東京湾におけるフッ素系界面活性剤の環境挙動

抄録

The perfluorinated surfactants, perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) have been reported to be present in the environment. Their behaviors in the environmental, however, are still unknown. In this study, we measured their concentrations in seawater and sediment from Tokyo Bay and in the waters of six major rivers that run into the bay. Then, their mass balances and behaviors in the bay were estimated. PFOS and PFOA existed mainly in the dissolved phase in water. The estimated annual input of PFOS from the rivers was 74 ∼ 346 kg · year^-1, which was similar to the total amount of PFOS outflow to the ocean (20 ∼ 350 kg · year^-1) and the amount of PFOS sedimentation to the bottom of the bay (1.3 kg · year^-1). On the other hand, the estimated annual input of PFOA from the rivers was 29 ∼ 148 kg · year^-1, which was much smaller than the total amount of PFOA outflow to the ocean (140 ∼ 1900 kg · year^-1). The amount of PFOA sedimentation was estimated to be negligible. These results suggest that the major source of PFOS in the bay is riverine transport. The results also indicate the existence of unknown PFOA sources around the coast of the bay and/or the possibility of a significant PFOA atmospheric deposition to the bay. The sediment was not a significant sink for the two compounds. Their environmental behaviors, therefore, are quite different from those of persistent organochlorine compounds.