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

Abstract

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. T...

Validation, using a chemometric approach, of gas chromatography–inductively coupled plasma–atomic emission spectrometry (GC–ICP–AES) for organotin determination

“…Today, these compounds are detected in water, sediment or soils, at various levels of concentration ranging from some nanograms up to some µg (Sn) L -1 in freshwater, for example [5,6]. At the same time, their ecotoxicological impact has been recognised, since the most toxic species, such as tributyltin (TBT) or triphenyltin (TPhT), can, even at ng (Sn) L -1 levels, disturb aquatic life.…”