Pertinence d'une sélection des pesticides à mesurer dans un réseau de surveillance de la qualité des eaux superficielles à l'aide d'une méthode simplifiée d'évaluation des risques

L'une des difficultés rencontrées couramment dans la conception des réseaux de mesure - au moins en ce qui concerne les micropolluants - porte sur la sélection des paramètres à mesurer. C'est notamment le cas pour les pesticides, dont plusieurs centaines sont utilisées en agriculture, mais qu'il est impossible de surveiller dans les eaux en totalité pour des raisons à la fois techniques et économiques. C'est la raison pour laquelle les autorités françaises ont fait procéder à la mise au point d'une méthode de sélection des matières actives utilisées en agriculture basée sur l'évaluation du risque. Dans cette méthode, l'exposition est figurée par un rang combinant les données relatives aux usages des matières actives (superficie, dose par ha) et leurs caractéristiques physico-chimiques. Le danger est représenté par la toxicité, soit pour l'homme, soit pour les espèces aquatiques. Cette approche a été appliquée à l'échelle nationale et dans un certain nombre de régions françaises, dont l'Alsace et la Lorraine. Les résultats des mesures de pesticides réalisées ensuite pendant un an ont été confrontés aux indices d'exposition obtenus. Les substances détectées le plus fréquemment correspondent effectivement à celles dotées des rangs d'exposition les plus élevés (ajustement exponentiel, r2≈0.82) ; cependant, le diuron apparaît à une fréquence plus élevée que celle attendue, en raison de ses usages non agricoles. La corrélation est moins bonne pour les substances dont les rangs d'exposition sont proches de la valeur considérée comme significative pour les eaux superficielles, ce qui peut provenir soit de l'utilisation de données erronées lors de la sélection, soit d'un poids insuffisant attribué à certains facteurs dans la méthode de sélection, soit enfin d'aléas météorologiques.Monitoring of micropollutants is a rather recent activity (10-15 years), at least in surface waters; because of the need for sophisticated analytical methods and of the potential number of analytes, this type of activity is confronted with important economic constraints, which require that one make a selection among the range of substances to monitor. Among organic micropollutants, pesticides constitute a well-identified category, since they are used mainly in agriculture; this use on broad surfaces may have important impacts on the quality of surface water. Various methods have been used to select those pesticides likely to have the greatest impacts on water quality; some of these methods might be considered to be "hazard assessment", whereas others correspond to simplified "risk assessment" methods (this appears particularly true for pesticides, of which several hundreds are used in agriculture). Recently, a French panel of experts mandated by different Ministries designed a selection method called SIRIS, which allows one to define three different lists of pesticides according to the media to be monitored (surface or ground-water) and to the monitoring objectives (ecosystem protection, drinking water production). This paper deals with the application of the SIRIS method at a regional level, in the context of a permanent survey of river quality.As a simplified risk assessment method, SIRIS combines data on hazard and exposure; hazard is estimated by a single parameter, either toxicity for aquatic species or acceptable daily intake (ADI). Exposure represents the probability that a transfer to water bodies may occur; for surface water, this probability is influenced by the crop acreage, the applied dose (kg/ha), the solubility, the pesticide half-life, the hydrolysis and the distribution coefficient between water and organic matter (Koc). These factors are considered in this hierarchical order, and for each substance a score is assigned to each of these factors among three possible values ("o"=slight, "m"=medium, "d"=high, according to the relative influence on transfer); finally exposure is estimated by a relative rank obtained by a combination of these values following a "penalisation" principle. Two tables are available for applying this approach at a regional level: the first contains the values (o,m,d) assigned to more than 300 substances by the expert panel for solubility, half-life, etc., and should be completed with crop acreage and dose. The second table provides the ranks corresponding to the different combinations of o,m,d values. A final rank of 35 was considered by consensus to be a pragmatic threshold for the transfer to surface water. This method was applied in 1996 in two regions in France (Alsace and Lorraine) separately; most of the selected chemicals (but unfortunately not all, due to technical constraints) were then analysed monthly in surface waters (24 sampling points, yielding 144 samples in Alsace and 169 in Lorraine). Occurrences fell between 0% and 60% in Alsace, and between 0% and 90% in Lorraine; in both regions, the most frequently detected chemicals were atrazine and diuron.The relevance of the selection method may be discussed under several aspects: the choice of the factors, their order, the position of thresholds corresponding to o,m,d values, the value of the overall threshold, and the availability of the data. Some pesticides are not ranked only because no data were available concerning their solubility, hydrolysis rate or Koc, but the relative importance of such gaps cannot be appreciated with the current set of data. Other items may be assessed through the comparison of the exposure rank versus the occurrence. This relationship takes an exponential shape, with some anomalies: for example, the occurrence of diuron in Alsace is higher than expected, based on its exposure rank. This situation can be explained by the fact that there are non-agricultural uses of this substance, such that the exposure rank appears to be underestimated. For other substances, like aldicarb and chlorpyrifos-ethyl, discrepancies are observed between the exposure rank and occurrences, when comparing with substances with higher exposure ranks. This anomaly may be due to poor data quality. For carbendazime, the occurrence in Lorraine appears underestimated, probably because of a dry period deficit after the application. Finally, chlortoluron received the same rank in the 2 regions, but is more frequently detected in Lorraine; crop acreage may have been overestimated in Alsace. However, the dataset is still limited to one year of sampling; some discrepancies may appear less important when more data are available. For chemicals with ranks > 50, there is a good exponential fit between ranks and occurrences (y=0.0235*e0.0739x ; r2=0.82). This observation means that pesticides with ranks >50 are systematically encountered in surface waters; however, the current threshold (35) should be maintained, because some substances with ranks <50 are also detected. Thus, the SIRIS method appears to be a good tool for selecting agricultural pesticides for monitoring purposes at a regional level

