a trans-generational phenotypic effect, we measured mentum shape variations in the offspring derived from the measured adults. Overall, our results point out a very limited phenotypic response to contaminated sediments, suggesting that a multiple exposure is not necessarily sufficient to generate phenotypic defects. Adult traits were no more affected than larval traits, discarding the hypothesis that adult phenotypes would be more sensitive biomarkers. Finally, no effect was detected on the offspring generation, suggesting that no trans-generational effect occurs. This general lack of effect suggests that the use of phenotypic defects in C. riparius as an indicator of sediment contamination should be considered cautiously.

The aim of the present study was to assess the potential use of biochemical markers and mentum deformities as indicators of long-term exposure to lead (Pb) in Chironomus riparius larvae. To do this, the authors measured 3 biochemical markers (i.e., malondialdehyde level, metallothionein concentration, and energy reserve content) as well as larval growth and mentum deformities after 16-d exposure to sediment containing Pb. The concentrations studied ranged from 3.5 mg/kg to 505.5 mg/kg dry weight. Despite the bioaccumulation of Pb in C. riparius bodies, frequencies of both mentum deformities and the dry weight were not significantly different between the control and stressed groups. On the contrary, Pb exposure caused a significant increase of both malondialdehyde level and metallothionein concentration. The increase of body Pb concentrations did not significantly modify body copper and zinc concentrations. Moreover, we observed a decrease of total lipid content and an increase of glycogen content as a function of a dose-response relationship, while no variation in protein concentrations was observed. Despite the adverse effects observed at the biochemical level, larval development was not affected. These results suggested that measurements of malondialdehyde level, metallothionein concentration, and energy reserve content can be used as relevant biomarkers of long-term sublethal exposure to Pb in C. riparius larvae.

Deformities and fluctuating asymmetry in chironomid larvae have been proposed as sensitive indicators of biological stress and are commonly used to assess the ecological impact of human activities. In particular, they have been associated in Chironomus riparius, the most commonly used species, with heavy metal and pesticide river pollution. In this study, the effect of lead and 4-nonylphenol on mouthpart morphological variation of Chironomus riparius larvae was investigated by traditional and geometric morphometrics. For this purpose, first to fourth instar larvae were exposed to sediment spiked with lead (from 3.0 to 456.9 mg/kg dry weight) or 4-NP (from 0.1 to 198.8 mg/kg dry weight). Mentum phenotypic response to pollutants was assessed by four parameters: (1) the frequency of deformities, (2) fluctuating asymmetry of mentum length, (3) fluctuating asymmetry of mentum shape and (4) the mentum mean shape changes. Despite the bioaccumulation of pollutants in the chironomid’s body, no significant differences between control and stressed groups were found for mouthpart deformities and fluctuating asymmetry of mentum length. Slight effects on mentum shape fluctuating asymmetry were observed for two stressed groups. Significant mean shape changes, consisting of tooth size increase and tooth closing, were detected for lead and 4-NP exposure respectively. Those variations, however, were negligible in comparison to mentum shape changes due to genetic effects. These results suggest that the use of mentum variation as an indicator of toxic stress in Chironomus riparius should be considered cautiously.

International audience; Sedimentary records of salinity indicators are largely used to reconstruct past climatic changes in lacustrine systems where chemistry is sensitive to hydroclimatic conditions. In large fresh lakes of the East African Rift such as Lakes Tanganyika and Malawi, salinity is often considered constant and other paleoclimatological proxy data are used. However, a relation between lake surface chloride concentration and hydroclimatic regime was previously demonstrated at the century scale in Lake Tanganyika. This relation is transposed to Lake Malawi on the base of similarity between hydrochemical budgets of both lakes that are computed for the whole lake and epilimnion. Whereas numerous physico-chemical difficulties make generally debatable use of lake pore water chemistry, as illustrated here by diffusion modelling, the dissolved chloride concentration profile from a core sampled in northern Lake Malawi is considered as a potential indicator of limnological–hydroclimatic condition changes for the last 200 years. A decrease in pore water chloride concentration between 1840 AD and present situation is directly associated to a metalimnetic water salinity decrease. The chronology of this event is synchronous with diatom productivity change demonstrated by Johnson et al. (2001) at the end of the Little Ice Age (LIA). A conceptual model of Lake Malawi, based on salinity, organic carbon and its “dead” watershed contribution, lake-level and productivity changes since the mid 19th century is presented. A new scenario is proposed, based on thermal stratification reinforcement at the end of the LIA. Lake productivity and chemistry depend on stratification strength, water column mixing rate and on climatic variability. During the LIA, nutrient distribution profiles were more homogeneous with depth due to the climatically (colder and drier climatic conditions than today) induced destabilisation of the mixing barrier. The productive system is then auto-supplied and does not require external silicon supply while chloride concentration is higher due to closure of the basin. Stratification has become more stable since the end of the LIA, as in nearby Lake Tanganyika where it is linked to air temperature global increase. Results demonstrated that chloride is a suitable indicator of the present and past hydroclimatic and hydrodynamic regimes. This work shows that in Lake Malawi, assessment of “dead” carbon (or old “refractive watershed carbon”) contribution to the TOC is a key parameter to set chronological frame from $^{14}$C ages.

