Biodegradation of a nonylphenol ethoxylate by the autochthonous microflorain lake water with observations on the influence of light

Alkylphenol polyethoxylates (APE) are routinely used as additives in pestic ide formulations. Biodegradation of APEs results in the accumulation of per sistent short chain mono-, di- and tri-ethoxylates (AP1EO, AP2EO AP3EO) tha t are more toxic than the parent compounds and potentially oestrogenic. Acc umulation of persistent APE metabolites in shallow or ephemeral waters may pose a hazard to aquatic fauna. This study has followed the degradation and formation of individual oligomers in freshwater in static die-away tests w ith and without illumination. Over 33 days in darkness there was a progress ive and complete loss of long chain oligomers (NP8-17EO), transient increas es and subsequent loss of short to medium chain oligomers (NP4-7EO), and la rge persistent increases (similar to 1000%) in short chain oligomers (NP1-3 EO). In the presence of illumination, biodegradation was retarded and heter otrophic bacterial proliferation was inhibited. After 33 days there was com plete loss of long chain oligomers (NP9-17EO), incomplete loss of medium ch ain oligomers (NP6-8EO) and increases in short chain oligomers(NP1-5EO). (C ) 2000 Elsevier Science Ltd. All rights reserved.