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Environmental fate & pathways

Phototransformation in water

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Description of key information

The rate of degradation was rapid with half life of approximately 4 days.

Key value for chemical safety assessment

Half-life in water:
4 d

Additional information

The stability of low (5ppm) and high (500ppm) concentration solutions of the test substance in water, in a dilute solution of ‘Gramoxone’ in water and in a dilute solution of acetone in water; exposed to sunlight at prevailing ambient temperatures was investigated. The following solutions were used to determine the photodegradability: solution1: 5ppm solution of labelled 14C-test substance in distilled water, solution 2: 5 ppm solution of labelled 14C-test substance in 1% ‘Gramoxone U.K. formulation’ in water, solution 3: 5ppm solution of labelled 14C-test substance in a 4% acetone-water solution, solution 4: 500 ppm solution of unlabelled test substance in a 4% acetone water solution, and solution 5: 5 ppm 14C-diquat solution in water. The results show that aqueous solutions of the test substance are readily photodegradable in bright sunlight. The rate of degradation was rapid with half-life of approximately 4 days. In the presence of ‘Gramoxone’ the degradation pattern changed but the rate of decay of the test substance was unchanged.