Ecotoxicological impact of material emissions from water-filled rubber gates on aquatic organisms

Water-filled rubber gates are increasingly being installed in rivers and canals as variable barriers for the regulation of water levels. The synthetic cylindrical membranes are in direct and continuous contact with the water body and especially after prolonged water retention inside the enclosed membrane, leached rubber additives may accumulate and enter the river in increased quantities. This study provides the first comprehensive and systematic investigation of material emissions from membranes used for inflatable rubber gates. For this purpose, materials of three different authentic rubber gate membranes were characterized and subjected to leaching in deionized water for subsequent ecotoxicological and chemical analyses. Leachates from all three materials caused significant acute toxic effects on algae, daphnia and luminescent bacteria. Furthermore, two membranes released chemicals causing estrogenic and anti-androgenic effects, one of which also induced aryl hydrocarbon receptor-mediated effects. In parallel, phenanthrene, pyrene, naphthalene, bisphenol A and 4-hydroxydiphenylamine (4HDPA) were detected in several samples by chemical analyses. Zinc was also released in elevated quantities from all tested materials. While 4HDPA and zinc significantly contributed to the estrogenic and acute toxic effects, respectively, the overall ecotoxicological effects could not be fully explained by the selected target compounds. The results of the laboratory experiments and the environmental relevance of materials were confirmed by the field sampling conducted. In total, the comparative assessment presented in this study can support the selection of environmentally compatible membrane materials and provides a basis for improving formulations of rubber materials.