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(T/EH116) Biodegradation of a mixture of nonylphenol ethoxylates by the natural microflora of lake water and the implication for their use in pesticide formulations. Mann, Reinier1, Boddy, Michael2, 1 2 ABSTRACT- The hazards associated with "inert" pesticide-ingredients have received little attention. Alkylphenol polyethoxylates (APE) are routinely used as additives in pesticide formulations. Biodegradation of APEs results in the accumulation of persistent short chain mono-, di- and tri-ethoxylates (APEO1, APEO2 APEO3) that are more toxic than the parent compounds and potentially oestrogenic. Accumulation of persistent APE metabolites in shallow or ephemeral waters may pose a hazard to aquatic fauna. This study has followed the degradation of a mixture of nonylphenol ethoxylate (NPE) oligomers in freshwater in static die-away tests with and without illumination. Forty litre tanks, filled with water sourced from a lake within the grounds of Curtin University, was dosed with 4.5 mg/L NPE (Teric GN8, Huntsman Surfactants). The oligomer profile of the surfactant within the tanks was analysed over time by High Performance Liquid Chromatography (HPLC). Also, heteroptrophic bacteria counts were performed using an agar plating technique. Over 33 days in darkness there was a progressive and complete loss of long chain oligomers (NPEO8-17), transient increases and subsequent loss of short to medium chain oligomers (NPEO4-7), and large persistent increases (~1000%) in short chain oligomers (NPEO1-3). In the presence of illumination, biodegradation was retarded and heterotrophic bacterial proliferation was inhibited. After 33 days there was complete loss of long chain oligomers (NPEO9-17), incomplete loss of medium chain oligomers (NPEO6-8) and increases in short chain oligomers (NPEO1-5). Biodegradation of alkylphenol ethoxylates may be so slow as to span the entire embryonic and larval development time of aquatic fauna. Key words: nonylphenol, surfactant, degradation, ethoxylate |
