Lactofen

Biodegradation in soil

Description of key information

(2-Ethoxy-1-methyl-2-oxoethyl)-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate is completely degraded in soil biotically (half-life approximately 2.2 d) with the esterase product 5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate decreasing to 42 % of initial radioactivity from approximately 52 % after 1 week , and 14.5 % detected in the released carbon dioxide.
Anaerobic biodegradation of (2-Ethoxy-1-methyl-2-oxoethyl)-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate led to the esterase product, 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid and there were only minor differences compared to the aerobic degradation. Minor amounts of the esterase product were reduced at the nitro group, yielding 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2 -amino benzoic acid and its corresponding intramolecular ammonium salt, respectively.

Key value for chemical safety assessment

Half-life in soil:

2.2 d

at the temperature of:

21 °C

Additional information

The potential of soil to degrade (2-Ethoxy-1-methyl-2-oxoethyl)-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate was examined in regard to 4 aspects

1. Degradation by soil fungi

2. Degradation by soil bacteria

3. Aerobic degradation in soil

4. Anaerobic degradation in soil

with the following results: 1. The degradation of (2-Ethoxy-1-methyl-2-oxoethyl)-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate by eleven species of fungi widespread in soil was examined in the laboratory. All but one of the fungi species rapidly degraded (2-Ethoxy-1-methyl-2-oxoethyl)-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate to a single

product after 120 h in shake-flask cultures at 27°C. In the sterile control, (2-Ethoxy-1-methyl-2-oxoethyl)-5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate was not degraded. By Thin Layer Chromatography, High Performance Liquid Chromatography and Mass Spectrometry the metabolite formed by esterase activity was demonstrated to be 5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoic acid.

2. Similarily, nine bacterial strains were tested for their potential to degrade (2-Ethoxy-1-methyl-2-oxoethyl)-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate in shake flask cultures at 30°C in the laboratory.

All strains were able to degrade (2-Ethoxy-1-methyl-2-oxoethyl)-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate within 7 d significantly. Two strains of Bacillus were the most effective and completely degraded the test substance. The other 7 bacterial strains were less active in (2-Ethoxy-1-methyl-2-oxoethyl)-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate degradation than the fungi tested in another study of the same authors, and unreacted test substance remained after 7 d of incubation. All nine strains formed a different major metabolite.

3. Aerobic biodegradation of (2-Ethoxy-1-methyl-2-oxoethyl)-5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate in soil extending the examinations reported in the previous studies from 30 to 90 d of incubation.

(2-Ethoxy-1-methyl-2-oxoethyl)-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate is completely degraded in soil biotically (half-life approximately 2.2 d). After 90 d, the concentration of the identified esterase product, 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid, had fallen from approximately 52 % after 7 d to 42 % of the applied radioactivity of 14C-(2-Ethoxy-1-methyl-2-oxoethyl)-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate. After 90 days the 14carbon dioxide formation amounted to 14.5% of the applied radioactivity.

4. Anaerobic biodegradation of (2-Ethoxy-1-methyl-2-oxoethyl)-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate in soil was followed for 30 or 60 d after 30 d of aerobic incubation in the laboratory.

After 30 or 60 d of anaerobic biodegradation (60 or 90 d in total), the esterase product, 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid, was found and there were only minor differences compared to the aerobic degradation. These differences were:

1. Minor amounts of the esterase product were reduced at the nitro group, yielding 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2 -amino benzoic acid and its corresponding intramolecular ammonium salt, respectively.

2. Carbon dioxide release amounted only 3.4 % suggesting the formation of additional transformation/degradation intermediates