Biodegradation and fish toxicity of nonionic surfactants

In order to investigate the fate and toxicity to fish of nonionic surfactants in the environment, biodegradation tests of river sediments and river water were carried out. In the biodegradation test of river sediments, residual surfactants in the water phase and sediments were analyzed by the colorimetric cobalt-thiocyanate method (CTAS) and high performance liquid chromatography (HPLC) with a fluorimetric detector. Two kinds of nonionic surfactants, polyoxyethylene nonylphenol ether (C//9APE//9) and polyoxyethylene alcohol ether (C//1//2AE//7), were degraded by river sediments under both stirring and standing conditions. In the river die-away test of C//9APE//9, the reduction of toxicity to fish of C//9APE//9 was observed in the course of biodegradation (after 10 days). LC//5//0 of primary biodegradation intermediates, Met 1 and 2, was almost at the same level as that of C//9APE//9. This result suggests that the reduction of toxicity to fish is due to further biodegradation of C//9APE//9 through Met 1 and 2.