Lessons from a large scale deployment of DGT in the Seine basin

Diffusive Gradient in Thin film (DGT) is a speciation technique now commonly used in the scientific literature to assess metallic contamination in water. However applications usually take place in a same watercourse or in neighbouring sites. We propose here to present the first results of a large scale deployment of DGTs. The main objective of the project, which is supported by the French water agency of the Seine-Normandie basin, is to evaluate the potential of passive samplers as monitoring tools. DGT devices were deployed in 45 sites, on 30 locations in the entire Seine river basin. The sampling area was 500 km long and 200 km wide around Paris. The total sampling period lasted over the whole 2009 year. Restricted gels of 0.78 were used to measure labile Cd, Cr, Co, Cu, Mn, Ni, Pb and Zn. In parallel, raw and filtered water samples were collected to measure total and dissolved metals. General physico-chemical parameters were also measured. The whole set of measurements constitute a rich dataset including large and small rivers, and reference as well as impacted sites. The results first allow us to draw a map of total, dissolved and labile metal concentrations, representing the spatial variability of metal contamination in the Seine basin. Moreover, considering the temporal variability, different behaviours, depending on the metal, can be identified. The large scale deployment of DGT in the Seine river basin was successful: all the samples have been interpreted and are exploitable, whereas the dissolved metal samples are sometimes under the detection limit. We have then built a representative data set on the water contamination in labile metal of an urban impacted basin. The results are also interpreted as labile percentage, showing the operationally possible values of lability in contrasted environmental conditions. A first approach of the factors influencing the lability highlights the significance of the nature of the organic matter to interpret the lability of the metals

Leçons d'une campagne de déploiement de DGT à grande échelle dans le bassin de la Seine

International audienceDiffusive Gradient in Thin film (DGT) is a speciation technique now commonly used in the scientific literature to assess metallic contamination in water. However, applications usually take place in a same watercourse or in neighbouring sites. The study presented here shows the first results of a large scale deployment in the Seine basin, around Paris in France. The data set acquired allows us to draw several lessons from it about the level of contamination of the basin and the behaviour of the labile fraction defined by DGT

Evaluation de la relation entre pression anthropique et concentrations en HAP dans les eaux de surface du bassin de la Seine par utilisation de méthodes multivariées

International audienceUnderstanding the relation between polycyclic aromatic hydrocarbons (PAHs) in freshwater and anthropogenic pressure is fundamental to finding a solution to reduce the presence of PAHs in water, and thus their potential impact on aquatic life. In this paper we propose to gain greater insight into the ariability, sources and partitioning of PAHs in labile (or freely dissolved= not associated to the organic matter), dissolved and particulate phases in freshwater. This study was conducted using land use data as a marker of anthropogenic pressure and coupling it with chemical measurements. This study was conducted on 30 sites in the Seine River basin, which is subjected to a strong human impact and exhibits awide range of land uses. Half of the siteswere studied twice. Labile PAHs were measured by semi-permeable membrane devices (SPMDs), and dissolved and particulate phases by grab samples. Partial least squares regressions were performed between chemical measurements and data of anthropogenic pressure. The results indicate different sources for the dissolved phase and particles. Dissolved and labile phases were more related to the population density of the watershed, while particles were more related to a local pressure. Season and land use data are necessary information to correctly interpret and compare PAH concentrations from different sites. Furthermore, the whole data set of the 45 field deployments comprising labile, dissolved, total and particulate PAH concentrations as well as the physico-chemical parameters is available in the supplementary information

Evaluation de la couche limite de diffusion avec la technique DGT du labotaoire au déploiement terrain

International audienceDiffusive Gradient in Thin film (DGT) is a speciation technique now commonly used in the scientific literature to assess metallic contamination in water. It consists of several layers of chelating resin, hydrogel and protective membranes. The thickness of the layer of diffusion is a key parameter to evaluate the labile concentration of metals by DGT. As any solid immersed in water, there is a region around DGT where tangential velocity of water decreases, creating a diffusive boundary layer (DBL). At first, its thickness has been considered negligible compared to the gel layer in well-stirred solutions. But recent studies highlights that in water courses with low flow, DBL has to be considered because it can affect the evaluation of the labile concentration. All estimations of DBL are obtained with DGT equipped with classical diffusive gels. Briefly, it is the use of different thicknesses of gels, associated with the capacity of complexes of Cd, Pb, Zn to dissociate rapidly, that allows to calculate a value of DBL. The aim of the study was to determine DBL with another type of gel, which has more restricted pores, and to define a simple method to evaluate DBL in this configuration that we can apply to field data. The idea is that the complexes sampled are different, and the diffusion in the gel is slower, so we verified that the DBL established with restricted gels matched the model proposed by previous studies for diffusive gels. DBL has been assessed for Cd, Cr, Co, Cu, Mn, Ni, Pb, V, Zn at the same time, in controlled conditions in the laboratory, with varying stirring speed and water composition. Different values of DBL have been calculated. The robustness of the method has been then tested by applying it to mesocosm experiment, where DBL was also evaluated with DGT equipped with diffusive gels. The experimental system consisted in canals with different flow velocities receiving effluent from a waste water treatment plant. The best estimation of the physical DBL was given by Co in this case. Finally, the feasibility of calculating a DBL in real conditions of a large scale field deployment, with only two different thicknesses is discussed

Evaluation du potentiel d'émission d'alkylphénols et de bisphénol A par lessivage des matériaux de construction, des pièces et des consommables automobiles

