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International audience; The development of populated areas near mining activities, an important source of metal contamination, poses a challenge for urban sustainability and public health, which must be addressed in a multidisciplinary way. Street dusts are a relevant indicator of environmental pollution, as they are an important exposure pathway and record recent metal accumulation. Risk assessment is an effective tool to evaluate and manage these risks. The majority of these analyses, however, do not evaluate the particle size used to represent environmental exposure, despite its importance, historically using a broad range.

International audience; Aquatic ecosystems are generally subjected to multiple perturbations due to simultaneous or successive combinations of various natural and anthropogenic environmental pressures. To better assess and predict the resulting ecological consequences, increasing attention should be given to the accumulation of stresses on freshwater ecosystems and its effects on the vulnerability of aquatic organisms, including microbial communities, which play crucial functional roles. Here we used a microcosm study to assess the influence of an experimental warming on the vulnerability of phototrophic and heterotrophic periphytic communities to acute and chronic copper (Cu) toxicity. Natural periphytic communities were submitted for 4 weeks to three different temperatures (18, 23, and 28°C) in microcosms contaminated (at about 15 µg L-1) or not with Cu. The vulnerability of both phototrophic and heterotrophic microbial communities to subsequent acute Cu stress was then assessed by measuring their levels of sensitivity to Cu from bioassays targeting phototrophic (photosynthetic activity) and heterotrophic (β-glucosidase and leucine aminopeptidase extracellular enzymatic activities) microbial functions. We postulated that both the increase in temperature and the chronic Cu exposure would modify microbial community structure, thus leading to changes in the capacity of phototrophic and heterotrophic communities to tolerate subsequent acute exposure to Cu. Our results demonstrated that the influence of temperature on the vulnerability of phototrophic and heterotrophic microbial communities to Cu toxicity can vary greatly according to function studied. These findings emphasize the importance of considering different functional compartments and different functional descriptors to better assess the vulnerability of periphyton to multiple stresses and predict the risks induced by multiple stressors for ecosystem balance and functioning.

Passive sampling has been developed to obtain, at lower cost, more representative evaluations of the average concentrations of contaminants in aquatic environments. An innovative silicone-based passive sampler (named PACSiR, for Polar Apolar Composite Silicone Rubber) was designed to address sampling, detection and quantification of a wide range of organic contaminants (native or metabolites) present at ultratrace levels in waters. The PACSiR passive samplers, of small size (2 cm length), were applied in different aquatic media (surface or underground waters), typically for periods of 1 week, to evaluate the contamination by a wide range of pesticides and metabolites. They were also tested for their capacity to monitor several hormones and pharmaceuticals. The nature and mass of contaminants sorbed on the passive samplers exposed in situ were used as qualitative or comparative measures, to highlight the presence of compounds or to easily assess trends and gradients of contamination in aquatic environments. For quantitative purposes, the estimation of the average concentration of contaminants in water required the prior determination of kinetic parameters (sampling rate, equilibration time) through laboratory experiments. We demonstrated that this reactive, single-use and low cost passive sampler can be used for multiple research or operational purposes, thanks to the different levels of data acquisition, from qualitative to quantitative approach.

Passive sampling has been developed as an alternative to grab or average automated sampling to obtain, at lower cost, more realistic estimates of the average concentrations of contaminants in aquatic environments. This technique allows the in situ accumulation of chemicals from large amounts of water, resulting in ultratrace level detection and smoothed integrative sampling over exposition periods ranging from days to months. In small agricultural watersheds, pesticide concentrations quickly fluctuate due to episodic rainfall events and resulting transfers from fields to rivers via various pathways (runoff, infiltration, lateral flows...). In this context, an innovative silicone-based passive sampler (named PACSiR, for Polar Apolar Composite Silicone Rubber) was designed to address sampling, detection and quantification of a wide range of organic contaminants (native or metabolites) in waters. The PACSiR passive samplers, of small size (2 cm length), were applied in different aquatic media (surface or underground waters) to estimate the levels of contamination by pesticides of different families. The nature and mass of contaminants sorbed on the passive samplers exposed in the field were used as qualitative or comparative measures, to highlight the presence of compounds or to easily assess trends and gradients of contamination in aquatic environments. For quantitative purposes, the estimation of the average concentration of contaminants in water required the prior determination of kinetic parameters (sampling rate, equilibration time) through laboratory experiments. In this study, PACSiR passive samplers were deployed in situ, typically for periods of 1 week, to evaluate the contamination of agricultural watercourses by a wide range of pesticides and metabolites under different agro-pedo-climatic conditions. These small tools were also successfully used to assess the variation of pesticide concentrations in time and space in subsurface waters thanks to the use of piezometers. In typical small agricultural watersheds, comparative studies between upstream and downstream sites allowed to highlight clear gradients of contamination in rivers and to put forward the role of wetland buffer zones. Finally, we could determine average concentrations with their associated uncertainties for about 30 pesticides and metabolites that were previously calibrated in laboratory. The values achieved with this new passive sampler were in accordance with average concentrations obtained with active grab or automated sampling techniques. We demonstrated that this reactive, single-use and low cost passive sampler can be used for multiple research or operational purposes, thanks to the different levels of data acquisition, from qualitative to quantitative approach.

