Évaluation des risques écologiques causés par des matériaux de dragage: roposition d'une approche adaptée aux dépôts en gravière en eau

Une procédure d'évaluation des risques pour l'écosystème aquatique engendrés par un dépôt de matériaux de dragage dans une gravière type a été élaborée, et testée avec des échantillons de sédiments d'un canal du Nord-Est de la France. La procédure comporte une étape d'évaluation sommaire des risques, à partir de quotients des concentrations mesurées par les critères de danger correspondants, et une étape d'évaluation détaillée où des essais de toxicité et de lixiviation en colonnes sont mis en œuvre. Le scénario testé retient trois hypothèses, qui concernent (a) les effets sur les peuplements d'invertébrés benthiques, représentés notamment par Hyalella azteca et Chironomus riparius, (b) les effets sur les peuplements d'organismes pélagiques, représentés par Chlorella vulgaris, Ceriodaphnia dubia, et Brachionus calyciflorus, et (c) la pollution de la nappe alluviale associée. Différentes modalités d'exposition (essais normalisés, microcosmes) ont été testées. Dans le contexte particulier des trois sédiments étudiés, ces hypothèses se sont avérées plus ou moins discriminantes, la pollution de la nappe étant la plus sensible. Des améliorations de la procédure doivent être envisagées qui concernent à la fois la formulation des hypothèses (risques à court et long terme sur les organismes pélagiques), et les protocoles d'essai, tant pour les organismes du sédiment (rôle de la nourriture notamment) que pour les essais de lixiviation en colonnes.When contaminated by metals or synthetic organic compounds, dredged sediments may have negative impacts on receiving ecosystems. Therefore, there is a need for an operational risk assessment approach. Such a framework is proposed for dredged material deposits in open gravel quarries, which is a rather common means of disposal in France. The first step of the assessment relies upon chemical characterisation of the sediments; the resulting concentrations are divided by "probable effect concentrations" and pooled together, in order to calculate a global hazard quotient. According to the value of this quotient, several decisions can be taken: (a) undertake a detailed risk assessment, (b) dispose of the materials without further constraints, or (c) in case of uncertainty, do some biological testing (with Hyalella azteca and Chironomus riparius) in order to allow decisions. The second step is a detailed ecological risk assessment. Three different assessment endpoints have been proposed, which are (1) the deposit should have no effect on the structure and abundance of benthic invertebrates in the quarry, (2) it should have no long term effect on pelagic species, and (3) it should not cause groundwater pollution, as such quarries are in fact cross sections of shallow alluvial groundwater aquifers. A fourth assessment endpoint should be introduced, regarding health risks for recreational uses, including fishing, but this endpoint was not implemented in the current version of the approach. The analysis phase includes aquatic bioassays (bacteria - Metplate TM-, algae, microcrustaceans Ceriodaphnia dubia, rotifers Brachionus calyciflorus), and leaching assays in columns under ascendant flow.The proposed approach was tested with 3 sediments from a canal located in the north-eastern region of France. Microcosm assays were introduced in parallel to the proposed tests, in order to explore alternatives to standardised bioassays. According to their hazard quotient, the 3 sediments showed a contamination gradient; one of them should not have entered the detailed risk assessment phase, while another would have been further tested with H. azteca and C. riparius. In that case, this latter sediment would not have entered the detailed phase either, as it was not toxic to these species. However, the detailed risk assessment approach was applied to the three sediments, so as to test completely the relevance of the framework.The three sediments were not significantly toxic to either C. riparius or H. azteca. However, some effects were observed in microcosms, including genotoxicity to molluscs. In this case, no risk characterisation could be made. Pore waters extracted from the three sediments were not toxic or slightly toxic to bacteria, algae, and C. dubia; an EC10 value could be determined only for B. calyciflorus. Therefore, due to exposure calculations, it seems there is a risk to pelagic species. However, as 3 bioassays out of 4 were negative or inconclusive, a refinement step would seem to be necessary. The highest concentrations of cadmium, copper, chromium, nickel and zinc were measured in the first lixiviates of the most contaminated sediment. Yet, even in that case, the total extracted fraction remained less than 10% of the total load. This fraction was below 1% for the other sediments, whatever the metal. Maximum concentrations and predicted concentrations at 1 year were compared to drinking water standards. This comparison showed a real risk of degrading groundwater quality for that most contaminated sediment, and a transient risk due to cadmium and nickel for the following one on the contamination gradient.Considering these results, the design of the first step of the proposed assessment approach may be discussed, as one sediment which would not have been assessed in depth according to its hazard quotient did show a risk to pelagic species. This discrepancy underlines the fact that some sediment toxicity may exist below the lowest threshold. As it would be unrealistic to enter systematically into detailed risk assessments, the proposed thresholds in the decision diagram must be pragmatic compromises rather than absolutely safe boundaries. Moreover, protocol improvements are needed for sediment toxicity bioassays. Chronic endpoints are preferable, as they are more sensitive and more relevant. Another issue is related to the role of additional food: not adding food may increase the apparent toxicity, but the sediment organic content, which is an alternative food source, may also be a contaminant carrier. Furthermore, the second assessment endpoint (risk to pelagic species) should be reformulated, as it includes in fact two different questions. Short-term risks related to the deposition phase could be assessed with standardised bioassays like C. dubia survival and reproduction and algal growth, while longer term risks related to contaminant diffusion could be assessed with microcosms. Genotoxic effects were observed at rather high levels, as compared to published results. This result stresses the interest of introducing sensitive and early markers in the risk assessment process, although their real meaning for ecosystems is not yet fully elucidated. Finally, the leaching tests in columns are not completely satisfactory, as the column filling implies that one must first dry the sediments, which will alter their structure. Other application trials along with field validation studies should be carried out prior to the introduction of this scenario in operational or regulatory frameworks

