Alternative antifouling biocides become less active in sediments?

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Environmental fate of the new antifouling compound, triphenylborane-pyridine (TPBP), was evaluated in terms of its kinetics with sediments and ecotoxicity of its degradation products. Phenol and biphenyl was detected as major degradation products via biodegradation with natural seawater and via photodegradation with near ultra-violet irradiation. TPBP was adsorbed with sediment depending on organic matter contents of sediments and was not desorbed from the sediments. TPBP adsorbed with sediments produced phenol and biphenyl. Ecotoxicity of the two degradation products detected and other putative products such as benzene, diphenylborane, and monophenylborane was much lower than one of TPBP. The fate of TPBP in natural environment was estimated as follows: TPBP released from ship bottom paint is incorporated with suspended solids and finally fall into sediments. TPBP will be partly photodegraded in upper water column but may be less degraded in sediments with less organic matter contents at sea bottom, this may lead possible adverse effects on benthic organisms.A toxicity kit, TOX Screen 2 using Photobacterium leiognathi SB, was applied for sediment toxicity evaluation. Test bacteria was directly exposed to natural sediments using an improved method to interpolate the effects by turbidity and color of sediment on biochemiluminescence. Pollution of the sediment s collected in three bays were quantitatively evaluated with EC50 based on wet weight of sediments. No toxicity was detected in Othuchi Bay, moderate toxicity was detected in some specimen from Maizuru Bay, and high toxicity was bind in several sediments from Osaka Bay. The toxicity was dependent on the organic matter contents of sediments. More research is needed to investigate how the toxicity observed was related with the persistence of antifouling biocides and other toxic chemicals.