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On the basis of the AOPWIN v1.92 calculation, which is based on the structural analogue of Blankophor TP 0306, CAS 16470 -24 -9, it is assumed that the test substance is indirectly photodegradable by reacting with hydroxyl radicals in the atmosphere with half-lives ranging from 1.56 hours (trans-isomer) to 1.61 hours (cis-isomer) taking into account a 24-h day and a mean OH radical concentration of 0.5E06 radicals per cm³ (Bieberstein, 2013).

For hydrolysis one study is available for the structural surrogate CAS 16470 -24 -9. In this study, which was conducted by Ciba-Geigy (1992), the stability of the tested substance could be demonstrated (hydrolysis < 10%) at pH 4, 7 and 9 at 50°C. The half-life of CAS 16470 -24 -9 is determined to be greater than 1 year.

In dilute solutions and in presence of sunlight,the structural analogue of Blankophor, CAS 16470 -24 -9, undergoes reversible isomerization of the stilbene moiety. In this process, two isomeric forms occur. The E- and Z-isomers are under environmental conditions in equilibrium within a few minutes. The parent substances used as fluorescent whitening agent consist of the E-isomer, while isomerization to the Z-form leads to complete loss of fluorescence. The study on CAS 16470 -24 -9 demonstrates that at solar latitude 60°, at 25°C, and on surface layer depths of 0 to 5 m the remaining E-isomer fraction is 17.8 to 13.3, respectively. The preceeding isomer equilibrium influences the photo-degradation rate. The half-life for photo-oxidation in natural water (Lake Greifensee) was measured for the same substance and under the same light conditions on the surface layer: 313 min (CAS 16470-24-9). The experimental kinetic data are used to calculate photochemical half-lives as a function of surface layer depth, optical density of the water, and time of the year.

As for CAS 16470 -24 -9, for Blankophor TP 0306 photodegradation in surface water is expected as well.