Assessment of the Biodegradability and ecotoxicty of a nonylphenol ethoxylate surfactant in littoral waters

Abstract

Biodegradability and ecotoxicity of the nonionic surfactant Tergitol® NP9 were studied in sea water samples collected from the Gulf of Cadiz (Spain). In order to study the biodegradation process we followed the guideline 835.3160 "Biodegradability in sea water" proposed by the United States Environmental Protection Agency (USEPA). Growth inhibition tests on different marine microalgae species and mortality tests on a marine crustacean (Artemia franciscana) were carried out. Biodegradation process was modelled according to a first order kinetic model. Lag time and half-life were 0.75 and 4.95 days, respectively, which indicates that Tergitol® NP9 can be mineralised in sea water. Depending on the microalgae, 96-h EC50 values ranged from 3.45 to 25.82 mg L-1. 48-h and 72-h LC50 to A. franciscana were 41.2 and 30.34 mg L-1, respectively. Marine crustacean was more resistant than the microalgae. Surfactant tolerance on microalgae followed this order: T. chuii > D. salina > N. gaditana > I. galbana ≈ C. gracilis.