Experimental study and modelling of the transfer of zinc in a low reactive sand column in the presence of acetate.

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Assessment of biofilm destabilisation and consequent facilitated zinc transport.

International audienceIn infiltration basins, such as in any kind of porous media, bacteria may form biofilms. When conditions induce destabilization of this biofilm, resulting colloids are transported by the hydraulic flow. Some studies have focused on the role played by these bacterial colloids in pollutants transport in soil. This study deals with the ability of Pseudomonas putida to retain zinc and investigates the facilitated transport of this metal. Batch and columns experiments have been carried out. Bacteria display a great affinity for zinc in batch experiments and facilitated transport have been highlighted in a small extent, for the moment. A scenario of stabilization/destabilization of the biofilm has been designed and may be employed for further investigations

The interaction between wetland nutrient content and plant quality controls aquatic plant decomposition

International audienceWe conducted an in situ decomposition experiment to better understand how habitat nutrient content controls aquatic plant decomposition and, more precisely, to determine the relative importance of the wetland conditions in decomposition, and the intrinsic degradability of plant tissues. We collected the green leaves of three aquatic plant species with contrasting plant strategies from three wetlands of differing nutrient contents, and allowed them todecompose in seven wetlands along a nutrient gradient. The plant mass loss was higher for competitive and ruderal species collected in nutrient richer wetlands as well as when they were led to decompose in nutrient richer wetlands. Plant water content correlated with mass loss for the competitive and ruderal species, which may explain the increase in mass loss with increasing nutrient content in the collection wetlands. Litter decomposition rate may be enhanced by wetland eutrophication, because of both the modification of wetland decomposition conditions and by changes in plant tissue quality

Evaluation écotoxicologique de sédiments contaminés ou de matériaux de dragage. (II) Présentation des méthodes d'essai

This report presents an application of the proposed risk assessment methodology to sediments from the "Canal de l'Est" (South branch, Vosges, France). Three different sections of the canal have been studied. Metals, PAHs have been analysed on bulk sediments, and drained and pore water. Bioassays have been applied following the framework exposed in the report on methodology. In the first scenario (deposition in an open gravel quarry), three assessment endpoints are considered successively: risk to benthic invertebrates, risk to aquatic species, and risk to groundwater quality. In the case of the sediments from the "Canal de l'Est", only the third leads to a significant risk. In the second scenario (deposition on soil), three assumptions are examined either: risk to plants, risk to aquatic species following run-off on the deposit, and risk to groundwater quality. In the case of the sediments from the "Canal de l'Est", only the first one is characterised by a significant risk; however, the exposure assessment should be refined.A la suite des réflexions sur la démarche d'évaluation et de caractérisation des risques, et à la présentation des méthodes d'essai qui font l'objet des deux premiers rapports de cette étude, celui-ci s'emploie à leur application à un cas concret sur les sédiments du Canal de l'Est Branche Sud (Vosges), où trois biefs sont étudiés. Des analyses chimiques des différents sédiments, et eaux d'égouttage et interstitielles extraites sont réalisées. Les deux scénarios, mise en gravière et dépôt sur sol sont envisagés et les essais biologiques correspondants sont faits. Les résultats obtenus sont analysés en fonction de la caractérisation des risques. Pour le scénario gravière, les hypothèses de l'approche détaillée à savoir: ne pas perturber la structure et les peuplements d'invertébrés benthiques, ne pas entraîner d'effets à long terme sur les organismes de la colonne d'eau, protéger les usages nobles de la nappe alluviale sont examinées. Seule la troisième hypothèse conduit à un risque significatif. Pour le scénario sol, les hypothèses de non-effet sur les plantes, de l'absence d'effet sur les organismes aquatiques et la comparaison avec les limites de potabilité avec les concentrations déterminées dans les colonnes de percolation sont étudiées. Seul le risque pour les plantes apparaît significatif dans ce cas ; l'évaluation de l'exposition mériterait toutefois d'être affinée

[Role of community pharmacist in the management of patients in ophthalmology].

