Spéciation des organoétains dans les eaux et sédiments du bassin Adour-Garonne

De par leurs nombreuses propriétés physico- chimiques, les organoétains sont très utilisés dans l’industrie et en agriculture et entrent dans la composition de nombreux produits domestiques. Ils sont cependant extrêmement toxiques et la Communauté Européenne les a classés parmi les substances prioritaires dans le domaine de l’eau.Un suivi des organoétains a été réalisé sur onze rivières du bassin Adour-Garonne et sur l’estuaire de l’Adour. Ces composés y sont systématiquement présents, les butylétains et les octylétains étant les espèces les plus fréquemment détectées. Les concentrations varient de la limite de détection (0.2-0.5 ng(Sn)/l en moyenne) à 50 ng(Sn)/l dans les eaux, et de 15 à 300 µg(Sn)/kg dans les sédiments dulcicoles. Des pics de contamination ont été observés en fin de printemps et d’été, dans plusieurs rivières. Ils correspondent à la présence des mono- butyl- et -phénylétains principalement, leurs concentrations pouvant atteindre 700 à 900 ng(Sn)/l d’eau. Les rivières les plus contaminées sont la Garonne, le Gave de Pau, l’Adour, la Charente et le Thoré. Dans les matières en suspension de l’estuaire de l’Adour les concentrations atteignent quelques mg(Sn)/kg. L’ensemble des données recueillies a permis de mieux comprendre les origines et le devenir des organoétains dans le cycle hydrologique.Because of their physico-chemical properties, organotin compounds (OTC) are widely used in industry and are present in a significant number of agricultural pesticides and domestic products. They are highly toxic and the European Community has listed them as priority pollutants in the aquatic environment. Organotins have been monitored in the Adour- Garonne basin and the Adour estuary. They are systematically present in the rivers, with butyl- and octyltins being the species most frequently detected. These species, especially octyltins, probably come from the continuous leaching of plastic tubes. The OTC concentrations ranged from just over detection limits (≥ 0.2-0.5 ng (Sn)/L) to 50 ng (Sn)/L in water and from 15 to 300 µg (Sn)/kg in freshwater sediment. Important seasonal variations were also observed. Thus, at the end of spring and summer, very high monophenyltin (MPhT) concentrations of up to 700-900 ng (Sn)/L were found in the dissolved phase. This phenomenon could be partly attributed to specific triphenyltin (TPhT)-based agricultural treatments, MPhT being one of the TPhT degradation products. High monobutyltin (MBT) concentrations of up to 150 ng (Sn)/L were also detected during the same period. This latter compound comes from leaching of plastics and from tri- and di-butyltin (TBT, DBT) degradation. It represents 80 to 100% of the butyl species found in sediments.Considering OTC concentrations, speciation and toxicity, the most contaminated rivers appeared to be the Garonne, Gave de Pau, Adour, Charente and Thoré. Urban activities have significant influence on the levels of OTC contamination for most of the rivers, demonstrating continuous OTC inputs from domestic and industrial treatment plants. This is especially the case for the Charente and Thoré rivers, where some specific industrial activities devoted to leather and wood are present close to the sampling points.A statistical study was performed on the different physico-chemical parameters (temperature, water flow rate, dissolved oxygen concentration) and OTC concentrations. A significant positive correlation between water flow rate and organotin concentrations in the dissolved phase was observed. This correlation was very important when only sampling points far from potential OTC sources were considered, the octyltin concentrations showing the strongest correlation. These observations confirm the presence of a continuous OTC diffusion into aquatic media. A comparison between the present results in Adour-Garonne and OTC monitoring performed in the Rhin- Meuse basin shows that the level of contamination was quite similar in the two basins, especially considering rivers without fluvial traffic. A similar correlation existed between OTC concentrations in the dissolved phase and water flow rate.Special attention was given to the Adour sub-basin because of its particular geographic position and especially the large built-up area in the estuary. Butyltins remain the main OTC compound present, in terms both of frequency and concentration. According to the different sampling points in this sub-basin, mean OTC concentrations in the estuary did not appear to be really influenced by human activities located upstream, the concentrations in this part reaching 50 ng (Sn)/L in the dissolved phase. In contrast, OTC amounts found in the estuary were considerable higher. The built-up area of the estuary had a strong influence on concentrations, which were 6 to 14 times higher in the city centre than those upstream from the city (in an agricultural region). In addition to the influence of local sources, both a strong dilution effect and significant adsorption/ sedimentation phenomena in the downstream region of the estuary could be important. In the suspended matter of the Adour estuary, organotin concentrations were extremely high, reaching concentrations as high as mg (Sn)/kg. Such concentrations have already been reported for nearby regions of the harbour [Bravo et al. (2004)]. However, in the present case, there should be considerable concern considering the possible environmental consequences. The estuarine sediments appeared obviously contaminated by butyltins, but the concentrations were lower than those that could be expected (2000 µg (Sn)/ kg maximum). This observation could be explained by water flow rates as well as the tide, which could export large amounts of suspended matter outside the estuary. MPhT and TPhT were also detected, especially in sediments from the extreme downstream region of the estuary. Their presence could be attributed to the marina. The different solid/ dissolved partition coefficients were also evaluated. These partition coefficients ranged from over 40x104 for sediments up to 200x104 for suspended matter. Finally, the information on the Adour sub-basin showed that the estuary was more strongly contaminated than the upstream region.Generally, all these data have contributed to the first evaluation of OTC contamination in the Adour-Garonne basin, and identified organotin sources. The statistical study, comparisons between the different parts of the aquatic environment, and the observation of solid/ liquid distributions lead to a better understanding of the environmental fate of OTCs. Even if differences exist between the level of contamination in freshwater and estuarine environments, the ubiquitous presence of OTC must remain a subject of concern, especially with regard to the high toxicity of organotins. For example, TBT and TPhT have lethal effects on trout and algal species at aquatic concentrations in the µg (Sn)/L range or even below this concentration [TOOBY et al. (1975), WONG et al. (1982)]. Considering this high toxicity, other studies will have to be performed in order to increase the current database concerning OTC in rivers. It is also important to know the conditions that control OTC uptake by biota, and in order to propose effective environmental management strategies

