PARENT SESSION

1B+C Abiotic Transformations + Biodegradation
Poster Hall
8:30 AM - Monday, 28 April 2003
Chair: Peijnenburg, W.¹, ¹
Co-chair: Jafvert, C.T.², Gombar, V.K.³, ^{2 3}

(MOP/45) OH-radical reactivity and direct photolysis of triphenyltin hydroxide in aqueous.

Palm, Wolf-Ulrich ¹, Kopetzky, Raimo¹, Ruck, Wolfgang¹, ¹ University of Lüneburg, Lüneburg, Germany

ABSTRACT- Photolytical degradation reactions in aqueous solution of the fungicide triphenyltin hydroxide (TPT), a compound with typical physicochemical properties of a persistent organic pollutant (POP), were investigated. The determination of the OH-rate constant of TPT, UV-spectra in aqueous solution and the revisited determination of the quantum yield using detailed light intensities will be discussed. The quantum yield of TPT was found to be near unity ( ± 2 = 1.25 ± 0.26 at 254 nm and T = 295 - 298 K). Using nitrobenzene as reference compound the OH-rate constant of TPT was determined to be k_OH ± 2 = (9.4 ± 3) × 10⁹ M^-1 s^-1 at T = 295 K. Although the quantum yield of TPT is among the highest values found for a pesticide, the degradation by sunlight is negligible due to a missing overlap of the UV spectrum of TPT and typical sun-light spectra. Rate constants and physicochemical properties were used to discuss the environmental fate of TPT. The OH-rate constant of dissolved TPT leads to a lifetime of about one week in surface waters. Henry's Law constant of TPT was predicted to be higher than 10 ⁵ M/atm. Pure gas-phase experiments of TPT at 298 K are assumed to be impossible (due to the predicted very low vapour pressure) and not important to assess the degradation of TPT in the environment. As for all semivolatile compounds practically no quantitative values are known of the degradation in the much more important adsorbed state. This also holds for TPT adsorbed especially on humic acids in surface waters and on aerosols in the gas phase. Lifetimes obtained for the dissolved state are assumed to be minimum values and experiments to investigate the degradation of TPT in the presence of humic acids in aqueous solutions are under way.

Key words: quantum yield, triphenyltin hydroxide, OH-rate constant, degradation