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Environmental fate & pathways

Biodegradation in soil

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Description of key information

The half lives in aerobic soils (DT50) of the substance were between 2.3 to 10.6 days at 20°C in the different soils. Under anaerobic conditions, the substance degraded slower with a half life of approx. 48.5 – 59.5 days at 20°C.

Key value for chemical safety assessment

Half-life in soil:
10.6 d
at the temperature of:
20 °C

Additional information

The behaviour of the substance has been extensively investigated. The objective of the studies was to determine the metabolic pathway, degradation rate and half-life of the substance under aerobic and anaerobic conditions in soil. For this purpose, the concentrations of the substance and its metabolites in soil, their rate of formation and degradation and their identity were determined with radioactive labelled test item under laboratory conditions. Additionally, volatile metabolites including 14CO2 and bound residues were quantified to establish material balances.

An aerobic soil environment will have a significant contribution to the overall degradation of the substance. The substance is oxidized to degradation products which were further mineralized to CO2.

The route of degradation of the substance, in soil has been investigated in two aerobic soil metabolism studies (Sneikus, 2005 and Mislankar, 2006) with the substance firstly uniformly 14C-labelled in the sulfonylbenzamide and secondly in uniformly 14C-labelled in the methoxybenzoyl ring. Four different soils were in each study and under aerobic conditions,14C-labelled cyprosulfamide (S- and M-label) was rapidly degraded in soil with a half life in the range of 2.3 to 10.6 days at 20°C assuming single first order degradation kinetics.

An additional anaerobic study investigates the biotic degradation under anaerobic conditions (Mislankar, 2006). The test compound was found to be subject to degradation in a flooded anaerobic soil environment under laboratory conditions. This laboratory study showed that under anaerobic conditions, the degradation of cyprosulfamide (S- and M-label) in a sandy loam soil was significantly lower as still a 10 – 11 % portion of parent substance remained unchanged after 180 days. A regression analysis of the residue levels resulted in a degradation half life of 48.5 – 59.5 days at 20°C assuming first order degradation kinetics.