4-(2-chlorophenyl)-N-cyclohexyl-N-ethyl-5-oxo-4,5-dihydro-1H-tetrazole-1-carboxamide

Phototransformation in water

Additional information

Data on the phototransformation in water is not a standard requirement under Regulation (EC) No. 1907/2006 Annexes VII - X. However, a study is available investigating the phototransformation of the test substance in water (1997), which is summarised here. The quantum yield of direct photodegradation of the test substance in aqueous solution was determined according to the ECETOC - method in polychromatic light.

In both irradiation experiments with simulated sunlight (artificial light source) in a merry-go-round apparatus a weak degradation of the test substance and a weak photoproduct formation was measured by HPLC-UV during the irradiation period. This indicated a good stability of the test substance against direct photodegradation in aqueous solution relative to other compounds irradiated under the same study conditions. From the UV absorption data and the degradation kinetics of both experiments the quantum yield was calculated to be ɸ = 4.94 x 10^-3.

The estimates based on two different arithmetic models (GC-SOLAR and Frank & Klöpffer) by means of the resulting quantum yield and the light absorption in the environmentally relevant range of wavelengths were well comparable when using the identical marginal conditions.

Environmental direct photolysis half-lives are given in the following tables:

GC-SOLAR program:

Season	Environmental direct photolysis half-life of the test substance [days]
	30^thdegree latitude	40^thdegree latitude	50^thdegree latitude	60^thdegree latitude
Spring	83	118	194	355
Summer	64	76	96	133
Fall	129	228	> 1 yr	> 1 yr
Winter	245	> 1 yr	> 1 yr	> 1 yr

Marginal conditions: pure water from close to the surface (0 - 5 cm depth), 10th degree of longitude, clear sky, typical ozone concentrations in the atmosphere, half-lives integrated over the entire day.

 

Frank & Klöpffer program:

Month	Photolysis constant [1/sec.]	Environmental photolysis half-life of the test substance [days]
		minimum	mean	maximum
January	0.836E-09	> 1 yr	> 1 yr	> 1 yr
February	0.318E-08	> 1 yr	> 1 yr	> 1 yr
March	0.113E-07	370	> 1 yr	> 1 yr
April	0.293E-07	150	270	> 1 yr
May	0.470E-07	110	170	> 1 yr
June	0.611E-07	88	130	> 1 yr
July	0.578E-07	92	140	> 1 yr
August	0.523E-07	100	150	> 1 yr
September	0.245E-07	190	330	> 1 yr
October	0.894E-08	> 1 yr	> 1 yr	> 1 yr
November	0.171E-08	> 1 yr	> 1 yr	> 1 yr
December	0.443E-09	> 1 yr	> 1 yr	> 1 yr

Marginal conditions: pure water from close to the surface (0-5 cm depth), stagnant water, geographic and climatic conditions of Germany (50th degree of lat.), no contribution of another mono- or bimolecular elimination process.

Direct photodegradation in aqueous solution is expected to contribute to elimination of the test substance in the environment to a low extent only. But this assessment does not consider any indirect photodegradation mechanisms.