Registration Dossier

Environmental fate & pathways

Biodegradation in soil

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

Diuron degrades slowly in soil under environmental conditions. The half live is 118-372 days.

Key value for chemical safety assessment

Additional information

Aerobic degreadtion of Diuron was tested in two studies using two different soil types, with similar results. Following incubation in sterile and non-sterile silt loam soil at 25 °C under aerobic conditions for up to 365 days, Diuron degraded slowly. Following first order kinetics, degradation half-life of Diuron in the non-sterile soil was determined to be 372 days (r2 = 0.976). In the sterile soil, the half-life was calculated to be 1920 days (r2 = 0.950). This indicates that degradation is mainly microbial resulting in only one major metabolite (DCPMU) which reached a maximum of 22% AR at study termination (Hawkins et al., 1990).

Following incubation in a slight humic sand at 20 ± 2 °C in the dark under aerobic conditions for up to 101 days, Diuron again degraded slowly. Results determined a maximum of 97.2 % AR at day 0 to 54.3 % AR at the end of the incubation period (day 101) and calculated a DT50 of 118 days following first order kinetics with log transformed data. One major metabolite (DCPMU) reached a maximum of 19.1 % AR at day 54 (De Vries, 1996)

On the basis of these results from soil dissipation tests it can be concluded that Diuron degrades slowly in soil under environmental conditions. The DT 50 values range from 118 days (De Vries, 1996) to 372 d

following first order kinetics with log transformed data (Hawkins, 1990) .