Several minor metabolites were observed in the study. All were ?5%. The structural diversity of the 9 metabolites indicated that the degradation process was very complex and involved dealkylation, oxidation of the alkyl amine group, reduction of the nitro groups, dimerization to produce azoxy compounds and benzimidazole ring formation. Mineralization accounts for 1.7% AR at day 125. Bound residues account for 42.3% AR at day 125. Further analysis of the bound residues at day 189 showed that 15.9%, 3.4%, 16.5%, 12.5% of the applied radioactivity was associated with the humin (irreversibly bound), ?-humus, fulvic acid and humic acid fractions, respectively.