National audienceLa contamination en alkylphenols (AP) et en bisphenolA (BPA) des eaux de ruissellement urbaine est avérée. Les sources potentielles de ces contaminants dans les eaux de ruissellement sont endogènes au bassin versant et sont liées en particulier à la circulation automobile et au lessivage des matériaux constituant l’enveloppe bâtie et les infrastructures urbaines. Cet article synthétise les résultats d’un travail expérimental mené sur une sélection de matériaux de construction, de matériaux et de consommables automobiles entrant en contact avec la pluie afin d’évaluer leur potentiel d’émission d’alkylphénols, alkylphénols éthoxylés et bisphénolA dans le ruissellement. 36 échantillons de matériaux, neufs et usagés, appartenant à 8 grandes familles de matériaux de construction (PVC, béton, polycarbonate, bitume modifié SBS, matériaux de drainage) et de matériaux automobiles (carrosserie, pneus) ont été soumis à des tests de lixiviation au méthanol puis, pour une sélection d’entre eux, à l’eau. Les résultats démontrent la présence ubiquiste des composés recherchés dans les matériaux urbains, ainsi que leur caractère extractible à l’eau. Les composés avec les plus forts taux d’émission sont le bisphénolA et le nonylphénol. Les émissions dans l’eau en bisphénolA les plus importantes (10 à 300 ng/g) ont été mesurées pour le polycarbonate, les pneumatiques, certaines carrosseries de voiture et les PVC. Le nonylphénol a été lixivié en quantité importante (1 à 10 ng/g) depuis les PVC, certains bétons, les bitumes modifiés SBS et les échantillons de carrosserie. Les pneus sont les seuls matériaux présentant une forte émission en octylphénol (1 à 10 ng/g). L’analyse de fluides automobiles a confirmé la présence de BPA (0.3 à 5.5 g .l-1) et de nonylphénol (2.3 à 2.9 mgg .l-1) dans les liquides de frein, tandis que APs et BPA peuvent être trouvés à l’état de trace dans les liquides de refroidissement et lave glaces

Influence of environmental conditions on the accumulation of PAHs in various passive samplers

Over the last twenty years, several passive samplers have been developed to improve the monitoring of contaminants in aquatic systems. The amount of contaminant in situ accumulated during long periods of exposure enabled the determination of a time-weighted average concentration in water, provided exchange kinetic parameters are known. The aim of this work was to improve the knowledge of the influence of the environmental conditions on accumulation kinetics in passive samplers. The impact of the water velocity and the presence of biofilm at the surface of the sampler have been more particularly assessed. PAHs have been chosen as model hydrophobic compounds. Three passive samplers have been studied: semipermeable membranes devices (SPMDs) and polymeric membranes (LDPE and PDMS). A stainless steel channel of 6 m length has been constructed with 3 successive sections with different width and controlled velocities (0.02 to 0.09 m/s) and has been fed with wastewater at different stages of the treatment. Kinetics have been determined with passive samplers previously spiked with Performance Reference Compounds and exposed for two weeks. Dissolved concentration has been measured three times during the exposition period. A relation has been observed between the water velocity and the accumulation or elimination kinetics for all passive samplers tested regardless of the water composition. For SPMDs, the presence of biofilm at the surface has not strongly influenced exchange kinetics

First overview of synthetic fibers in indoor and outdoor air

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Ability of polymeric membranes to take into account pollution peaks: Exposure to continuous and discontinuous PAH pollution in pilot river.

Over the last years, polymeric membranes have been used as passive samplers to assess hydrophobic organic contaminant concentrations in aquatic environments. The amount of contaminant accumulated in situ during long exposure periods enables the determination of a so called time-weighted average dissolved concentration in water, which is supposed to assimilate the contamination variations over time (Huckins et al., 1993). The objectives of this study were (i) to show if polymeric membranes are reliable to quantify micropollutants in the receiving environment by comparing the actual exposure concentration to the mean concentration estimated by the sampler; (ii) to understand how polymeric membranes assimilate a concentration that varies over time. After being spiked with PRCs, two types of polymeric membranes (LDPE and PDMS) were deployed during 21 days in channels bypassing the French river Gave in Lacq. The flow rate was controlled in the channels and three scenarios of pollution were tested. The first scenario reproduced chronic pollution by continuous injection of PAHs (anthracene, chrysene and benzo[a]pyrene). Two levels were tested: Environmental Quality Standard (EQS) level and 1/3 of the EQS level. The second scenario reproduced an accidental pollution by an injection of PAHs in the river during the first 3 days of the 21-day exposure. The third scenario was a discontinuous pollution with injection of PAHs during 3 periods of 3 days separated by 4 days. For the two latest scenarios, the same quantity of PAHs was released than during the first scenario. A duplicate of each sampler were retrieved at various time intervals to follow the PAH accumulation and the PRC elimination. During the experiment, grab samples of water were regularly analysed. PRC elimination and PAH accumulation were simultaneously observed for all the compounds allowing the determination of the time-weighted average dissolved concentrations in water for each duration of exposure. For the first scenario with continuous injections of PAHs, the concentrations calculated from passive samplers were the same for all exposure durations and consistent with the quantity of PAHs released in the channel. These results validated the laboratory calibration of kinetic parameters (presented in another IPSW abstract: Lorgeoux et al. 2013) and the use of PRC to correct in situ environmental exposure conditions. For the second and third scenarios with discontinuous injections, the accumulated quantities of PAHs followed the means of exposure concentrations. For the heaviest PAHs (chrysene and benzo[a]pyrene) the calculated concentrations were consistent with the average concentrations of grab samples. This demonstrates that polymeric membranes really incorporate changes in concentration over time for these molecules. For anthracene, the results also were conclusive for the scenario with 3 injections of 3 days. But for a single injection during the first 3 days of the 21-day period, most anthracene were desorbed leading to a measured concentration underestimated compared to the theoretical value. For PAHs of low molecular weight, the exchange kinetics seems too fast to assimilate a pollution peak in the time-weighted concentration