engleski

Fate of febantel in the aquatic environment-the role of abiotic elimination processes

Febantel is an anthelmintic drug active against a range of gastrointestinal parasites in animals. Despite the fact that it has been detected in aquatic environment (water and sediment), there is no information on its fate in the environment. Therefore, we studied abiotic elimination processes of febantel in the aquatic environment. The results of direct and indirect photodegradation experiments showed that febantel was persistent against simulated solar radiation. Hydrolytic elimination kinetics of febantel was dependent on pH and temperature with half-lives in the range from 210 min to 99 days. Febantel metabolites, fenbendazole and fenbendazole sulfon, were identified as major degradation products using high resolution mass spectrometry. The proposed hydrolytic degradation pathway included primarily the base catalyzed hydrolysis and further aromatization as the driving force to imidazole ring of fenbendazole to the related benzo-imidazole derivatives. Aquatic toxicity of febantel and its hydrolytic mixture were evaluated toward the luminescence bacteria Vibrio fischeri. Furthermore, the mechanism and kinetics of sorption, the impact of ionic strength and the influence of pH were examined. Experimental data showed that the best agreement was obtained with the linear model (r2>0.99), while the rate of sorption is the best described with the kinetic model of pseudo-second-order. An elevated level of sorption of febantel onto the sediment was observed with KOC ranged from 1490 L kg-1 to 3894 L kg-1 for five sediment samples with different physicochemical characteristics. Based on the obtained data it could be concluded that febantel is expected to be found predominantly in sediment.

anthelmintic ; photolysis ; hydrolysis ; sorption ; degradation products ; toxicity

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