Do the levels of industrial pollutants influence the distribution and abundance of dinoflagellate cysts in the recently-deposited sediment of a Mediterranean coastal ecosystem?

We studied the relationships between sediment industrial pollutants concentrations, sediment characteristics and the dinoflagellate cyst abundance within a coastal lagoon by investigating a total of 55 sampling stations within the Bizerte lagoon, a highly anthropized Mediterranean ecosystem. The sediment of Bizerte lagoon is char- acterized by a high dinocyst abundance, reaching a maximum value of 2742 cysts·g−1 of dry sediment. The investigated cyst diversity was characterized by the presence of 22 dominant dinocyst morphotypes belonging to 11 genera. Two dinoflagellate species dominated the assemblage: Alexandrium pseudogonyaulax and Protoperidinium claudicans, representing 29 to 89% and 5 to 38% of the total cyst abundance, respectively, depending on the station. Seven morphotypes belonging to potentially toxic species were detected, including Alexandrium minutum, A. pseudogonyaulax, Alexandrium catenella/tamarense species complex, Lingulodinium polyedrum, Gonyaulax cf. spinifera complex, Prorocentrum micans and Protoceratium reticulatum. Pearson correlation values showed a positive correlation (α = 0.05) between cyst abundance and both water content and fine silt sediment content. Clustering revealed that the highest abundance of cysts corresponds to stations presenting the higher amounts of heavy metals. The simultaneous autoregressive model (SAM) highlighted a significant correlation (α = 0.05) between cyst accumulation and two main factors: sediment water content and sediment content for several heavy metals, including Hg, Cd, Cu, Ni and Cr. These results suggest that the degree of heavy metal pollution could influence cyst accumulation patterns.peer-reviewe

OPTIMISATION D'UNE TECHNIQUE ANALYTIQUE COUPLEE (GC-PFPD) POUR LA SPECIATION DES COMPOSES ORGANOSTANNIQUES-APPLICATION A LEUR SUIVI DANS LE CYCLE HYDROLOGIQUE

