Biodegradation of [14C] Ring-Labeled Nonylphenol Ethoxylate

Nonylphenol (NP) and the 9-mole ethoxylate of nonylphenol (NPE9) were synthesized with a uniform radioactive ¹⁴C label in the aromatic ring. The ¹⁴C]NP isomer distribution and ¹⁴C]NPE9 oligomer distribution closely matched that of commercial NPE9. Biodegradation of ¹⁴C]NPE9 was examined under conditions simulating a river water environment, and changes in the oligomer distribution and mineralization to ¹⁴CO₂ were monitored for 128 days. Over 40% of the ¹⁴C]NPE aromatic ring carbon was converted to ¹⁴CO₂ 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.