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Environmental fate & pathways

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The photodegradation of benzophenone in air was calculated using the generally accepted calculation model EPI Suite v.4.0, AOPWIN v1.92. Based on a reaction rate constant k(OH)=3.5549 x 10E-12 cm³/molecule x s and taking into account the OH radical concentration of 5 x 10E5 radicals/cm³, a half-life t1/2=4.5 days was calculated. Benzophenone is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions. After irradiation of aqueous solutions of benzophenone with artificial UV or sunlight 4 -hydroxy and 3 -hydroxybenzophenone were identified as photoproducts.

Benzophenone was shown to be photodegraded at low concentrations in pure water as well as in non-polluted surface water from East Lake and Changjiang River (Wuhan, China). The wavelength-averaged (250 -350 nm) quantum yields of benzophenone were determined to be 0.0013 +/- 0.001. Half-life times (1/2) of 16.23, 10.62, and 8.672 h were determined for the photlytic degradation of benzophenone in pure water, East Lake water, and Changjiang water. It could be shown that the presence of Cl(-), Fe(3 +), and humic acids, the initial benzophenone concentration, a continuous benzophenone input, the presence of benzophenone analogues influenced the degradation rate.