コプロスタノールを指標とした大阪湾の屎尿汚染

抄録

Fecal pollution of Osaka Bay was investigated by using coprostanol (5β-cholestan-3β-ol) as an indicator. Coprostanol in the surface seawater was extracted by n-hexane, and coprostanol and cholesterol in the surface sediment were extracted by alkaline digestion. Silylated coprostanol and cholesterol were determined by using a gas chromatograph-mass spectrometer equipped with multi-ion detector. Average concentration of coprostanol in the surface seawaters was 53 ng/l (max. 150 ng/l, min. 9.3 ng/l). This level was about 20 times higher than those of other areas of the Seto Inland Sea. Average concentration of coprostanol in the surf ace sediments was 1.5 μ/g (max. 3.9 μg/g, min. 0.3 μg/g). This level was about 10 times higher than the level of eastern Hiuchinada, central part of the Seto Inland Sea. Dense population in the coastal land of Osaka Bay, Osaka, Kobe and other cities, and the insufficient sewage and feces treatment facilities in the urban area may be causes for the remarkable fecal pollution. Coprostanol in Osaka Bay comes from the coastal land through rivers. Particularly, the Yodo River, which was the biggest river flowing to the Seto Inland Sea, was the most significant fecal source of Osaka Bay. Comparison between the distribution of coprostanol in the surface seawaters and in the surface sediments suggests that in the estuarine area coprostanol, which is adsorbed in paticulates, precipitates rapidly, while dissolved coprostanol is transported through the surface sea- water to offshore and remains in seawater relatively for a long time.