METABOLISM OF FENAMIPHOS IN 16 SOILS ORIGINATING FROM DIFFERENT GEOGRAPHIC AREAS

The metabolism of the plant protectant Nemacur (1; common name fenamiphos) was investigated in 16 soils from 11 countries with different climates. The metabolism study was conducted under aerobic conditions at two different temperatures. The active ingredient used was phenyl ring-1-C-14-labeled. In all soils the degradation products fenamiphos sulfoxide (2), fenamiphos sulfone (3), 3-methyl-4-(methylsulfinyl) phenol (5), 3-methyl-4-(methylsulfonyl)phenol (6), and 3-methyl-4-(methylsulfonyl)anisole (7) as well as (CO2)-C-14 could be detected in various amounts. Although the soils had been selected for their diverse heterogeneity, the degradation pathway was the same in all soils. After incubation for 90 days at a temperature of 22-degrees-C, between 2.3% and 66.8% of the total toxic residues (TTR; 1 + 2 + 3) were still detectable in the soil. During this period, 1.1-39.0% of the applied radioactivity was mineralized and between 18.5% and 61.8% bound to the soils. After application and incubation of C-14-labeled metabolites 3-methyl-4-(methylsulfinyl)phenol (5),3-methyl-4-(methylsulfonyl)phenol (6), and 3-methyl-4-(methylthio)phenol (4), in a Parabraunerde from Germany, a large proportion of the radioactivity was no longer extractable.