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Environmental fate & pathways

Biodegradation in soil

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Description of key information

Based on the available studies on biodegradation, diquat C16-18 is degraded quickly into a metabolite which has a lower sorption potential than the parent. Due to the formation of the metabolite as observed in a SCAS test (van Ginkel et al, 2010) diquat C16-18 can not be considered as readily biodegradable. It is very unlikely that a quick further degradation of the metabolite will occur in soil. Further testing in soil is thereful not expected to deliver more information. 
For soil therefore a half life value of 30000 days is used as a worst-case until better soil data become available.

Key value for chemical safety assessment

Half-life in soil:
30 000 d

Additional information

Soil Based on the available studies on biodegradation, diquat C16-18 is degraded quickly into a metabolite which has a lower sorption potential than the parent. Due to the formation of the metabolite as observed in a SCAS test (van Ginkel et al, 2010) diquat C16-18 can not be considered as readily biodegradable. It is very unlikely that a quick further degradation of the metabolite will occur in soil. Further testing in soil is thereful not expected to deliver more information. For soil therefore a half life value of 30000 days is used as a worst-case until better soil data become available.

The half-life of the bioavailable fraction of N,N,N’,N’,N’’-pentamethyl-N-C16-18 (even numbered) C18 unsat.-alkyl-1,3-propanediammonium chloride

in the water phase of soils is expected to be in the order of a few days, which is based on experiments with dialkyldimethylammonium salts (van Ginkel et al, 2003).