In view of the toxicity thresholds of organotin compounds and of the draft European standards in water, very sensitive analytical techniques are needed in order to carry out pollution controls in the hydrological cycle. The technique of gas chromatographic speciation-pulsed flame photometry detection (GC-PFPD) has been optimized. This technique proved interesting in terms of Quality, speed and cost of testing for environmental pollution control. Monitoring in the environment has shown the existence of a background noise of contamination by these compounds irrespective of the type of water considered. Concentrations at levels of concern were measured, showing the persistence of these compounds in the environment and the need for regular control. A preliminary study of the sorption of these compounds on sludge from sewage treatment plants was conducted showing their strong ability to adsorb on sludgeCompte tenu des seuils de toxicité des composés organostanniques et des projets de normes européennes dans les eaux, des techniques d'analyse très sensibles sont nécessaires afin de réaliser des contrôles de pollution dans le cycle hydrologique. La technique de spéciation par chromatographie en phase gazeuse - détection par photométrie de flamme pulsée (GC-PFPD) a été optimisée. Cette technique s'est révélée intéressante en termes de qualité, rapidité et coût des analyses pour le contrôle de la pollution environnementale. Des suivis dans l'environnement ont montré l'existence d'un bruit de fond de contamination par ces composés quel que soit le type d'eau considéré. Des concentrations à des niveaux préoccupants ont été mesurées, montrant la persistance de ces composés dans l'environnement et la nécessité d'un contrôle régulier. Une étude préliminaire de la sorption de ces composés sur les boues de stations d'épuration a été menée montrant leur forte aptitude à s'adsorber sur les boues

OPTIMISATION D'UNE TECHNIQUE ANALYTIQUE COUPLEE (GC-PFPD) POUR LA SPECIATION DES COMPOSES ORGANOSTANNIQUES-APPLICATION A LEUR SUIVI DANS LE CYCLE HYDROLOGIQUE

In view of the toxicity thresholds of organotin compounds and of the draft European standards in water, very sensitive analytical techniques are needed in order to carry out pollution controls in the hydrological cycle. The technique of gas chromatographic speciation-pulsed flame photometry detection (GC-PFPD) has been optimized. This technique proved interesting in terms of Quality, speed and cost of testing for environmental pollution control. Monitoring in the environment has shown the existence of a background noise of contamination by these compounds irrespective of the type of water considered. Concentrations at levels of concern were measured, showing the persistence of these compounds in the environment and the need for regular control. A preliminary study of the sorption of these compounds on sludge from sewage treatment plants was conducted showing their strong ability to adsorb on sludgeCompte tenu des seuils de toxicité des composés organostanniques et des projets de normes européennes dans les eaux, des techniques d'analyse très sensibles sont nécessaires afin de réaliser des contrôles de pollution dans le cycle hydrologique. La technique de spéciation par chromatographie en phase gazeuse - détection par photométrie de flamme pulsée (GC-PFPD) a été optimisée. Cette technique s'est révélée intéressante en termes de qualité, rapidité et coût des analyses pour le contrôle de la pollution environnementale. Des suivis dans l'environnement ont montré l'existence d'un bruit de fond de contamination par ces composés quel que soit le type d'eau considéré. Des concentrations à des niveaux préoccupants ont été mesurées, montrant la persistance de ces composés dans l'environnement et la nécessité d'un contrôle régulier. Une étude préliminaire de la sorption de ces composés sur les boues de stations d'épuration a été menée montrant leur forte aptitude à s'adsorber sur les boues

Optimisation using experimental designs of the sample pretreatment: application to the control of the organotins in sewage sludge by GC-FPD

International audienceThe optimisation of the simultaneous extraction of the butyl- and phenyltins from sewage sludge and their derivatization using sodium tetraethylborate (NaBEt4) are reported. The methodology of experimental designs was used which allowed the evaluation of the influence of eight analytical parameters on the peak areas (S) and decomposition (D) of triphenyltin (according to its poor stability). The stirring times during extraction and derivatization as well as the NaBEt4 amount were found the most important factors. The optimal operating conditions were determined by modelling S and D. Several samples of urban sewage sludge were analysed and results compared with those obtained by other analytical methods, in order to verify the convenience of the optimised method

Photo-oxidation of tributyltin, dibutylin and monobutyltin In water and marine sediments

International audienc

Optimisation of the storage of natural freshwaters before organotin speciation

cited By 28International audienceThe speciation of organotin compounds is essential due to the species-dependent toxicity, especially in natural waters. Precautions have to be taken during sampling and storage of waters in order to prevent degradations and losses. Experimental design methodology has been used to study the conditions of stability of organotins after water sampling in rivers. The modelling of results allows the determination of optimal conditions of preservation. After acidification at pH=4 with nitric acid, the storage in polyethylene containers at 4°C in the dark is suitable to preserve the most degradable trisubstituted (butyl-and phenyl-) species over 1 month.These conditions of sampling and storage are applied to two different freshwaters. The rate of species decomposition appears to be only dependent on the water nature, whatever the organotin concentrations in the sample. Speciation could be so preserved between 1 and 3 months

Photo-oxidation of Tributyltin, Dibutyltin and Monobutyltin in Water and Marine Sediments

International audienc