Les biocapteurs appliqués au contrôle des eaux: Revue - État de l'art

Cet article présente l'ensemble des biocapteurs en cours d'étude et proposés pour le contrôle en continu, automatisé et in situ de la qualité des eaux. Le principe des systèmes, étudiés jusqu'ici majoritairement en laboratoire et sur pilote, sera donné avec leurs performances au plan sensibilité et spécificité de détection des polluants hydriques. Ces performances conditionnent leur domaine d'application : les systèmes très sensibles étant affectés au contrôle des eaux d'alimentation et des eaux souterraines, les moins sensibles au contrôle des effluents très contaminés.Les biocapteurs peuvent se caractériser par deux de leurs composantes principales :- le réactif biologique ou biocatalyseur, sensible au(x) polluant(s); - le détecteur appelé transducteur, qui traduit la réponse biologique du biocatalyseur en un signal électrique. Le transducteur peut être de type optique, électrochimique, ampérométrique principalement, ou piézoélectrique. Trois grands types de biocapteurs peuvent être distingués selon la nature du biocatalyseur :- les bioréacteurs, basés sur l'étude des réponses comportementales des vertébrés (poissons) et d'autres organismes aquatiques (microcrustacés, bivalves): - les biosondes cellulaires reposant sur l'étude des fonctions métaboliques telles que la respiration, la bioluminescence, la photosynthèse de microorganismes immobilisés (bactéries, microalgues, levures) ou libres (boues activées) dans le milieu analysé: - les biocapteurs "d'affinité" basés sur l'utilisation d'enzymes ou d'anticorps, chargés de détecter respectivement les substrats et inhibiteurs enzymatiques spécifiques, ou les substances antigéniques vis à vis desquelles les anticorps ont été développés. Ces systèmes sont, par principe, les plus spécifiques mais aussi les plus sensibles. Ils ne couvrent, cependant, qu'une gamme encore très limitée de micropolluants hydriques. Le degré d'autonomie d'un biocapteur, sa facilité d'utilisation et de maintenance et sa fiabilité, sont des éléments qui rentrent en ligne de compte dans les performances. Ces qualités devront être évaluées lors de la phase de validation in situ, essentielle et déterminante pour juger de l'intérêt du système en conditions de fonctionnement réel.ContextThis paper reviews the use of biosensors for environmental biomonitoring and especially for the detection of water pollutants. These systems are developed in view of on-line applications, continuous and real time analysis. The principle and the design of the different systems proposed for this purpose are described with their performances deduced from pilot or in situ studies carried out up to now. Automation and autonomy, sensitivity and specificity are critical points that will determine the success of their applications in biomonitoring and the kind of application that can be envisaged. It is necessary they require minimal human intervention for maintenance and working . The more sensitive systems can be used for the monitoring of drinking and ground waters, the less sensitive ones for the monitoring of complex effluents, more heavily contaminated.Biosensors can be distinguished on the basis of the type of biocatalyst associated with thetransducer: the biological signal delivered by the biocatalyst is transmitted to a detector, also called transducer. The transducer, which may be an optical, electrochemical or piezoelectrical detector, transforms the biological response into an electric signal. This signal can be easily amplified and interpreted in terms of the toxicity and level of pollution of the analyzed sample.Three categories of biosensors can be defined:- biosensors using aquatic vertebrates and invertebrates: fish, microcrustacea, bivalves. Their behavior in the tested medium is studied as the criterion for toxicity; - cellular sensors, measuring physiological and biochemical functions such as respiration, bioluminescence, and photosynthesis, in microorganisms immobilized on the transducer (bacteria, yeast, microalgae,..) or suspended in the tested medium (activated sludge); - biosensors measuring an "affinity" response and a specific binding between enzyme/substrate or antibody/antigen. These systems use enzymes or antibodies immobilized in close contact with the transducer; they may detect the (analogs of) enzymatic substrates and inhibitors, or the (analogs of) antigenic substances binding to the antibody. These systems appear promising on the basis of their sensitivity. At present they can be applied for the detection of triazines and phenols. Such systems need to be developed and extended to other pollutants in order to cover the wide range of aquatic contaminants. User-friendliness, attendance and maintenance requirements, and service life are other critical aspects affecting the performances of a biosensor. These qualities need to be evaluated during the validation step of the equipment. In situ validation is essential for evaluating the relevance of the system in environmental biomonitoring and its applications. It is probable that among the numerous systems proposed as biosensors, only a few will be considered as suitable tools for on-line monitoring of waters