International audience; Monitoring hydrophobic contaminants in surface freshwaters requires measuring contaminant concentrations in the particulate fraction (sediment or suspended particulate matter, SPM) of the water column. Particle traps (PTs) have been recently developed to sample SPM as cost-efficient, easy to operate and time-integrative tools. But the representativeness of SPM collected with PTs is not fully understood, notably in terms of grain size distribution and particulate organic carbon (POC) content, which could both skew particulate contaminant concentrations. The aim of this study was to evaluate the representativeness of SPM characteristics (i.e. grain size distribution and POC content) and associated contaminants (i.e. polychlorinated biphenyls, PCBs; mercury, Hg) in samples collected in a large river using PTs for differing hydrological conditions. Samples collected using PTs (n = 74) were compared with samples collected during the same time period by continuous flow centrifugation (CFC). The grain size distribution of PT samples shifted with increasing water discharge: the proportion of very fine silts (2-6 µm) decreased while that of coarse silts (27-74 µm) increased. Regardless of water discharge, POC contents were different likely due to integration by PT of high POC-content phytoplankton blooms or low POC-content flood events. Differences in PCBs and Hg concentrations were usually within the range of analytical uncertainties and could not be related to grain size or POC content shifts. Occasional Hg-enriched inputs may have led to higher Hg concentrations in a few PT samples (n = 4) which highlights the time-integrative capacity of the PTs. The differences of annual Hg and PCB fluxes calculated either from PT samples or CFC samples were generally below 20%. Despite some inherent limitations (e.g. grain size distribution bias), our findings suggest that PT sampling is a valuable technique to assess reliable spatial and temporal trends of particulate contaminants such as PCBs and Hg within a river monitoring network.

International audience; Several types of passive samplers have been developed for the time-integrative monitoring of various organic contaminants in the aquatic environment. The passive SBSE (p-SBSE) has been recently demonstrated to be a suitable passive sampler for pesticides monitoring in agricultural watersheds. Nevertheless, for the determination of time-weighted average (TWA) concentrations, a calibration of the passive samplers under controlled conditions has to be performed prior to field exposure in order to determine for each pesticides accumulation kinetics and sampling rates (Rs). Many calibration systems have been described in the literature, but we could not find any comparison of these experimental systems for a same passive sampler and tested compounds. The aim of this study was to test two different laboratory experimental systems (continuous flow and static mode) for the calibration of p-SBSE for 16 pesticides with a wide range of physico-chemical properties (log Kow 2.2 – 5.1). We evaluated the performances of both systems in terms of consumption of water and pesticides, and stability of flow rate, temperature and pesticides concentration during the calibration experiments. The continuous flow calibration was performed in 15 glass channels (3 L each and a triplicate of p-SBSE per channel) and was based on a constant supply of water contaminated with the studied pesticides. The nominal concentrations ranged from 0.2 to 40 µg/L depending on the pesticides. The static mode calibration consisted in placing the passive samplers (up to 24 p-SBSE) in a 30 L-stainless steel tank containing spiked silicone sheets (8 sheets used), as a diffuse source of pesticides in order to generate a constant water contamination during the calibration period. The nominal concentrations of pesticides ranged from 0.1 to 150 µg/L. We performed the calibration at 20°C during 7 days for both experimental systems. The flow velocity was 2.5 cm.s-1 in the continuous flow calibration, and 10 cm.s-1 in the static mode calibration. For both systems, the temperature and the water flow velocity were stable during the calibration (20°C ± 1 for temperature, and RSD lower than 14% (n=240) for flow velocity measurements). The main advantage of the continuous flow calibration system is that the hydrodynamic conditions are close to the in situ conditions. However, it requires huge volumes of water (2000 L) and a large amount of pesticides (3.5 g) for spiked water renewal in order to maintain hydrophobic pesticide concentrations stable. Moreover, the system is relatively complex to operate due to the large number of pumps that need to be accurately calibrated. On the contrary, the static mode calibration system allows a limited consumption of water (30 L) and pesticides (0.1 g) as water renewal was not needed. This system is easy to use and stable contaminant concentrations in water can simply be maintained. However, it requires a previous step for spiking the silicone sheets which implies to know the exchange kinetics between silicone sheet, water and passive samplers before calibration. Both systems enabled to obtain curvilinear sorption profiles for 16 pesticides that were used for the determination of Rs. For hydrophilic compounds, the calculated Rs are similar with both systems, whereas for hydrophobic pesticides, the Rs obtained with the batch mode calibration system are generally greater, which can be relied to the difference of flow velocity between the two systems.

