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Environmental fate & pathways

Phototransformation in water

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Description of key information

In surface water it is expected that the substance degrade by photochemical processes

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Additional information

In dilute solutions and in presence of sunlight, the structural analogue of Blankophor TP 1160 (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 preceding 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 its structural analogue, for Blankophor TP 1160 photodegradation in surface water is expected as well.