Is PCBs concentration variability between and within freshwater fish species explained by their contamination pathways?

Many chemical, physiological, and trophic factors are known to affect ioaccumulation of polychlorinated biphenyls (PCBs) in biota. Understanding the primary factors affecting fish contamination is critical for predicting and assessing risks to upper-trophic level consumers, including humans. Here we identify PCB contamination pathways that could explain within- and between-species variability in fish concentration levels. Three freshwater river fish species (barbel, chub and bream) were sampled at three sites along the Rhone River (France) where fish consumption is partially prohibited because of PCB levels exceeding the European health-based benchmark. The trophic position was assessed using an innovative approach based on stable isotope analyses and Bayesian inference, which takes into account both isotope data variability and parameter uncertainty. The effect of foraging habitat on fish contamination was addressed using stable isotope mixing models. The fish trophic position and PCB concentrations were found to be unrelated while the exploitation of sediment detrital carbon as a food source appeared to be a critical factor affecting fish contamination. Fish length, PCB concentration of the sediment, and individual fish foraging habitat (exploitation of detrital versus planktonic carbon sources) explained 80% of within- and between-species variability observed in PCB concentrations. These results, obtained for species that have overlapping TPs and exploit different carbon sources, reveal that the important factor in fish PCB contamination is not only what fish consume, but also and essentially the feeding location

Bioaccumulation of perfluoroalkyl compounds in midge (Chironomus riparius) larvae exposed to sediment

Midge larvae (Chironomus riparius) were exposed to sediments from a deposition sampled at a site along the Rhône River (France) downstream of an industrial site releasing various perfluorinated chemicals. This sediment is characterized by high concentrations of perfluoroundecanoic acid (PFUnA) and perfluorotridecanoic acid (PFTrDA) and a low perfluorooctane sulfonate (PFOS) concentration. Concentrations of 23 perfluoroalkyl compounds, including C4eC14 carboxylate acids, C4eC10 sulfonates, and seven precursors, were analyzed in overlying and pore water, sediment, and larvae. Midge larvae accumulated carboxylate acids (C11eC14), PFOS, and two precursors (perfluorooctane sulfonamide: FOSA and 6:2 fluorotelomer sulfonic acid, 6:2 FTSA). These substances accumulated mainly during the fourth instar larvae exponential growth phase. Accumulation of 6:2 FTSA, PFUnA, and PFOS occured via trophic and tegumentary routes. Other compounds mainly accumulated from food. Kinetics followed a partition model, from which uptake and elimination constants were derived

