Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Hydrolysis :

The hydrolytic behaviour of glufosinate-ammonium as function of the pH value (5, 7, 9) at 25 °C was investigated over 30 days according to the EPA-guideline, subdivision N, §161-1 (Görlitz & Klöckner, 1986; M-110354-03-1). Glufosinate-ammonium was stable to hydrolytic conversion under sterile abiotic conditions at 25 °C and pH 5, 7 and 9. No DT50 was therefore determined. No transformation products were formed.

It is concluded that abiotic hydrolysis of glufosinate-ammonium does not contribute to the elimination from the natural aquatic environment.

Photolysis :

The aqueous photolysis of glufosinate-ammonium was studied to determine the route of degradation, the nature of photolytic products and the rate of photolysis (Sarafin et al., 1989; M-123935-01). Sterile aqueous solutions (approx.1.5mg/L) in acetate (pH 5), phosphate (pH 7) and borate (pH 9) buffer were irradiated in a laboratory experiment. The irradiation was performed under temperature control at 25 ± 2 °C (dark controls at 21 ± 2 °C). The samples were irradiated for up to 192 hours. The duration as mean value corresponded to 35 days under outdoor conditions (12 hours sunlight per day). No other compounds except the test item were found in the buffer solutions after termination of irradiation. There was practically no formation of14CO2or other volatile degradates.

It can be stated that glufosinate-ammonium is photolytically stable in sterile aqueous solutions.

Results were similar for conditions of indirect photolytic transformation (Stumpf, K. & Schink, C., 1992; M-137377-01-1) in sterile natural water (pH 5.7) at 25 °C under light conditions of Europe, i.e. 52° north. Values of the DT50 of 1.3 to 2.2 years were calculated with no major transformation products formed.

Direct or indirect photolytic transformation in water therefore does not significantly contribute to the elimination of glufosinate-ammonium residues from the aquatic environment.

No quantum yield was determined due to a lack of absorption of light by glufosinate-ammonium in the relevant wavelength range of visible light.

The photodegradation of 3,4-14C-labelled glufosinate-ammonium was studied on the surface of a sandy loam soil (Stumpf et al., 1989; M-123938-01-1). Glufosinate-ammonium was recovered quantitatively following irradiation on sterile soil surfaces. Glufosinate-ammonium was therefore stable towards photolytically induced transformation processes. No transformation products were formed being specific for photolytic degradation.

Conclusively, photolytical transformation processes on soil surfaces do not play a role for the elimination of glufosinate-ammonium residues from the soil environment.

Overall conclusion:

Abiotic degradation is not relevant process for glufosinate-ammonium as neither hydrolytic and photolytic degradation in water nor photolytic degradation in soil do present the major degradation route in the environment. The degradation is mainly mediated by microbial processes.