International audience; The Andes mountain range provides the setting for watersheds with high natural background of metals and for mining operations that enhance contaminant mobilization, notably in Northern and Central Chile. Dissolved and solid metal species are actively transported by streams to the Pacific Ocean from area and point sources, like acid drainage. We examine the response of metal rich particle suspensions downstream zones of mixing where shifts in the chemical environment occur. We propose a conceptual model which is used to analyze the fate of copper in the upper Mapocho watershed. The main source of copper is the Yerba Loca river, a naturally impacted stream with pH ranging from 3 to 7 and high concentrations of Cu (0.8 - 6.3 mg/L), Al (1.3 - 7.6 mg/L) and Fe (0.4 - 4.2 mg/L). Steep chemical shifts occur after the confluences with the San Francisco and the Molina rivers. We characterized stream chemistry, hydrological variables and suspended particles, including particle size distribution (PSD), turbidity, and total suspended solids. A marked seasonal behavior was observed, with a higher total Cu flux during smelting periods and a shift towards the dissolved phase during summer. When acid drainage is discharged into a receiving stream, incomplete mixing occurs thereby promoting the formation of a range of metal-rich solids with a characteristic PSD. Similarly, areas of chemical heterogeneity control the partition of metals associated to suspended geomaterials coming from bank and slope erosion. A highly dynamic process ensues where metastable phases shift to new equilibria as fully mixed conditions are reached. Depending on the reaction kinetics, some particles persist despite being exposed to thermodynamically unfavorable chemical environments. The persistence of metal-rich particles downstream zones of acid drainage mixing is important because it ultimately controls the flux of metals being delivered to the ocean by watersheds impacted by acid drainage.

Les stations d'épuration domestiques n'ont pas été conçues pour traiter les micropolluants. Elles en éliminent cependant une quantité non négligeable, essentiellement par sorption sur les boues, associée à une dégradation par voie biologique pour certaines substances. Cet article synthétise les principaux acquis récents concernant le comportement des micropolluants dans les filières de traitement des eaux (primaires, secondaires, tertiaires) et dans les filières boues associées. Il présente également les recherches en cours sur l'amélioration des procédés de traitement et leurs perspectives. / Domestic wastewater treatment plants were not designed for micropollutants removal. They perform substantial removal of several micropollutants, mainly by sorption process onto biological sludge and by biodegradation from the liquid phase for some substances. This article presents the main recent advances on the fate of micropollutants through primary, secondary and tertiary treatment processes. It also addresses research in progress for the optimization of micropollutants removal.

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International audience; Passive sampling techniques have been developed as an alternative method for in situ integrative monitoring of trace levels of neutral pesticides in environmental waters. The objective of this work was to develop a new receiving phase for pesticides with a wide range of polarities in a single step. We describe the development of three new composite silicone rubbers, combining polydimethylsiloxane mechanical and sorption properties with solid-phase extraction sorbents, prepared as a receiving phase for passive sampling. A composite silicone rubber composed of polydimethylsiloxane/poly(divinylbenzene-co-N-vinylpyrrolidone) was selected by batch experiments for its high sorption properties for pesticides with octanol-water partition coefficients ranging from 2.3 to 5.5. We named this composite material "Polar/Apolar Composite Silicone Rubber". A structural study by scanning electron microscopy confirmed the homogeneous dispersion of the sorbent particles and the encapsulation of particles within the polydimethylsiloxane matrix. We also demonstrate that this composite material is resistant to common solvents used for the back-extraction of analytes and has a maximal resistance temperature of 350°C. Therefore, the characteristics of the "Polar/Apolar Composite Silicone Rubber" meet most of the criteria for use as a receiving phase for the passive sampling of pesticides.

International audience; The urban and periurban area of Copiapó in the arid Atacama desert has more than 30 abandoned mine tailings, one active copper smelter, and 150,000 inhabitants. Fast development of the mining industry during the 19th century and unplanned growth has led to public concern about the presence of metals in soils and street dust. Recent floods and mud currents in the Copiapó watershed have introduced new solid material in about 40% of the urban area. We conducted a geochemical screening before and after the disaster in March 2015. We found concentrations as high as 1000 mg/kg of copper and 180 mg/kg of arsenic in urban soils. Since effective control measures require connecting sites of metal enrichment with the possible sources, we have performed a statistical analysis of metal association and complemented it with other analyses like x-ray diffraction. Cluster analyses of elemental compositions suggest that mud and tailing have different origins from the rest of the matrices, while soils and street dust have a similar one. Some clusters have a mix of matrices that suggest anthropogenic enrichment of some areas of Copiapó. Our initial results indicate that a correlation between observed enrichment and the copper smelter can be hypothesized for Cu, Pb, and Zn. Further spatial, statistical, and chemical analyses are needed to further confirm such findings, complemented with a thorough analysis of the baseline values that could be considered representative of the area. Future work include Principal Component Analysis (PCA) and Positive matrix factorization (PMF) to test the link contaminant sources and metal occurrence, while scanning electron microscopy can be used to identify the presence of smelter-related particles. The information generated by this research will be a necessary input for defining urban planning strategies and land use guidelines, defining health risk assessment studies, and for future evaluation of intervention priorities.