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

Pesticide risk assessment and management in a globally changing world—report from a European interdisciplinary workshop

[Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCA [Axe_IRSTEA]DTAM-QT2-ADAPTATION [TR2_IRSTEA]ARCEAU [TR2_IRSTEA]DTAMGlobal climate change will affect worldwide agriculture in many ways. The anticipated or already occurring changes raise concerns about the sustainability of production and the ability of agriculture to feed human populations. This appeals to sustainable agriculture providing ecosystem services more efficiently than today, and accordingly to substantial evolutions of pesticide risk assessment (RA) and risk management (RM). The RA/RM issues were discussed by two European research networks in a 2011 workshop. The RA-RM-monitoring conceptual cycle tends to be virtual, with poor connections between certain steps. The design of more comprehensive emissions scenarios could improve the accuracy of predicted runoff transport, while the microcosm/mesocosm approach could help establish causal relationships between fate / exposure and populations / communities. Combined with ecological modelling, effects can be extrapolated to higher spatial and temporal scales. Risk management of diffuse sources should be designed simultaneously at the watershed and individual plot scales. Monitoring is key to assessing the effectiveness of risk reduction measures reduce and evaluate the overall quality of the aquatic compartment. More flexible monitoring strategies clearly linked to RM decisions are therefore needed. Although some technical questions remain, it is time to apply passive samplers more routinely. A set of research and development needs covering the whole RA/RM cycle is listed in conclusion

Détection en continu de la toxicité des eaux

The continuous monitoring of the pollution sources of surface waters, of underground waters and of drinking water distributors is made possible by the use of biosensors. Biosensors allow a quick response in the case of pollution and an in situ, continuous and automatisable control of the water environments. They are the biological sensors of toxicity, which give real time information on the effects of pollutants and consequently, on the quality of the environment where they are immersed. The biological systems used cover a large variety of reactants from biomolecules (enzymes or antibodies) to higher animals (bivalves, crustacea, fish), cellular organisms (bacteria, molds, microalguae, animal cells), and even vegetal or animal tissues. Biosensors with enzymatic or immunological electrodes and those which contain a cell organelle have a high specificity towards one or more groups of pollutants. The cellular, tissue biosensors or those using higher organisms have a wider detection spectrum than that of the former. Biosensors with immunochemical sensors are the most sensitive, whereas biosensors with microalguae and those based on daphnia mobility have the highest performance. / La surveillance en continu des sources de contamination des eaux de surface, des eaux souterraines et des prises d'eaux potables est possible grâce à l'utilisation de biocapteurs. Les biocapteurs permettent d'obtenir une réponse rapide en cas de pollution et se prêtent à un contrôle in situ, en continu et automatisable des milieux hydriques. Ce sont des détecteurs biologiques de toxicité, donnant une information en temps réel sur les effets des polluants et donc sur la qualité du milieu dans lequel ils sont plongés. Les systèmes biologiques utilisés couvrent une gamme très large de réactifs allant des biomolécules (enzymes ou anticorps) aux organismes supérieurs (bivalves, crustacés, poissons), en passant par des organismes cellulaires (bactéries, levures, microalgues, cellules animales) et même des tissus d'organismes végétaux et animaux. Le niveau de pollution correspondant au seuil d'alerte est déterminé statistiquement : il dépend d'une part de la sensibilité du réactif biologique et d'autre part de la variabilité de la réponse étudiée dans les conditions normales. Les biocapteurs à électrodes enzymatiques, immunologiques et ceux qui mettent en jeu des organites cellulaires ont une spécificité élevée vis-à-vis d'un ou de quelques groupes de polluants. Les biocapteurs cellulaires, tissulaires ou utilisant des organismes supérieurs ont un spectre de détection plus large que les précédents. Les biocapteurs à capteurs immunochimiques sont les plus sensibles, alors que les biocapteurs à microalgues sont les plus performants