Behaviour of anionic and nonionic surfactants and their persistent metabolites in the Venice lagoon. Italy

Aerobic biodegradation of aliphatic alcohol polyethoxylates (AEs) was tested under screening test conditions (Organization for Economic Cooperation and Development [OECD] 301E protocol) using recently developed analytic methodologies for the specific determination of AEs and their neutral (polyethylene glycols [PEGs]) and carboxylic (carboxylated PEGs and AEs) aerobic metabolites. Biodegradation screening tests were performed under the same conditions on three typical, commercial AE blends and an individual, linear AE ethoxymer. The linear and monobranched AEs underwent a fast primary biodegradation, whereas the multibranched AEs underwent a slower biodegradation. Based on the formation and oligomeric distribution of PEGs and the lack of detection of other biointermediates before the formation of PEGs, the central cleavage of the AE molecule appeared to be the mechanism for primary biodegradation of the linear and monobranched AEs in the tested commercial blends. As a result, the shorter AE ethoxymers biodegraded faster than the longer ones. No PEGs were detected during biodegradation of the multibranched AEs. In addition, PEGs biodegraded more slowly than the parent AEs and were removed by hydrolysis, thus leading to shorter PEG oligomers, and by oxidative hydrolysis, thus forming carboxylated PEGs.