Summary The hydroclimatic and geothermal controls on the salinity of small tropical crater lakes Masoko, Katubwi, Kyambangunguru, Ilamba and Kingiri, aligned with the Mbaka fault line, north of Lake Malawi, are investigated by water stable isotopes which are used to trace evaporative processes as to establish lake water balances, and by chloride concentrations allowing to identify the main salinity sources. This region shows positive excess in the exchanges between atmosphere and lake surfaces (P – E > 0). With the exception of Lake Ilamba, the lakes are closed surface basins and their levels are relatively stable. As catchment inflows cannot be neglected, groundwater outflows have to compensate for this excess, the isotopic budgets show that these lakes constitute a series of windows on the local shallow aquifer. In addition, the estimated losses by evaporation cannot solely account for the lake salinity observed, as the most saline lake differs from not the most evaporated. Lake salinity is then investigated from chloride concentrations and seems to be controlled by inflows, which results from the mixing between (i) fresh and (ii) hydrothermal ground waters. The contrasts in lake salinity (almost one order of magnitude) are first related to the hydrothermal contribution, which increases with the proximity of the Mbaka fault. Second, due to positive exchange with the atmosphere, the lake salinity appears systematically diluted in regard to the respective inflows. This dilution effect increases as the fraction of total inputs lost by evaporation or the lake water residence time increases. This current hydrological study shows that local wetter conditions are not inconsistent with higher lake salinity and allows to conciliate the questioned and apparent contradictory Lake Masoko wetter and salty paleoenvironmental and paleoclimatic records for the last glacial maximum and Younger Dryas time intervals. Further, in a general manner, this work addresses the case of lake submitted to wet environment and highlights the potential contribution of hydrothermal water on lakes salinization, occurring in active regions, such as the East African Rift System.

This paper presents a multi-disciplinary characterisation of processes that influence sedimentation and lake water chemistry in the northern part of the Lake Malawi (or Lake Nyasa), East Africa. This characterisation is based on geophysical (heat-flow), tectonic, hydrological, hydrochemical (major elements, stable isotopes) and sedimentological (seismic profiles, core mineralogy) studies of data acquired from 1990 to 1994 during the CASIMIR project (Comparative Analysis of Sedimentary Infill Mechanisms in Rifts).Sub-surface activity is expressed through seismic and volcanic activity, as well as elevated heat-flow values, both beneath the lake and the surrounding area; hydrothermal activity is observed in the watershed however it was not clearly identified in the sub-lacustrine environment. Relatively high heat-flow values (80–90 mW/m2) and the chemical composition of hydrothermal fluids in hot springs suggest the presence of a magmatic body at depth.The influence of Quaternary tectonic activity on sedimentary dynamics and infilling is observed not only on land but also in the lake through high-resolution seismic profiles. The main feature is a general tilting of the Kyela Plain as shown by a shift in the river course. The Quaternary stacking pattern of seven sedimentary sequences identified on a grid of high-resolution seismic reflection profiles represents a complete long-term lake-level cycle, from a lake lowstand at about 320 m below the present level to the present-day lake highstand. The North-Kiwira and Songwe River delta systems, composed of a number of stacked lobes, were developed in response to the interplay between gradual lake-level rise, tectonic movement and sediment input. The river dynamics is also recorded in a short core by a mineralogical evolution probably due to a decrease of detrital inputs from the Songwe River in response to hydroclimatic changes. Such changes are very important as this northern part of the watershed is considered as a recharge zone for the entire lake. Sedimentological patterns (from shallow depth to about 240 m water depth) and hydrochemistry are both influenced by watershed characteristics (pedology, geology, vegetation, hydrology, climate, etc.) but also by lacustrine biological processes: diatom productivity in epilimnetic water and degradation or preservation in deeper waters.Physico-chemistry and isotopic data of epi- and metalimnetic waters document the importance of the various water sources but also of evaporation and mixing processes linked to the thermo-haline stratification. Even if hydrothernal discharges have not been observed in the lake, they contribute to the lake chemistry at least through riverine inputs (Kiwira River).

Novatech 2019, LYON, FRANCE, 01-/07/2019 - 05/07/2019; The pooling of results from three French projects (Matriochkas, MicroMégas and Roulépur), within the framework of a working group on methodological harmonisation, makes it possible to analyse the performance of a wide range of stormwater control measures (SCMs) in terms of micropollutant load reduction. Data covers 12 management systems, in 9 different urban contexts. The results highlight the diversity of runoff contamination levels and of their distribution between dissolved and particulate phases. They show significant reductions in particulate pollutants for all filtration-based systems, and less for those that only allow sedimentation. Performance is more limited for the dissolved phase, for which concentration reduction is limited and significant load reductions are only achieved due to a reduction in runoff volumes in structures promoting evapotranspiration.; La mise en commun de résultats issus des projets français Matriochkas, MicroMégas et Roulépur, dans le cadre d'un groupe de travail d'échanges et d'harmonisation méthodologiques, permet d'analyser l'efficacité de la gestion alternative des eaux pluviales en termes de réduction des flux de micropolluants, pour 12 dispositifs de gestion et 9 contextes urbains différents. Les résultats soulignent la diversité des niveaux de contamination des eaux de ruissellement, et de leur distribution entre phases dissoutes et particulaires. Ils démontrent des abattements importants des polluants particulaires pour l'ensemble des systèmes basés sur la filtration, et moindre pour ceux ne permettant que la sédimentation. Les performances sont plus limitées pour les concentrations dissoutes, de sorte que seul un abattement des volumes de ruissellement, dans les ouvrages favorisant l'évapotranspiration, permet une réduction significative des flux de micropolluants dissous

International audience