Biodegradation of [14C] ring-labeled nonylphenol ethoxylate

Nonylphenol (NP) and the 9-mole ethoxylate of nonylphenol (NPE9) were synthesized with a uniform radioactive C-14 label in the aromatic ring. The [C-14] NP isomer distribution and [C-14] NPE9 oligomer distribution closely matched that of commercial NPE9. Biodegradation of [C-14] NPE9 was examined under conditions simulating a river water environment, and changes in the oligomer distribution and mineralization to (CO2)-C-14 were monitored for 128 days. Over 40% of the [C-14] NPE aromatic ring carbon was converted to (CO2)-C-14 and another 21% was incorporated into the biomass. Primary degradation of NPE ( conversion to metabolites other than NP, NPE ethoxylates, and NPE carboxylates) was estimated to be 87 - 97%. NP was a minor metabolite, accounting for less than 0.4% of the initial NPE. These studies demonstrate that the phenolic ring of NPE is opened, metabolized, and mineralized in the aquatic environment.