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Environmental fate & pathways

Phototransformation in soil

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Description of key information

The test substance degraded slowly on irradiated sandy loam soil, with an extrapolated half-life of 149 days.

Key value for chemical safety assessment

Half-life in soil:
149 d

Additional information

Key study (American Cyanamid Company, PD-M Volume 23-39, 1986)

The photostability of the test substance on thin-layer soil surfaces was investigated in a study equivalent to OPPTS Guideline 835.2210 to determine the photolysis rate and the chemical nature of the major photoproducts formed. The photolysis of the carbon-14 labeled test substance was studied on sandy loam soil. The compound was applied to the soil surface at a rate equivalent to 1.5 lb ae/acre, then exposed continuously for 28 days to light from borosilicate filtered Xenon-arc lamp in a custom-made environmental chamber. The soils were irradiated approximately 80 cm from the light, which was operated continuously at 6,000 watt. The light produced by the lamp is comparable to summer sunlight in Chicago, Illinois. The test substance degraded slowly on irradiated soil. There was 11% degradation of the test substance over the 28 days of continuous irradiation. None of the at least five degradation products accounted for >10% of the applied dose. The half-life under the conditions of this test was calculated to be 149 days.