International audienceOBJECTIVES: To assess the role of community pharmacists in ophthalmology, to evaluate the frequency of giving patients advice, and to report their difficulties in daily practice. MATERIAL AND METHODS: An anonymous questionnaire consisting of 13 questions was sent to 620 community pharmacists of Burgundy (France). Pharmacists were asked about their ophthalmic products, their ophthalmic activity in giving patients advice on ocular symptoms, and patients' expectations. For analysis, community pharmacies were separated into three groups: pharmacies in rural areas (under 2000 inhabitants), pharmacies in an urban zone with fewer than 10,000 inhabitants, and pharmacies in an urban zone with more than 10,000 inhabitants. RESULTS: The response rate was 46.9%. Ophthalmic products were mainly glasses for presbyopia (84.5%), eye care hygiene products (76.0%), and contact lens solutions (55.3%). Ophthalmic vitamin supplements were sold by 36.8% of pharmacists, mainly in urban areas. On average, the pharmacist was consulted for ocular problems seven times a week. Acute benign symptoms were most frequent. Advice on prescriptions came next. Then, information on contact lenses and chronic ocular disease were given (cataract, glaucoma, visual acuity loss, age-related maculopathy). Finally, the pharmacist either sold the patient an ocular treatment or oriented the patient to an ophthalmologist when needed. DISCUSSION: The pharmacist and his staff are active players in providing advice on ocular diseases and taking care of patients. Moreover, pharmacists have to manage ocular therapeutics, urgent symptoms, and chronic diseases. However, in our study, 46.0% of pharmacists felt confident with their knowledge on ophthalmology, 36.4% did not give their opinion, and 7.0% were uncomfortable with some questions. Most community pharmacists mentioned a lack of continuing education from pharmaceutical companies and postgraduate education on ocular diseases and treatment, mainly for age-related maculopathy

Effect of the settlement of sediments on water infiltration in two urban infiltration basins

International audienceThe sealing of surfaces in urban areas makes storm water management compulsory. The suspended solids from surface runoff water accumulate in infiltration basins and may impact on water infiltration. This paper describes a study of the effect of the settlement of sedimentary layers on the water infiltration capacity of two urban infiltrations basins. In situ water infiltration experiments were performed (1) to quantify the effect of sediment on water infiltration at local scale and (2) to derive the complete characterization of the unsaturated hydraulic properties of sediments and subsoils by using the BEST algorithm. These properties were used to model the effect of sediments on 1D water infiltrations at basin scale, simulating real operating conditions for three model rainfalls (shower, rainfall and light rainfall) and the full year 2008. The results clearly prove that sediments reduce local water infiltration capacities, due to their lower saturated hydraulic conductivities (Ks). Moreover, numerical results have shown that this finding could have a drastic impact on water infiltration at the basin scale through increasing the number and duration of water pondings. From the technical point of view, this study underlines the need for efficient monitoring of infiltration basin sedimentation and its impact on water infiltration capacity

Approche méthodologique de l’évaluation des risques écotoxicologiques liés à la mise en dépôt sur sol de sédiments de dragage

National audienceThe implementation of an ecological risk assessment framework is presented for dredged material deposits on soil closed to a canal and a groundwater, and tested with sediment samples from a French North-Eastern canal. This framework includes two steps: a screening risk assessment, based on contaminant concentrations, and a detailed risk assessment based on toxicity bioassays and column leaching tests. The tested framework includes three assumptions, which are related (a) to effects to plants (Lolium perenne L.), (b) effects to aquatic organisms (Escherichia coli, Chlorella vulgaris, Ceriodaphnia dubia, and Xenopus laevis) and (c) to groundwater contamination. Several exposure conditions were tested, including standardised bioassays. According to the specific tested sediments, the three assumptions were more or less discriminatory, soil and groundwater pollution being the most sensitives. The assessment procedure has to be improved on several aspects, particularly assessment endpoint design for risk to ecosystems (e.g.: integration of pollutants bioaccumulation), bioassays protocols and column leaching test design.Une méthodologie d’évaluation des risques écotoxicologiques engendrés par un dépôt de sédiments de dragage sur un sol situé à proximité d’un canal et à la surface d’une nappe phréatique exploitée a été élaborée et testée avec des échantillons de sédiments d’un canal du Nord-Est de la France. La procédure générale comporte une étape d’évaluation simplifiée des risques, basée essentiellement sur la mesure des concentrations en polluants dans les sédiments, et une étape d’évaluation détaillée des risques où des essais d’écotoxicité et de percolation en colonnes sont mis en œuvre. Le scénario testé retient trois hypothèses, qui concernent (a) les effets sur les végétaux de la prairie périphérique du dépôt, représentés par Lolium perenne L., (b) les effets sur les organismes aquatiques du canal, représentés par Escherichia coli, Chlorella vulgaris, Ceriodaphnia dubia, et Xenopus laevis, et (c) la pollution de la nappe alluviale associée. Différentes modalités d’exposition (essais normalisés ou standardisés) ont été testées. Dans le cas particulier des trois sédiments étudiés, ces hypothèses se sont avérées plus ou moins discriminantes, la pollution de la prairie et de la nappe étant les plus sensibles. Des améliorations de la méthodologie sont envisagées concernant à la fois la sélection des variables biologiques (intégration des effets liés à la bioaccumulation des polluants, par exemple), et les protocoles des bioessais et de percolation en colonne